Biotransformation of 20(S)-protopanaxadiol by Aspergillus niger AS 3.1858

The biotransformation of 20(S)-protopanaxadiol (1) by Aspergillus niger AS 3.1858 was conducted. Seven metabolites 26-hydroxyl-20(S)-protopanaxadiol (2); 23, 24-en-25-hydroxyl-20(S)-protopanaxadiol (3); 25, 26-en-20(S)-protopanaxadiol (4); (E)-20, 22-en-25-hydroxyl-20(S)-protopanaxadiol (5); 25, 26-en-24(R)-hydroxyl-20(S)-protopanaxadiol (6); 25, 26-en-24(S)-hydroxyl-20(S)-protopanaxadiol (7); and 23, 24-en-25-ethoxyl-20(S)-protopanaxadiol (8) were afforded. Among them, 6, 7, and 8 are new compounds. The chemical structures of these metabolites were elucidated based on extensive spectral data including 2D NMR and HRMS. In addition, the cytotoxicity of substrate and all transformed products was evaluated by MTT assay using a panel of seven human tumor cell lines (Du-145, Hela, K562, K562/ADR, SH-SY5Y, HepG2, and MCF-7 cells) and one normal cell line Vero.