Assessment of Phenolic Content and Photoprotective Potential of Thespesia populnea, Cascabela thevetia, and Abutilon indicum as Natural Ingredients for Herbal Sunscreen Development

The present study aimed to develop herbal sunscreen formulations from flowers of Thespesia populnea (L.) Sol. ex Corrêa and Cascabela thevetia (L.) Lippold and leaves of Abutilon indicum (L.) Sweet. Total phenolic content was determined by the Folin-Ciocalteu method. The UV-filtering potency and the Sun Protection Factor (SPF) of the methanolic extracts of the above plants were subsequently determined. Thereafter, the extract was incorporated into the aqueous cream base at 25%, 50%, and 75% (w/w) and the SPF values of the prepared formulations were evaluated. The methanolic flower extract of T. populnea had the highest total phenolic content (244.814 mg Gallic Acid Equivalent (GAE)/g ± 0.005) and A. indicum had the intermediate total phenolic content (72.284 mg Gallic Acid Equivalent (GAE)/g ± 0.001); while the flower extract of C. thevetia had the lowest content (32.718 mg GAE/g ± 0.002). The initial SPF value of the crude flower extract of T. populnea (37.56 ± 0.33) showed minimal change after incorporation at 75% into the aqueous cream base. This 75% formulation surpassed the other two formulations and the commercial sunscreen (positive control) in terms of the higher SPF and broader spectrum of UV absorption. Its SPF value altered only slightly during the storage for 21 days in light conditions and was photostable. Preliminary observations demonstrated the appropriateness of T. populnea for the formulation of herbal sunscreens at the commercial stage.