4- Ascorbic acid (Vitamin C):
Ascorbic acid and its derivatives are used as an antioxidant because its capacity to reduce back o-dopaquinone to dopa, thus avoiding melanin formation, also it have a protective effect against skin damage induced by UV- irradiation (Policarpio and Lue, 2009). However, ascorbic acid has other adverse affects as it can induce a large increase of free radicals with traces of metal ions. To improve its stability, skin absorption and hypopigmenting effect, some ascorbate esters, such as the magnesium ascorbyl-2-phosphate (MAP), has been synthesized. Daily application of a cream containing 10% of this ascorbic acid derivative has been found to produce a significant whitening effect in patients with melasma. Ascorbic acid has been demonstrated as an effective depigmenting strategy in a randomized, double-blind, placebo-controlled trial (Solano et al., 2006)