Comparative assessment of nutritional composition, phenolic compounds, antioxidative and antidiabetic properties of pilosocereus gounellei and Cereus Jamacaru: two unexplored cactus fruits from the Brazilian semi-arid

ABSTRACT

In this study, we determine the chemical composition, bioactive compounds profile, antioxidant capacity and antidiabetic potential of two cactus fruits. Pilosocereus gounellei had the highest contents of ash (6.84%), lipid (7.79%), maltose (1.02 mg g⁻¹), soluble fiber (10.85%) and minerals such as Mg. Thirteen volatile compounds (alcohols, terpenes, aldehydes and esters) were found in the fruits. Although higher amounts of quinic acid and quercetrin were found in Cereus Jamacaru, Pilosocereus gounellei had a higher content of p-coumaric acid and rutin. Regarding the functional potential, Cereus Jamacaru had the highest content of total phenolics (65.17 GAE g⁻¹), total flavonoids (26.06 mg EC g⁻¹), antioxidant capacity (28.67; 49.86; 158.79 µM TE g⁻¹ for DPPH, ABTS and ORAC, respectively) and highest inhibition for α-amylase (84.84 ± 0.41%) and protein glycation. In view of their nutritional and bioactive characteristics, these species have great potential to be used in preparations with functional claims.

KEYWORDS:

• Cactaceae
• nutritional value
• p-coumaric acid
• rutin
• antioxidant capacity
• health benefits
• antihyperglycemic
• antiglycation activity

1. Introduction

Unconventional food plants have edible parts, but their acceptance is limited because they are often associated with diets of low-income populations, and consumers are not aware of their nutritional and biological properties (De Assis et al., 2019). Cactaceae are drought-resistant plants found in semi-arid regions and hold significant socioeconomic importance for rural communities in certain regions of Brazil (de Araújo et al., 2021). Cactaceae, known for their varied shapes and sizes, succulent stems, and edible fruits, serve multiple purposes. They are used as ornamental plants, a source of human food and as fodder for ruminant animals. While some species like Opuntia ficus-indica are commercially established, others such as Pilosocereus gounellei and Cereus jamacaru remain largely unexplored (de Araújo et al., 2021; Ramírez-Rodríguez et al., 2020).

Pilosocereus gounellei, commonly known as xique-xique, is a Cactaceae species abundant in the semi-arid region, offering considerable industrial potential. It is widely utilized as fodder for cattle, sheep and goats during extended drought periods (Bezerril, 2017). Additionally, it finds applications in human nutrition and is recognized for its traditional use in addressing inflammatory and diabetic conditions (De Assis et al., 2019; Oliveira et al., 2021). The fruit of Pilosocereus gounellei weigh between 41 and 48 g, have a diameter ranging from 4.6 to 4.9 cm, a length from 3.5 to 3.9 cm, and feature mucilaginous pink-purple pulp (de Araújo et al., 2021; Silva et al., 2018).

Cereus jamacaru, commonly known as mandacaru, is widespread in the Brazilian Caatinga and plays a crucial role as a livestock food source during droughts in the Northeast region. In traditional medicine, mandacaru fruit are used as a diuretic, to reduce blood pressure, and to treat ulcers and infections (de Araújo et al., 2021; Schwarz et al., 2010). Its fruit, measuring 5 to 12 cm in length and 7 to 12 cm in diameter, display colors ranging from orange to red and have a white, mucilaginous and sweet-tasting edible pulp (Santos et al., 2020).

Despite their socioeconomic significance for local populations, there is limited literature on the chemical composition of these cactus, impacting their use and commercial potential. Furthermore, it is recognized that the chemical composition, as well as the functional potential of vegetables with food potential for inclusion in the population can be affected and influenced by the fraction of fruit studied and factors such as genotype, ripening stage, soil and climate conditions, etc (Araújo, Farias, et al., 2020). In this sense, the main objective of this study was to analyze the nutritional composition, carbohydrate profile, volatile compounds and organic compounds, as well as the antioxidant and antidiabetic potential of xique-xique and mandacaru fruits.

2. Material and methods

2.1. Plant material and sample preparation

Xique-xique and mandacaru fruits were harvested in August and September 2021 in Solânea, Paraíba (6°44’47“S, 35°43’57” W). Botanical identification was carried out, and specimens (Accession No. 208,839 and 208,840) were archived in the Herbarium-UEC at the State University of Campinas (UEC-UNICAMP). The project was duly registered in the National System for the Management of Genetic and Associated Traditional Knowledge (SisGen – N° ABFC0D8). Following the collection, fruits (containing pulp, peel and seeds) underwent washing, processing with a Philips Walita juicer, immediate freezing (−20°C), subsequent freeze-drying (Terroni Equipamentos Científicos, LS 3000, São Carlos, SP, Brazil), and grinding using an Ika knife grinder (model A 11 B S32, Campinas, SP, Brazil). The resulting powders were carefully stored in opaque packaging at −20°C to mitigate potential alterations in chemical composition.

2.2. Centesimal composition and mineral content

For the determination of the proximate composition, freeze-dried samples of both fruits were employed. Moisture content, protein levels and dietary fiber contents were analyzed following the Official Methods of Analysis (AOAC, 2006). Ash and total sugars were assessed in accordance with the methodology outlined by IAL (Instituto Adolfo Lutz, 2008). Lipid content was determined using the method of Bligh & Dyer (1959). Total fiber was computed as the difference using the formula: 100% - % ash - % lipid - % protein - % total carbohydrate. All analyses were conducted in triplicate, and results were expressed based on freeze-dried material (fd) for publication. Mineral content assessment was performed by Flame atomic absorption spectrophotometry (FAAS, Analyst 200, PerkinElmer, Waltham, U.S.A.) according to the protocol detailed by J. G. S. Silva et al. (2017).

2.3. Chromatographic analysis of sugars and oligosaccharides

The preparation of the samples and the analysis of the carbohydrate profile followed the methodology outlined by Farias et al. (2020). The carbohydrate profile analysis employed high-performance anion exchange chromatography coupled to a pulsed amperometric detection system (HPAEC-PAD), specifically utilizing the DIONEX ICS-5000 model from Thermo Fisher Scientific, Waltham, U.S.A.. The analytical setup included a Carbopac PA1 column (250 × 4 mm, particle size of 10 μm) for mono/disaccharides and polyols (glucose, fructose, sucrose, maltose, arabinose, cellobiose, raffinose, verbascose, stachyose, xylitol, sorbitol, and mannitol) and a CarboPac PA100 column (250 × 4 mm, particle size of 8.5 μm) for fructo- and malto-oligosaccharides (nystose, 1-kestose, fructofuranosylnistose, maltooligosaccharides, maltotriose, maltotetraose, maltopentose, maltohexaose, and maltoheptaose). All analyses were conducted in triplicate. Carbohydrates were identified by comparing retention times of standards and samples and the results were reported in mg/g fd.

2.4. Profile of volatile compounds

Volatile compounds were extracted and identified according to the methodology described by Araújo, de Paulo Farias, et al. (2020). The extracted compounds were separated using in an Agilent 7890A gas chromatography system (Agilent Technologies) equipped with a GC DB-WAX column (30 m × 0.25 mm × 0.15 μm) and Agilent 5975C inert MSD with Triple-Axis Detector, using He as carrier gas. The volatile compounds were desorbed for 5 min by inserting the SPME fiber into a GC injector (270°C). The GC oven temperature was programmed to hold at 70°C for 1 min, then to increase to 140°C at 3°C/min and finally 210°C for 5°C/min. The total analysis time was 39.33 min. Compounds were identified using NIST 14.0 database and Linear Retention Index (LRI) calculated with a series of n-alkanes (C7-C40).

2.5. Organic compounds and antioxidant and antidiabetic activities

2.5.1. Preparation and obtaining the extract

The compounds present in xique-xique and mandacaru fruits were extracted using the method outlined by Araújo, de Paulo Farias, et al. (2020), with slight modifications. Briefly, 1 g of lyophilized samples was extracted with a 15 mL ethanol-water mixture (8:2, v/v) using ultrasound (UNIQUE, model UCS-2850, 25 kHz, 120 W, Brazil) for 10 min at room temperature. The mixture was then centrifuged (Hettich Zentrifugen, model Rotanta 460 R, Tuttlingen, Germany) at 4000 g for 5 min at 5°C. After centrifugation, the supernatants were collected, and the residues underwent two additional extractions under the same conditions. The combined supernatants were subjected to solvent removal through vacuum evaporation at 40°C (Rotavapor model RII, Büchi Labortechnik, Flawil, Switzerland). The resulting aqueous phase was concentrated to 10 mL using water and stored at −80°C for further analysis.

2.5.2. Identification and quantification of phenolic compounds

Phenolic compounds were identified and quantified using an Acquity UHPLC chromatograph coupled to an Acquity TQD mass spectrometer (Micromass-Waters Manchester, England) with an ESI source, C18 BEH Waters Acquity column (2.1 mm x 50 mm x 1.7 µm), according to the methodology described by Cassola et al. (2019). A specific chromatographic method for the samples was developed with the following conditions: phase A composed of acidic water (0.1% formic acid) and phase B of acetonitrile (HPLC grade). The gradient started and remained at 95% A and 5% B for 1 min, then increased to 100% B for 8 min and returned to initial conditions for 1 min, totaling 10 min. The flow rate was 0.2 ml/min and the injection volume was 7 µL. The results were obtained through the use of calibration curves constructed with some available standard compounds and expressed in mg 100 g⁻¹ fd.

2.5.3. Determination of total phenol content

The determination of the total phenol content was conducted following the method proposed by Singleton et al. (1999) with minor modifications. Briefly, 30 µL of phenolic extract from fruits were added with 150 µL of 10% Folin-Ciocalteau, 120 µL of 7.5% NaHCO₃ and incubated for 6 min at 45°C. Absorbances were measured at 760 nm and the results were expressed as mg gallic acid equivalent (GAE) g⁻¹ fd.

2.5.4. Determination of total flavonoid content

The total flavonoid content was determined according to the method proposed by Zhishen et al. (1999). In the experimental protocol, 30 μL of phenolic extracts were combined with 110 μL of ultrapure water. Subsequently, 8 μL of 5% NaNO2 was added, and the reaction allowed to proceed for 5 min. Following this, 8 μL of 10% AlCl3 was introduced, and an additional 6-min incubation period was observed. Finally, 50 μL of 1 M NaOH and 70 μL of ultrapure water were added to the reaction mixture. The absorbance of the resultant solution was measured at 510 nm and the total flavonoid content was quantified and expressed as milligrams of catechin equivalent (CE) g⁻¹ fd.

2.5.5. DPPH assay

The assay was performed according to the method proposed by Brand-Williams et al. (1995) with some modifications. The DPPH solution was prepared by accurately weighing 4 mg of the radical and dissolving it in 100 mL of ethanol. Absorbance readings were conducted at 517 nm using a microplate reader. Trolox served as the standard for the construction of the analytical curve, and the quantified results were expressed as micromoles of Trolox equivalent (TE) fd.

2.5.6. ABTS+ scavenging assay

Total antioxidant activity was determined by the ABTS⁺ assay, obtained by reacting 5 mL ABTS (7 mM) with 88 µl of 140 mM potassium persulfate, as described by Re et al. (1999). After ABTS⁺ formation, it was diluted with distilled water to an absorbance value of 0.700 ± 0.02 to 734 nm in a microplate reader. Trolox was used for the elaboration of the analytical curve and the results were expressed as µM TE g⁻¹ fd.

2.5.7. Oxygen radical absorbance capacity (ORAC)

ORAC assays were performed according to Prior et al. (2003) with slight modifications. Samples, standards, and reagents (AAPH and fluorescein) were prepared in 75 mM potassium phosphate buffer at pH 7.4. Each well received 20 μL of Trolox standard or previously diluted extracts, 120 μL of fluorescein (0.378 μg mL-1, pH 7.4), and 60 μL of AAPH [2,2-Azobis-(2-methylamidinopropane)-dihydrochloride] (108 mg/mL). Fluorescence intensity, recorded at 37°C immediately post AAPH addition, was monitored in 60-s cycles for 80 cycles and the results expressed as µM TE g⁻¹ fd.

2.5.8. α-amylase activity

The inhibition of α-amylase activity was evaluated according to the methodology described by Van Quan et al. (2019) with modifications. Briefly, 20 μL of each extract was pre-incubated for 10 min at 25°C with 20 μL of 1 U/mL porcine pancreatic α-amylase solution (EC 3.2.1.1, type VI-A, Sigma Chemical Co., Saint Louis, U.S.A.) dissolved in 0.1 M sodium phosphate buffer (pH 6.9) containing 0.006 M sodium chloride. Then, 30 μL of starch solution (0.25%) was added and incubated again for 6 min at 25°C. To stop the reaction, 20 μL of hydrochloric acid (1 M) was pipetted. Next, 120 μL of Lugol’s aqueous solution (250 μL of 5% solution) was added to develop the dark blue color. The absorbance was read at 565 nm in a microplate reader and the results were expressed as % inhibition.

2.5.9. α -glucosidase activity

α-glucosidase inhibition activity was evaluated according to Van Quan et al. (2019). Briefly, an amount of 20 μL of each extract was mixed with 20 μL of 0.1 M potassium phosphate buffer (pH 7) and 40 μL of α-glucosidase (from Saccharomyces cerevisiae, Sigma-Aldrich, St Louis, MO, U.S.A.) (0.5 U/mL in 0.1 M potassium phosphate buffer, pH 7). After 6 min of incubation at 25°C, a 20 μL aliquot of 5 mM ρ-nitrophenyl-α-D-glucopyranoside (pNPG) substrate (in 0.1 M potassium phosphate buffer, pH 7) was added and the mixture was incubated for another 8 min. The reaction was terminated by the addition of 100 μL of 0.2 M Na₂CO₃, and the absorbance was recorded at 405 nm. The inhibitory activity of the extracts on α-glucosidase was expressed as % inhibition.

2.5.10. Antiglycation potential

The antiglycation potential of the extracts was determined according to the protocol described by Sri Harsha et al. (2013) with modifications. Briefly, 200 mM potassium phosphate buffer (pH 7.4) containing 0.02% sodium azide, 50 mg/mL bovine serum albumin (BSA) in phosphate buffer, 1.25 M fructose in phosphate buffer and the sample extract were mixed. The control consisted of phosphate buffer instead of the antiglycation agent and for the blank, fructose and the antiglycation agent were replaced by phosphate buffer. The mixtures were incubated at 37°C for 3 days in a water bath in the absence of light. The bloom of the mixture was measured in a microplate reader at an excitation/emission wavelength of 350/420 nm, respectively, and the results were expressed as a percentage of glycation inhibition.

2.6. Statistical analysis

The experiment followed a completely randomized design, all analyzes were performed in triplicate and the results were reported as mean ± standard deviation. Statistical analysis involved analysis of variance (ANOVA), and significant differences among treatment means were determined using the t-test at a significance level of p ≤ .05. The Statistica software version 7.0 was utilized for data analysis.

3. Results and discussion

3.1. Proximal composition

Table 1 illustrates the proximal composition values of xique-xique and mandacaru fruits. Statistical analysis indicates notable variations between the two fruits in specific parameters. Xique-xique exhibits higher levels of ash (6.84%) and lipid (7.79%), whereas mandacaru presents 1.28 and 3.35 fold higher values for sugars and moisture, respectively. There are no significant differences in protein content (p ≤ .05) between the two fruits. Regarding the fiber content of the fruits, it was possible to observe that mandacaru had a higher content of insoluble fibers (30.48 ± 1.83) when compared to xique-xique (29.55 ± 1.19), but no statistical difference was observed (p ≤ .05). On the other hand, xique-xique fruit had a soluble fiber content 2.76 fold higher than mandacaru. A comprehensive understanding of the centesimal composition is pivotal for assessing the nutritional merit of a food item and advocating for its regular consumption. Proximate composition studies on native Brazilian cactus, such as xique-xique and mandacaru, are relatively scarce. Previous reports cite values of 92.5% and 85.82% for moisture, 1.1% and 0.64% for ash, 0.4% and 1.8% for protein, and 5.7% and 9.76% for carbohydrates in the edible fractions of xique-xique and mandacaru, respectively (Do Nascimento et al.,2011, 2012). The fiber values found for mandacaru were approximately 1.77 fold lower than those found by Soares et al. (2021), who reported values of 61.07 ± 5.99 g/100 g dry matter (DM) in the pulp of this fruit. On the other hand, our findings indicate higher total fiber content when compared to a jam containing xique-xique fruits (2.60 ± 0.01 g/100 g) (Bezerril et al., 2021).

Table 1. Proximate composition, mineral and sugar content of xique-xique (pilosocereus gounellei) and mandacaru (Cereus jamacaru) fruits.

	Fruit
	Xique-xique	Mandacaru
Proximate composition (%)
Ash	6.84 ± 0.01*	4.99 ± 0.24
Protein	12.35 ± 0.67	13.01 ± 0.16
Sugar	27.06 ± 0.77	34.78 ± 1.47*
Lipid	7.79 ± 0.11*	5.22 ± 0.12
Moisture	3.23 ± 0.03	10.84 ± 0.22*
Insoluble fiber	29.55 ± 1.19	30.48 ± 1.83
Soluble fiber	10.85 ± 0.87*	3.92 ± 0.65
Minerals (mg 100 g^−1)
Ca	191.05 ± 1.41	202.14 ± 7.55
Mg	468.54 ± 3.95*	253.57 ± 6.98
Fe	3.06 ± 0.13*	2.33 ± 0.02
Zn	4.05 ± 0.10*	2.58 ± 0.07
K	2552.74 ± 24.24*	2062.30 ± 16.24
Cu	0.56 ± 0.03	0.76 ± 0.03*
Mn	2.35 ± 0.03*	0.38 ± 0.11
Na	134.64 ± 2.17*	98.58 ± 9.24
Mono and disaccharides (mg g^−1)
Glucose	23.29 ± 0.11	92.72 ± 2.37*
Fructose	53.14 ± 0.26	215.89 ± 7.69*
Sucrose	1.03 ± 0.13	nd
Maltose	1.02 ± 0.10*	0.81 ± 0.01
Oligosacharide (mg g^−1)
Nystose (GF3)	nd	10.44 ± 0.19

*Significant difference at 5% probability level by t-test (p ≤ .05). Values expressed on freeze-dried material (fd). nd: Not detected.

Concerning mineral content, xique-xique displayed elevated values, surpassing those of mandacaru by factors of 1.84, 1.31, 1.60, 1.23, and 1.36 for Mg, Fe, Zn, K, and Na, respectively. Notably, the Mn content in xique-xique was 6.18 times higher than that observed in mandacaru. However, mandacaru exhibited the highest Cu content (0.76). The mineral composition of these cactus has been recently documented in a study by Magalhães. According to the author, values of 1.4; 9.4; 38.2; 8.7; 0.3 g kg⁻¹ dry matter (DM); 79.8; 2.3; 28.9; 261.9 and 39.4 mg kg⁻¹ DM were found for P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn in mandacaru, respectively. For xique-xique, the values of these minerals were 0.7; 8.6; 56.1; 16.2; 0.6 g kg⁻¹ DM; 88.7; 3.5; 47.5; 1880.6 and 49.0 mg kg⁻¹ DM, respectively (Magalhães et al., 2019).

Minerals, while required in minimal concentrations in food, exert fundamental roles in metabolic processes and cellular homeostasis. Potassium, functioning as an intracellular cation, is integral to normal cell functionality. Magnesium, crucial for bone health, contributes to the maintenance of calcium and potassium levels. Calcium, essential for teeth and bone structure plays a pivotal role in muscle contraction and is indispensable for proper immune system functioning. Manganese plays a role in bone formation and actively participates in metabolic reactions involving lipids, carbohydrates, and proteins (Araújo, Farias, et al., 2020; Bezerril et al., 2021).

In light of this context, the fruits of xique-xique and mandacaru offer a viable solution to address the micronutrient needs, providing a potential safeguard against disorders associated with insufficient mineral intake. The detailed carbohydrate content of the investigated fruits is outlined in Table 1, revealing a noteworthy distinction in sugar levels between the fruits, as confirmed by statistical analysis (p ≤ .05). Mandacaru exhibited heightened levels of monosaccharides, specifically glucose and fructose, surpassing those found in xique-xique by factors of 3.98 and 4.06, respectively. In contrast, xique-xique demonstrated a higher concentration of maltose (1.02) and was the exclusive source of sucrose. The study also explored other carbohydrates, including arabinose, cellobiose, raffinose, verbascose, stachyose, and various polyols such as xylitol, sorbitol, and mannitol. However, none of these were detected in either fruit. These findings contribute to our understanding of the distinct carbohydrate profiles of mandacaru and xique-xique fruits.

Limited research has focused on understanding the sugar content in these plant species. Specifically, there are few studies on xique-xique, mostly exploring sugars in its cladodes and derived products. Therefore, this study is the first to investigate the sugar composition of both xique-xique and mandacaru fruits as a whole. Carvalho and colleagues previously found concentrations of glucose, fructose, sucrose, arabinose, and xylose in the juice from xique-xique cladodes to be 10.75 ± 0.05, 7.89 ± 0.01, 2.58 ± 0.02, 0.56 ± 0.01, and 0.25 ± 0.02 mg per 100 ml, respectively (Carvalho et al., 2021). In the fruits of Opuntia ficus-indica, a well-studied cactus species, researchers have identified and measured various sugars. According to a recent study by Albergamo et al., the pulp of Opuntia ficus-indica contains approximately 42.57 g of glucose, 6.78 g of xylose, 13.56 g of arabinose, and 4.75 g of mannose per 100 g of dry weight (Albergamo et al., 2022).

Fructooligosaccharides (FOS) are beneficial compounds that, when fermented by gut bacteria, yield short-chain fatty acids such as propionate, butyrate, lactate, and acetate. These fatty acids play a vital role in maintaining the overall health of the host organism (Farias et al., 2019). Specifically, a type of fructooligosaccharide called nystose was found only in mandacaru, at a concentration of 10.44 ± 0.19 mg per gram. Other fructooligosaccharides (1-kestose and fructofuranosylnistose) and maltooligosaccharides (maltotriose, maltotetraose, maltopentose, maltohexaose, and maltoheptaose) were studied but were not present in either of the evaluated fruits.

In a recent study, the prebiotic potential of a beverage derived from Opuntia ficus-indica fruit was investigated. The analysis identified different oligosaccharides in the beverage, specifically kestose at 30.27 ± 0.02 mg per 100 mL, nystose at 42.75 ± 0.11 mg per 100 mL, and raffinose at 20.42 ± 0.23 mg per 100 mL (de Albuquerque et al., 2021).

3.2. Volatile organic compounds

Aroma is one of the most important attributes of a food, as it directly contributes to the quality and acceptance of food products. Several molecules are responsible for the formation of this attribute and include esters, aldehydes, alcohols, terpenes and/or their derivatives that contribute to the most diverse aromas in food products (Bicas et al., 2011; Paulino et al., 2022).

Table 2 displays the volatile compounds identified in xique-xique and mandacaru fruits. Despite their modest aromatic characteristics, approximately 13 distinct compounds, including alcohols, terpenes, aldehydes, and esters, were detected. Xique-xique contained eight identified compounds, whereas mandacaru had six. Nonanal was the only compound common to both, and mandacaru uniquely featured the terpene linalool, constituting 5.42% of the total compound composition.

Table 2. Volatile compounds found in xique-xique (pilosocereus gonellei) and mandacaru (Cereus jamacaru) fruits.

Compounds	LRIexp	RT (min)	Area (%)
	Xique-xique
Decane, 2,3,5,8-tetramethyl	1221.94	5.404	1.239
Decane, 2,4,6-trimethyl	1284.35	6.772	0.415
Nonanal	1389.21	9.621	0.851
2-Octenal	1512.21	10.737	0.299
1-Hexanol, 2-ethyl-	1859.70	12.923	0.358
2-Nonenal	1625.15	14,228	0.422
1,6-Octadien-3-ol, 3,7-dimethyl	1643.76	14.868	0.811
1-Octanol	1656.41	15.303	0.322
	Mandacaru
2-Hexanal	1214.96	5.251	0.323
Nonanal	1387.58	9.575	0.476
Linalool oxide	1441.85	11.275	0.338
Methyl formate	1449.81	11.532	0.388
Decanal	1494.14	12.963	0.835
Linalool	1549.90	14.868	5.419

Linalool (2,6-dimethyl-2,7-octadien-6-ol) is an acyclic monoterpene alcohol that can be found naturally in a variety of aromatic plants. This terpene is recognized due to its refreshing, floral and woody aroma, being widely used in perfumes, cosmetics, processed foods and beverages as a fragrance and flavor agent. In addition, it has been recognized as a bioactive compound due to its anticancer, antimicrobial, neuroprotective, hepatoprotective, renal and lung protective properties (An et al., 2021). In this sense, the presence of volatile compounds in unexplored species such as xique-xique and mandacaru is of great importance to encourage their use in the food, cosmetics and pharmaceutical industries, since compounds such as terpenes, in addition to contributing to the pleasant aroma of products are also recognized for their various health-beneficial properties and can therefore be used as potential therapeutic agents for disease prevention/treatment (Paulino et al., 2022).

Limited literature exists on the volatile compound profiles of fruits within the Cactaceae family. Nonetheless, certain terpenoids, including β-pinene, camphene, α-phellandrene, ρ-cymene, limonene, 1,8-cineole, β-ocimene, 3-carene, γ-terpinene, linalool, and α-farnesene, have been identified in the fruits of Opuntia ficus-indica (Oumato et al., 2016). Similarly, Luo and colleagues documented the existence of compounds such as α-amyrin and β-amyrin in the peel of both Hylocereus polyrhizus and Hylocereus undatus fruits (Luo et al., 2014).

3.3. Organic compounds and antioxidant and antidiabetic activities

3.3.1. Identification of compounds

Some phenolic compounds were also identified and quantified in both fruits in comparison with standards and can be seen in Table 3. Statistical analysis demonstrated that the highest content of rutin (14.72 ± 1.80 mg/100 g) and p-coumaric acid (7.75 ± 0.68 mg/100 g) were found in xique-xique. On the other hand, the values of quinic acid (123.85 ± 8.32 mg/100 g) and quercetrin (0.20 ± 0.01 mg/100 g) in mandacaru fruit were 2.67 and 1.81 times higher than those found in xique-xique, respectively. Compounds such as catechin and epicatechin were quantified only in xique-xique, and prior studies have reported the presence of these compounds in xique-xique fruits. Bezerril et al. identified flavanols (catechin, epicatechin, epigallocatechin gallate, procyanidin B1, and procyanidin B2), flavonols (quercetin 3-glycoside, rutin, and kaempferol glycoside), flavanones (hesperidin) and various phenolic acids, such as gallic, caffeic, syringic, and chlorogenic acids in the xique-xique fruit jam (Bezerril et al., 2021). In a separate study, xique-xique fruit juice was found to contain procyanidin A2, caftaric acid, trans-resveratrol, cis-resveratrol and naringenin, in addition to the previously documented components (Oliveira et al., 2021).

Table 3. Content of phenolic compounds in xique-xique (pilosocereus gonellei) and mandacaru (Cereus jamacaru) fruits.

Compound	Fruit
	Xique-xique	Mandacaru
Quinic acid	48.25 ± 2.33	123.85 ± 8.32*
Rutin	14.72 ± 1.80*	0.71 ± 0.07
p-cumaric acid	7.75 ± 0.68*	3.51 ± 0.41
Quercetrin	0.11 ± 0.01	0.20 ± 0.01*
Catechin	0.06 ± 0.001	-
Epicatechin	0.053 ± 0.006	-

*Significant difference at 5% probability level by t-test (p ≤ .05). Values expressed as mg 100 g⁻¹ fd.

Polyphenols are secondary metabolites derived from plants, attracting considerable attention in the scientific community due to their varied health-promoting benefits when included in diets (Araújo, de Paulo Farias, et al., 2020). Polyphenols are known for their antioxidant power and play a crucial role in managing diseases like diabetes. They help lower blood glucose levels, reduce oxidative stress, inhibit protein glycation and suppress dipeptidyl peptidase-IV activity. Additionally, they activate biochemical pathways that enhance β-cell functions (Araújo, de Paulo Farias, et al., 2020; de Paulo Farias et al., 2021).

3.3.2. Phenolic, flavonoid content and antioxidant capacity

The analysis of total phenolics, total flavonoids and antioxidant capacity of mandacaru and xique-xique fruits is summarized in Table 4. Statistical analysis demonstrates a significant difference (p ≤ .05) between the two fruits. Mandacaru exhibits a 1.88-fold higher total phenolic content and a 1.28-fold higher total flavonoid content compared to xique-xique. These findings suggest variations in the antioxidant-related compounds, emphasizing the potential health benefits associated with mandacaru fruit. Phenolic compounds are secondary metabolites of plants widely recognized for their antioxidant potential. The high content of phenolic compounds and total flavonoids reported exhibited a notable influence on the antioxidant capacity of the species studied here.

Table 4. Total phenolics, total flavonoids and antioxidant capacity of xique-xique (pilosocereus gounellei) and mandacaru (Cereus jamacaru) fruits.

Parameters	Fruit
	Xique-xique	Mandacaru
Total Phenolics^a	34.62 ± 0.33	65.17 ± 0.24*
Total Flavonoids^b	20.34 ± 0.30	26.06 ± 0.14*
DPPH^c	13.46 ± 0.41	28.67 ± 0.08*
ABTS^c	39.58 ± 0.19	49.86 ± 0.38*
ORAC^c	89.42 ± 11.23	158.79 ± 16.28*

Equal letters in the line do not differ statistically by the Tukey test (p ≤ .05).

^aResults expressed as mg GAE g⁻¹ fd.

^bResults expressed as mg CE g⁻¹ fd.

^cResults expressed as µM TE g⁻¹ fd.

Mandacaru exhibited superior antioxidant potential across the three evaluated assays compared to xique-xique, with respective fold differences of 2.13 (DPPH), 1.26 (ABTS), and 1.77 (ORAC). The outcomes of this study surpass those reported by Santos et al. (2020). In their evaluation of mandacaru pulp, they observed values of 32.69 mg GAE 100 g⁻¹ for total phenolics, 7.55 μmol Trolox g⁻¹ for ABTS, and 5.70 g g-1 for DPPH, which are comparatively lower than the findings in the present investigation.

Lower results than those found in our work (695.33 ± 114.01 mg GAE 100 g⁻¹ for total phenolics and 15.29 ± 1.51 g g⁻¹ of DPPH for antioxidant capacity) were also reported in the extract obtained from the pulp of mandacaru fruits by Soares et al. (2021). Regarding xique-xique, lower values were also reported in the extract obtained from the fruits for total flavonoid content (2.417 ± 0.417 mg QE g⁻¹) and antioxidant capacity (11.3 ± 0.12 and 10.4 ± 0.24 μg mL⁻¹) for the DPPH and ABTS assays, respectively (Maciel et al., 2015).

3.3.3. Antidiabetic activity

As can be seen, the potential of xique-xique and mandacaru fruits to inhibit the activity of digestive enzymes such as α-amylase and α-glucosidase, in addition to the ability to inhibit protein glycation, can be found in Table 5. Inhibition or even reduction of the activity of enzymes such as α-amylase and α-glucosidase is fundamental for carbohydrate metabolism and control of hyperglycemia, in addition to acting in the reduction of micro and macrovascular complications and the formation of advanced glycation agents, serving as a promising alternative in controlling diabetes (de Paulo Farias et al., 2021).

Table 5. Antidiabetic potential of xique-xique (pilosocereus gounellei) and mandacaru (Cereus jamacaru) fruits.

Parameters	Fruit		Acarbose
	Xique-xique	Mandacaru
α-amylase	76.37 ± 2.26^b	84.84 ± 0.41^a	82.77 ± 1.02^a
α -glucosidase	18.63 ± 0.44^b	8.05 ± 0.01^c	41.07 ± 0.95^a
Antiglycation potential	51.07 ± 5.22	57.33 ± 2.20	-

Results expressed as % of inhibition.

At the tested concentration of 100 mg/g of phenolic extract, there was no statistical difference between mandacaru fruit and acarbose at 100 μM for α-amylase, however mandacaru presented a higher inhibition potential (84.84 ± 0.4%) than xique-xique fruit (76.37 ± 2.26%). On the other hand, for the α-glucosidase enzyme, at the tested concentration of 10 mg/g of phenolic extract, xique-xique fruit showed a potential approximately 43.21 times greater than mandacaru. However, these were lower than the values observed for commercial inhibitor. According to Sancho and Pastore (2012), the possible mechanisms by which some phenolic compounds can inhibit the activity of digestive enzymes include competitive interactions between polyphenols and enzyme substrates, or even through the reduction of catalytic activity due to interactions of these compounds with the active site of the enzymes.

In addition to reducing oxidative stress and inhibiting digestive enzymes, phenolic compounds naturally present in various fruits can also inhibit or regulate protein glycation. According to de Paulo Farias et al. (2021), protein glycation can result in the formation of advanced glycation products, promoting oxidative stress, inflammation, injury and even tissue death, and is therefore considered one of the most important complications in diabetic patients. Our results show that mandacaru fruit demonstrated a higher antiglial potential (57.33 ± 2.20%) when compared to xique-xique fruit (51.07 ± 5.22%), but no statistical difference was observed between the two species studied in the concentration of 50 mg/g of phenolic compounds extract. These results are lower than those observed by Rhizlan and collaborators for Opuntia ficus indica seed oil, a species from the same family as xique-xique and mandacaru fruits, who reported that at a concentration of 0.98 mg/mL it presented a potential inhibition of protein glycation of 87.46 ± 0.83% (Rhizlan et al., 2023).

The outcomes of our study highlight the notable functional capabilities of fruit from lesser-known indigenous species, namely xique-xique and mandacaru. This suggests that these species can be effectively employed in the development of a variety of functional food products.

4. Conclusion

Fruits from the Brazilian semi-arid region, such as xique-xique and mandacaru, offer untapped reservoirs of nutrients and bioactive compounds. Xique-xique exhibits elevated levels of ash, lipids, maltose, and minerals like Mg, Fe, Zn, K, Mn and Na. In contrast, mandacaru presents higher concentrations of glucose, fructose and nystose. Whereas xique-xique has a greater number of volatile compounds, mandacaru stands out for containing linalool, a terpene with notable technological and functional significance. Mandacaru fruit had a higher amount of quinic acid and quercetrin, on the other hand, xique-xique had a higher content of p-coumaric acid, rutin, catechin and epicatechin.

Notably, mandacaru demonstrates superior functional potential with higher total phenolics, total flavonoids and antioxidant capacity. Furthermore, it demonstrated greater potential for inhibiting α-amylase and protein glycation, while xique-xique demonstrated greater potential for inhibiting α-glucosidase. These findings highlight the species-specific nature of the chemical composition and functional attributes and may encourage new research with in vivo and clinical trials that seek to highlight the functional potential of native fruit species that have been little explored to date, but that have great potential to be discovered. In addition, our results can also contribute and support future efforts to promote the cultivation and commercialization of these species, contributing to agricultural development in semi-arid regions.

Acknowledgments

The authors thank the São Paulo Research Foundation, FAPESP-Brazil (grant number 2015/50333-1) and Coordination for the Improvement of Higher Education Personnel, CAPES-Brazil (Finance Code 001) for their financial support. A.C.H.F. Sawaya thanks National Council for Scientific and Technological Development - CNPQ for a grant (306100/2021-5). F. F. de Araújo (grant# 2020/15163-6 and 2022/04530-3), and D. P. Farias (grant#2020/00225-6) thank the FAPESP.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the São Paulo Research Foundation, FAPESP-Brazil [grant numbers 2015/50333-1; 2020/15163-6; 2022/04530-3; 2020/00225-6], Coordination for the Improvement of Higher Education Personnel, CAPES-Brazil (Finance Code 001) and National Council for Scientific and Technological Development - CNPQ for a [grant 306100/2021-5].