Ultrasound-assisted extraction of polyphenols from Thymus serpyllum and its antioxidant activity

Abstract

The present study was designed to establish and optimize a method for extracting natural bioactive compounds from Thymus serpyllum which possess antioxidant, antimicrobial, antispasmodic and stimulant properties. Ultrasound-assisted extraction (UAE) is a welle-stablished method in the processing of plant material, particularly for extraction of bioactive substances such as polyphenols. The influential factors including extraction time (3, 7 and 10 min), solid:solvent ratio (1:10, 1:20 and 1:30) and particle size (0.3, 0.7 and 1.5 mm), have been studied to optimize the extraction process, while using 30% ethanol as an extraction medium and amplitude set to 65%. The yield of UAE was expressed via total phenol content and antioxidant activity of the obtained extracts. The optimum process parameters were found to be: extraction time, 3 min; solid:solvent ratio, 1:30; particle size, 0.3 mm. Under these conditions, the yield of total polyphenols was raised up to 23.03 mg/L GA and the highest antioxidant activity was recorded (10.32 mmol/mg Trolox and IC50 of 3.00 mg/ml).