Black Soybean Seed Coat Extract Improves Endothelial Function and Upregulates Oxidative Stress Marker Expression in Healthy Volunteers by Stimulating Nitric Oxide Production in Endothelial Cells.

Black soybean seed coat extract (BE) contains multiple bioactive polyphenols, including flavan-3-ols and anthocyanins. BE improves endothelial function; however, it is unclear whether BE protects endothelial cells from senescence. In this study, we examined the effects of BE on endothelial cell senescence and vascular function in healthy individuals. High concentrations of glucose were used to induce senescence in bovine aortic endothelial cells incubated with BE. Senescence, vascular function, and oxidative stress markers were measured. Incubation with BE remarkably inhibited senescence-associated β -galactosidase and lactate dehydrogenase activities and dose dependently reduced intracellular reactive oxygen species levels in bovine aortic endothelial cells. BE treatment increased the levels of endothelial nitric oxide synthase (eNOS) mRNA and endothelial nitric oxide (NO) metabolites and increased the mRNA expression of klotho , a gene associated with an antiaging phenotype. To examine the effects of BE in humans, we conducted a clinical study using the second derivative of the fingertip photoplethysmogram to investigate vascular function and aging in 24 healthy volunteers. The participants consumed BE supplements (100 mg/day) or a placebo for 2 weeks. When compared with the placebo group, the BE group showed considerably improved vascular function, NO metabolite levels, and oxidative stress. These results suggest that BE supplementation improves endothelial function, possibly through antioxidant activity and NO production, and may consequently reduce the cardiovascular risk associated with aging. BE supplementation may be an effective and safe approach to reduce the risk of atherosclerosis and cardiovascular disease; however, additional studies investigating chronic vascular inflammation are needed.