The Synergistic Efficacy of Natural and Inorganic UV Filter Combinations on the SPF Value of Sunscreen Cream Preparations

Sunscreen is an important product for protecting the skin from the harmful effects of the sun's UV rays. Ethanol extract of watery rose apple leaf (WRAL) contains flavonoids, which acts as natural UV filters. Titanium dioxide (TD), an inorganic filter, provides broad spectrum protection. This study aims to develop a sunscreen cream by combining WRAL extract and TD, and to investigate the synergistic efficacy based on the SPF value. This study began with characterizing the total flavonoid content of the WRAL extract. Five formulations were prepared using either single or combined UV filters at varying ratios. These formulations results were evaluated for physical properties and SPF value determined in vitro. The optimum formula underwent accelerated stability, skin hydration and irritation tests. The WRAL extract contains a total flavonoids content of 46.33 ± 1.02 mg QE/g extract. Then, F3 cream, containing 10% WRAL extract and 6% TD, was found to be the optimum formula. The results showed that the cream met quality requirements, with a pH of 6.12 ± 0.01, spreadability of 5.5 ± 0.15 cm, viscosity of 60 ± 10 dPas, and SPF value of 40.22 ± 0. The cream was physically stable at 25°C and under heating-cooling conditions during storage, improved skin hydration, did not cause skin irritation and the most preferred formula. Thus, the cream preparation containing WRAL extract as a natural UV filter and titanium dioxide as an inorganic UV filter is a promising sunscreen formulation, offering new opportunities for the development of skin care products.