NORMAL-PHASE AND BONDED-PHASE LIQUID-CHROMATOGRAPHY WITH PHOTODIODE-ARRAY DETECTION OF MAYTANSINOIDS

Maytansinoids obtained from Maytenus species are known as potential an ti-cancer drugs. Investigation of new plant species for the presence o f unknown maytansinoids as well as synthetic work requires a reliable analytical and semipreparative normal-phase separation which can disti nguish between known and unknown compounds independently from retentio n times and which would be compatible to LC-MS interfacing for further studies. A thorough study of numerous maytansinoids on silica gel and on diol-, aminopropyl- and cyanopropyl-bonded phases, suggests a comp lex retention mechanism based on molecular size as well as on specific interaction with the stationary phase while limiting a selectivity ef fect of the mobile phase. Utilizing a Varian 9065 photodiode array det ector a spectral library of the separated substances was generated. Th is library simplifies the identification of known compounds in a matri x of unknowns such as fractions of plant extracts even if baseline sep aration is not achieved. Unlike reversed-phase separations that have b een described in the literature the presented method allows an easy sa mple recovery in a semipreparative separation.