Black Rice Extract Attenuates UVB-Induced Hyperpigmentation by Inhibiting IL-1b and MITF Gene Expression

Ultraviolet-B (UVB) radiation is a major environmental factor that induces inflammation, oxidative stress, and melanogenesis, contributing to skin hyperpigmentation. Black rice, which is rich in flavonoids and other antioxidant compounds, may offer a natural approach for mitigating UVB-induced pigmentation. This study investigated the effects of black rice extract on ultraviolet-B (UVB)-induced hyperpigmentation in C57BL/6J mice, with a focus on the expression of the interleukin-1b (IL-1b) and melanocyte-inducing transcription factor (MITF) genes. Black rice extract was obtained via ethanol maceration, yielding 8.70% and exhibiting high flavonoid content (90.30±4.02mg/100g) and potent antioxidant activity (IC50 = 67.98±8.16 ppm). UVB irradiation (390 mJ/cm2) induced visible skin darkening in mice after 14 days. Gene expression analysis using qRT-PCR revealed that black rice extract cream (BREC) at concentrations of 7.5% and 15% significantly reduced IL-1b expression compared to the negative control group (p < 0.05). BREC also decreased MITF expression, with the 15% concentration showing the lowest levels (0.93±0.18) compared to the negative control (2.09±1.30). Statistical analysis revealed significant differences in IL-1b and MITF expression among treatment groups (p < 0.05). These findings suggest that black rice extract effectively mitigates UVB-induced hyperpigmentation by modulating the expression of IL-1b and MITF genes in a dose-dependent manner.