Ultrasonic-assisted extraction optimization of the flavonoid compounds from Vernonia amygdalina Del. leaves using response surface method.

Vernonia amygdalina Del. leaves have been used empirically in the alternative therapies of several diseases. The leaves have potential for cancer treatment, antiplasmodial, antimicrobial, anti-inflammatory, antioxidant, antidiabetic, anthelmintic and as an alternative medicine for Covid-19. Extraction with ultrasound assisted (UAE) was developed for extraction effectiveness in providing high yield, activity of antioxidant (as DPPH scavenging activity) and the flavonoid content (TFC), and it has been maximized by the Box-Behnken design (BBD) of the response surface method. Extraction process conditions were varied: ethanol concentration (0 to 100 %v), feed-solvent ratio (1:10 to1:50 g /mL), processing time (20 to 60 min), processing temperature (30 to 80 °C) and stirring speed (8,000 to 30,000 rpm). The results found that the best extraction process conditions were obtained at 50 %v ethanol concentration, feed-solvent ratio 1:40 g/mL, time of extraction 30 minutes, the temperature of 70°C, and stirring speed of 30,000 rpm. The effect of three variables (ethanol concentration-A; time -B; and temperature -C) was optimized, and the quadratic model significantly complemented the experimental data with R2 values of 0.9086; 0.9770 and 0.9535 (extract yield, antioxidant activity and TFC). Optimal conditions were obtained at a solvent concentration of 43.25%v, time of extraction 30.67 minutes, and the processing temperature of 69.42 °C, for the highest extract yield (20.66%w), compared with 10% yield for conventional extraction for similar operating condition. Furthermore, the extract produced antioxidant activity (86.93%) and TFC (66.03 mg QE/g d.w.). The study also showed that UAE optimization using BBD predicts favorable conditions for extracting the flavonoid content of Vernonia amygdalina Del. leaves. [ABSTRACT FROM AUTHOR]