Isolation and Characterization of Antioxidant Compounds from Withania somnifera

The study focused on isolating and characterising antioxidant compounds of the medicinal plant Withania somnifera, which has been used in traditional Indian medicine as an adaptogen and therapeutic agent. Soxhlet extraction was used to obtain methanolic extracts, and the obtained crude extract was then subjected to column chromatography, which gave four fractions (F1-F4). The antioxidant potential of these fractions was determined using three common in vitro tests —DPPH, ABTS, and FRAP — to fully assess their free radical scavenging and reducing capacities. F4 was the most active fraction (125 mg of antioxidant activity per 50 g of plant material) and showed the most potent antioxidant activity in all assays, showing a higher content of bioactive components. UV-Vis spectroscopy, FTIR, and NMR were applied to further characterise the chemical profiles of the isolated compounds by the confirmation of the characteristic functional groups of antioxidant activity, hydroxyl, carbonyl, and aromatic rings, and structural characteristics typical of withanolides and flavonoid derivatives. One-way ANOVA statistical analysis showed that there was a significant difference in the antioxidant efficacy of the fractions (p < 0.05), and the Tukey HSD post hoc test further confirmed that the fraction F4 was the most active. These results indicate the utility of chromatographic isolation and spectroscopic analysis in the determination of the potent antioxidant-rich fraction, and the potential of W. Withania somnifera as a good source of natural antioxidants with pharmaceutical and nutraceutical uses.