Microbial Transformation of 10-Deacetyl-7-epitaxol and 1β-Hydroxybaccatin I by Fungi from the Inner Bark of Taxus yunnanensis

Abstract

Fungi present in the inner bark of the yew tree Taxus yunnanensis were studied for the capability to biotransform natural taxoids. On the basis of screening, three fungi, Microsphaeropsis onychiuri, Mucor sp. and Alternaria alternata, were revealed to be able to selectively hydrolyze and epimerize two taxoids, 10-deacetyl-7-epitaxol (1) and 1β-hydroxybaccatin I (2), previously isolated from the bark of the same yew species. After preparative-scale incubation of 10-deacetyl-7-epitaxol with M. onychiuri and Mucor sp., three metabolites were isolated and characterized as 10-deacetylbaccatin V (3), 10-deacetyltaxol (4), and 10-deacetylbaccatin III (5). Incubation of 1β-hydroxybaccatin I with A. alternata, on the other hand, gave 5-deacetyl-1β-hydroxybaccatin I (6), 13-deacetyl-1β-hydroxybaccatin I (7), and 5,13-dideacetyl-1β-hydroxybaccatin I (8).