| Summary: | <i>Oenothera laciniata</i> Hill is a perennial herb traditionally used to alleviate inflammatory complications. This study investigated the antioxidant and anti-melanogenic activities of <i>O. laciniata</i>. The methanolic extract (OLM) of <i>O. laciniata</i> and its different fractions, including ethyl acetate (OLEF), <i>n</i>-butanol (OLBF), and water (OLWF) fractions, were prepared. Antioxidant activities were evaluated by total phenolic content, the radical-scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH<sup>•</sup>), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS<sup>+•</sup>), and superoxide anion (O2<sup>−•</sup>), reducing capacity, and metal chelating ability. OLM and its fractions exhibited potent antioxidant activity in these in vitro assays, with a correlation between radical-scavenging activity and total phenolic content. OLM and its fractions inhibited the mushroom tyrosinase activity superior to the reference control, ascorbic acid. In B16-F10 melanoma cells, OLM and its fractions significantly decreased melanin production and tyrosinase activity. Mechanistic investigations revealed that OLM and its fractions inhibited tyrosinase and TRP-2 expressions via downregulating MITF and phosphorylated CREB and differentially inducing ERK or JNK phosphorylation. Additionally, OLM and its fractions caused no significant cytotoxicity towards B16-F10 or skin fibroblast cells at concentrations used in these cellular assays. These findings demonstrated the potential of <i>O. laciniata</i> extracts as the ideal skin protective agent with dual antioxidant and anti-melanogenic activities.
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