Comparative studies on the antioxidant activities of nine common food legumes against copper-induced human low-density lipoprotein oxidation in vitro

ABSTRACT:  Epidemiological studies demonstrated that the consumption of dietary antioxidant was associated with the prevention of atherosclerosis. The aim of this study was to investigate the antioxidant activities of the hydrophilic extracts from 9 selected legumes based on copper-induced human LDL oxidation model in vitro . The antioxidant activities were assessed on the basis of the formation of conjugated dienes (lag time of oxidation) and thiobarbituric acid reactive substances (TBARS) as the early and later stage markers of LDL oxidation. The results showed that the extracts of black beans ( Phaseolus vulgaris L.), lentils ( Lens culinaris ), black soybeans ( Glycine max ), and red kidney beans ( Phaseolus vulgaris L.) had significant ( P < 0.05) longer LDL oxidation lag times (128.8, 124.2, 107.7, and 111.1 min, respectively) than the LDL control group (94.9 min). No significant lag-time lengthening was observed in other tested legume extracts. On the other hand, black beans, lentils, black soybeans, red kidney beans, and pinto beans exhibited higher antioxidant capacities (Trolox equivalents) than yellow peas, green peas, chickpea, and yellow soybeans in both LDL-conjugated dienes assay and LDL-TBARS assay. Meanwhile, the antioxidant activities of these legumes against LDL-lipid peroxidation in the above assays were found to correlate very significantly ( P < 0.01) with their phenolic substances, and DPPH radical scavenging activity and ORAC (oxygen radical absorbance capacity). These results suggest that consuming black beans, lentils, black soybeans, and red kidney beans may have potential in preventing the development of atherosclerosis from the perspective of inhibiting LDL oxidation.