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).