Preliminary Evaluation of Photoprotective Potential in Flowers of Osbeckia octandra (L.) DC. for Development of Herbal Sunscreen Formulations

Introduction: Excessive exposure to ultraviolet (UV) radiation of the solar spectrum is often linked with the onset of conditions like inflammation, photoaging, immunosuppression, hyperpigmentation, and photocarcinogenesis. Although synthetic sunscreens have emerged as protectants against this harmful UV radiation, there is an increasing demand for sunscreens of herbal origin, which are believed to have low side-effect profiles in comparison to their synthetic counterparts. In order to cater for this need, the present study aimed at developing herbal sunscreen formulations from flowers of Osbeckia octandra DC, a purple-coloured wildflower widely distributed across different geographical regions in Sri Lanka. Methodology: The UV filtering potency and subsequently, the sun protection factor (SPF) in the methanolic extract of O. octandra was initially determined. Thereafter this extract was incorporated into the aqueous cream base at 25%, 50%, and 75% (w/w) and the SPF values and photostability of the prepared formulations were evaluated. Results: The initial SPF value of the crude extract (39.91 ± 1.93) had hardly changed even after incorporating it 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 or dark conditions and was photostable. Conclusion: Our preliminary observations demonstrated the appropriateness of O. octandra for the formulation of herbal sunscreens at the commercial stage. Keywords: Herbal sunscreens, Osbeckia octandra, Photoprotection, Sun protection factor, UV radiation