Ethanolic Extract of Caulerpa racemosa Inhibits Melanogenesis via Downregulation of Microphthalmia-Associated Transcription Factor and Activation of Extracellular Signal-Regulated Kinase

The application of natural bioactive compounds in cosmeceutical products, particularly as skin-lightening agents, has received increasing interest. Caulerpa racemosa, a green macroalga of the Chlorophyta division, contains beneficial nutrients that are applicable as food and cosmeceutical ingredients. This study investigated the in vitro effect of the ethanolic extract of C. racemosa (CR) on regulation of melanogenic-related signaling and gene expression in SK-MEL-5 human melanoma-derived cells. Identification of bioactive components revealed that catechin, rutin, and quercetin as flavonoid contents were found in CR extract, analyzed using HPLC. The expressions of microphthalmia-associated transcription factor (MITF), extracellular signal-regulated kinase (ERK) signaling molecules, and melanogenic-related molecules were analyzed via Western blotting and qPCR. The CR extract treatment applied to SK-MEL-5 cells decreased the MITF protein expression level, which correlated with increased pERK expression, and no cytotoxic effect was observed. The subsequent treatment reduced the expression of melanogenesis-related genes (TYR, TYRP1, MC1R, and DCT) that were downstream targets of MITF. This study provides preliminary evidence that CR extract may modulate melanogenesis-related signaling. However, the specific bioactive compounds responsible for the observed effects remain to be identified, as the extract contains a complex mixture of phytochemicals. Further fractionation studies are needed to pinpoint the active constituents. The variability of extract composition due to seasonal and geographical factors should be considered for future standardization.