Effects of Microwave-Assisted Extraction Parameters on the Recovery Yield and Total Phenolic Content of Vernonia amygdalina Leaf Extracts with Different Methods of Drying

vernonia amygdalina leaf has a significant importance in food and traditional medicine. it has been reported to possess various pharmacological effects. this study was carried out to investigate the influence of microwave-assisted extraction factors on the extraction from v. amygdalina leaves. the results highlighted that an increase in temperature deteriorated the yields of v. amygdalina leaf. thus, shade-dried samples gave the highest yields at the irradiation times of 10 and 2 min, microwave power of 500 and 600 w, the temperature of 100 and 80°c, the feed-to-solvent ratio of 1:10, and ethanol concentration of 60% v/v using water and ethanol as the extracting solvents, respectively. likewise, the antioxidant assay resulted in ic50 values of 260±1.1 µg/ml dpph and 149.78± 0.81µg/ml abts for water and 204±0.92µg/ml dpph and 31.17±1.4µg/ml abts for ethanol. therefore, the synergistic mechanism of mass and heat transfer may be accounted for the accelerated extraction due to microwave energy.