Abiotic elicitation of gymnemic acid in the suspension cultures of Gymnema sylvestre

Elicitation is one of the few strategies that find commercial application in the enhancement of secondary metabolite production from plants as well as cell culture systems. Due to their immense medicinal value, production of saponins in suspension cultures has been attempted by many researchers. Gymnema sylvestre is a rich source of gymnemic acids (saponins) that find application in the treatment of diabetes. The present study is an attempt to evaluate the effect of various metal salts (cadmium chloride, mercuric chloride, silver nitrate, cupric chloride, cobaltous chloride and calcium chloride) in eliciting the response from G. sylvestre suspension cultures. The maximum gymnemic acid production in the suspensions was achieved on day 12 of culture, though the maximum biomass was obtained on day 16. Among the different salts, CdCl₂ gave maximum response (59.97 mg/gDCW) at 2 mM concentration after a 24 h time period, while, AgNO₃ gave the least response (18.35 mg/gDCW) on incubation of 48 h at 1 mM concentration, in terms of gymnemic acid accumulation. The accumulation of gymnemic acid was found to be dependent on treatment time and concentration of the elicitor. The enhanced gymnemic acid production shown by the suspensions in response to the metal salts indicates their role in evoking the plant defense mechanisms. These elicitation studies help in providing a platform for improved commercial supply of bioactive gymnemic acids.