Cell cycle modulatory and apoptotic effects of plant-derived anticancer drugs in clinical use or development

Drugs derived from natural products, particularly from plants, are the leads of clinically used anticancer agents. Plant-derived anticancer agents in clinical use consist of the Vinca alkaloids, vinblastine and vincristine, camptothecin derivatives, paclitaxel, etoposide and teniposide, homoharringtonine and elliptinium. Extensive research has led to the identification of promising plant-derived anticancer agents in clinical development, namely flavopiridol, combretastatins and roscovitine. These compounds share common antitumor activities and signaling pathways targeting tumor cell cycle and cell death. This review presents the discovery of plant-derived anticancer agents, their biologic activities, with emphasis on cell cycle and apoptotic effects and combination strategies for treatment optimization.