MICROWAVE-ASSISTED EXTRACTION OF POLYPHENOL-RICH EXTRACT AND EVALUATION OF DPPH RADICAL SCAVENGING ACTIVITY FROM LEAVES OF VITEX NEGUNDO L. (VERBENACEAE)

This research investigates the ultrasound-assisted extraction (UAE) of polyphenol-rich extracts from leaves of Vitex negundo L. (Verbenaceae) and evaluates their antioxidant activity. Dried leaf powder, cultivated in Ho Chi Minh City, Vietnam, was extracted using 60% ethanol under varying conditions of sample-to-solvent ratio, temperature, and time. Optimal extraction was achieved at a ratio of 1:10 (g/ml), 50°C, and 40 minutes, resulting in the highest total polyphenol (72.90 mg GAE/g) and flavonoid contents (179.94 mg QE/g). The final concentrated extract showed a moisture content of 4.90%, extraction yield of 27.94%, and retained 42.84 mg GAE/g of polyphenols and 165.67 mg QE/g of flavonoids. Antioxidant capacity was assessed via DPPH radical scavenging assay. The extract exhibited moderate activity with an IC₅₀ of 66.08 μg/ml, compared to 12.61 μg/ml for ascorbic acid and 4.48 μg/ml for BHA. The results demonstrate that V. negundo leaves are a promising source of natural antioxidants. UAE was shown to be an effective and green technique for enhancing extraction efficiency. These findings support the potential application of V. negundo leaf extract in functional foods and phytopharmaceuticals.