ANTIOXIDANT ACTIVITY OF FLAVONOIDS FROM THE STEM OF THE MEXICAN OREGANO (Lippia graveolens HBK var. berlandieri Schauer)

Abstract

México is the main exporter around the world of Mexican orégano (Lippia greveolens) with 35-40 % of the international market; its high demand is due to the quality of essential oil containes in the leaf. It is gathered as a complementary activity to the rainfed agriculture in arid and semi arid zones. The stem has not been exploited and the scarce studies on phytochemical and pharmacological aspects encouraged us to conduct this research. The type of flavonoids and the antioxidant activity of crude extracts of the stem of Lippia graveolens H.B.K. var. Berlandieri Schauer gathered in the Mezquital, Durango México, were evaluated. The extracts were prepared by maceration of the milled stem at room temperature with successive extractions of hexane, ethyl acetate and methanol. The aqueous extract was prepared by boiling the stem in water (10 %) and then liofilized. The fluid extracts of ethyl acetate and methanol were fractionated by column chromatography on silica gel G. Two fractions of the ethyl acetate extract and one of the methanolic extract were analized by liquid
chromatography coupled to mass spectrometry. We detected pilosin, cirsimartin, narigenin, kaempferol, isokaemferide, a derivative of catechin and a non identified. hexoside of quercetin The antioxidant activity of the extracts was evaluated by the method of the radical 2,2-diphenyl-1-picryl hydracyl (DPPH). The reduction of the radical by the extracts was higher than 91.2% in 10 mg L^-1, except for the aqueous extract in which reduction was 87.6 % in 50 mg L^-1. The IC50 values were relevant for the ethyl acetate extract (solid: 11.24 ± 1.10; fluid extract: 12.94 ± 0.63). These results shows the presence in the stem of bioactive molecules useful for the development of drugs from natural products.