Erythema Protection Efficacy of Plant-Derivative Compounds in Mice Based on Narrow-Band Reflectance Spectroscopy Data

<b>Background</b>: Plants represent an important source of photoprotective compounds that are capable of protecting human skin from solar-induced damage. In this study we investigated the suitability of a murine model for estimating the Erythema Protection Efficacy (EPE) of natural compound. <b>Methods</b>: UVB-induced skin erythema in albino BALB/c mice was quantified using a Mexameter MX18 MDD colorimeter. The ARRIVE principle was followed. The Minimum Erythema Dose (MED) was determined based on Log₁₀ dose-erythema response curves. EPE values for UV filters (e.g., titanium dioxide or zinc oxide) and selected plant-derived compounds (apigenin, caffeic acid, epigallocatechin gallate, kaempferol, and pinocembrin) were calculated as the ratio between the MED of protected skin and that of unprotected skin. <b>Results</b>: The UVB-induced erythema in both female and male mouse skin followed a linear response. Erythema intensity varied by sex and by the dorsal skin area examined. MED values ranged from 39 to 57 mJ/cm² in female mice and from 71 to 80 mJ/cm² in male mice. In both sexes, MED increased linearly with the logarithm of the radiation dose. All tested compounds (apigenin, caffeic acid, epigallocatechin gallate, kaempferol, and pinocembrin) provided protection against UV-radiation-induced erythema in mouse skin. Among them, apigenin, caffeic acid, and kaempferol exhibited the highest EPE values, indicating strong potential for incorporation into sunscreen formulations. <b>Conclusions</b>: The murine EPE metric proved to be a useful tool for identifying plant-derived compounds with potential relevance for the photoprotection of human skin.