Glycosides grape skin extract

Because standards of HCTA are not commercially available, for quantitative analysis chlorogenic acid or free hydroxycinnamic acids are used as external standards. Standards of flavonols commercially available are quercetin and myricetin glucoside and other flavonols glycoside (e.g. rutin). Alternatively, the single HCTA and flavonols can be isolated from a grape skins extract by performing semipreparative HPLC. 

Revilla et al. [81] identified 30 anthocyanin analogues, including 3-0-glycosides and 6-coumaroyl-3-0-glycosides of delphinidin, cyanidin, petunidin, peonidin, and malvidin, 6-acety 1-3-glycosides of malvidin and peonidin, in extracts of red grape skin and in red wines. The combination of UV-DAD and MS detection proved to be essential for identification. 

Recently, Romani et al. [200] published a sophisticated solid phase extraction procedure for the qualitative analysis of grape skins. In a first extraction on Extrelut 20 (kieselguhr, Merck) polyphenols are separated from anthocyanins. The polyphenols are subsequently fractionated on a C-18 cartridge (Bond Elut , Varian) into phenolic acids and esters, procyanidins, flavonol glycosides and acylated anthocyanins. 

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