Optimization of ultrasound-assisted extraction of okra (Abelmoschus esculentus (L.) Moench) polysaccharides based on response surface methodology and antioxidant activity.

This study determined the optimal conditions for ultrasound-assisted extraction of a water-soluble polysaccharide, Raw Okra Polysaccharide, from the fruit of okra using response surface methodology. The optimal extraction temperature, extraction time and ultrasonic power were 59°C, 30min and 522W, respectively, giving a yield of 10.35±0.11%. ROP was further isolated, lyophilized and purified using a DEAE-Sepharose Fast Flow column and Sepharose CL-6B column, revealing three elution peaks subsequently designated ROP -1, -2, and -3, respectively. Of these, ROP-2 showed the highest yield, and was therefore selected for physicochemical analysis and evaluation of antioxidant activity. Gas chromatography, fourier transform infrared spectroscopy, and high-performance liquid chromatography were used to characterize the primary structural features and molecular weight, revealing that ROP-2 is composed of glucose, mannose, galactose, arabinose, xylose, fructose, and rhamnose (molar percentages: 28.8, 12.5, 13.1, 15.9, 9.2, 13.7, and 6.8%, respectively) and has an average molecular weight of 1.92×105Da. A superoxide radical scavenging assay and DPPH radical scavenging assay further revealed the significant in vitro antioxidant activity of ROP-2. These findings present an effective technique for extraction of the natural antioxidant ROP-2, warranting further analysis of its potential application in the food industry.