Plant extract that has anti-inflammatory properties.  In addition, licorice root contains constituents that interrupt the stimulation of an enzyme that activates melanin production, so this part of the plant can be effective for improving dark spots and hyperpigmentation. [2,3]
Licorice has shown to have efficacy against acne-causing bacteria. One of its components, known as glabridin, is a potent antioxidant and anti-inflammatory ingredient, which is why licorice often shows up in products meant for sensitive, reddened skin. [4,5]
Licorice extract has several active compounds that may stimulate or suppress the formation of melanin. According to one study, "Glabridin, the main ingredient in the hydrophobic fraction of licorice extract, inhibits tyrosinase activity in cultured B16 murine melanoma cells, at concentrations from 0.1 to 1.0 µg ml-1, without affecting DNA synthesis. Other active compounds, such as glabrene, isoliquiritigenin licuraside, isoliquiritin, and licochalcone A, isolated from licorice extracts, were also shown to inhibit tyrosinase activity."
- Rahnama M, Mehrabani D, Japoni S, Edjtehadi M, Saberi M. The healing effect of licorice (Glycyrrhiza glabra) on Helicobacter pylori infected peptic ulcers. J Res Med Sci. 2013;18(6):532-533.
- Ebanks J, Wickett R, Boissy R. Mechanisms Regulating Skin Pigmentation: The Rise and Fall of Complexion Coloration. Int J Mol Sci.. 2009;10(9):4066-4087.
- Davis E, Callender V. Postinflammatory Hyperpigmentation. J Clin Aesthet Dermatol. 2010;3(7):20-3.
- Simmler C, Pauli G, Chen S. Phytochemistry and biological properties of glabridin. Fitoterapia. 2013;90:160-84.
- Veratti E, Rossi T, Giudice S, Benassi L, Bertazzoni G, Morini D, Azzoni P, Bruni E, Giannetti A, Magnoni C. 18beta-glycyrrhetinic acid and glabridin prevent oxidative DNA fragmentation in UVB-irradiated human keratinocyte cultures. Anticancer Res. 2011;31(6):2209-15.
- Wenyuan Z, Jie G. The use of botanical extracts as topical skin-lightening agents for the improvement of skin pigmentation disorders. J Investig Dermatol Symp Proc. 2008;13(1):20-4.