Volatile compounds from pitanga fruit (Eugenia uniflora L.)
Introduction
Secondary metabolites in foods and their potential effects on human health are attracting increasing interest. Consumers, who are also increasingly aware of diet-related health problems are demanding natural foods that are expected to be safe and health promoting.
Exotic fruits, whose use was once restricted to people living in limited geographic areas, are gaining popularity worldwide owing to their nutritional value and exotic flavours that appeal to the consumer. Furthermore, such fruits may contain compounds with important therapeutic properties against human diseases. The pitanga (Eugenia uniflora L.) is a tree widely distributed in South American countries, mainly in Brazil, Argentina, Uruguay and Paraguay (Consolini & Sarubbio, 2002). Pitanga fruits are round, about 3 cm in diameter, with eight furrows on the surface, and their colour ranges from orange to purple (Bezerra, Junior, & Lederman, 2000). Pitanga has an exotic and pleasant flavour that has not yet been chemically characterized. The identification of the volatile constituents of pitanga is therefore important for the delineation of processing procedures aimed at retaining the pleasant and unique pitanga flavour in industrialized products. In the Brazilian food industry, pitanga has mostly been used to produce juice, which has high economic potential, owing to its consumer appeal, arising from its high concentrations of antioxidant compounds, such as anthocyanins, flavonols and carotenoids (Lima, Melo, & Lima, 2002).
Studies have also shown that the pitanga fruit may be useful for preventing human diseases. In Brazilian folk medicine, pitanga fruit is used as an anti-diarrheic, diuretic, anti-rheumatic, anti-febrile and anti-diabetic agent. Recently, extracts from pitanga leaves have been found to show pronounced anti-inflammatory action (Schapoval, Silveira, Miranda, Alice, & Henriques, 1994), considerable contractile activity, with a resulting effect on intestinal transit (Gbolade, Ilesanmi, & Aladesnmi, 1996), endothelium-dependent vasorelaxant effects (Wazlawik et al., 1997) and hypotensive effects (Consolini et al., 1999, Consolini and Sarubbio, 2002), and to inhibit the increase of plasma glucose and triglyceride levels (Arai et al., 1999, Matsumura et al., 2000). Some compounds present in pitanga leaf extracts have also been shown to inhibit the Epstein–Barr virus, known to be closely associated with nasopharyngeal carcinoma (Lee, Chiou, Yen, & Yang, 2000), and to have antimicrobial activity (Adebajo et al., 1989, Holetz et al., 2002) and antifungal activity (Lima et al., 1993, Souza et al., 2002). Owing to these promising and diverse pharmacological effects, there is an increasing interest in the isolation and synthesis of pitanga constituents (Kanazawa et al., 2000, Lee et al., 1997).
It is widely known, from epidemiological studies, that consumption of fruits and vegetables imparts many health benefits, owing mainly to their organic micronutrients, such as carotenoids, polyphenolics, tocopherols, and vitamin C. Pitanga fruit is one such source of functional compounds; its juice is rich in vitamins and antioxidant compounds. The volatile constituents of the pitanga fruit have not however been, fully characterized. Therefore, this study was conducted to identify the major volatile compounds from pitanga fruits, so that its pleasant and characteristic flavour can be understood. This knowledge can aid attempts to stimulate consumption of industrialized pitanga fruit products with their potential therapeutic effects and health benefits.
Section snippets
Raw material
Pitanga fruits (Eugenia uniflora L.), harvested from a plantation in the State of Pernambuco, Brazil, were acquired (ripe) from a fruit and vegetable market centre (CEASA – São Paulo, Brazil). The fruits that were immature or over ripe were discarded, providing uniform samples, with fruits in the same stage of ripeness. The ripe fruits were processed in the Laboratory of Natural Products in the Faculty of Animal Science and Food Engineering at the Sao Paulo State University – Pirassununga, SP.
Results and discussion
Fig. 1 shows the total ion chromatogram for the volatiles of only one sample from the pitanga fruit trapped on to Porapak-Q during 4 h. Fifty-four chromatographic peaks can be clearly detected, and Table 1 shows the 29 volatile compounds that could be identified by mass spectra comparison. The retention indices were calculated for all compounds using a homologous series of n-alkanes under the same operational conditions. The majority of them are monoterpenes, among which trans-β-ocimene
Acknowledgments
We thank Dr. Sergio Ari Ribeiro for helpful assistance, and the Brazilian research foundations FAPESP (04/07011-9) and CNPq for financial support.
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