Potentials of Plant Products as Anticancer Agents

Cancer has remained a major health concern. Advances in existing therapeutic modalities have failed to provide cure, prevent a relapse and are always accompanied by serious and often times debilitating side effects. Extensive screening of plants for anticancer activity has produced some encouraging and impressive results. More than 40,000 plant species have reportedly been screened for anticancer effects. Some of such plants include - Podophyllum hexandrum, Podophyllum petatum, Catharanthus rosea, Taxus brevifolia, Taxus baccata, Camptotheca accuminata etc. Anticancer principles from plants include among others, alkaloids of Vinca rosea (Vinblastine and Vincristine), Ocheosia elliptica (ellipticine and a - methoxyellipticine), toxin of Ipomea batatas and ricin from Ricinus communis . Mechanisms proposed to underlie the anticancer effect of these plants include mitotic arrest in the S, G, and metaphase phases, inhibition of normal mitotic spindle formation, inhibition of microtubule depolymerization and topoisomerase inhibition. Some of these plants/principles are already in use while some are in the clinical trial stages of drug development. Active plant principle can also provide templates upon which synthetic and semi-synthetic derivatives can be produced such as the active analogue of Camptothecin: 9-aminocamptothecin, topotecan and irinotecan. The success recorded from the relatively small number of plant species so far screened out of an estimated plant population of half a million worldwide indicate the enormous therapeutic potential inherent in natural endowments of plant origin. With more than 90% of the plant population still unexploited, plants definitely hold hope for the discovery of potent anticancer agents with minimal side effects/toxicity profile and capable of preventing a relapse.