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Antioxidant activity and total phenolic content of selected Greek Labiatae plant species. Methanolic extract of Phlomis lanata as a source of natural antioxidant compounds
The family of Lamiaceae consists of approximately 200 genera of cosmopolitan distribution. During a screening program for the discovery of antioxidant bioactive compounds from plant of the Greek flora [1, 2], several extracts of plants belonging to this family showed significant activity. In our efforts to discover possible new sources of natural antioxidants, a number of extracts obtained from several Lamiacae species (e.g. Mentha sp., Marubium sp., Nepeta sp., Satureja sp., Phlomis sp.) were prepared by ASE (Accelerated Solvent Extraction) technique. The free radical scavenging activity (DPPH) and the total phenolics content (Folin-Ciocalteu method) of all these extracts were evaluated. The methanolic extract of Phlomis lanata showed remarkable capacity to inhibit the DPPH radical (98.5% at 200µg/ml, IC50=62µg/ml) and high phenolic content (179.1mg GAE/g of extract) and it was further studied. Phlomis is a genus of the family Lamiaceae consisting of ca. 100 species (12 found in Europe) of herbs and shrubs. Different classes of glycosides comprising of terpenoids, iridoids, phenylpropanoids and flavonoids have been identified from this genus. It is well known that phenylpropanoids and flavonoids possess significant biological activities (e.g. cytotoxic, cytostatic, antiinflammatory), which are associated to their antioxidant capacity. In the purpose to identify the major components of the methanolic extract of Phlomis lanata, several chromatographic (e.g. CC, HPLC, FCPC) and spectroscopic (NMR) techniques were used. The results of phytochemical analysis showed that the above mentioned extract contains iridoids (lamiide and auroside), flavonoids (chrysoeriol 7-O-(3''-(E)-p-coumaroyl)-β-D-glucopyranoside) and phenylpropanoid glycosides (acteoside, forsythoside B, leucosceptoside B).
Acknowledgements: The project is co-funded by the European Social Fund and National Resources – (EPEAEK II) PYTHAGORAS
References: 1. Aligiannis, N. et al. (2003)J. Agric. Food Chem. 51: 7308–7312; 2. Kyriakopoulou, E. et al. (2001)J.Nat.Prod.64:1095–1097