Microbial transformation of asiatic acid.

Asiatic acid (1), a major pentacyclic triterpene of Centella asiatica, was subjected to transformation by Penicillium lilacinum ACCC 31890, Fusarium equiseti CGMCC 3.3658, and Streptomyces griseus CGMCC 4.18 strains. Incubation of asiatic acid with P. lilacinum ACCC 31890 and F. equiseti CGMCC 3.3658 gave an identical product: 2α,3β,15α,23-tetrahydroxyurs-12-en-28-oic acid (2). Biotransformation of asiatic acid by S. griseus CGMCC 4.18 resulted in three derivatives: 2α,3β,21β,23-tetrahydroxyurs-12-en-28-oic acid (3), 2α,3β,23-trihydroxyurs-12-en-28, 30-dioic acid (4), and 2α,3β,23,30-tetrahydroxyurs-12-en-28-oic acid (5). The structures of those derivatives were deduced from their spectral data. Products (2), (3), and (4) were new compounds. In addition, the in vitro cytotoxicities of those derivatives along with 1 were evaluated with several human cancer cell lines.