Atividade fotoprotetora e análise da variação sazonal de Plectranthus amboinicus

Abstract

Excessive exposure to the sun causes damage to the skin and ultimately cancer. Therefore, it is recommended to use sunscreens as a preventive way of skin protection. The use of natural products, mainly with the presence of phenolic compounds, has added high potential in the protective industry due to its capacity for protection, tolerability and sustainability. Thus, Lamiaceae family is the plant family with the largest number of representatives used in the cosmetic industry, among them, the species of the genus Plectranthus. Plectranthus amboinicus is known for the presence of phenolic compounds and volatile oils, widely used for several diseases, mainly of the respiratory and gastrointestinal tracts. Thus, the aim of this study was to determine the photoprotective and antioxidant activities of the species and the seasonal variation occurred in the extract, as well as the implications of solar radiation and precipitation for the extract. For this, the profile of the crude ethanolic extract (CEE) was determined by HPLC-MSn and an analytical method by HPLC-DAD was developed and validated for quantification of the major compound, rosmarinic acid. For the determination of photoprotective activity, the sun protection factor (SPF) was determined by Mansur's in vitro method. The antioxidant activity was assessed using the DPPH method and the content of phenolic compounds was determined using the Folin-Ciocalteu method. The content of total flavonoids was also determined by the colorimetric method using Aluminum Chloride. In addition, seasonal variations in SPF and antioxidant activity, the content of total phenolics and flavonoids, as well as rosmarinic acid, were determined. So, through principal component analysis (PCA), correlations of the incidence of solar radiation and precipitation with the components described above was seen. As a result, the presence of 31 phenolic compounds in the extract was identified through HPLC-MSn, where 18 were reported for the first time in the species. The analytical method developed by HPLC-DAD was validated, showing specificity, linearity, precision, intermediate precision, accuracy and robustness according to the specifications required by ANVISA (RE nº 166/2017). The P. amboinicus CEE had a total phenolic content of 142.39 ± 1.12 mg GAE/g, a rosmarinic acid content of 22.48 ± 0.07 μg/ml, EC50 equal to 112.39 μg/ml and SPF = 12.63. Through the seasonal analysis, it was seen that the best month for harvesting the plant is July, which presented an SPF = 14.79. Solar radiation had an influence on antioxidant activity, but little influence on the increase in SPF and precipitation had no influence on both activities. Thus, it is concluded that P. amboinicus has great potential for the development of a sunscreen with innovative characteristics, with a high SPF and antioxidant activity, covering both lines of defense.