Biotransformation of phlorizin by human intestinal flora and inhibition of biotransformation products on tyrosinase activity

Phlorizin (1) was anaerobically incubated with human intestinal bacteria and five biotransformation products (2-6) were obtained. Their structures were elucidated as phloretin (2), phloroglucinol (3), phloretic acid (4), 2,3,4-trihydroxybenzenepropanoic acid (5), and phloretic acid methyl ester (6) on the basis of their spectroscopic data. Using high-performance liquid chromatography equipped with a diode array detector, chromatographic separation of 1-4 was performed on an analytical C-18 column. The time course of the biotransformation was studied to probe into the biotransformation mechanism of 1 by human intestinal flora. The abilities of isolated strains to transform 1 were also investigated in order to find an optimal transformation strain. In addition, the inhibitory activity of parent compound 1 and its three main biotransformation products 2-4 on mushroom tyrosinase was estimated. The result showed that 2 has better inhibitory effect on tyrosinase activity than 1. (C) 2011 Elsevier Ltd. All rights reserved.