Chemical composition and UVA-protecting activity of extracts from Ligustrum vulgare and Olea europaea Leaves

Plants belonging to the family Oleaceae have been traditionally used in treatment of various inflammatory skin disorders. One of the most well-known species is Olea europaea L. (olive), cultivated in the Mediterranean countries. Another species is Ligustrum vulgare L. (common privet), occurring particularly in Northern Europe and Asia. The aim of the study was a comparison of the composition of aqueous and ethanolic extracts from leaves of O. europaea and L. vulgare (HPLC-DAD-MS), and determination of the total content of phenolics and flavonoids, as well as the content of the major compound, oleuropein. Secondly, we aimed to study the protective effect of extracts on reactive oxygen species (ROS) production by human fibroblast cells (NHDF), cell viability (MTT assay), and apoptosis rate (Annexin V/propidium iodide staining) after UVA-irradiation. The phytochemical analysis allowed us to identify compounds belonging to the groups of flavonoids, phenylpropanoids and secoiridoids in the extracts. The compounds from the group of lignans (olivil) were identified as being unique to O. europaea extracts. Echinacoside, ligustroflavone and ligustaloside A were identified in L. vulgare extracts in contrast to olive preparations. It was established that the aqueous and ethanolic extracts from leaves of both species, except the privet aqueous extract at a concentration of 5 μg/ml, did not show any significant inhibition of ROS production after UVA-irradiation in the model of NHDF cell line. The aqueous extracts of both species at concentrations of 5 and 25 μg/ml had a protective effect on the viability of UVA-treated cells in contrast to the ethanolic extract. In conclusion, no significant difference in the activity of olive and privet leaf extracts has been observed, which suggests that both plant materials’ extracts, particularly aqueous ones, are effective herbal medicines and photoprotectors, which – to some extent – confirms the use of their preparations in skin disorders