Isolation and Determination of Polymeric Polyphenols Using Sephadex LH-20 and Analysis of Grape Tissue Extracts

Abstract

A simple chromatographic method using Sephadex LH-20 was developed to separate non-polymeric and polymeric phenols. Non-polymeric phenols are eluted from the gel by 60% methanol. A subsequent elution with 50% acetone enables quantitative recovery of polymeric phenols. The phenolic concentration in each fraction is then measured using the Folin Ciocalteu procedure. The method was used to measure concentrations of polymeric phenols in grape seed, skin, stem, and leaf tissue extracts. Seeds were found to contain the highest and most uniform concentrations of polymeric phenols. Stems and leaves contained similar concentrations of polymeric phenols. Skins contained the lowest and most variable concentrations of polymeric phenols. The Sephadex LH-20 method and HPLC peak area ratios gave very similar estimates of the percentage of polymeric phenols in tissue extracts. However, the former method enables isolation and quantitative analysis of polymeric phenols. Thus, the Sephadex procedure provides results that can be used in efforts to produce a "balance sheet" summary of all phenols present in grape extracts or wines.