Enhancing production of pharmaceutically valuable alkaloids in plant cells, tissues and extracts of Catharanthus roseus
The important pharmaceutically valuable anticancer alkaloids, Vinblastine and Vincristine, are produced by Madagascar periwinkle plant called Catharanthus roseus (C. roseus). Given their cytotoxicity, these vinca alkaloids are produced in very minuscule quantities and are abundant in the aerial parts of the plant. For example, Vincristine has suffered from the disadvantage of very low yieldsin industrial production; one-tonne leavesfrom traditionally cultivated plants could produce 0.5 - 50g crude extract of Vincristine and yet its current world demand lies between 3 – 10kg per annum (Koul et al., 2013). The high cost of isolating pharmaceutical drugs has led to research efforts to increase the content of alkaloids in C. roseus seedlings, cell and tissue cultures. In the present study, enhancing production levels of the four pharmaceutically valuable alkaloids of C.roseus, namely: Vincristine, Vinblastine, Ajmalicine and Vindoline was investigated in vitro, in callus differentiation through somatic embryogenesis, cell suspension cultures through elicitation, as well as ex-vitro in highly differentiated hairy roots derived from seedlings inoculated with Agrobacterium rhizogenes. There was a significant eight-fold percentage recovery of Vinblastine in the second stage of somatic embryogenesis when compared to percentage recovery in the wild type plants. The other stage 3 of somatic embryogenesis which was the unsuccessful plant conversion stage of development exhibited a significant four-fold low level of Vinblastine relative to that in the maturation stage but two-fold higher with that of wild type plant. The ex vitro generated hairy roots exhibited a 6.5-fold percentage recovery of Ajmalicine levels when compared to the wild type plant, while the other compounds could not be detected in the roots. This exhibited the importance of light or sunlight in order for plants to synthesize Vindoline, and consequently, the absence of Vindoline would mean that the plant hairy roots could not synthesize Vinblastine and Vincristine