Antineoplastic agents, 122. Constituents of Combretum caffrum.

TLDR: An investigation of the South African tree Combretum caffrum (Combretaceae) for antineoplastic constituents was conducted by employing the astrocytoma bioassay (9ASK) and a substance designated combretastatin was isolated and found to display significant astroCyte reversal and murine P-388 lymphocytic leukemia cell growth inhibition.

Abstract: An investigation of the South African tree Combretum caffrum (Combretaceae) for antineoplastic constituents was conducted by employing the astrocytoma bioassay (9ASK). By this approach and a combination of solvent partition, steric exclusion, and adsorption chromatographic procedures, a substance designated combretastatin [1a] was isolated and found to display significant (71-90% astrocyte reversal at 1-100 micrograms/ml dose levels) astrocyte reversal and murine P-388 lymphocytic leukemia (PS) cell growth inhibition (ED50 0.011 micrograms/ml). The structure of (-)-combretastatin was elucidated by X-ray crystal structure analysis and confirmed by total synthesis. The absolute configuration at C-10 was assigned the R-configuration on the basis of Horeau esterification techniques. Other prominent, albeit PS-inactive, constituents were found to be 3,3',4'-tri-O-methylellagic acid [2] and acacetin [3].