Novel method to isolate Withaferin A from Withania somnifera roots and its bioactivity

Withania somnifera is Ayurvedic medicine to treat depression and inflammation. It contains many phytochemicals (withaferin A, withanine, withanolides, and tropine), however, withaferin A is most active. It was extracted from W. somnifera roots with ethanol and the alcoholic extract was re-extracted in sequence with different solvents (hexane, ether, chloroform, ethyl acetate, and methanol). Each solvent extract was divided into two halves. One kept under room temperature (30±2°C) and the other under low temperature (4±2°C). High yield of crystalline withaferin A was obtained in ether extract at 4±2°C than at room temperature. Withaferin A was tested for antibacterial and antifungal activity at different concentrations. It showed strong activity against Bacillus subtilis at all test concentrations and moderate activity against Escherichia coli and Staphylococcus aureus. It showed similar antifungal activity as ketoconazole against the Aspergillus niger at 200 μg mL⁻¹. This method is inexpensive and appropriate to isolate withaferin A from W. somnifera root.