Comparison of the Fatty Acid Profiles of Edible Native Fruit Seeds from Southern Brazil

Abstract

Three different Myrtaceae species and one species of Annonaceae were analyzed for the fatty acid composition of their seed oil. All species were characterized by high concentrations of unsaturated fatty acids that ranged from 54.61 to 91.65 g/100 g of the total fatty acid content. The main fatty acid presented by Feijoa sellowiana was linoleic acid (84.44 g/100 g). Oleic acid was the main fatty acid found in the seed oil from Myrcianthes pungens and Rollinia sylvatica, whose contents were 57.03 and 54.41 g/100 g, respectively. For Eugenia uniflora oil seed, the main fatty acid detected was palmitic acid (40.07 g/100 g).

Keywords:

• Myrtaceae
• Annonaceae
• Seed oil
• Fatty acids
• Linoleic acid
• Oleic acid
• Palmitic acid

INTRODUCTION

Biomolecules in fruits and vegetables have attracted a great deal of attention mainly for their role in preventing diseases. Epidemiological studies have shown that there is a clear and significant positive association between intake of these natural food products, consumed regularly as part of the diet, and reduced rates of mortality due to heart disease, common cancers, and other degenerative diseases.[1] The lipid composition of fruits and vegetables has lately received particular attention because of consumer concern over the ratio of saturated/unsaturated fatty acids in the diet.

Fatty acids carry out many functions that are necessary for normal physiological health. Consumers are especially interested in essential fatty acids with an emphasis on the health potential of polyunsaturated fatty acids. Diets that are high in monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) are associated with reduced risk of cardiovascular disease and atherogenesis. In contrast, it is well established that consumption of a diet high in saturated fat is associated with impaired insulin sensitivity and an increase in the incidence of obesity, type 2 diabetes, coronary heart disease, and atherosclerosis.[2] In addition, a number of benefits have been attributed to the fatty acid oleic acid, such as activity in cholesterol metabolism and a protective role against cardiovascular diseases.[3]

The lack of information about chemical substances, especially fatty acids, found in Myrtaceae and Annonaceae species, allied to the possibility of obtaining new food sources for unsaturated fatty acids, has aroused interest in analyzing the lipid composition of seeds from species belonging to these families found in Brazil. Therefore, the aim of this study was to determine the fatty acid composition of the oil from the seeds of the following species native to southern Brazil: Myrcianthes pungens, Eugenia uniflora, Feijoa sellowiana (Myrtaceae species), and Rollinia sylvatica (Annonaceae) (Fig. 1).

Figure 1 Fruits from Brazil: (a) Rollinia sylvatica; (b) Feijoa sellowiana; (c) Myrcianthes pungens; (d) Eugenia uniflora. (Color figure available online.)

Myrtaceae is a family of at least 133 genera and more than 3800 species. It has centers of diversity in Australia, southeast Asia, and tropical to temperate southern America, although it has little representation in Africa.[4] In Brazil, this family is well represented in the southern state of Rio Grande do Sul. The presence of Myrtaceae fruits in the diet varies, although the fruits of several species are used since they represent a rich and nutritional food choice. These species are most widely consumed fresh or in preparations including candies, jellies, juices, and ice creams.

Eugenia uniflora L. (known commonly in Portuguese as “pitanga”) is a tree widely distributed in South American countries, mainly in Brazil, Argentina, Uruguay, and Paraguay. The fruits are round, about 3 cm in diameter, and their color ranges from orange to purple. In the Brazilian food industry, pitanga has mostly been used to produce juice, which has a high economic potential owing to its consumer appeal arising from its high concentrations of antioxidant compounds, flavonols, and carotenoids. The essential oil composition of the fruits was previously investigated by our group and the major compounds detected were (E)-β-ocimene (7.4 g/100 g), α-selinene (7.2 g/100 g), germacrene B (7.2 g/100 g), and hexadecanoic acid (11.7 g/100 g).[5]

Feijoa sellowiana Berg (common name “feijoa”) is an evergreen bush native to southern South America, where it is widely distributed. The fruit of this bush may be a source of antibacterial, antioxidant, anti-inflammatory, and, perhaps, antimutagenic agents. The acetonic extract from F. sellowiana fruits is able to inhibit the production of nitric oxide (NO) because of the presence of flavones and stearic acid.[6]

Myrcianthes pungens (O. Berg) D. Legrand (known popularly as “guabiju”) is a plant that presents a small fruit with purple coloration, containing white pulp with a sweet flavor, and is rich in polyphenolic compounds, including anthocyanins and flavonol glycosides. Apel et al.[7] investigated the volatile oil composition of leaves from this species and identified 36 compounds, among which β-caryophyllene was the main constituent. In the analysis of the essential oil of the fruits, the major components were limonene (10.9 g/100 g) and β-caryophyllene (21.8 g/100 g).[5]

Annonaceae is a homogenous botanic family in tropical and subtropical areas. Many members of Annonaceae are used in folk medicine for the antiparasitic or antitumoral treatment of intestinal diseases. In recent years, many interesting compounds termed tetrahydrofuranic acetogenins (or annonaceous acetogenins) have been reported to be present in this family and they have gained the attention of organic chemists and biochemists because of their novel structure and wide range of bioactivities.[8]

Rollinia sylvatica (A. St.-Hil.) Martius (known popularly as “araticum”) is a tree native to the south of Brazil that bears a typical fruit known also as “araticum-do-mato” or “embira,” “cortiça,” and “cortiça-amarela.” Its fruits are the smaller type of Rollinia fruit that ripen to a brownish-yellow color and contain white pulp with a very pleasant, sweet flavor, with fairly large seeds. The fruits are widely consumed fresh by indigenous people or used to prepare juice, ice cream, or jelly. A previous phytochemical investigation of Rollinia species revealed the presence of acetogenins, steroids, lignans, essential oil, and alkaloids.[9] From dried fruits of this species, a modified fatty acid, sylvaticin, a tetrahydroxy annonaceous acetogenin with nonadjacent tetrahydrofuran rings, was isolated. This compound presented cytotoxicity against human tumor cells, as well as insect control properties.[10]

EXPERIMENTAL PROCEDURES

Plant Material

The material analyzed comprised seeds from fruits collected in July 2006, from cultivars of the germplasm bank maintained by the Clima Temperado Research Center of Embrapa (Empresa Brasileira de Pesquisa Agropecuária, Ministério da Agricultura, Pecuária e Abastecimento), Pelotas, Rio Grande do Sul, Brazil, located at 31°40′47″S latitude, 52°26′24″SW longitude, and an altitude of 60 meters. The seeds obtained were dried at an ambient temperature and later were triturated in a knife mill.

Extraction of the Fixed Oils

Hexane was used for the extraction of the fixed oil from the seeds in an exhaustive static maceration process, repeated three times with each extraction lasting about 24 h. The proportion of crushed seeds per milliliter of solvent was approximately 1:5 (m/v). These samples were filtered and all extractions of the same fruit seed were grouped in a single bottle and dried at ambient temperature.

FAME Transesterification

Fatty acid methyl esters (FAME) were obtained by alkaline transesterification according to the Adolfo Lutz Institute,[11] with modifications. In this method, approximately 80 mg of the oil was placed in a centrifugal pipe, then 3 ml of hexane solvent and 4 ml of the mixture NaOH/MeOH 0.5 M were added. After this, the pipe was placed in a hot water bath (40°C) for 4 min, and then cooled in running water before adding 5 ml of the esterification solution (NH₄Cl/H₂SO₄/MeOH). The pipe was shaken and placed in a hot water bath for a further 5 min. It was then cooled in running water again. Four ml of NaCl saturated solution were added together with 3 ml of hexane. The pipe was agitated on a vortex mixer and, finally, the separated phases were collected for injection in a gas chromatograph (GC).

Gas Chromatography

The fatty acid methyl esters were analyzed by gas chromatography using a Shimadzu GC17A QP-5000 apparatus (Shimadzu, Kyoto, Japan) equipped with a quadruple mass spectrum (MS) system. The esters were separated on a VS-23 capillary column (30 m × 0.25 mm). The oven temperature was kept at 50°C for 5 min, followed by a 3°C/min ramp to 240°C and finally held there for an additional 5-min period. Helium was used as the carrier gas at a flow rate of 1.0 ml/min. The injector and detector temperatures were maintained at 260°C. FAMEs were identified by comparison of their retention times with those of pure reference standards (FAME mix: 18919-1, Supelco).

RESULTS AND DISCUSSION

This study of the fatty acid composition of seed oils from Myrtaceae species and Rollinia sylvatica (Annonaceae) presented a seed oil yield of 2.5 g/100 g for pitanga, 5.41 g/100 g for guabiju, 10.78 g/100 g for feijoa, and 12.11 g/100 g dry seeds for araticum. The concentrations of different fatty acids varied across different families and also among different species of the same family. A total of eight fatty acids were identified (Table 1). Figures 2–5 show the gas chromatograms of the respective seed oils. All species were characterized by high concentrations of unsaturated fatty acids (UFA) that ranged from 54.61 g/100 g to 91.65 g/100 g of the total fatty acid content. In the seed oil from F. sellowiana, there was a high prevalence of unsaturated fatty acids, with 84.44 g/100 g of linoleic acid. Among the species of Myrtaceae analyzed in this study, M. pungens and E. uniflora showed the highest number of different fatty acids in their oil composition (six components).

Table 1 Fatty acid compositions (g/100 g of total fatty acids) of seed oils from the Myrtaceae and Annonaceae species

Fatty acid	M. pungens	F. sellowiana	E. uniflora	R. sylvatica
Palmitic acid (C16:0)	25.96 ± 0.59	5.55 ± 0.76	40.07 ± 2.39	20.84 ± 0.84
Palmitoleic acid (C16:1)	—	—	2.26 ± 0.3798	—
Stearic acid (C18:0)	5.28 ± 0.37	2.81 ± 0.79	5.32 ± 0.89	4.26 ± 0.33
Oleic acid (C18:1)	57.03 ± 0.45	7.21 ± 0.53	16.41 ± 2.69	54.41 ± 1.43
Linoleic acid (C18:2n-6)	9.57 ± 0.23	84.44 ± 2.06	30.11 ± 3.81	20.49 ± 0.30
Gamma-linolenic acid (C18:3n-3)	—	—	5.83 ± 0.83	—
Cis-11-eicosenoic acid (C20:1)	1.97 ± 0.21	tr	—	—
Linolenic acid (C18:3n-3)	0.20 ± 0.29	—	—	—
∑SFA	31.24 ± 0.48	8.36 ± 0.77	45.39 ± 1.64	25.1 ± 0.58
∑MUFA	57.07 ± 0.30	7.21 ± 1.29	18.67 ± 1.93	54.41 ± 0.86
∑PUFA	11.74 ± 0.30	84.44 ± 1.29	35.94 ± 1.29	20.49 ± 1.29
∑TUFA	68.77 ± 0.30	91.65 ± 1.29	54.61 ± 1.93	74.9 ± 0.86

Figure 2 GC/MS chromatogram obtained for seed oils from Myrcianthes pungens. (Color figure available online.)

Figure 3 GC/MS chromatogram for fruit seed oils from Feijoa sellowiana. (Color figure available online.)

Figure 4 GC/MS chromatogram obtained for seed oils from Eugenia uniflora. (Color figure available online.)

Figure 5 GC/MS chromatogram for seed oils from Rollinia sylvatica. (Color figure available online.)

Polyunsaturated fatty acids modulate the activities of enzymes, carriers, and membrane receptors (LDL receptors, antibodies, insulin and neurotransmitter receptors, drug receptors, etc.). Furthermore, they are involved in the production of eicosanoids (prostaglandins, prostacyclins, thromboxanes, and leukotrienes), signal transduction, and the activation of nuclear transcription factors.[12] Swagell et al.[13] demonstrated a number of important effects of fatty acids on gene expression that may be implicated in the well-established association between dietary fat intake and human health.

Oleic acid was the main monounsaturated fatty acid (MUFA) found in the seed oil from M. pungens and R. sylvatica, whose contents were 57.03 g/100 g and 54.41 g/100 g, respectively. For E. uniflora seed oil, the main component observed was the saturated fatty acid (SFA) palmitic acid (40.07 g/100 g). This was the only species that presented an SFA as the main compound of the seed oil.

To a lesser extent, another SFA, stearic acid, was also found in all species (2.81–5.32 g/100 g). Palmitoleic acid, another MUFA identified, was found only in E. uniflora (2.26 g/100 g), together with the polyunsaturated fatty acid (PUFA) gamma-linolenic acid (5.83 g/100 g). PUFAs were predominant in F. sellowiana, in which linoleic acid was the main component (84.44 g/100 g). Other PUFAs present included linolenic acid, found only in M. pungens (0.20%), at a very low level, and cis-11-eicosenoic acid, which was detected at a low level only in M. pungens (1.97 g/100 g) and in F. sellowiana (traces). Another finding of this study concerns the comparison between the families (Myrtaceae and Annonaceae), where the eight fatty acids found in the seed oils from their species were the same and the only variation was in the concentrations of these compounds.

These fatty acids were found in some apple and pear seed oils, in a study performed by Yukui et al.[14] who reported oleic acid as the main compound in both fruits, ranging from 43.03 g/100 g for apple seed oil to 56.80 g/100 g oil for pear seed oil. The long-chain unsaturated fatty acids, such as linoleic and oleic acids, present bactericidal properties against important pathogenic microorganisms, including methicillin-resistant Staphylococcus aureus,[15] Helicobacter pylori,[16] and Mycobacteria.[17] The antibacterial actions of long-chain unsaturated fatty acids are usually attributed to inhibition of pathogenic microorganisms.[15–17]

Knowing that the fatty acid composition is important in terms of both the functional and the nutritional characteristics of the oils, in another study on the fatty acid composition of the fixed seed oil from Caryocar coriaceum Wittm the authors found oleic (57.15 g/100 g) and palmitic (35.53 g/110 g) acids as the main compounds in the oil investigated. Moreover, this work demonstrated that the topical application of the fixed oil of this species was capable of reducing inflammation in xylene-induced acute ear edema in a dose-dependent fashion, with these results being attributed to the presence of UFAs in this oil.[18]

It was also reported that a mixture of fatty acids from a natural source, including palmitic, oleic, linoleic, and linolenic acids, exerts an anti-inflammatory action in various in vitro and in vivo experimental models.[19] It is well established that oils with a balanced fatty acid composition may beneficially modulate antioxidant status in the body.[20,21] Essential fatty acids (EFAs) can improve the secretion of insulin in diabetic patients and also help to combat some diseases associated with this, such as retinopathy and other complications.[22] Considering these findings, we can suggest that the daily consumption of amounts of fatty acids may prevent the development of many human pathologies, thereby improving the quality of health in the population.

CONCLUSION

The present work demonstrated the presence of saturated (less content) and unsaturated fatty acids (main compounds) in fruit seed oils from Brazil. Among the unsaturated compounds, oleic acid was found to be the major compound in two oils studied (from M. pungens, 57.03 g/100 g and from R. sylvatica, 54.41 g/100 g). High levels of the essential fatty acid, linoleic acid, were also detected, ranging from 9.57 to 84.44 g/100 g of total fatty acid content. The results above suggest that species of Myrtaceae and Annonaceae families can be used as a source of vegetable oil rich in unsaturated fatty acids, and that not only the pulp, but also the seeds, can be incorporated in the human diet. Additionally, the seeds, which are considered to be a byproduct of the food industry, have the potential for application in the food, pharmaceutical, cosmetic, and perfume industries.

ACKNOWLEDGMENTS

The authors would like to acknowledge CNPq, Capes, and UFRGS for their financial support.