Soybean and wild soybean genetic diversity for new functional food resources, focusing on tocopherol, lutein, and saponin

Soybean has been a major protein source for people in East and Southeast Asia. It contains numerous secondary metabolites that are useful for human and animal health, such as isoflavones, polyphenols, tocopherols, lutein, carotenoids, and saponins. Isoflavones are the most popular nutraceutical compounds of soybean. Several soybean varieties having high isoflavones have been developed and utilized as functional food resources. Tocopherols, lutein, and saponins are also antioxidants present in soybean seeds. Tocopherols are known as vitamin E, whereas lutein has potential to prevent age-related macular degeneration. DDMP saponins in soybean is reported to inhibit HIV infection in vitro and prevent colon cancer. Screening of soybean germplasm showed that soybean holds a large genetic diversity of content and composition of tocopherols, lutein and saponins that can be utilized to breed new soybean cultivars. In addition, the wild counterpart of soybean (wild soybean) can also be source of genetic variations useful for soybean breeding. This review will summarize studies on genetic diversity of tocopherols, lutein, and saponins found in soybean and wild soybean.