Ethanolic extraction of flavonoids, phenolics and antioxidants from Vernonia amygdalina leaf using two-level factorial design

Vernonia amygdalina leaves are mostly consumed in Asia and Africa, due to its potential as a good source of antioxidants. In this study, a two-level factorial design was used to evaluate the significant extraction parameters in achieving higher recovery yield of extract, total phenolic content, total flavonoid content, and antioxidants from Vernonia amygdalina leaf. Microwave-assisted extraction technique was employed using aqueous ethanol. The independent parameters were irradiation time (1–5 min), microwave power level (500–700 W), temperature (60–80 °C), feed-to-solvent ratio (1:8–1:12 g/ml), and ethanol concentration (40–80%). Amongst the examined parameters, ethanol concentration, irradiation time, microwave power level, and feed-to-solvent ratio were significant (p < 0.05), whereas, extraction temperature was insignificant. Therefore, the recovery yield of extract, total phenolic content, total flavonoid content, and antioxidants from the ethanolic extraction of Vernonia amygdalina leaf using MAE technique are significantly affected by ethanol concentration, irradiation time, microwave power and feed-to-solvent ratio.