Influence of solvents and techniques for extraction of phenolic phytochemicals linked with antioxidant and enzyme inhibition potential of Ocimum tenuiflorum Linn

Ocimum tenuiflorum Linn. (Synonym: O. sanctum; Common name: Krishna Tulsi; Purple Basil) is a household herb of India which is traditionally revered for its diverse medicinal properties. The therapeutic properties of this plant have been linked to its array of polyphenolic repository. Thus, the current study was designed to optimize the suitable solvent and extraction technique for maximum recovery of the polyphenols from this herb, to achieve maximum therapeutic benefits linked with its antioxidant and enzyme inhibition properties. Dried aerial parts of the plant were powdered and extracted repeatedly 3 times with different solvents (methanol, 95% methanol, ethanol, 95% ethanol, ethyl-acetate and acetone) at ambient temperature. Different extraction techniques like cold maceration, soxhlet extraction, heat reflux, microwave assisted extraction, ultrasonic assisted extraction and ultrasonic assisted ionic liquid-based extraction were also performed. Variation in the extractive yield, recovery of the total polyphenol, total flavonoid, total tannin and total anthocyanin content in these extracts were estimated along with antioxidant (DPPH, ABTS, FRAP, PMD) and enzyme inhibition (α-glucosidase and pancreatic lipase) properties. Maximum yield of crude extract (23.5%) was obtained with 95% methanol with highest content of phenolic phytochemicals which also exhibited superior antioxidant and enzyme inhibition capacity. Whereas, cold maceration was found to be the best technique to recover maximum polyphenolic compounds with highest in-vitro bioactivities. Thus, it can be concluded that hydro-methanolic solvent and cold maceration technique can be used for the extraction of O. tenuiflorum L. as it yielded maximum polyphenolic phytochemicals and best therapeutics properties.