Growth stage‑specific Accumulation of Cardiac Glycosides in Two Variants of Calotropis gigantea (L.) W.T. Aiton

Background: Calotropis gigantea (L.) W.T. Aiton, belonging to the family Apocynaceae, is a source of many bioactive cardiac glycosides. Accumulation of secondary metabolites in plants depends upon various external and internal factors, including the plant age or growth stage. Objectives: The main aim of this study was to identify the correct variant and growth stage of C. gigantea for the maximum yield of targeted metabolites. Materials and Methods: In the present experiment, three different tissues, that is, leaf, stem, and root, of 3–12‑month‑old white flower variant (WFV) and purple flower variant (PFV) of C. gigantea were investigated to find out the growth stage‑specific accumulation pattern of five cardiac glycosides (CGs) and their three genins. Results: Highest concentrations of calotropin, uscharin, and uscharidin were found in the stem of five‑month‑old WFV. Frugoside and uzarigenin were at peak levels in the stem of a nine‑month‑old member of the same variant. Calotropagenin and coroglaucigenin were at maximum levels in the root and leaf of 8‑ and 10‑month‑old members, respectively, of this variant too. The only CG accumulated at maximum level in the root of 11-month-old PFV was asclepin and its quantity was comparable to 8‑month‑old WFV root. Conclusion: It was observed that the WFV was superior to PFV, considering the accumulation of most of the CGs. Therefore, it can be concluded that the specific tissues of 5–10‑month‑old members of WFV are optimum for an economic yield of respective CGs.