Comprehensive phenolic composition analysis and evaluation of Yak-Kong soybean (Glycine max) for the prevention of atherosclerosis

•Yak-Kong, a small black soybean with a green embryo, is rich in proanthocyanidins.•Procyanidin A dimers and phloridzin are newly found in soybean seed coat.•Significant amount of coumestrol is found in Yak-Kong soybean embryo.•Both Yak-Kong seed coat and embryo attenuated monocyte-endothelial cell adhesion.

Yak-Kong (YK) (Glycine max), a small black soybean cultivar with a green embryo, was evaluated for functional constituents with a focus on atherosclerosis prevention. In comparison to common yellow and black soybean cultivars, YK contains significantly higher concentrations of antioxidants, particularly in its seed coat. A comprehensive phenolic composition analysis revealed that proanthocyanidins were the major phenolic group in YK. In contrast to other proanthocyanidin-rich foods, YK was rich in bioavailable proanthocyanidins (with a degree of polymerization ≤3) specifically with A-type dimers. Significant concentrations of phloridzin and coumestrol were also exclusively found in YK seed coat and the embryo, respectively. Extracts of both the proanthocyanidin-rich seed coat and isoflavonoid-rich embryo of YK attenuated adhesion of THP-1 to LPS-stimulated human umbilical vascular endothelial cells, suggesting that they are important sources of coronary heart disease-preventive phenolics. YK has promising potential for further development as a functional food source targeted at atherosclerosis prevention.