Abstract
Biotransformation of glycyrrhizin by Aspergillus niger was investigated and one new compound (1) and one known compound (2) were isolated and identified from the biotransformation products. These were 7β,15α-dihydroxy-3,11-dioxo-oleana-12-en-30-oic acid (1) and 15α-hydroxy-3,11-dione-oleana-12-en-30-oic acid (2). A biotransformation pathway was proposed from HPLC analyses at different reaction times. The biotransformation by A. niger included two stages: first, the two glucuronic acid residues at the C-3 position of glycyrrhizin were hydrolyzed to produce glycyrrhetic acid; and second, glycyrrhetic acid was oxidized and hydroxylated to compounds 1 and 2.