In vitro solar protection factor, antioxidant activity, and stability of a topical formulation containing Benitaka grape (Vitis vinifera L.) peel extract

A flavonoid enriched extract (FE) was obtained from grape peels, and in vitro SPF, antioxidant activity, and effects on cell viability of this extract were tested with the intent to develop a cosmetic product. A formulation was developed with the FE, and the stability of this mixture was evaluated in terms of pH, density, viscosity, and SPF (90-days). FE showed no cytotoxicity to human keratinocytes and an in vitro SPF of 18.56 (UV-spectrophotometry). Further, FE showed a UVA protection factor of 3.17 ± 0.2, a critical wavelength of 318.0 ± 0.1 and a UVA/UVB of 0.9. Antioxidant activity assays resulted in 92.08% and 86.85% of activity against DPPH and ABTS (IC₅₀ = 296.90 ± 1.2 µg/mL and 643.13 ± 0.9 µg/mL), respectively. Finally, SPF of formulation with FE was 12.45. Results from the in vitro SPF and product stability tests (especially storage under refrigeration), indicate that FE is a promising compound for use as an innovative sunscreen formulation.