A BIOASSAY APPROACH TO COMPLEMENT CHEMICAL STANDARDIZATION OF ASHWAGANDHA ROOT EXTRACTS

Abstract

Withania somnifera (L.) Dunal, popularly known as ashwagandha, is an Indian plant that has long been utilized in Ayurveda for its adaptogenic effects, as evidenced by several clinical and preclinical research publications. Using an in-vitro acetylcholinesterase inhibition assay (AChE), we performed bioassay-guided fractionation of the ethanolic extract of ashwagandha roots. The inhibitory activity was found to be concentrated in the fractions containing withanolides, and the active fractions were purified to yield nine distinct withanolides. Five of these had a considerable inhibitory effect against acetylcholinesterase (IC50 <10 µg/ml), with 12-deoxywithastramonolide being the most active (IC50-1.54 µg/ml). Ashwagandha extracts are typically standardized to the content of withanolides by chromatographic methods like HPLC. We evaluated if acetylcholinesterase inhibition assay can be utilized for biological standardization of commercial batches that can complement the current chromatographic methods. Nine different commercially produced batches of Ashwagandha extracts were evaluated with acetylcholinesterase inhibition in-vitro, HPLC profiling, and quantitative determination of nine withanolides. The IC50 values ranged from 15 µg/ml to 95 µg/ml, while the total content of nine withanolides varied between 2.78%w/w to 3.58%w/w. Given the inherent variability in withanolide content, an acetylcholinesterase inhibition assay can be utilized to enhance quality control of commercially available ashwagandha extracts.