Extraction Optimization for Phenolic- and Withanolide-Rich Fractions from Withania somnifera Roots: Identification and Quantification of Withaferin A, 12-Deoxywithastromonolide, and Withanolide A in Plant Materials and Marketed Formulations Using a Reversed-Phase HPLC-Photodiode Array Detection Method

摘要

Background: Both the roots and leaves of Withania somnifera are products of commerce. They contain active compounds of therapeutic value and mostly different withanolides. Several pharmacological activities of W. somnifera have links to one or more withanolides. The presence of phenolic compounds in extracts could play a vital role in the reduction of blood glucose levels in diabetic subjects. Objective: The present study was carried out for the selection of a solvent to prepare extracts rich in phenolics, withaferin A (WA), 12-deoxywithastromonolide (12WD), and withanolide A (WDA). A simple, rapid HPLC method was also developed for the identification and quantification of WA, 12WD, and WDA. Methods: The extraction efficiency of aqueous alcoholic solvents including hexane, chloroform, ethyl acetate, and methanol were compared for three selected withanolides and total phenolic content. The contents of WA, 12WD, and WDA and total phenolics were determined in the extracts. The quality of nine formulations containing W. sominfera were also compared in terms of the content of WA, 12WD, and WDA and total phenolics. Results: The maximum extract yield and the total withanolide and phenolic content were obtained from aqueous alcoholic compositions at 50:50 (v/v), 70:30 (v/v), and 100:0 (v/v), respectively. In the case of organic solvents, chloroform and ethyl acetate yielded the highest concentrations of phenolics and three withanolides, respectively. The total phenolic content in formulations was in the range of 1.84-3.13%, and total withanolide content showed wide variability. Conclusions: The outcome of the present investigation could be utilized for the selection of extraction solvents to prepare W. somnifera enriched extracts and their quality monitoring by using the developed and validated HPLC-Photodiode array detection method. Highlights: A process for preparation of phenolics and withanolides (withaferin A, 12-deoxywithastramonolide and withanolide A) enriched extracts of Withania somnifera. Simple and rapid HPLC method was also developed and validated as per the ICH guidelines for identification and quantification of three major withanolides. The developed HPLC method was applied to analyze the quality of extracts and marketed herbal products (mono, as well as poly constituents). Optimized extraction process could be utilized for upscaling process development in preparation of enriched extracts from Withania somnifera, crop improvement, bio-prospection studies and quality control.