Seasonal Changes in the Levels of Polyphenols in Guava Fruit and Leaves and some their Properties

Abstract

With the purpose of utilizing tropical and subtropical fruits more effectively, abundant polyphenols found in guava (Psidium guajava L.) fruit and leaves were examined seasonally in both qualitative and quantitative aspects. 1) The method reported by Peri and Pompei was recognized to be highly useful for determining various polyphenols in crude extracts of guava. 2) Young guava fruit (picked on 18 th August and weighting 2.9g) contained 620 mg of total polyphenols per 100 g fresh weight and 68% of the polyphenols was shown to be condensed tannin. As the fruit grew up, their contents of condensed tannin decreased remarkably. 3) Proanthocyanidin levels in the guava fruit also decreased with the increase in fruit weight from August to October. 4) Gel permeation chromatographic analyses of polyphenols suggest that high molecular weight polyphenols of more than 14,000 disappeared with fruit development. 5) The polyphenol level of guava picked on 3rd August was about 10 times that of young fruit (picked on 18th August) and 84% of the total polyphenols was found to be condensed tannin. The levels decreased markedly at the late of August. 6) (+)-Catechin and (+)-gallocatechin were identified by a reversed phase HPLC in the extracts of guava fruit and leaves. These results indicate that a large percentage of polyphenols in guava fruit and leaves is a type of flavans, especially proanthocyanidin heteropolymers that are composed of (+)-catechin and (+)-gallocatechin, and these compounds decrease remarkably at the early stage of fruit development or at the late of August in the leaves.