Antioxidant activity of methanolic extracts of Lamium album and Lamium maculatum species from wild populations in the Romanian Eastern Carpathians

Lamium genus includes species which, due to their medicinal properties, were studied for specific classes of biologically active compounds, mainly iridoids, terpenic compounds and polyphenols. Lamium plants are used in official and folk medicine as antiproliferative, antioxidant, antiinflammatory agents, for treatment of skin and respiratory disorders. The aim of this study was to assess the phenolic content of L. album L. and L. maculatum L. methanolic extracts, and their antioxidant capacity. The phytochemical analysis was performed by means of thin layer chromatography (TLC – qualitative analysis) and spectrophotometry (quantitative analysis). The antioxidant activity was determined by two complementary test systems: DPPH and ABTS assays. The plant material consisted of L. album and L. maculatum herba samples harvested from the Romanian Eastern Carpathians, in 2013 and 2014. For the antioxidant assays, there were selected several samples harvested in 2014 from the same site. The TLC fingerprint showed the presence of phenolic acids (chlorogenic, caffeic acids) and flavonoids (rutin). The spectrophotometric analysis highlighted a higher phenolic content in L. maculatum samples (105.86 mg gallic acid equiv./g dry extract), when compared with L. album samples (72.63 mg/g d.e.). L. maculatum extract showed a higher antioxidant activity than L. album extract in both antioxidant assays. For the DPPH assay the EC50 (µg/mL) values were 32.3 ± 0.1 for L. maculatum extract and 63.5 ± 0.7 for L. album extract, while in the ABTS assay EC50 (µg/mL) values were 13.2 ± 0.1 for L. maculatum extract and 19.9 ± 0.5 for L. album extract. The antioxidant activity of the tested extracts is due mainly to the phenolic content. Thus, the tested Lamium species show potential for the development of natural products with therapeutic use. Acknowledgement: The work was sustained from the Bilateral Collaboration Project RO-MD (694/2013) and the project PN 09 – 360401 (BIODIV) financed by ANCSI, Romania.