Australian Native Plum: A Review of the Phytochemical and Health Effects

ABSTRACT

As a kind of ubiquitous fruit extensively used as food and medicine from the dawn of human civilization, plums are universally available in the market and are well-known for their massive nutritious components and sensory value. Nonetheless, the nutritional value of Australian native plums is often either overlooked or underestimated. They contain substantial phytochemical components. Extracts from the peel, pulp, and seeds of native plums can participate in cell signaling pathways and scavenge free radicals while inhibiting pathogenic microorganisms, including bacteria, fungi, and viruses. As indicated by an increasing amount of evidence, these compounds can lower the occurrence of chronic diseases. Native plums are found to have cardiovascular and liver-protective properties, which are high in dietary fiber and low in fat, making them a great addition to any diet. Apart from their high nutritional value, they also have striking economic potential. Their pulp can be applied to food and beverages, while their trunk can be used as wood to make furniture. This review discusses five native plums: Kakadu Plum (Terminalia ferdinandiana), Davidsons Plum (Davidsonia jerseyana), Illawarra Plum (Podocarpus elatus), Burdekin Plum (Pleiogynium timorense), and Nonda Plum (Parinari nonda) and introduces their suitable planting environment, phytochemical composition, sensory properties, and application.

KEYWORDS:

• Application
• biological activities
• native plums
• phytochemicals composition
• phenols

Introduction

As increasingly recognized by epidemiology and body function research, fruits are linked to a lower chance of numerous illnesses that harm human health, including chronic illnesses, cancer, inflammation, as well as neurodegenerative disorders. This advantage can be ascribed to bioactive substances in foods with anti-inflammatory, antioxidant, and cytoprotective characteristics, such as phenolics, carotenoids, and ascorbic acid.^[1] As one of the healthiest and most nutrient-dense fruits, plums are also rich in bioactive substances. They contain various antioxidants, including flavonoids, vitamin C, and pectin.^[2] Native plums are nutritious fruits that grow naturally in a range of habitats. Australian natural environment, with moist soil and mild climate, are suitable for plum cultivation. Hence, wide unique varieties have been developed in Australia. The aboriginal people have used Australian native plums as food and medicine for thousands of years,^[3] which is advantageous for them cultivate a low-carb and high-fiber diet, thereby reducing thei risk of obesity, diabetes, and heart disease. As forcefully demonstrated by considerable proof that naive plums can offer enormous potential economic benefits. More importantly, a host of research point out to Australian native plums as functional foods, for the reason that Australian native plums and can provide consumers with health benefits, such as antibacterial and antioxidant properties. However, the value of these native plums has not been sufficiently developed and valued. On the basis of previous research, native plums research are more focused on using raw materials rather than on turning them into by-products.^[4] Native plums extracts can be processed into cosmetic ingredients and raw materials for industrial manufacturing.

On that account, this review is devoted to examining the potential health benefits of several common Australian native plums, understanding the environment in which the native plums are grown and studying phytochemical compounds, as well as their roles and current applications. The aim is to encourage large-scale commercial production of native plums and to stimulate the interest of academics in native plums as a potential functional food across disciplines.

Native plum botanical classification and cultivation environments

Plum, which belongs to the Prunus genus, originating from the Asian continent, is taken from the Greek word “Prounos” or “Proumnos”.^[5] It is a member of the Rosaceae family, of which the Almond family is a subfamily with over 400 species, including plums, apricots, and cherries.^[6,7] Rosaceae, one of the most economical plant families, is the 19th largest plant family.^[8] Plums have been farmed since prehistoric times. It is worth mentioning that plums are currently widely grown in China, Japan, Korea, and other parts of the world.^[9,10] Furthermore, most plum trees flourish in mild or temperate climates, but they can tolerate hot summers and cold winters as well. Australian weather is ideal for growing plums,^[11,12] and Australian varieties are unique. The southern states of Australia are the central regions producing plums, with more than half of the production taking place in Victoria’s Goulburn Valley. Native plums are also produced in Young, Orange, and Perth in Western Australia.^[13] It is also important to note that Australian native plums are highly adaptable and have low soil requirements. As a consequence, sandy soils with moist, well-drained climates in warm regions are best for planting plums. Due to the shallow root system, it is susceptible to saline-alkali soil and waterlogging. The roots can quickly rot in standing water in the soil. Nevertheless, they have strong growth abilities and resistance to polluted air, which is why some indigenous varieties are often used as garden ornamentals.^[14,15] Figure 1 exhibits five species of native plums commonly found in Australia. The scientific classification and suitable environment for the selected five native plums is demonstrated in Table 1.^[16–20]

Figure 1. The five different types of native plums in Australia: from left to right are Kakadu Plum, Davidson Plum, Illawarra Plum, Burdekin Plum, Nonda Plum.

Table 1. The taxonomy and plant environment of native plum.

Species	Terminalia ferdinandiana	Davidsonia jerseyana	Podocarpus elatus	Pleiogynium timorense	Parinari nonda
Domain	Eukarya	Eukarya	Eukarya	Eukarya	Eukarya
Kingdom	Plantae	Plantae	Plantae	Plantae	Plantae
Subkingdom	Tracheophytes	Tracheophytes	Tracheophytes	Tracheophytes	Tracheophytes
Division	Angiosperms	Angiosperms	Gymnosperms	Angiosperms	Angiosperms
Class	Eudicots	Eudicots	Pinophyta	Eudicots	Eudicots
Subclass	Rosidae	Rosids	Pinopsida	Rosids	Rosids
Order	Myrtales	Oxalidales	Pinales	Sapindales	Malpighias
Family	Combretaceae	Cunoniaceae	Podocarpaceae	Anacardiaceae	Chrysobalanaceae
Genus	Terminalia	Davidsonia	Podocarpus	Pleiogynium	Parinari
Species	T. ferdinandiana	D. pruriens	P. elatus	P. timoriense	P. nonda
Mature period	March-June	June-August	March-July	June-September	August-November
Suitable environment	Naturally hot and coastal environments	Adequate soil moisture and good soil nutrition	Sandy soil	Tropical rainforest environment, grow in cold, dry land	Sunny position, deep and well-drained sandy
Environment preference	Tropical area	Protection from full sun and wind	Resistant salt spray and a damp climate	Fertile, well-drained soil with full sun	pH 5.5–7 soil with average annual rainfall 1100–1600 mm
Main growing place	Western Australia border to the west of Arnhem Land	Northern New South Wales	Queensland and eastern New South Wales	Dry tropical rainforest, near the coast in Queensland	Northern Australia
Reference	^[Citation16,Citation17]	^[Citation13]	^[Citation18]	^[Citation19]	^[Citation20]

Kakadu plum

Kakadu plum, a fruit distributed in northern Australia, is also known as Terminalia ferdinandiana.^[16] Its peel is light green and pitted. The shape is an oval fruit, over half an inch (1.5–2 cm) in size. Its taste is slightly sour and the smell is a mixture of baked apple and pear. Each Kakadu plum weighs between 0.1 and 0.2 oz (2–5 g).^[21] Aboriginal people often used it in Australia’s undiscovered history to replenish energy or quench their thirst on hunting trips.^[22] While the Aboriginal peoples in northwest Australia eat it as a portion of traditional food, the Aboriginal people living in Arnhem see it as a medicinal herb.^[23]

Davidsons plum

Davidson plum, Davidsonia jerseyana, is unique to a small northern New South Wales region on the east coast of Australia.^[24] Its fruit usually grows on tree trunks and branches, with a bluish-black peel and a bright red or pink pulp. It has sour taste with earthy aroma.^[13,19] They are widely recognized throughout Aboriginal cultures, and they are sometimes eaten dipped in salt and sugar, but they are most frequently consumed fresh. Meanwhile, early settlers used D. jerseyana to make jams, jellies, and dry red wine.^[3,25]

Illawarra plum

Illawarra plum, also known as Podocarpus elatus, often grows in the temperate to subtropical regions of New South Wales and Queensland.^[26] The edible part of the plant is a fleshy swollen stem similar in size and appearance to a large dark purple grape. It should be noted that it differs from other varieties resides in that it has no cones but develops from seeds attached to stems attached to branches.^[27] The fruit has a subtle pine flavor, and the thickest part of its seeds is edible.^[28] It has a sweet taste and soft texture. In accordance with European and Aboriginal settlers in New South Wales, P. elatus is one of the tastiest bush foods.

Burdekin plum

Burdekin plum, also known as Pleiogynium timorense, grows primarily in Queensland. It has a dark grey trunk with glossy compound leaves. It has a thin layer of delicate flesh and is dark purple on the surface with smooth and glossy skin.^[29] It differs from other varieties in that it does not ripen on the tree, but after its harvest.^[30] Relying on the cultivar, the pulp might be red, green-white, or a mix of the two hues. Varieties of white pulp fall into the sweet-sour category, whereas red pulp choices have a more sour flavor.^[31] Australian settlers and explorers enjoyed P. timorense as well as did the Aboriginal tribes.

Nonda plum

Nonda plum, Parinari nonda, is a small tree or shrub. It can usually be found in northern Australia, which tends to favor dry, sandy soil and can bear edible fruit with seeds surrounded by brown hairs.^[32] The fruit is oval and has an orange peel, resembling a loquat. It smells earthy. It has a hard endocarp and is bony with a rough and reticulate outer surface,^[33] and leaves are pendulous. Its flesh has little moisture and tastes slightly dry.

Phytochemicals in native plum

Carbohydrates, proteins, fats, polyphenolic compounds, amino acids, fatty acids, minerals, fiber, and ascorbic acid are the critical nutritional components of native plums.^[34] Native plums are abundant in vitamins such as vitamin A, vitamin C (ascorbic acid), folic acid, and vitamin K. Minerals present in native plums include potassium, phosphorus, magnesium, iron, and zinc. They are also a superb fat-burning fruit since they are rich in dietary fiber but low in fat and only occupy 36–76 calories per 100 g of energy. The secondary metabolites in native plums are phytochemicals. It comprises phenolic, and anthocyanin, including cyanide-3-rutinoside, which possesses antioxidant and anticancer properties.^[35]

Nutrients compounds

Macronutrients

As a paramount energy source during fruit ripening, carbohydrates are the most prevalent macronutrient in fruits and vegetables, ranging from 50% to 80% of dry weight.^[36] Table 2 illustrates the types and contents of nutrients in native plums. The most prevalent carbohydrates in plants are sugars, starches, and non-starch polysaccharides, such as cellulose and hemicellulose.^[43] According to an analysis of Australian native plums, the sugar content varies from 9.9–16.2 g/100 g, and the total sugar content is between 3.9–9.9 g/100 g.^[44] Sugars and starches are the only energy sources in native plums capable of being digested, absorbed, and processed by the human body.^[45] Non-starch polysaccharides cannot be consumed as an energy source since they are difficult to digest but have physiological effects that are advantageous to human health.^[46,47] The major carbohydrates in native plums are sucrose and glucose, with a tiny amount of fructose present, which might be owing to the complex structure of polysaccharides from the native plum peel.^[48] The peel also contains some measurable amounts of glucose, fructose, and inositol, as well as trace amounts of arabinose and xylose.^[49] As a result of the correlation between sucrose concentration and flavor, native plums with greater sugar content have superior aroma.^[50] In addition to serving as a sweetener, sucrose may be a vital energy source, regulate the gastrointestinal tract, and restore advocacy immunity. By adopting gas chromatography, native plums also have reflected starch and raffinose, a soluble but indigestible sugar. The seeds of native plums also contain massive nutritional fiber.^[9,51]

Table 2. The nutritional properties of native plums.

Classification	Nutrients	Species	Unit	amount (per 100g)	Daily value percentage (DV)	Reference
Carbohydrates	Dietary Fiber	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	g	1.4–2.3	4–9%	^[,Citation42]
	Sugars	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	g	9.92–16.4
Fat & Fatty Acids	Fat	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	g	0.2–0.5	;
	Total Omega-6 fatty acids	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	68.9–72.6
Protein & Amino Acids	Arginine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	10.2–14.81	1–2%
	Aspartic acid	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense	mg	396–581
	Alanine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense	mg	28–46.2
	Cystine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Parinari nonda	mg	1.8–3.3
	Glutamic acid	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	32.7–57.8
	Glycine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	9.–14.8
	Histidine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	9.–14.8
	Isoleucine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	12.7–23.1
	Leucine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	11.9–24.7
	Lysine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	13.2–26.4
	Methionine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	7–13.2
	Proline	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	31–44.6
	Phenylalanine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	19–23.1
	Serine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	14.3–38
	Tryptophan	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	9.–14.8
	Tyrosine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda		8–13.2
	Valine	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	16.01–26.40
Vitamins	Vitamin A	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mcg	17–28	2–3%
	Vitamin C	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	9.5–15.7	11–26%
	Vitamin E	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.26–0.4	1–2%
	Vitamin K	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mcg	6.4–10.6	5–13%
	Vitamin B1	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.019–0.028	2–3%
	Vitamin B2	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.026–0.034	2–3%
	Vitamin B3	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.417–0.7	3%
	Vitamin B5	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.135–0.2	2–3%
	Vitamin B6	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.029–0.035	2%
	Vitamin B9	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mcg	5	1%
	Choline	Terminalia ferdinandiana, Davidsonia jerseyana, Pleiogynium timorense	mg	1.9–3.1	–
	Carotene	Terminalia ferdinandiana, Davidsonia jerseyana	mcg	134–190	–
Minerals	Calcium	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	6–9.9	0–1%
	Magnesium	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	7–11.6	2–3%
	Phosphorus	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	16–26.4	2–3%
	Potassium	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	16–25.9	2–7%
	Zinc	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.1–0.2	1%
	Copper	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.06–0.1	5–7%
	Manganese	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.052–0.1	2–4%
	Iron	Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana, Pleiogynium timorense, Parinari nonda	mg	0.17–0.3	1–2%
	Fluoride	Terminalia ferdinandiana	mcg	2	–

With regard to fat, native plums are mainly monounsaturated and polyunsaturated fats and are healthy food with zero cholesterol.^[52] Fatty acids are an essential energy source but comprise only a tiny portion of the fruit’s composition. As can be seen in Table 2,^[31,37–42] 100 g of native plums contain only 0.2–0.5 g of fat.^[39] Despite having a low-fat level, these lipids serve as transporters for the beneficial chemicals and vitamins in native plums and reduce the risk of cardiovascular disease. Omega-6 fatty acids are also found in native plums. Linoleic acid and linolenic acid are the predominant polyunsaturated fatty acids in the fruit, whereas the principal saturated and monounsaturated fatty acids in native plums are butyric and oleic acids, respectively.^[53,54] The lipids in native plums are present in the cotyledon tissue of the inner core in the form of intracellular oil droplets. The cotyledon tissue of the inner core of native plums contains the lipids as intracellular oil droplets. Furthermore, in line with Botsman,^[55] the lipid content and composition of native plums were primarily influenced by their genotype but also by outside variables, including the time of harvest and the soil quality of the planting region.^[56] Since these fatty acids are not generated spontaneously by the body, people who consume native plums can aid in the healing of damaged cell membrane and associated nervous system tissue. They can also lower total cholesterol and high-density lipoprotein (HDL) levels. What’s more, native plum seeds can be a significant source of indispensable fatty acids for feed due to their high level of saturated fatty acids.

Proteins conduct a crucial role in tissue healing and enzyme manufacturing other than being crucial structural components of cells. However, native plums are not an abundant source of protein.^[57] Since seeds have the most considerable protein content, they can serve as a replacement or dietary supplement for purchasers whose access to other protein sources is constrained or hampered.^[53] Protein content alters as the fruit matures, which asides by a V-shaped pattern. In the early stages of fruit formation, the protein content can heighten little by little; in the middle and late stages of fruit formation, there is a corresponding decrease, and in the last few months before harvest, the protein content would increase remarkably.^[43] Native plums are rich in glutamate,^[45] which is used in protein synthesis to control acid-base balance and nitrogen transport. The most abundant amino acids in seeds are arginine and aspartic acid.^[58] Aspartate is a nitrogen donor and transfers nitrogen to urea, while arginine is a precursor to produce urea and nitric oxide.^[59]

Vitamins and minerals

The overall content of minerals and vitamins in plums is not too excessive in fruits. Nonetheless, native plums contain abundant potassium, calcium, magnesium, phosphorus, sulphur, and nitrogen. Potassium has a role in energy metabolism, sugar generation, cell growth, and neurotransmission other than being essential for both.^[60] Phosphorus can improve the coordination of body functions and help regulate the release of oxygen.^[61] Calcium can preserve healthy bones and teeth while lowering the risk of osteoporosis.^[62] Furthermore, it is one of the components that keep the body’s ion balance in check and aids in controlling muscle contraction and nerve stability.^[45] Magnesium is present in bones, soft tissues, and compartments where cellular responses occur. However, Drogoudi, et al.^[63] found that various kinds of plums grown in the same environment had considerable changes in the amount of a single mineral element, which persuasively demonstrates that genetic variables in the variety can also influence the content of a single mineral element.^[43] Vitamins are essential nutrients for the human body, and each diverse vitamin has a specific function for metabolism and growth. Native plums have significant quantities of vitamin C and very moderate amounts of vitamin E.^[5,64] Native plums have higher quantities of vitamin C than a majority of other fruits, but their levels change seasonally, with the maximum levels of vitamin C observed in the fruit during the hot summer months, suggesting that temperature influences ascorbic acid production during fruit growth.^[65] Native plums are also a pivotal source of natural folic acid.^[45] Since it is an essential vitamin that our bodies cannot synthesize on their own, it must be consumed through food and as a supplement. It is also necessary for adenosine synthesis and an abundance of methylation reactions in the body. One hundred grams  of T. ferdinandiana contains up to 100 µg of folic acid, but D. jerseyana does not contain folic acid.^[61]

Phenolic compounds

Polyphenols are abundant in native plums, which include a multitude of distinct phenolic chemicals.^[66] Phenolic compounds, the largest class of phytochemicals, are predominantly produced by plant metabolism through the shikimic acid pathway and are well-known for their remarkable biological effects, such as antioxidant and antibacterial activity. Apart from that, the basic structure of phenolic compounds has a phenolic ring with one or more hydroxyl groups. As a consequence of multiple factors, such as genetics, environment, and culture, the structure of phenolic compounds may change, resulting in differences in quantity and quality.^[67] Flavonoids, followed by phenolic acids, make up the ten kinds of phenolic compounds found in native plums. Among native plum constituents, epicatechin, neochlorogenic acid, and proanthocyanidins are the most abundant free phenols, while catechin and epicatechin form the most abundant bound phenols.^[66] Table 3 shows the types and contents of flavonoids and phenolic acids in native plums.^{[16,39,48,68–79]}

Table 3. Phenolic compounds properties in native plums.

Subgroups	Name	Phenolic compounds	Chemical structure	Species	Average content(/100g)	Main position	Reference
Flavonoids	Anthocyanin	Cyanidin-3-galactoside		Terminalia ferdinandiana, Podocarpus elatus, Davidsonia jerseyana	7.99 mg	Peel, Pulp	^[Citation68]
		Cyanidin-3-glucoside		Pleiogynium timorense, Podocarpus elatus	330–335 mg	Peel	^[Citation69]
	Anthocyanin	Cyanidin-3-rutinoside		Terminalia ferdinandiana, Davidsonia jerseyana, Podocarpus elatus, Pleiogynium timorense	205 mg	Seed, Peel	^[Citation70]
		Cyanidin-3-acetylglucoside		Podocarpus elatus	2.9 mg	Seed, Pulp, Peel	^[Citation71]
	Flavanols	Epiafzelechin		Terminalia ferdinandiana,	0.29 mg	Peel, Seed	^[Citation72]
		(+)-Catechin		Davidsonia jerseyana, Pleiogynium timorense, Terminalia ferdinandiana	–	Seed, Pulp	^[Citation72]
		Epigallocatechin		Terminalia ferdinandiana, Podocarpus elatus	–	Peel, Pulp	^[Citation16]
	Flavanols	Gallocatechin		Terminalia ferdinandiana, Podocarpus elatus	–	Pulp	^[Citation16]
		Procyanidin B1		Terminalia ferdinandiana	8.84 mg	Pulp	^[Citation39]
		Procyanidin B2		Terminalia ferdinandiana	5.20 mg	Pulp	^[Citation39]
	Flavonols	Quercetin		Terminalia ferdinandiana, Davidsonia jerseyana, Pleiogynium timorense, Podocarpus elatus, Parinari nonda	0.51 mg	Peel, Pulp	^[Citation73]
		Kaempferol		Terminalia ferdinandiana, Pleiogynium timorense	0.53 mg	Pulp	^[Citation74]
		Luteolin		Terminalia ferdinandiana, Davidsonia jerseyana, Pleiogynium timorense, Podocarpus elatus, Parinari nonda	0.10 mg	Seed	^[Citation39]
	Flavonoids	Myricetin		Podocarpus elatus	0.15 mg	Peel	^[Citation75]
	Flavanone	Naringenin		Terminalia ferdinandiana	0.09 mg	Seed	^[Citation73]
	Dihydrochalcones	Phloretin		Terminalia ferdinandiana	0.14 mg	Pulp	^[Citation48]
Phenolic acids	Hydroxybenzoic acids	Gallic acid		Terminalia ferdinandiana, Davidsonia jerseyana, Pleiogynium timorense, Podocarpus elatus, Parinari nonda	1.56 mg	Peel, Pulp, Seed	^[Citation68]
		Ellagic acid		Terminalia ferdinandiana, Davidsonia jerseyana, Pleiogynium timorense, Podocarpus elatus, Parinari nonda	43.87 mg	Peel, Pulp, Seed,	^[Citation69]
		Salicylic acid		Davidsonia jerseyana	20 mg	Peel	^[Citation76]
	Hydroxybenzoic acids	Shikimic acid		Davidsonia jerseyana	1.68 mg	Peel	^[Citation76]
	Hydroxycinnamic acids	Caffeic acid		Pleiogynium timorense	3.37 mg	Pulp	^[Citation77]
		3-O-Caffeoylquinic acid		Pleiogynium timorense, Davidsonia jerseyana	75.88 mg	Peel, Pulp	^[Citation78]
	Hydroxycinnamic acids	4-O-Caffeoylquinic acid		Pleiogynium timorense, Davidsonia jerseyana	31.25 mg	Peel, Pulp	^[Citation79]
		5-O-Caffeoylquinic acid		Pleiogynium timorense, Davidsonia jerseyana	38.79 mg	Peel, Pulp	^[Citation79]
	Hydroxycinnamic acids	Ferulic acid		Terminalia ferdinandiana, Davidsonia jerseyana, Podocarpus elatus, Pleiogynium timorense	9.63 mg	Pulp	^[Citation79]

Flavonoids

Flavonoids are the most prevalent phenolic phytochemicals, and they control the color and flavor of food. There are multiple dissimilar flavonoids found in the leaves and fruits of native plums, including flavonoids, flavonols, as well as isoflavones, dihydroflavonoids, and dihydrochalcone.^[69,71,80]

The structural formula of flavonol is a 3-hydroxy brass skeleton.^[81] The three mains dietary flavonols, kaempferol, quercetin, and myricetin are often found as glycosides. The quercetin in native plums is usually presented as a glucoside or methyl glucoside conjugate. Its B-ring has a catechol gene, which makes it a paramount antioxidant with metal-binding abilities.^[82] The presence of kaempferol in the fruit conducts a pivotal in immune support and reinforces other antioxidants’ free radical scavenging effects.^[83] In native plums, anthocyanins are the most abundant phenolic compounds.^[6,74] Since anthocyanins lack ketone oxygen at the 4-position of the C ring, their structure is on the basis of phenylbenzopyran and typically has a positive charge on the oxygen atom at that location.^[84] Each carbon atom on the B ring can be substituted with a different anthocyanin owing to diverse substituents. The varied substituents of 3-, 5-, and 7- in the B ring result in the synthesis of Cyanidin-3-galactoside, Cyanidin-3-glucoside, and Cyanidin-3-rutinoside (Table 3). P. elatus contains high levels of anthocyanin 3-glucoside and pelargonidin 3-glucoside, and P. timorense also has a high concentration of anthocyanin 3-glucoside.^[31] These components are often detected around the peels and seeds of native plums,^[85] which causes them to appear red or purple.

Phenolic acids

Phenolic acids are phytochemicals widely distributed in fruit seed, pulp, and peel.^[71] Both hydroxybenzoic acid and hydroxycinnamic acid make up their two subgroups. The 7-carbon hydroxybenzoic acid, produced from benzoic acid, typically has a C6-C1 structure. The degree of hydroxylation and methylation in the aromatic ring can impose certain influence on the structure.^[86] P-hydroxybenzoic acid (PHBA), vanillic acid, protocatechuic acid, syringic acid, salicylic acid, and gallic acid are all hydroxybenzoic acids. The generation of phenolic acid is generally carried out via the shikimic acid or malonic acid pathway.^[86] The majority of the precursors for phenolic acid synthesis mediated by shikimic acid are derived from carbohydrates in glycolysis and aromatic amino acids, phenylalanine, and tryptophan produced via the pentose phosphate pathway, which is supported by fungi and bacteria that are endophytic to plants. As exhibited in Table 3, a sequence of phenolic acids can be found in native plums. The primary phenolic acid components in native plums are ellagic and gallic acid.^[87] Gallic acid is also the most abundant phenolic acid in nature, and its concentration in native plums is predominantly high, mainly in pulps, but both peels and seeds contain this ingredient.^[88]

Genetics, age, environment, and agronomic techniques all have a role in the buildup of phenolic acids in native plums.^[86] Owing to the influence of these variables on phenolic acid production and degradation, there is a considerable variation in phenolic acid levels across species and between cultivars of the same species. For this reason, the content of phenolic acid may vary significantly from study to study as a result of variances in analytical techniques.

Sensory attributes

The researchers invited different testers to do a sensory analysis of Australian native plums. Most people have displayed a positive response to plums, especially the by-products of these Australian native plums.^[61] In practical terms, the quality of native plum is not only associated with the external characteristics of plums, such as the color of pulp and peel, but also linked with the chemical composition, including total titratable acidity, organic acids, and cell wall polysaccharides, which often affect the texture of Australian native plums.

Firmness

The firmness of native plums primarily rests with the degree of pectin esterification in the fruit.^[89] With the prolongation of storage time, the pectin in native plum changes, and this change is the direct factor leading to the decrease of firmness in native plums. In the research conducted by Sekse and Wermund ^[90] adopted two kinds of plums as experimental samples to investigate both the sensory changes of the samples and the hardness of the samples after picking. It was concluded that the hardness of the mature fruits continued to decrease with the augment of storage time.

Total soluble solids

Total soluble solids are strongly associated with the eating quality of Australian native plums. During the ripening and senescence of fruits, soluble solids will continue to accumulate and be consumed. Furthermore, changes in the content of soluble solids can exert a pivotal influence on the flavor and taste of fruits. People often use a digital refractometer to detect the content of soluble solids. As exhibited by the experiment of using the digital refractometer to analyze the trend of change of dissolve solids in guava fruit, its soluble solids content of the fruit just picked is below 7.8%. As the fruit matures, its content is the highest during the eating period, and the eating quality and storage effect are the best.^[91] Moreover, Fyfe, et al.^[45] determined the content of soluble solids in Australian native plums with different maturity levels and found that the content of soluble solids in mature plums is high, and mature plums are considered to be a good dietary source of folic acid.

Cell wall polysaccharides

The components in the cell wall polysaccharides of Australian native plums mainly include pectin, cellulose, and hemicellulose. Cell wall polysaccharides conduct a paramount role in maintaining fruit texture and sensory quality. Regarding the pectin substance, it mainly exists in the cell wall of plants and in the middle layer between cells and is the matrix polysaccharide of the cell wall of the fruit. Pectin substance structure can be divided into three categories.^[92] The first common structure is through the covalent bonding of pectin substances and hemicelluloses, which in turn are cross-linked with other components by means of secondary bonds. The second is the bonding structure of cations. For instance, the presence of calcium ions can cause insolubility changes of some low-fat pectin components, and simultaneously reduce the swelling of some high-fat pectin components. The third structure is the mechanical association of macromolecules in pectin with other cell wall polymers. And this structure is correlated with solubility. As persuasively demonstrated by the research findings, fruit ripening is accompanied by changes in the content of pectin substances,^[93] pectin substances appear long-chain shortening and polymer demethylation esterification. The firmness of Australian native plums during storage after harvest is inseparable from the degree of esterification of pectin. With the continuous hydrolysis of pectin, the tissue softens, and the firmness of the fruit gradually decreases.^[93] The experiment of Ornelas-Paz, et al.^[94] confirmed the link between fruit firmness and pectin. In addition, Duan, et al.^[95] studied the changes of pectin substances during the softening process of bananas and found that as the fruit matures and softens, the content of water-soluble pectin (WSP) continues to increase, while the content of acid-soluble pectin (ASP) decreases continuously, and the hardness of bananas decreases rapidly This study further proved that there is an intrinsic association between pectin substances and aroma ripening and softening. Cellulose and hemicellulose in the cell wall also affect the sensory properties of the fruit. Cellulose, the main component of plant cell walls, is a macromolecular polysaccharide composed of glucose.^[96] Hemicellulose is a heterogeneous polymer composed of multiple different types of monosaccharides, including xylose, arabinose, and galactose.^[97] The structure of cellulose and hemicellulose during fruit ripening is correlated with the changes of fruit sensory quality.^[98,99] If the content of cellulose and hemicellulose in the fruit increases, the taste of the fruit will become hard. As conspicuously revealed by the research on muskmelon conducted by Elhassan and Abu-Goukh,^[100] the reduction of cellulose content in the cell wall during muskmelon fruit ripening was related to the ripening and softening of the fruit. Aside from that, as clearly indicated by the studies on apples, the content of hemicellulose fluctuates during the storage of the fruit.^[101]

Biological activities

Numerous studies have demonstrated the advantages of a diet high in phenolic compounds on human health. Australian native plums are phenolic-rich fruits that comprise a complex of polyphenolic compounds with antibacterial, antioxidant, and anti-inflammatory properties (Table 4),^{[16,22,39,45,69,102–107]} all of which can confer diverse biological and pharmacological activities.^[64,75,108]

Table 4. Biological properties in native plums.

Bioactivity	Species and parts	Phenolic compounds	Findings	Reference
Antioxidant activity	Terminalia ferdinandiana seed	Gallic acid, Caffeic acid	Using the DPPH assay method involves mixing 100 μL of sample with 100 μL of DPPH solution and measuring the absorbance at 517 nm with a Tecan microplate reader, the methanol extract had the highest DPPH free radical scavenging activity, at 93%, followed by the water extract and ethanol extract.	^[Citation22]
	Davidsonia jerseyana pulp	Neochlorogenic acid, Caffeic acid	Iron Reduced Antioxidative Potency (FRAP) (2006) using ABTS and percent inhibition expressed as absorbance at 593 nm.	^[Citation102]
Antibacterial activity	Podocarpus elatus peel	Ellagic acid	Its water, ethanol, and acetone extracts were studied for their antibacterial effects against 12 different species of Vibrio cholerae and found that the ethanol extract was the most effective, while the water and acetone extracts were relatively less effective.	^[Citation102]
	Pleiogynium timorense peel	Catechin	With MIC values of 200, 500, and 500 mg/mL, respectively, its ethyl acetate extract demonstrated good antibacterial activity against Staphylococcus aureus, Bacillus cereus, and Escherichia coli, but no antibacterial action against typhoid fever. Salmonella, Candida albicans, and Aspergillus brasiliensis are all active.	^[Citation103]
	Terminalia ferdinandiana pulp	Proanthocyanidins	The gallotannins, which are ethyl gallate and gallocatechin concentration larger than that of ordinary fruit and may prevent the growth of a wide number of bacterial species, were discovered using LC-MS analysis.	^[Citation45]
Anti-inflammatory	Parinari nonda pulp	Resveratrol	After culturing Klebsiella pneumoniae and Staphylococcus aureus in agar for a length of time, adding its extracts showed a considerable decrease in the growth of the bacteria.	^[Citation104]
	Terminalia ferdinandiana peel	Isoflavones	Plum extract-treated and untreated cells were recorded using a 96-well microplate reader and nitrite accumulation was measured. And plum extract-treated cells contained less nitrite than untreated cells.	^[Citation105]
	Terminalia ferdinandiana pulp	Resveratrol	Qualitative HPLC-MS/MS analysis of methanol extracts detected the resveratrol glycoside piceid, which blocks inflammation by reducing the production of the active ingredient in human monocytes.	^[Citation16]
Anti-cancer	Terminalia ferdinandiana pulp	Chlorogenic, Neoprotochlorogenic acids	In tumor cell lines in vitro, ellagic acid inhibits cell detachment, proliferation inhibition, apoptosis, and cell cycle alterations.	^[Citation106]
	Davidsonia jerseyana pulp	Anthocyanin	The extract had an influence on the cell cycle, with the quantity of cells in the G0 and G1 stages of the division phase being greatly reduced, while the number of cells in the S phase rose.	^[Citation69]
Anti-osteoporosis	Dry Parinari nonda	Catechin	Treatment with extracts of dried fruit and stimulation with TNF-α found increased intracellular alkaline phosphatase activity, which in turn increased the formation of mineralized nodules. These enhance osteoblast activity and function.	^[Citation39]
	Terminalia ferdinandiana peel	Catechin	By using different doses of example dry extraction five to culture and treat macrophages to mark their osteoclast differentiation and activity, it was obtained that dried plums can effectively inhibit the differentiation of osteoclasts under normal and oxidative stress conditions.	^[Citation39]
Cardio-protection	Terminalia ferdinandiana pulp	Caffeine, Chlorogenic Acid	Two groups of rats were fed with plum juice and water for 7 weeks, respectively, and their heart weights and liver weights were compared. The heart and liver weights of the rats drinking the plum juice were found to be 0.5 and 5.3 g less, respectively, than the heart and liver weights of the rats drinking the water.	^[Citation107]

Antibacterial activity

It is noteworthy that antibacterial properties are inherently one of the defense mechanisms of plants, such as vegetables and fruits. To be specific, the ingredients with antibacterial activity are isoflavones and aldehydes. Native plums contain polyphenols that have been demonstrated to inhibit a wide range of bacteria, fungus, and yeasts, ubiquitous pathogenic microorganisms, such as Staphylococcus aureus and Escherichia coli.^[10] Ethyl acetate extracts of T. ferdinandiana peel have exhibited solid antibacterial activity. It inhibits the development of Proteus mirabilis and presents noticeable in vitro anti-bacterial properties.^[109] The extracts, seeds, peel, and pulps of native plums have been verified to hinder the development of common food pathogens, like Listeria monocytogenes. The presence of T. ferdinandiana extract caused morphological alterations, cell death, and significant inhibition of food-borne microorganisms, such as methicillin-resistant Staphylococcus aureus and clinically isolated Pseudomonas aeruginosa.^[16] Additionally, as already proven by relevant studies, the antibiotic substances included in T. ferdinandiana extract may disrupt bacterial cell membranes and cause cell lysis. Other intracellular molecules may also disappear in the presence of phenolic compounds and other low-molecular-weight substances like T. ferdinandiana K⁺ and PO₄^3-, and these antibacterial substances may even interact with bacterial DNA, resulting in cell death.^[110] Sommano, et al.^[72] reported that extracts of water and ethanol from the leaves, fruits, and root peels of native plums have inhibitory effects on the pathogen of chickpea fusarium wilt.

Antioxidant activity

Free metabolism produces free radicals. These chemicals damage cells and can give rise to several responses, including the oxidation of biological components and lipid peroxidation (DNA, protein). Plant polyphenols contain an ortho-position phenolic hydroxyl group in the hydroxyl group that is rapidly oxidized into a ketone structure and has a significant potential to trap free radicals such as reactive oxygen species. They have a very high capacity for antioxidant activity and free radical scavenging abilities.^[111,112] Resveratrol in native plums is a polyhydric phenolic compound. Moreover, its antioxidant activity is one of its important biological activities.^[113] The phenolic hydroxyl group (ArOH) of resveratrol provides hydrogen, while the hydrogen combines with the free radical (LOO-) to generate a stable LOOH, which itself becomes a phenoxy free radical (ArO-). For the reason that it is more stable than other free radicals, it protects the body from free radical damage.^[114] Quercetin is found in the flowers, leaves, and fruits of native plums,^[115] which has a large number of antioxidant mechanisms. To begin with, it is complex with a superoxide anion to reduce the generation of oxygen free radicals. Moreover, the reaction with lipid hydroperoxide inhibits the lipid peroxidation process. What’s more, it complexes with iron ions to prevent the formation of hydroxyl radicals. Furthermore, it inhibits aldose reductase and lessens the consumption of reducing coenzyme I (NADPH), thereby ameliorating the body’s antioxidant capacity.^[115–117] Using the DPPH (1,1 diphenyl-2-picrylhydrozyl) technique, T. ferdinandiana (peel, pulp, and seeds) extracts have undergone rigorous testing for their capacity to scavenge free radicals. T. ferdinandiana responded rapidly to DPPH free radicals, pulp and seed display striking effects, and the extraction effect of ethanol was better than methanol, acetone, and water.^[118] In the experiments of Akter, et al,^[119] the antioxidant capacity of T. ferdinandiana was tested, DPPH was used to assess the antioxidant potential, and expressed in gallic acid equivalents, all extracts demonstrated antioxidant activity in a concentration-dependent manner. The IC₅₀ value of T. ferdinandiana was 170.6 μg/mL, which was lower than the IC₅₀ values of other fruits, which forcefully illustrates that the antioxidant activity of T. ferdinandiana was high.

Anti-inflammatory activity

Along with many other biological and pharmacological characteristics, flavonoids, which comprise most phenolic compounds, are known to have anti-inflammatory activities. The benefits of flavonols lie in their antioxidant and free radical scavenging properties, which regulate cellular activity and NOS activity in inflammatory cells. Resveratrol is a crucial active substance in native plums. Resveratrol can inhibit the splicing of TNF-α precursor messenger RNA (pre-mRNA), which is bound up with the anti-inflammatory effect of resveratrol.^[16] Epigallocatechin gallate (EGCG) in native plums can inhibit cyclooxygenase-2 inhibitors (COX-2) and inducible nitric oxide synthase (iNOS) expression induced by interleukin-1, thereby inhibiting the occurrence of arthritis.^[120,121] The stilbene and tannin components in T. ferdinandiana exhibit good inhibitory effects on the bacterial strain rheumatoid arthritis.^[23] Ethanol extract of native plums peel has also been proven to have anti-inflammatory properties.^[57] T. ferdinandiana can lessen COX-2 and alleviate 2,4,6-trinitrobenzenesulfonic acid (TNBS) induced.^[3] Furthermore, T. ferdinandiana has been demonstrated to suppress a multitude of microbiological causes of autoimmune inflammatory disorders as a consequence its therapeutic potential as an antibacterial agent.^[122] Shivashankara, et al.^[123] observed that administration of the extract dramatically decreased inflammation in an acute rat paw edema model induced by pro-carrageenan, a kaolin-carrageenan combination, and formaldehyde.

Anti-cancer effect

One of the leading causes of mortality in humans is malignant tumors that poses a major threat to human health and life. Bhosale, et al.^[79] claim that polyphenols can induce cancer cell regulation, inhibit cancer cell proliferation, and have an excellent preventive effect on cancer.^[118,124] A multitude of plants contain compounds that have both intervening and blocking effects on specific stages of cancer genesis. Apart from that, several epidemiological studies and animal experiments have proved that polyphenols can prevent and inhibit the incidence of cancer.^[125]

The anti-cancer effects of polyphenols are multifaceted and can inhibit different stages of carcinogenesis.^[77,126] Meanwhile, it is an effective anti-mutagen, which can reduce the carcinogenic effect of the mutagen and improve the precise repair ability of chromosomes to materialize the purpose of improving cellular immunity and inhibiting the growth of cancer cells.^[79] For instance, phenolic compounds exhibit anti-mutagenic effects in vitro and can inhibit carcinogen-induced skin, lung, esophagus, esophagus, duodenal, colon and rectal cancers in rodents.^[127] Catechins can not only reduce the carcinogenic effect of mutagen on normal cells, but also improve the self-repair ability of damaged delicate DNA. Therefore, it can actualize the purpose of improving cellular immunity and inhibiting the growth of cancer cells.^[128] In addition, flavonoids inhibit cytochrome P450 enzymes and promote phase II enzymes such as UDP-glucuronyl transferase to prevent the metabolic activation of carcinogenic agents.^[129] The native plum extract has substantial inhibitory activity against cancer cell lines as a consequence of its capacity to induce apoptosis in cancer cells. Dried native plums may help prevent colon cancer, affect the gut flora, and reduce the risk of colon cancer. Owing to the fact that they contain high levels of fiber and sorbitol, building up beneficial colonic flora components in the distal colon, thereby reducing colonic transit time and promoting the retention of beneficial flora in the colon, preventing DNA damage in colonic epithelial cells. For dried T. ferdinandiana, in vivo experiments were performed on HepG2 human hepatocellular carcinoma and found to inhibit elevated ROS (reactive oxygen species) levels in HepG2 cells and protect HepG2 cells from ethanol-induced cell death. For HT-29 cancer cells, the ethanolic extract of T. ferdinandiana pulp induced DNA damage in HT-29 cells, giving rise to apoptosis.

Anti-osteoporosis effect

Polyphenols and resveratrol have curative effects on the prevention and treatment of osteoporosis.^[130] Dried native plums help avoid fractures and bone loss and enhance bone formation for the reason that the polyphenols in native plums can heighten the expression of lysine peptidyl oxidase by positively regulating the transcription factor Runx2, the osteoblast-specific transcription factor Osterix and growth-promoting factor-1 (IGF-1). It can also attenuate osteoclastogenic signals and enhance osteoblast viability and function.^[131,132] In the process of culturing antler progenitor cells, alkaline phosphatase was employed as a marker. As conspicuously revealed by the research findings, polyphenols increased alkaline phosphatase activity through activating the Wnt/β pathway.^[133] Increased osteoblast activity is implied by an increase in alkaline phosphatase, a biochemical marker of bone production.

Anti-cardiovascular effect

Plant polyphenols can noticeably prevent and block lipid peroxidation.^[134] To be specific, it can inhibit the aggregation and adhesion of platelets and enzymes in lipid metabolism, and induce vasodilation, thereby relieving thrombosis, lowering blood pressure, and treating atherosclerosis.^[135] More importantly, polyphenols can exert protective effects on cardiac tube endothelium and regulate blood lipid components.^[136] As evidently revealed by the research conducted by Dong, et al,^[137] a high-fat diet was used to simultaneously feed the high-fat model and the phenolic compound group. After 14 weeks of feeding, each group detected the blood lipid, SOD, and lipid peroxide contents. The formation has an inhibitory effect. Hirsch, et al.^[138] observed the preventive effect of phenolics on hyperlipidemia in rats and the effect on apolipoprotein and arteriosclerosis index, which demonstrated phenolic compounds can lessen the levels of peripheral blood triglycerides, total cholesterol, and low-density lipoprotein while raising high-density lipoprotein (HDL) levels. This suggests that it has the effect of preventing and treating hyperlipidemia.

The traditional and potential application of native plum

Traditionally, as noted above, native plums are freshly foraged and eaten by aboriginal Australians. Concerning T. ferdinandiana, aboriginal people eat the raw fruit, while white settlers dip the fruit in salt and sugar and eat it. For P. elatus, people would choose to eat the fruit’s pulp and seeds. Owing to their wide range of nutrients, Australian native plums are a natural green source for several innovative cuisines, functional foods, and cosmetics. They are used in a variety of foods, including drinks, spice blends, jams, sauces, and condiments, such as Davidson plum’s sweet chili sauce and Illawarra plum’s jam. Native plums are also increasingly used in new beverages, including wine (Davidson plum, Burdekin plum) and beer (Kakadu plum, Illawarra plum, Nonda plum). Moreover, P. elatus and P. timorense are also highlighted as novel botanical ingredients for gin production. Native plums exhibit their unique flavor profile, enhancing the product’s versatility. Table 5 displays the traditional and current uses of Australian native plums in the food industry.

Table 5. The sensory properties of processed foods of native plums.

Species	Traditional use	Food	Sensory properties	Specific products
Terminalia ferdinandiana	Seeds and Pulp: Eat raw on hunting trips to help refresh and provide energy. Bark: Used medicinally, boiling the sap and bark to help treat skin diseases and sores, for drinking, for colds and flu.	Kakadu plum jam	Appearance: dark green, glossy Aroma: pickled and fermented flavors Flavor: sweet and sour with a rich stewed fruit flavor Texture: thickness	Native Oz Bushfoods -Kakadu Plum Jam Bits of Australia – Kakadu Plum Jam
		Kakadu plum yogurt	Appearance: milky white, uniform color Aroma: light fragrance Flavor: sweet and sour Texture: smooth, creamy	Something Wild – Kakadu Plum Yoghurt
		Kakadu plum beverage	Appearance: light or dark yellow Aroma: Lemony, sweet Flavor: sweet and sour	Forward Drinking- Kakadu Plum Wine Etch APL – Bush Apple, Kakadu Plum
Davidsonia jerseyana	Pulp: eat raw (after 1788 it was customary to eat it with sugar and salt)	Davidson’s plum jam	Appearance: deep reddish purple Aroma: Pickled and fermented, complemented by orange and cloves Flavor: tart Texture: thickness	Rainforest Foods – Davidson’s Plum Jam The Bushtucker Shop – Davidson’s Plum Jam
		Davidson’s plum wine	Appearance: bright red Aroma: Earthy with musk Flavor: sweet and sour	Monceau − 2022 Davidson’s Plum Wine Rainforest Heart – Davidson’s Plum Fortified Fruit Wine
Podocarpus elatus	Pulp: eat raw	Illawarra plum jam	Appearance: dark purple Aroma: mild pine Flavor: sweet Texture: Smooth and soft	Rainforest Foods – Illawarra Plum Jam
		Illawarra plum wine	Appearance: dark purple red Aroma: mild pine, chocolatey Flavor: sweet Texture: lush and smooth	South Coast Distillery -Illawarra Plum Gin Headlands Distilling Co. -Liqueur of the Illawarra Plum

Australian native plums are a great natural source for a variety of functional foods and cosmetics due to their phytochemical properties. Furthermore, demand for native plums is rising as a result of the growing interest in Australian bush food on a global scale. Native plum extracts contain phenolic compounds that have biological properties, such as antibacterial and anti-inflammatory. Figure 2 shows the future direction for the application of Australian native plums. They may function as natural preservatives in the first place. T. ferdinandiana leaves extract can limit the growth of food spoilage bacteria, prolonging the cold storage life of fish.^[4] T. ferdinandiana is currently used to extend the shelf life of shrimp from 2–4 days to 14 days. T. ferdinandiana extract would also be used in the frozen food business.^[55] Aside from that, native plums can be used as food colorants. Natural food pigments are quite safe, and since most of them can be added in unlimited amounts, their application range has expanded quickly. Native plum peel has a high content of anthocyanins. As a water-soluble natural pigment, anthocyanin are responsible for different colors.^[139] Nonetheless, the stability of anthocyanins is easily affected by temperature and light intensity, it is tremendously pivotal to study how to preserve anthocyanins in native plums during processing and storage. Native plums can also be applied to the development of food spices, such as sweeteners. There is currently an increasing demand for flavoring agents derived from natural sources in the market, and Australian native plums are attracting the interest of developers with their unique flavor, texture and aroma.^[58] Australian native plums are rich in dihydroflavonoids, which can be converted into dihydrochalcone glycosides to reveal a sweet taste. Powdered dried Kakadu plum peels are offered for sale and are used to flavor protein balls, breakfast bowls, and smoothies.^[140,141] Richmond, et al.^[4] confirmed that aroma increases through cooking. Furthermore, the phytochemicals of Australian native plums are also factors that promote them into functional products. For the time being, the extracts of these native plums have been applied in the functional food and cosmetic industries. Specifically, native plums are rich in vitamin C, which is not only conducive to help in the production of collagen in the body, but also advantageous for the normal and healthy function of immune system by increasing the body’s absorption of dietary iron.

Figure 2. Potential applications of Australian native plums.

Conclusion

Overall, Australian native plums are widely distributed in southern Australia with some production in northern Australia and are rich in nutrients and can also provide numerous health benefits. They are also the main food crops that provide essential nutrients for Indigenous people and are also used in food, cosmetics, and furniture. The chemical composition of Australian native plums contains carbohydrates, proteins, fats, phenolic compounds, minerals, and vitamin. Native plums contribute to a healthy diet with high fiber and low fat. Moreover, native plums are high in phenolic components, including gallic acid, ellagic acid, flavanols, and flavanone. Due to their remarkable impact on human health and potential as a source of active chemicals, phenolic compounds are the most valued elements of native plums. Antioxidant activity, antibacterial activity, anti-inflammatory activity, anti-tumor activity, anti-osteoporosis impact, and anti-cardiovascular disease effect are some of the pharmacological properties of native plums.

Nevertheless, there are still studies that have not specifically identified the compounds present in Australian native plum extracts, and the structure and quality of phytochemical elements in Australian native plums should still be further explored to better understand their mechanisms. Some kind of native plums already have great application in cosmetics. Nonetheless, further exploration and research are essential to develop and probe into application of other varieties of native plums.

Acknowledgments

We would like to thank The Future Food Hallmark Research Initiative at the University of Melbourne, Australia. We would like to thank researchers of the Dr. Hafiz Suleria group from the School of Agriculture and Food, Faculty of Science, the University of Melbourne for their incredible support.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

Dr Hafiz Suleria is the recipient of an Australian Research Council—Discovery Early Career Award (ARC-DECRA—DE220100055) funded by the Australian Government. This research was funded by the University of Melbourne under the McKenzie Fellowship Scheme (Grant No. UoM-18/21), the Future Food Hallmark Research Initiative Funds (Grant No. UoM-21/23) and Collaborative Research Development Grant (Grant No. UoM-21/23) funded by the Faculty of Science, the University of Melbourne, Australia.