Effect of heavy metal elicitation on antioxidants and andrographolide content in cell suspension cultures of Andrographis paniculata

Andrographolide, a bicyclic diterpene from Andrographis paniculata is of immense pharmaceutical importance. A. paniculata, an annual herb from Acanthaceae is widespread in the Indian subcontinent. Heavy metals act as abiotic elicitors. The study deals with the effect of mercury (Hg), cadmium (Cd) and arsenic (As) on andrographolide content, phenols and flavonoids and each of their correlation with the metal chelating and radical scavenging activity, in cell suspension cultures of A. paniculata. Andrographolide was estimated using HPLC, while other estimation methods were used for other metabolites. Four different concentrations of each of the heavy metal salts CdCl2, As2O3 and HgCl2, were administered in liquid MS media containing 1 g of cells. Media without any metal served as control. Higher concentrations of Cd and As imparted a positive effect on andrographolide content, Hg imparted a negative effect. The cells were most sensitive to Hg and most tolerant to Cd. Cd could be the best choice as an elicitor for increased production of andrographolide. While phenols show a positive correlation with antioxidants, flavonoids and andrographolides do not show a positive correlation with antioxidants.