Structure-Activity Relationship of Antioxidant and Antitumor Polyphenols

Abstract

Antitumor activities of polyphenols can be classified into several types. The host-mediated antitumor activity of polyphenols is specifically exhibited by some ellagitannin oligomers of molecular weight (mw) over 1500, among which the macrocyclic oligomers show a high er ratio of active compounds than the others. Inhibitions of tumor initiation and promotion, which are affected by antioxidant and binding activities, are exhibited in various potencies, being influenced by the structure and mw of polyphenols. Compounds such as (-)-epigallocatechin gallate (EGCG) and ellagic acid, of low mw, which show notable anti tumor activities, are exceptions to the mw-activity relationship found for most polyphenols. An inverted mw-activity correlation was found for the inhibition of mutagenicity between Trp-P-1 (and Trp-P-2, etc.) and N-methyl-N'-nitro-N-ni troso guanidine (MNN G). Ellagi tannins having hexahydroxydiphenoyl (HHDP) group(s) in the molecule gene rally show more potent antioxidant activity against autoxidation of linoleate. Among the polyphenols of similar mw, the number and environment of the hydroxyl group in each molecule have decisive effects on anti tumor activity.