Dietetic and hypocholesterolaemic action of black soy peptide in dietary obese rats

To investigate the effect of peptides from black soy (rat's eye) bean (Rhynchosia volubilis Lour.) on weight gain and lipid composition, Sprague-Dawley male rats were fed either a black soy peptide (BSP; 2, 6 or 10% of energy)-containing diet or a casein control diet (20% of energy) enriched with 36% fat and 1% cholesterol for 28 days. Compared with the casein group, the BSP groups showed significant attenuation of body, liver and epididymal adipose tissue weight gains (P < 0.05). Moreover, rats that consumed BSP had a lower total cholesterol concentration and low-density lipoprotein/high-density lipoprotein (LDL/HDL) ratio in serum and a lower level of hepatic triglycerides as well as higher excretion of faeces compared with those fed only casein (P < 0.05). Molecular weights of peptides from black soy were mainly below 10 kDa, and Arg/Lys and Gly/Met ratios in BSP were five and three times of those in casein respectively. It is concluded that BSP can be a potent nutraceutical component for anti-obesity and hypolipidaemic benefits. (c) 2007 Society of Chemical Industry.