Abstract: Objective: To study the antioxidant and antiobesity effects of melanoidin from Yunnan grown arabica. Methods: Total melanoidins from medium roasted arabica were extracted by hot water extraction method, and then were fractionated into three fractions: > 100 kDa (M1), 10-100 kDa (M2) and < 10 kDa (M3) by ultrafiltration. The antioxidant capacity of four samples was determined by hydroxyl radical scavenging, 1,1-diphenyl-2-picrylhydrazyl radical scavenging and total reducing power assays. The effects of the total melanoidins at different concentrations on body mass, body fat content, blood lipid levels, body fat ratio, adipose tissue morphology and liver tissue morphology in a rat model of high-fat dietinduced obesity were determined. Results: All melanoidin samples had antioxidant activity varying with molecular mass at identical concentrations. The total melanoidins at all doses reduced body mass and body fat content in the obese rats. Histological examination showed that the liver tissue structure in the melanoidin treated rats at medium and high doses remained intact, accompanied by homogeneous hepatocytes and cytoplasm as well as clear nuclei. In addition to being intact and orderly arranged, the hepatocytes of the high-dose treated rats were smaller than those of the model group. Conclusion: The total melanoidins and three fractions from Yunnan grown arabica all had strong antioxidant capacity. The total melanoidins had an antiobesity effect by inhibiting body mass gain and reducing fat accumulation in the liver and consequently protecting the liver.

Key words: Yunnan grown arabica, melanoidins, antioxidant effect, antiobesity effect