Characterization of phenolic compounds in jocote (Spondias purpurea L.) peels by ultra high-performance liquid chromatography/electrospray ionization mass spectrometry
Introduction
The Anacardiaceae family comprises more than 70 genera and over 600 species, which are mainly trees and shrubs growing in tropical, subtropical and temperate zones. The family is subdivided in 5 tribes: Anacardieae, Spondiadeae, Rhoeae, Semecarpeae, and Dobineeae (Wannan, 2006). Some members of the Anacardieae and Rhoeae tribes, such as cashew (Anacardium occidentale L.), mango (Mangifera indica L.), sumac (Rhus sp.), and pistachio (Pistacia vera L.) are important food plants. The Spondiadeae tribe includes 17 genera and 140 species, with about 14–15 species belonging to the genus Spondias (Bachelier and Endress, 2009, Duvall, 2006, Macía and Barfod, 2000). From a phytochemical point of view, members of the Anacardiaceae family are rich in secondary plant metabolites, in particular phenolic compounds, with interesting biological activities. Therefore, many species of this family have also been used as medicinal plants (Wiart, 2006). Some members such as Toxicodendron species (poison ivy, poison oak) contain toxic components which cause severe contact allergies (Gladman, 2006).
Jocote (Spondias purpurea L.) is a plant native to the (sub-) tropical semi-arid forests of Mesoamerica. Its name derives from the Nahuatl word ‘(ateya)xocotl’, which means ‘fruit’. Jocote is also known as red mombin, purple mombin, ciruela, seriguela, and Spanish plum. The small trees (3–10 m) produce oval drupe-like, smooth and shiny fruits that ripen throughout the year, depending on the variety, and vary widely in color from green to yellow, orange, red, and violet. The fruits are up to 5.5 cm long and weigh 12–28 g. Their texture varies from chalky to creamy and juicy, and their taste may be bitter-sweet or acidic. The fibrous and lignified endocarp surrounds malformed seed remnants and takes up most of the fruit but is not edible. Fruits are consumed ripe or unripe with salt, with or without the skin, raw, boiled, dried, in desserts, as preserves or as beverages (Cuevas, 1994, Miller and Schaal, 2005, Pimenta-Barrios and Ramírez-Hernández, 2003). Fruits and other parts of the jocote tree and related species have also been used for the treatment of various ailments such as diarrhea, ulcers, thrush, dysentery, and bloating. Aqueous and methanolic leaf extracts are reported to have antibacterial properties (Agra et al., 2007, Ayoka et al., 2008, Baraona-Cockrell, 2000, Bernhardt, 2008). Bark extracts of Spondias purpurea L. showed antibacterial activity but were inactive against protozoa (Gachet et al., 2010).
In view of the numerous medicinal uses of jocote it is surprising that phytochemical investigations on this interesting plant are scarce (Kozioł & Macía, 1998) and limited mainly to volatiles (Ceva-Antunes, Ribeiro Bizzo, Silva, Carvalho, & Antunes, 2006), gum exudates (Martínez et al., 2008), and carotenoids (Murillo, Meléndez-Martínez, & Portugal, 2010). Studies performed on Spondias species other than Spondias purpurea L. indicate the presence of antioxidants but failed to provide information about the profile of phenolic compounds (Chalise et al., 2010, Genovese et al., 2008, Hazra et al., 2008, Rufino et al., 2010). During the past decade, reliable and efficient methods were established by our group for the characterization of various subclasses of polyphenols in mango fruits and by-products based on liquid chromatography with diode array and mass spectrometric detection. Particular attention has been given to flavonoids and xanthones (Schieber, Berardini, & Carle, 2003), gallotannins and benzophenone derivatives (Berardini, Carle, & Schieber, 2004), and alk(en)ylresocinols (Knödler, Berardini, Kammerer, Carle, & Schieber, 2007). In continuation of these investigations, the objective of this study was to characterize the profile of phenolic compounds of jocote peels. Since preliminary studies had revealed that the quantities of polyphenols in the flesh are very low, only the peels were taken into consideration. An analytical system based on ultra high-performance liquid chromatography coupled with diode array detection-electrospray ionization mass spectrometry (UHPLC–DAD–ESI-MSn) was established.
Section snippets
Standards and chemicals
Standards of phenolic acids (3,4,5 trihydroxybenzoic acid; 3-caffeoylquinic acid) and flavonoids (3,3′,4′,5,7-pentahydroxyflavone (quercetin dihydrate); quercetin 3-O-galactoside; quercetin 3-O-β-glucopyranoside; quercetin 3-O-rhamnoside; quercetin 3-O-rutinoside; quercetin 3,4′-O-diglucoside; 3,4′,5,7-tetrahydroxyflavone (kaempferol); kaempferol 3-O-glucoside; kaempferol 3-O-rutinoside; 3,3′,4′,5-tetrahydroxy-7-methoxyflavone (rhamnetin); 3,4′,5,7-tetrahydroxy-3′-methoxyflavone (isorhamnetin);
UHPLC–ESI-MSn analysis
In this study, over 20 phenolic compounds extracted from lyophilized samples of jocote peels were characterized using a novel UHPLC method with diode array and mass spectrometric detection. Compared to the methods used in previous studies on phenolics from mango (Schieber et al., 2003), artichoke (Schütz, Kammerer, Carle, & Schieber, 2004), and grape (Kammerer, Claus, Carle, & Schieber, 2004), this method is much faster and allows the separation of the phenolics in less than 20 min (Fig. 1). The
Conclusions
To the best of the authors' knowledge, this is the first report on the phenolic composition of jocote peel samples. Using a fast and sensitive UHPLC method coupled with mass spectrometry, 21 phenolic compounds could be detected and characterized, which is of particular interest given the increasing evidence of beneficial effects of phenolics on human health. This study may also be helpful for chemotaxonomic purposes because it broadens our knowledge about the profile of secondary plant
Acknowledgment
A.S. and M.G.G. acknowledge funding from the Canada Research Chairs Program.
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