Optimization of Ultrasound/Microwave-assisted Extraction of Polysaccharides from Hibiscus sabdariffa L. by Box-Behnken Response Surface Methodology

The extraction of polysaccharides from Hibiscus sabdariffa L. utilizing both ultrasound and microwave was optimized by Box-Behnken response surface methodology. For the single factor experiment the independent variables were the solvent-substrate ratio, extraction time and microwave power applied for the process. The resulting polysaccharides yields were compared among the various processes including the water, microwave-assisted, ultrasound-assisted, and ultrasonic/microwave-assisted extractions. The combination of ultrasonic and microwave was found to improve the efficiency and time-saving for the process. It was, therefore, further optimized using the Box-Behnken response surface method to finalize the extraction that required a solvent-substrate ratio of 20:1 (mL:g), an extraction duration of 15min, and a combined application of 150 W microwave power and 240 W ultrasound to reach a 3.51% polysaccharide yield from H. sabdariffa.