ANALYSIS OF TAXOL AND RELATED DITERPENOIDS FROM CELL-CULTURES BY LIQUID-CHROMATOGRAPHY ELECTROSPRAY MASS-SPECTROMETRY

Authentic taxanes (taxol, 10-deacetyltaxol, cephalomannine, 10-deacety lcephalomannine baccatin III) and extracts from cell cultures derived from various yew tree species have been analyzed by microbore high-per formance liquid chromatography (HPLC)-electrospray mass spectrometry ( ESMS). All gave excellent positive-ion ES spectra with dominant proton ated molecules at low nozzle-to-skimmer bias value (45 V). By increasi ng the voltage value to 85 V, fragmentation increased and structurally informative spectra were obtained. The fragments found were both of t he C-13 side-chain and of the taxane ring, so their analysis gave impo rtant information about the taxane structure and any chemical modifica tions at different positions of the molecule. When tandem MS was used (argon gas, 25 eV collision energy), fragments similar to those obtain ed from collision-induced dissociation in the source were detected. Th e cell culture extracts were analyzed by microbore HPLC-ESMS and excel lent spectra were obtained on 5-10 ng of separated compounds; even gre ater selectivity and sensitivity were obtained through use of selected -ion monitoring (SIM). With SIM, 100 pg of all taxanes could readily b e detected. In the HPLC-ESMS mode, only 10% of the eluent was mass-ana lyzed, so 90% would be available for recovery through fraction collect ing.