Utilization of sage by-products as raw material for antioxidants recovery-Ultrasound versus microwave-assisted extraction

In this work, sage (Salvia officinalis L.) by-products from filter tea factory, i.e. sage herbal dust, was valorized as raw material for extraction of phenolic antioxidants. Ultrasound-assisted (UAE) and microwave-assisted extraction (MAE) of polyphenols from sage herbal dust were separately optimized by simultaneous maximization of total phenols (TP) and total flavonoids (TF) yields. Box-Behnken experimental design and response surface methodology (RSM) was used for extraction optimization. In case of UAE, temperature (40, 60 and 80 °C), extraction time (40, 60 and 80 min) and ultrasonic power (24, 42 and 60 W/L) were independent variables, while optimized MAE parameters were ethanol concentration (40, 60 and 80%), extraction time (10, 20 and 30 min) and liquid to solid ratio (20, 30 and 40 mL/g). Antioxidant activity of sage extracts was determined by DPPH, FRAP and superoxide anion radical neutralization assays, and good correlation between polyphenols content and antioxidant activity was observed. According to results, it could be concluded that novel extraction techniques (UAE and MAE) provided significant advantages for recovery of sage polyphenols comparing to traditional methods.