Hydroquinone is used for temporary bleaching of hyperpigmented skin conditions such as chloasma (melasma), freckles, and lentigines. Tretinoin, also known as all-trans-retinoic acid (ATRA), is a naturally occurring derivative of vitamin A. As vitamin A (retinol) derivatives, retinoids are important regulators of cell reproduction, Kojic acid is a by-product in the fermentation process of malting rice, It is a mild inhibitor of the formation of pigment in plant and animal tissues.