“…80 Accurate quantitative HPLC analysis depends on complete resolution of paclitaxel from other taxanes with similar physicochemical properties; that is, separation can not be considered trivial as some taxanes have similar retention times. Figure 2 (a) HPLC-ESI-MS chromatogram of taxane standard (Hauser Inc., Boulder, CO, USA) containing 10-deacetylbaccatin III (1), baccatin III (2), 10-deacetyl-7-xylosyltaxol B (3), 10-deacetyl-7-xylosyltaxol (4), taxinine M (5), 10-deacetyl-7-xylosyltaxol C (6), 10-deacetyl-taxol (7), 7-xylosyltaxol (8), cephalomannine (9), 10-deacetyl-7-epitaxol (10), taxol (11), taxol C (12) and 7-epitaxol (13 82 NMR, although more convincing than the techniques cited above, requires relatively large amounts of purified paclitaxel, difficult to obtain in microbial cultures. Many fungi and some bacteria have been reported in the literature as paclitaxel producers with concentrations ranging from 0.024 to 800 ng ml À1 (Table 1).…”