Plant extract more commonly known as the satsuma. This medium-sized citrus fruit is native to Japan. Like all citrus extracts, it contains volatile fragrance chemicals that can be a source of irritation. Of course, it has antioxidant ability as do most plants, but ideally you should be seeking antioxidants that provide benefits rather than a mix of benefits and risks (Sources: Journal of Agriculture and Food Chemistry
, July 2008, pages 5,682-5,690; and Cancer Research
, September 2000, pages 5,059-5,066).
There is limited in-vitro and animal research demonstrating that citrus unshiu has melanin-inhibiting (skin lightening) properties. Whether or not that benefit can be parlayed to human skin is unknown, so this citrus fruit isn't one to bank on for improving discolorations (Source: Journal of Enzyme Inhibition and Medicinal Chemistry, February 2007 pages 91-98).