Secondary Metabolites of Medicinal Plants. Bharat Singh

and its analogue 10-hydroxycamptothecin in the tender leaves of C. acuminata saplings was studied. In screening experiments for plant growth regulators, thiourea, triacontanol, and ascorbic acid had no positive effects on the accumulation of the alkaloids. However, treatments with 40 chlormequat chloride, choline chloride, paclobutrazol, and daminozide (B₉) induced camptothecin and 10-hydroxycamptothecin accumulation in both preharvest and postharvest stages. Various concentrations of growth hormones were sprayed on tender leaves of C. acuminata saplings at preharvest and postharvest stages (Liu and Adams 1998). Treatment of chlormequat chloride dramatically enhanced 10-hydroxycamptothecin production by 308% in preharvest and by 100% in postharvest. In the preharvest treatment, spraying the leaves with choline chloride resulted in 94% increase of camptothecin, and spraying with growth hormones reached 167% increase of 10-hydroxycamptothecin; treatments with choline chloride resulted in maximum increase of camptothecin and 10-hydroxycamptothecin in postharvest. Treatments with daminozide had the highest impact on camptothecin and 10-hydroxycamptothecin accumulation. The optimal concentration of growth hormones for obtaining the highest levels of camptothecin and 10-hydroxycamptothecin was determined. In most cases, the preharvest treatment was better than the postharvest one. These preliminary results suggest that the application of plant growth regulators may be a useful and feasible method to increase camptothecin and 10-hydroxycamptothecin levels in C. acuminata (Zeng et al. 2012).

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