Extraction optimization, characterization and antioxidant activity in vitro of polysaccharides from mulberry (Morus alba L.) leaves

Extraction optimization, characterization and antioxidant activity in vitro of polysaccharides from mulberry leaves (MLP) were investigated in the present study. The optimal extraction conditions with an extraction yield of 10.0 ± 0.5% for MLP were determined as follows: extraction temperature 92 °C, extraction time 3.5 h and ratio (v/w, mL/g) of extraction solvent (water) to raw material 34. Two purified fractions, MLP-3a and MLP-3b with molecular weights of 80.99 and 3.64 kDa, respectively, were obtained from crude MLP by chromatography of DEAE-Cellulose 52 and Sephadex G-100. Fourier transform-infrared spectroscopy revealed that crude MLP, MLP-3a and MLP-3b were acidic polysaccharides. Furthermore, crude MLP and MLP-3a had more complicated monosaccharide compositions, while MLP-3b had a relatively higher content of uronic acid. Crude MLP, MLP-3a and MLP-3b exhibited potent Fe2+ chelating power and scavenging activities on 1,1-diphenyl-2-picrylhydrazyl, hydroxyl, superoxide and 2,2′-azinobis-(3-ethyl-benzothiazolin-6-sulfonic acid) radicals. The results suggested that MLP could be explored as natural antioxidant.