Antioxidant and Photoprotective Activities of Viola philippica Polyol Extracts

Viola philippica (VP), a traditional Chinese medicinal herb widely used for its antibacterial and antioxidant properties, has recently garnered attention for its potential in skin photoprotection. VP was extracted using glycerol (GLY), 1,3-propanediol (PDO), and 1,3-butanediol (BDO) at concentrations of 30%, 60%, and 90% (w/w) to evaluate its antioxidant and UV-protective properties. The total phenolic content (TPC) and total flavonoid content (TFC) of the nine extracts ranged from 34.73 to 71.45 mg GAEs/g and from 26.68 to 46.68 mg REs/g, respectively, with the highest TPC observed in 90% PDO and the highest TFC in 60% GLY. Antioxidant assays revealed IC50 values of 0.49–1.26 mg/mL (DPPH), 0.10–0.19 mg/mL (ABTS), and 1.58–460.95 mg/mL (OH). Notably, the 60% GLY, 30% PDO, and 90% PDO extracts demonstrated notable protective effects against UVB-induced cell damage, reducing intracellular ROS levels and preventing DNA damage. RNA-seq analysis revealed that the protective effects were associated with the modulation of key molecular pathways, including neutrophil extracellular trap formation and TNF, IL-17, and HIF-1 signaling. These findings suggest that Viola philippica polyol extracts, particularly those using 60% GLY, 30% PDO, and 90% PDO, have promising potential for skin photoprotection and could be utilized as natural antioxidants in cosmetic formulations.