Impact of cadmium and nitric oxide on withanolides and elemental contents of the medicinal herb, Withania somnifera (L.) Dunal

The growth of Withania somnifera seedlings, exposed to 1.0 mM of cadmium chloride (CdCl₂) or 0.5 mM sodium nitroprusside [SNP, a nitric oxide (NO) donor], was adversely affected. However, a combined treatment of both did not have an additive negative effect on their growth. Rather, SNP slightly negated the adverse effect of Cd. The contents of withanolides, therapeutically important active principles of the plant, increased significantly in roots as well as shoots of seedlings treated with Cd or SNP. Both of these provided together for a shorter duration of five days had an additive effect on the withanolides’ contents in roots, a phenomenon not observed after a similar ten-day treatment. Withanolides’ content of shoots of the seedlings treated with SNP alone for ten days was markedly below that in shoots of the controls. The stress-ameliorative effect of SNP was evident by the reduced contents of all withanolides in roots and those of withaferin A, withastramonolide and withanone in shoots of seedlings receiving both Cd and SNP for ten or five days, respectively. The maximum accumulation of Cd in the seedlings exposed to this heavy metal was in roots, a phenomenon negated by SNP during the first five days of its application along with Cd. Both Cd as well as SNP differently affected the accumulation of other elements in roots and shoots. Some of the observed effects of Cd on their accumulations were partially negated by SNP.