Optimization of ultrasound-assisted extraction of Helicteres hirsuta Lour. for enhanced total phenolic compound and antioxidant yield

Using response surface methodology, this study aimed to optimize five different ultrasound extraction parameters; including ultrasonic temperature, ultrasonic time, ultrasonic power, sample-to-solvent ratio and methanol concentration, for maximal extraction of bioactive compounds and antioxidant capacity from Helicteres hirsuta Lour. (H. hirsuta), which has been used as a traditional medicine for malaria and diabetes treatment. Results showed that either ultrasonic temperature or sample-to-solvent ratio had a greater influence on extraction efficiency of total phenolics, flavonoids and antioxidant capacity than that of methanol concentration. Optimal extraction conditions were determined to be ultrasonic temperature of 60 °C, ultrasonic time of 25 min, ultrasonic power of 150W, sample-to-solvent ratio of 3:100 g/mL, and a solvent composition of 40% (v/v) aqueous methanol. Under these conditions, 15.97 mg GAE/g of phenolics, 16.42 mg CE/g of flavonoids, and 13.34 g/100 g of extractable solids were obtained. The highest values for DPPH, ABTS and FRAP assays were also obtained under these conditions, with the exception of CUPRAC (88% maximum value). These optimal extraction conditions can be applied to prepare powdered crude extract for further isolation and purification of individual bioactive compounds for potential use in the pharmaceutical industry.