Black Ginseng–Deer Antler Peptide Composite Emulsion: Antimelanogenic and Antioxidant Effects In Vitro

This study aimed to develop a black ginseng–deer antler peptide composite emulsion (BGD) with antimelanogenic and antioxidant activities and to investigate its potential biological effects. The BGD formulation was optimized through response surface methodology, followed by assessment of its physicochemical characteristics, stability, preliminary skin safety, and in vitro antioxidant capacity. Its antimelanogenic and antioxidant effects were further investigated using α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis and H2O2-induced oxidative stress models in B16F10 cells, respectively. BGD showed good stability, with no visible skin irritation observed, and exhibited in vitro antioxidant activity. BGD inhibited cellular tyrosinase activity (4.86–35.82%) and melanin production (17.54–45.29%). These effects were accompanied by decreased expression of microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), and dopachrome tautomerase (DCT) (p < 0.01). Furthermore, BGD increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and NAD(P)H:quinone oxidoreductase 1 (NQO1), while decreasing Kelch-like ECH-associated protein 1 (Keap1) expression (p < 0.01). It also lowered intracellular reactive oxygen species (ROS) levels and improved biochemical indicators associated with redox imbalance (p < 0.01), suggesting a potential role in alleviating H2O2-induced cellular oxidative stress through modulation of the Nrf2/Keap1 pathway.