Photoprotective Activity of Plectranthus amboinicus Extracts and HPLC Quantification of Rosmarinic Acid

Overexposure to sunlight has harmful effects on the skin and can cause erythema and skin cancer. Photoprotective agents are important for preventing exposure to sunlight and are present in the composition of sunscreens. Globally, the use of filters based on natural products has gained interest in scientific studies; in addition to their sunscreen properties, these products demonstrate antioxidant, healing, and moisturizing activity. These favor adequate sun protection due to the wide spectrum of activities and are environmentally friendly. Plectranthus amboinicus (Lour.) Spreng., Lamiaceae, is used in traditional medicine to treat several conditions and is commonly known as “hortela-da-folha-grossa” in Brazil. This species presents phenolic compounds, including rosmarinic acid, and has been studied for photoprotection and antioxidant activity. The aim of this study was to evaluate the photoprotection potential and antioxidant activity, and to develop analytic methodology for extract standardization and validation. Thus, maximum absorbance, sun protection factor, DPPH radical scavenging activity, and total phenolic contents of P. amboinicus crude ethanolic extract were determined, and an HPLC analytical methodology was developed and validated to quantify rosmarinic acid. Analyses revealed that the extract presented good photoprotection (SPF = 12.63), promising antioxidant activity (EC50 = 112.39 μg/ml), total phenolic content (142.39 ± 1.12 mg GAE/g), and rosmarinic acid concentrations (22.5 μg/ml). In addition, an HPLC analytical method was validated for marker quantification. These results show that the extract has potential photoprotective and antioxidant activity, and this favors the isolation of a final product with protective characteristics that encompass broad spectrum action and biological protection.