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Photoprotective properties of lippia triphylla hydroalcoholic extract and in vitro safety evaluation

Abstract:

The aim of this research was to perform the assessment of the photoprotective effect of the hydroalcoholic extract of leaves of Lippia triphylla through ultraviolet B radiation (UV-B) induced cell death model on a strain of Escherichia coli ATCC 25922 and Mansur equation apply in order to determine the in vitro sun protection factor (SPF). Hydroalcoholic extract of the dry powered leaves of L. triphylla was obtained by cold maceration method and was subjected to preliminary phytochemical screening. The photoprotective effect of the plant extract at three concentration levels of 20, 200 and 2000 μg/mL and controls 2-ethylhexyl 4-methoxycinnamate (OMC) and 2-ethylhexyl 4-(dimethylamino) benzoate (PAMIDATE O) at the same concentration levels of sample were carried out using UV-B chamber and suitable quartz cells, determining the survivor bacteria number versus time. The safety of plant extract was evaluated by hen´s egg coriallantoic membrane irritation test (HET-CAM) and genotoxicity assay (micronuclei). Furthermore, total phenolic content was estimated by using Folin-Ciocalteu reagent, total flavonoid content was evaluated through of AlCl3 complexation method and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) was used to determine the in vitro radical scavenging capacity of plant extract. Phytochemical analysis of extract revealed the presence of major classes of phytochemicals such as flavonoids, tannins, triterpenes, steroids, etc.; but no alkaloids were detected. The hydroalcoholic extract showed an appreciable phenolics and flavonoids content, even though exhibited a mild antioxidant activity. The UV-B photoprotective activity of the plant extract was significant in comparison with the standard photoprotective chemicals, OMC and PAMIDATE O; due it does not show a statistical difference (p<0.05) when comparing the lower concentration of the hydroalcoholic extract (20 μg/mL) v.s. OMC and PAMIDATE O (20 μg/mL). The photoprotective effect of the plant extract was directly proportional to the concentration. Based on the results of this preliminary study, it can be concluded that L. triphylla is a very interesting source of natural photoprotective compounds which can be used to prevent many chronic disorders derived from UV-B radiation exposition through its inclusion in cosmetic formulations. Further detailed phytochemical studies are needed to identified the chemical compounds responsible of the photoprotective activity showed, although it could be phenylpropanoid derivatives of vebarcoside type, a noted chemical marker of the Verbenaceae and Scrophulariaceae families, of which has been reported a wide range of biological activities including anti-inflammatory, antioxidant, antibacterial, anti-tumor, anti-fungal, photoprotective as well as chelating effects.