Study of the effects of cadmium and nickel on the pattern of alkaloid production in Catharanthus roseus (L.) G. Don

Tropical plant، Catharanthus roseus contains worthy alkaloids such as vinblastine and ajmalicine. Since amount and pattern of alkaloid production could be affected by different environmental conditions، the effect of two elements of cadmium and nickel were investigated. Plants in the greenhouse conditions using a chemically inert substrate were cultivated and in a complete randomized block design were treated by different concentrations of cadmium and nickel until appearance of toxicity symptoms. The concentrations of cadmium and nickel، chlorophyll and total alkaloids of the leaves were measured. The patterns of alkaloids were determined by thin layer chromatography using of UV light and specific reagents of ceric ammonium sulfate and dragendorff. The results showed that toxicity symptoms of cadmium occurred at 10 µM or more and 50 µM or more for nickel which was accompanied with a decrease in chlorophyllconcentration and intervein chlorosis. By increase the concentration of metals، both the concentrations of metals and alkaloids increased in leaves but the concentrations of alkaloids decreased at very high concentration of cadmium. The chromatographic pattern of alkaloids was changed too. Treatment by cadmium and nickel caused appearance or intensified the bands of alkaloids with medium RF such as vincolidine or low RF such as serpentine. Indeed، cadmium and nickel by increase of the ample alkaloids، increase of the accumulation of rare alkaloids and increase in the ratio of alkaloid content to biomass، caused an increase to the total alkaloids.