Camptothecin and 10-hydroxycamptothecin accumulation in tender leaves of Camptotheca acuminata saplings after treatment with plant growth regulators

The effect of plant growth regulators (PGRs) on the accumulation of the alkaloid camptothecin (CPT) and its analogue 10-hydroxycamptothecin (HCPT) in tender leaves of Camptotheca acuminata saplings was studied. In screening experiments for PGRs, 40?mg/L dose of thiourea, triacontanol, and ascorbic acid (V_C) had no positive effects on the accumulation of the alkaloids. However, treatments with 40?mg/L of chlormequat chloride (CCC), choline chloride, paclobutrazol (PBZ), and daminozide (B₉) induced CPT and HCPT accumulation in both pre-harvest and postharvest stages. On that basis, five levels of PGRs at 0, 20, 40, 60, 80?mg/L were sprayed on tender leaves of C. acuminata saplings at pre-harvest and postharvest stages. Treatment by 40?mg/L CCC dramatically enhanced HCPT production by 308?% in pre-harvest, treatment by 60?mg/L CCC enhanced HCPT production by 100?% in postharvest. Spraying the leaves with 60?mg/L choline chloride resulted in 94?% increase of CPT and spraying with 40?mg/L of the PGRs reached 167?% increase of HCPT in the pre-harvest treatment, respectively; treatments with 60?mg/L choline chloride resulted in 64?% increase of CPT and 525?% increase of HCPT in postharvest, respectively. 52?% increase of CPT and 86?% increase of HCPT in pre-harvest, 22?% increase of CPT and 33?% increase of HCPT in postharvest were obtained by spraying leaves with 60?mg/L PBZ. Treatments with 40?mg/L B₉ had the highest impact on CPT (12?% increase in pre-harvest, 11?% increase in postharvest) and HCPT (167?% increase in pre-harvest, 173?% increase in postharvest) accumulation. The optimal PGR for obtaining the highest levels of CPT and HCPT was treatment with 60?mg/L choline chloride. In most case, the pre-harvest treatment was better than the postharvest one. These preliminary results suggest that the application of PGRs may be a useful and feasible method to increase CPT and HCPT levels in C. acuminata.