Determination of major anthocyanin pigments and flavonols in red grape skin of some table grape varieties ( Vitis vinifera sp. ) by high-performance liquid chromatography–photodiode array detection (HPLC-DAD)

摘要

Aim: The aim of this study was the investigation of the anthocyanin and flavonol content in grape skin extracts. Five prevalent anthocyanin-types and four flavonol-types were determined in the skin of three red table grape varieties widely cultivated in El-Tarf (Algeria).Methods and results: The identification of the compounds was performed by HPLC-DAD based on C-18 reversed phase column separation. Results from HPLC analysis showed that malvidin and petunidin-3-O-glucoside were the major anthocyanin glucoside, whereas quercetin-3-O-glucoside was the major flavonol among the four identified.Conclusion: The content of anthocyanins and flavonols in the grape skin of three grapevine (Vitis vinifera) varieties exhibits notable differences among the cultivars studied, confirming their importance in the varietal characterization. The highest concentrations of total anthocyanins and flavonols corresponded to the Gros noir variety. The results of the present study also indicate that the grape skin extracts of these Algerian cultivars can be used as easily accessible source of natural antioxidants.??Significance and impact of the study: To the best of our knowledge, this is the first report on the identification of different anthocyanins and flavonols in berry skin from some red grape varieties largely cultivated in this region of Algeria. IntroductionGrape (Vitis vinifera) is one of the world’s largest fruit crops, and its composition and properties have been extensively investigated, with several reports of the presence of large amounts of phenolic compounds. Most phenolic compounds found in grape can act as antioxidants. Grape skin is a source of natural pigments (anthocyanins and flavonols), which are known to possess broad pharmacological activities and therapeutic potentials (Bagchi et al., 2004; Leifert and Abeywardena, 2008). Anthocyanins, the major polyphenols found in red grape skins, have been reported to show cardioprotective effects against ischemic reperfusion injury and to possess other diverse biological properties and therefore are considered as secondary metabolites with potential nutritional value (Kallithraka et al., 2005; Das et al., 2007). Anthocyanins, being located in the berry skin, are the main flavonoids responsible for the red color of grape cultivars. It is well known that the anthocyanin concentration can vary widely among different vintages of a given cultivar, due to both environmental (seasonal conditions) and agronomical factors. Therefore, the anthocyanin profile has been used as a chemotaxonomic parameter for the classification of red Vitis vinifera varieties (Revilla et al., 2001; Mattivi et al., 2006). Grape anthocyanins are monoglucosides of five anthocyanidins, namely delphinidin, cyanidin, petunidin, peonidin and malvidin. The acylated anthocyanins are esters of the glucose moiety of the free anthocyanins with acetic, p-coumaric or caffeic acids. Flavonols are one of the most studied classes of polyphenolic phytochemicals, because of the importance pertaining to their antioxidant potency and other biological activities (O’Byrne et al., 2002). Flavonols constitute a group of flavonoids that vary in color from white to yellow and are closely related in structure to the flavones. Derivatives of the most commonly encountered aglycones, including quercetin, myricetin, kaempferol and isorhamnetin, have been found in grapes (Vitis vinifera sp.). The conjugates are exclusively 3-O-glycosides, whereas sugar attachment on other positions of the flavonol skeleton has never been reported. For isorhamnetin, only glucose derivatives have been identified, but myricetin, quercetin and kaempferol may also occur as glucuronides (Makris et al., 2006).The objective of the present study is to identify phenolic compounds in skin of red grape varieties grown in Mediterranean climate. The grapes of three varieties commonly used in Algeria (Cardinal, Gros noir and Muscat noir) were analyzed and compared for their anthocyanin and flavonol content. To the best of our knowledge, no research has examined the anthocyanin and flavonol content in these grape varieties grown in El-Tarf (Algeria).Materials and methods1. Plant materialSkins from three grape cultivars, namely Cardinal, Gros noir and Muscat noir, were examined. Grape samples were grown in the region of El-Tarf located in the north-east of Algeria (36° 45' 00" N; 81° 10' 00" E) and collected at maturity. The region has a Mediterranean climate, which is divided into a hot season from June to October and a rainy season from November to April. The rest of the year the region enjoys a mild and pleasant climate.2. Sample preparationBefore extraction, skins were manually separated from the whole berries and dried in oven at 50°C until constant weight. Dried grape skins were crushed in a grinder for 2 min and then used for extractions.3. Extraction of anthocyanins and flavonolsThe extraction procedures was done according to Cadot et al. (2012) and Bros