Phenolic compounds of seed coats of white and coloured varieties of pea (Pisum sativum L.) and their total antioxidant activity

Abstract

The purpose of this study was to compare the composition and contents of phenolic acids and condensed tannin in the seed coats of white and coloured varieties of pea and to examine the antioxidant properties of methanol and acetone extracts containing these phenolic compounds. The contents of phenolic acids were quantified by the HPLC analysis. The sum of free phenolic acids, those liberated from soluble esters and those liberated from soluble glycosides, was higher for coloured seed coat (78.53 g per g dry matter) than for the white seed coat (17.17 g/g dry matter). Protocatechuic, gentisic and vanillic acids were found dominant in the coloured seed coat, while ferulic and coumaric acids in the white seed coat. The content of condensed tannins was 1560 mg of catechin equivalent/100 g of coloured seed coat as determined by a vanillin assay. No condensed tannins were detected in the white seed coat. The antioxidant activity of extracts was measured by the oxidation of phosphatidylcholine to hydroxyperoxidephosphatidyl choline in the liposome system. Strong antioxidant properties were observed in a crude tannin extract from the coloured seed coat. These properties were slightly changed after the seed coat was cooked in water for 30, 60 and 90 min.