alpha-Arbutin.

α-Arbutin (4-Hydroxyphenyl α-D-glucopyranoside) is emerging as popular and effective skin whiteners, acting as tyrosinase inhibitor[1].
Alpha-Arbutin is a glycoside.
Arbutin is naturally found in plant sources such as Bearberry, Cranberry and Mulberry, which essentially prevents the formation of melanin (the pigment that creates skin colour). The chemically synthesised version of this plant extract is known as Alpha Arbutin which is used as a topical skin brightening agent to treat sun spots, pigmentation and scars caused by sun damage and breakouts. It also has antioxidant properties, which protect the skin from potential sun damage. Along with Retinol, it is a fairly common ingredient in anti-ageing products to treat age spots, fine lines and wrinkles.
It is a glycosylated hydroquinone molecule, meaning a sugar molecule that has replaced one of the hydroxyl (-OH) groups on hydroquinone. Hydroquinone is seen as the gold standard of skin lightening, but there are concerns surrounding this well-studied tyrosinase inhibitor, such as skin sensitization, melanocytotoxicity from oxidative byproducts, and exogenous ochronosis (blue-black splotchy pigmentation) as a result of long-term application.1,2 Alpha arbutin is a more tolerable alternative to hydroquinone and is sometimes referred to as “natural hydroquinone.” Alpha arbutin functions similarly to hydroquinone, due to its molecular structure, but with reduced irritation and melanocytotoxicity. Alpha arbutin does not pose a risk in regards to exogenous ochronosis and poses minimal irritation and sensitization risk, making it a more tolerable alternative to hydroquinone.
Arbutin is the best as compared to vitamin c because it has fewer side effects and more benefits like reducing dark spots, age spots, ageing, etc. Arbutin gives quicker results than vitamin C. Arbutin acts as hydroquinone, which means it has depigmenting factors. Vitamin C is not easily absorbed into the skin, whereas arbutin absorbs quickly into the skin.