A white powder composed of amino acids and fatty acids. It appears to have a positive impact on brown spots and skin discolorations, especially when combined with niacinamide. It is believed to work by interrupting the pathways in skin that stimulate excess melanin (skin pigment) production. Its effect is speculated to stop melanin from being formed, but not to the point where skin becomes depigmented (that would be bad).
Although this ingredient's research pales in comparison to what's known about hydroquinone and many forms of vitamin C, it is a promising ingredient that is worth considering in products meant to lighten brown spots and help even out skin tone (Sources: Journal of Cosmetic Dermatology, September 2011, pages 189–196 and December 2009, pages 260–266; and Clinical Experiments in Dermatology, July 2010, pages 476–476).