Ultrasonic extraction of total phenolics, total flavonoids, and antioxidant activities from Gymnema sylvestre

The study on ultrasonic extraction conditions aims to improve the yield of total phenolic content, total flavonoid content, and antioxidant activity from the leaves of Gymnema sylvestre by response surface methodology (RSM). The experimental arrangement according to the Box - Benhken method, the optimal extraction conditions were established for total phenolic content (Y1, %), total flavonoid content (Y2, %), and antioxidant activity (Y3, %), with four factors, are extraction temperature (X1) ultrasonic time (X2) concentration of ethanol solvent (X3), and ultrasonic power (X4). According to the model, the optimal conditions for ultrasonic extraction to obtain the highest content of biologically active compounds are extraction temperature of 62oC, ultrasonic time of 50 minutes, solvent concentration of 55%, and ultrasonic power is 300 W. Under this condition, the total phenolic content was 21.2±0.5 mg GAE/g, the total flavonoid content was 8.2±0.15 mg CE/g, and the highest antioxidant activity was 72.5±0.5%.