Variation in camptothecin content in Camptotheca acuminata leaves

Variations in camptothecin (CPT) content in relation to leaf characteristics namely leaf area, leaf biomass, and specific leaf area (leaf area divided by leaf biomass), and the influence of climatic factors on CPT content in saplings of Camptotheca acuminata Decne. were studied. Leaf area and CPT content showed a logarithmic relationship in young leaves similar to that between leaf biomass and CPT content, while CPT content was linearly correlated to specific leaf area. There was no apparent relationship between each leaf characteristic and CPT content in old leaves. CPT contents in sapling leaves showed large variation from May to September and were highly correlated to the variation in the level of climatic factors, where high average temperature, high evaporation capacity and low precipitation increased CPT content according to stepwise regression analysis. This suggests that adverse growing conditions can induce CPT accumulation to enhance chemical defense in C. acuminata. Young leaves with area of 70 cm2-100 cm2 gave the highest quantity of CPT per leaf, thus the optimal harvest period would be when young leaves expanded to these sizes. In addition, sample collection on dry days is preferable as it increases CPT content in raw materials.