Taxol and related taxanes. I. Taxanes of Taxus brevifolia bark.

The published procedures for the isolation of taxol from the Pacific yew (Taxus brevifolia) and other species of Taxus are cumbersome, and the yields of taxol are in the range of 0.0075-0.01%. This paper describes a simple and efficient procedure for the isolation of taxol and its major natural analogues from the bark of T. brevifolia consisting of a single chromatographic column (using silica gel, Florisil, or a reverse-phase C18-silica), followed by crystallization. Isolated yields of taxol from five "pooled" bark samples (blended from many different batches by the supplier) were in the range of 0.02-0.04%, and from bark collected from a more restricted locale, yields reached 0.06%. The procedure also yielded taxol analogues, such as 10-deacetylbaccatin III (0.02-0.04%), 10-deacetyltaxol-7-xyloside (0.06-0.1%), taxol-7-xyloside (0.005-0.01%), 10-deacetyltaxol (0.01-0.02%), 10-deacetylcephalomannine-7-xyloside (0.006-0.01%), and cephalomannine (0.005-0.007%). Of these, 10-deacetyltaxol-7-xyloside is the most abundant taxane in the Pacific yew bark.