POLYSACCHARIDES FROM MULBERRY LEAF IN RELATION TO THEIR ANTIOXIDANT ACTIVITY AND ANTIBACTERIAL ABILITY

ABSTRACT Polysaccharides play important roles in physiological and pathological effects. Experiments were conducted to compare various methods of polysaccharides extracted from a mulberry leaf using the orthotropic test, and then to determine the optimum extraction conditions. The antioxidant activity and antibacterial ability of mulberry polysaccharides were also evaluated. In this study, the optimum extraction conditions of mulberry polysaccharides were determined to be a ratio of mulberry leaf to water solution of 1:40 (w/v) for 1 h at 80C. Under these optimum conditions, a polysaccharide yield (11.3%) was obtained. Furthermore, the most effective enzymatic removal of proteins from mulberry polysaccharides was achieved using 2.5% protease for a 2.5‐h reaction at 40C, with 73.2% of the protein removal proportion and 86.4% of the polysaccharide proportion, while application of active carbon was the best treatment to remove pigments present in mulberry polysaccharides, with 81.4% of the pigment removal proportion and 71.7% of the polysaccharide proportion. In addition, the antioxidant activity and bactericidal ability of mulberry polysaccharides were evaluated. This study indicated that mulberry polysaccharides exhibited an obvious antioxidant activity in a dose‐dependent manner and distinct antibacterial ability. PRACTICAL APPLICATIONS There is increasing interest of utilizing polysaccharides from plant sources for their bioactive activities. As extraction conditions greatly influence polysaccharide yield and quality, great attention has been paid to the efficient extraction of polysaccharides from mulberry leaf. In this study, the optimum extraction conditions of polysaccharides from mulberry leaf were obtained using a ratio of mulberry leaf to water solution of 1:40 (w/v) for 1 h at 80C. Application of protease was the most effective in removing proteins, while active carbon was the best treatment to remove pigments present in mulberry polysaccharides. Moreover, mulberry polysaccharides exhibited a strong antioxidant activity and a good antibacterial ability. This study can help better utilize mulberry polysaccharides, especially as a readily accessible source of natural antioxidants and/or possible antibacterial agents in food or pharmaceutical industry.