Optimisation of microwave-assisted extraction parameters for antioxidants from waste Achillea millefolium dust

Abstract

Microwave-assisted extraction of polyphenols and flavonoids from waste Achillea millefolium (yarrow) dust was optimised using the response surface methodology. The influence of the extraction time (13–47s), ethanol concentration (53–87%), liquid/solid ratio (13–47mL/g) and microwave power (170 and 340W) was studied. The optimised conditions for the maximal recovery of polyphenols and flavonoids were as follows: 33s of extraction time, 70% of ethanol concentration, 40mL/g of liquid/solid ratio and 170W of microwave power. Under the optimal conditions, 237.74±2.08mg of gallic acid equivalents per g of extract dry matter of total polyphenols, and 42.95±1.32mg of quercetin equivalents per g of extract dry matter of total flavonoids were extracted. The optimal extract strongly reduced the diphenylpicrylhydrazyl radical (IC50 7.89μg/mL). The antioxidant activity of the obtained extracts was in correlation to the total polyphenol content in yarrow extracts. Compared to the conventional extractions (solid–liquid extraction (24h) and maceration (48h)) microwave-assisted extraction yielded extracts with higher polyphenol and flavonoid content and higher antioxidant activity in very short time (33s).