Antitumor Potential of the Isoflavonoids (+)- and (−)-2,3,9-Trimethoxypterocarpan: Mechanism-of-Action Studies

Synthetically derived samples of (+)-(6a S ,11a S )-2,3,9-trimethoxypterocarpan [(+)- 1 ] and its enantiomer [(−)- 1 ], both of which are examples of naturally occurring isoflavonoids, were evaluated, together with the corresponding racemate, as cytotoxic agents against the HL-60, HCT-116, OVCAR-8, and SF-295 tumor cell lines. As a result it was established that compound (+)- 1 was particularly active with OVCAR-8 cells being the most sensitive and responding in a dose-dependent manner. A study of cell viability and drug-induced morphological changes revealed the compound causes cell death through a mechanism characteristic of apoptosis. Finally, a computational study of the interactions of compound (+)- 1 and ( S )-monastrol, an established, synthetically derived, potent, and cell-permeant inhibitor of mitosis, with the kinesin-type protein Eg5 revealed that both bind to this receptor in a similar manner. Significantly, compound (+)- 1 binds with greater affinity, an effect attributed to the presence of the associated methoxy groups.