Transformation of xanthohumol by Aspergillus ochraceus

Abstract

Microbial transformation of xanthohumol isolated from agro-residue (spent hops), by Aspergillus ochraceus was investigated. A new aurone, (Z)-2″-(2‴-hydroxyisopropyl)-dihydrofurano[4″,5″:6,7]-3',4'-dihydroxy-4-methoxyaurone, was obtained as a main transformation product. Three minor metabolites were identified as 2″-(2‴-hydroxyisopropyl)-dihydrofurano[4″,5″:3',4']-2',4-dihydroxy-6'-methoxychalcone, (2S,2″S)-2″-(2‴-hydroxyisopropyl)-dihydrofurano[4″,5″:7,8]-4'-hydroxy-5-methoxyflavanone and (2S,2″R)-2″-(2‴-hydroxyisopropyl)-dihydrofurano[4″,5″:7,8]-4'-hydroxy-5-methoxyflavanone. Their structures were elucidated on the basis of spectroscopic evidences. The antioxidant properties of xanthohumol and its metabolites were investigated using the 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method. The major biotransformation product, was 8.6-fold stronger antioxidant than xanthohumol and 2.3-fold than ascorbic acid.

Keywords: Antioxidants; Aspergillus ochraceus; Aurone; Biotransformation; Flavonoid; Xanthohumol.