Ultrasonic Extraction, Antioxidant and Anti-glycation Activities of Polysaccharides from Gynura Divaricata Leaves

To date, there are numerous studies on Gynura divaricata mainly focused on isolation and biological activities of small chemical compounds such as polyphenols. Only few attentions have been paid on polysaccharides from G. divaricata leaves regarding the extraction, structural characterization and biological functions. Therefore, in this study, ultrasonic extraction, an efficient technique compared to the conventional methods, was applied via response surface methodology to determine the optimum conditions, which maximized the yield of G. divaricata polysaccharides (GDP). Moreover, its physico-chemical and biological properties including in vitro-antioxidant and anti-glycation activities were investigated. The GDP yield under the optimal condition (148 W ultrasonic power, 15 min extraction time and 18.5 ml/g ratio of water to raw material) was found to be 6.45% +/- 0.13, which was very close to the value predicted by the mathematical model. The primary characterization using various physico-chemical approaches revealed that GDP is a polysaccharide mainly composed of uronic acid (57.38%) and neutral sugars (40.94%) with molecular weight approximately of 960 kDa. In addition, GDP exhibited remarkable metal chelating antioxidant up to 30% of activity at 60 mg/100 ml and anti-glycation capacity reached 90% at 100 mg/100 ml. Ultrasound-assisted extraction was found to positively affect the GDP yield. The GDP exhibited highly potent antioxidant and anti-glycation properties which could be explored as a novel natural antioxidant and natural glycation inhibitor for food, pharmaceutical and cosmetics industries.