Context: The content of withanolides in the roots of Withania somnifera (L.) Dunal (Solanaceae) is important for therapeutic application. Earlier studies have shown that the deficiency of macro- and micronutrients affects the growth of W. somnifera. Therefore, we examined the effect of these deficiencies on the withanolides content of the roots.
Objective: To examine the effect of molybdenum accretion in nitrogen-, phosphorus-, calcium- and potassium-deficient soils on the accumulation of withanolides in the roots of W. somnifera. Different withanolides have different therapeutic applications hence major bioactive withanolides assume importance.
Materials and methods: Methanol extracts of the roots were subjected to HPTLC and individual withanolides were identified by comparing their Rf values with those of the authentic samples. Molybdenum was quantified by atomic absorption spectroscopy. Free radical scavenging activity was monitored by the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay.
Results: Molybdenum content in roots of nitrogen-, phosphorus-, calcium-, potassium-deficient, and control plants were 7.02 ± 2.1, 13.1 ± 1.6, 17.1 ± 0.9, 33.5 ± 3.3, and 33.9 ± 1.6 ppm, respectively. Levels of withaferine A increased with the increase in the Mo content in roots from 7.79 ± 2.2 mg/g to 12.57 ± 3.4 mg/g. Antioxidant activity of nitrogen-deficient plants was the lowest (24.7 ± 2.2%) compared to other groups.
Discussion and conclusion: It was observed that nitrogen metabolism-dependent molybdenum uptake influences the withanolides accumulation in the roots.
Keywords: Deoxywithastramonolide; HPTLC; withaferine A; withanoside V.