Abstract: Vanillin assay reaction conditions were examined and compared for determining proanthocyanidin with catechin and purified proanthocyanidins chosen from grape seed and sea buckthorn seed as reference standards respectively.Several param-eters mostly affecting the precision and accuracy of vanillin assay were optimized.The results showed that the kinetics of the three type reactions were markedly different.The critical evaluation of vanillin assay was summarized up as follows:for catechin the reaction can be carried out at 30℃ for 5 minutes(measured at 500 nm);for grape seed procyanidins the reaction can be carried out at 20℃ for 5 minutes(measured at 500 nm);and for sea buckthorn seed proanthocyanidins the reaction temperature can be controlled at 30℃ while the reaction time fixed at 15 min(measured at 505 nm).The reaction medium comprise 1 ml of sample,2.5 ml of vanillin solution in methanol and 2.5 ml of 5 mol/L H2SO4 in methanol.

Key words: proanthocyanidins, vanillin assay, sea buckthorn seed, grape seed