Glycyrrhiza glabra extract as a skin-whitening Agent: Identification of active components and CRTC1/MITF pathway-inhibition mechanism

Abstract

Ethnopharmacological relevance: Glycyrrhiza glabra. L is a traditional herbal medicine widely recognized for its skin-whitening properties; however, the specific active compounds and underlying molecular mechanisms responsible for these effects remain largely uncharacterized.

Aim of the study: To identify the bioactive constituents in G. glabra extract (GGE) responsible for its depigmenting effects and to elucidate the molecular mechanisms underlying their skin-whitening activity.

Methods: The depigmenting activity of GGE was assessed through NaOH lysis, DOPA oxidation assays, and high-performance liquid chromatography for component identification. Network pharmacology, western blotting, immunohistochemistry, and immunofluorescence were performed to investigate the effects of glabridin on pigmentation-related targets.

Results: Among the tested extracts, the 80 % ethanol extract of G. glabra (GGE80) exhibited the most potent inhibition of mushroom tyrosinase (TYR) activity in vitro, along with significantly reduced melanin content and TYR activity in B16F10 melanoma cells. GGE80 also suppressed melanin accumulation and downregulated the key melanogenesis-associated proteins. Seven major compounds were identified in GGE80: liquiritin, isoliquiritin, liquiritigenin, isoliquiritigenin, glycyrrhizic acid, 18β-glycyrrhetinic acid, and glabridin. Among these, liquiritin, isoliquiritigenin and glabridin were identified as the primary melanin-inhibitory agents. Of these, glabridin demonstrated the most potent, activity in both in vivo and in vitro models. Network pharmacology analysis revealed that glabridin targeted MITF, a central transcription factor regulating melanogenic enzymes. Mechanistic studies further indicated that glabridin reduced CREB phosphorylation and SOX10 protein expression, both critical regulators of MITF transcription. Additionally, glabridin inhibited the nuclear translocation of CRTC1, a CREB-regulated transcription coactivator, leading to its cytoplasmic retention and phosphorylation.

Conclusions: The GGE80 demonstrated the most significant whitening effects. Among its constituents, glabridin was identified as the key active compound responsible for inhibiting melanogenesis. Mechanistically, glabridin exerts its effects by suppressing CREB/CRTC1-mediated transcriptional activation of MITF.

Keywords: CRTC1; Glabridin; Glycyrrhiza glabra; MITF; Melanogenesis.