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 C18 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.