Alkaline Extraction and Antioxidant Activities of Polysaccharides Recovered from Curcuma longa L. (Zingiberaceae)

Alkaline extraction of polysaccharides from Curcuma longa L. (Zingiberaceae) was studied. The four parameters, ratio of water to raw material, extraction temperature, extraction time and concentration of NaOH, were optimized using the Box-Behnken design (BBD) with a quadratic regression model built by response surface methodology (RSM). The optimal extraction conditions found were: ratio of liquid to solid 40:1, extraction temperature 65 degrees C, extraction time 2.4 h and concentration of NaOH 1 mol/L, where the highest alkali extracted and water-soluble polysaccharide CLAP yield of 1.33% was achieved. The monosaccharide composition study demonstrated that CLAP is a heteropolysaccharide consisting of glucose and arabinose in the ratio of 4:1. In addition, the antioxidative activity of CLAP was investigated by measuring its scavenging ability on DPPH radical, hydroxyl radical, ABTS radical in vitro and its reducing power, self-oxidation of 1,2,3-phentriol. The results indicated that CLAP has good antioxidant activity.