Unsaturated fatty acids [oleic acid (C18:1), linoleic acid (C18:2), and alpha-linolenic acid (C18:3)], suppress pigmentation in vitro. A clinical study done with Korean women using topical linoleic acid showed significant improvement in melasma (28).
Idebenone, a potent antioxidant, is a benzoquinone that has shown depigmenting properties in pilot studies of patients with melasma and facial hyperpigmentation. Idebenone has been recently introduced to the U. S. market as Prevage.
Licorice extracts (Glycyrrhiza Glabra and Glycyrrhiza Uralensis), marketed as liquiritin, contains flavanoids and a glycoside called glycyrrhizin, and have shown utility in treating melasma (29).