Formulation and characterization studies of sunscreen formulations

Constant exposure to ultraviolet (UV) radiation is an important cause of sunburn, inflammation, photoaging, and skin cancer, along other types of skin damage. The structure within the skin—specifically, the epidermis and melanin content—determines how sensitive the skin is to UV radiation. Preventing these negative consequences requires the use of effective photoprotection techniques such antioxidants, broad-spectrum sunscreens, and protective gear. In-vivo and in-vitro SPF testing techniques are commonly used to assess sunscreen performance, with UV-Vis spectrophotometry being a crucial component of the latter. The use, classification, and testing of UV filters and sunscreen actives are outlined in regulatory recommendations issued by agencies including the FDA, EU, and Asian authorities. This study concentrated on the formulation and assessment of a series of sunscreen emulsions that include chlorogenic acid, a natural antioxidant, as the primary active component, alongside various plant-derived oils (sesame seed, olive, pomegranate seed, rosemary) and UV filters such as titanium dioxide, zinc oxide, and octocrylene. Fourteen formulations were created and evaluated for SPF, pH (for skin compatibility), viscosity, density, FTIR spectra, physical stability, and in vitro release of chlorogenic acid using a Franz diffusion cell. The maximum SPF value (13.95) was recorded in formulation F14, which incorporated 10% octocrylene and 1.5% chlorogenic acid. Mineral filters alone provide moderate protection, but chlorogenic acid was shown to improve SPF mostly when combined with chemical filters. Multiple formulations (F2, F4, F5) were discarded due to instability. The research indicates that the integration of physical and chemical UV filters with natural antioxidants presents a viable strategy for creating effective, stable, and skin-compatible sunscreen compositions.