Microwave extraction optimization using the response surface methodology of Fructus Meliae Toosendan polysaccharides and its antioxidant activity

Polysaccharides are the main active component of the Mongolian medicine Fructus Meliae Toosendan, but their effective extraction and antioxidant effects have not been reported. Therefore, the optimization of the microwave extraction of polysaccharides from Fructus Meliae Toosendan (FMTP) using the response interface method was carried out. Single-factor tests on four main factors (the solid-liquid ratio, microwave power, extraction time, and number of extractions) affecting the polysaccharide extraction rate in the microwave extraction process were carried out. Then, using the FMTP content as a response index, central composite tests on the four factors were conducted, and an optimization analysis using the response surface method was completed. Consequently, we obtained the optimum conditions for FMTP microwave extraction: a solvent-material ratio of 30.00 mL/mg, extraction power of 700 W, extraction time of 20 min, and two extractions. The FMTP extraction rate was 15.75% at the optimum conditions, consistent with the theoretical predictions. The crude polysaccharide was further purified to obtain high-purity FMTP polysaccharide, having a weight-average molecular mass of 1288 Da. The antioxidant activities of FMTP were evaluated using the hydroxyl superoxide anion, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and nitrite free radical scavenging assays and reducing power assay. The data show that FMTP has considerable antioxidant activity. Thus, polysaccharides from Fructus Meliae Toosendan could be used as a potential antioxidant agent in medicine or as a functional food.