HRGC FID and HRGC MSD analysis of the secondary metabolites obtained by different extraction methods from Lepechinia schiedeana, and in vitro evaluation of its antioxidant activity

Steam distillation (SD), simultaneous distillation-solvent extraction (SDE) , microwave-assisted solvent extraction (MWE), and supercritical (CO2) extr action (SFE) were used to isolate secondary metabolites from Lepechinia sch iedeana. The various extracts were analyzed by capillary gas-chromatography , on poly(dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kovats indexes, mass spectra, or st andard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, M WE, and SFE extracts, respectively. Ledol, C15H26O) was the major constitue nt (20.04-36.87%) in all extracts. Oxygenated sesquiterpenes (24.36-43.14%) , C10H16, monoterpenes (27.70-39.87%), and C15H24, sesquiterpenes (10.04-22 .22%) were the main groups of compounds present in SD, SDE, MWE, and SFE ex tracts. Heavy hydrocarbons (C-n > 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid syste m (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was indu ced in the presence of macerated Lepechinia plant. The protection of polyun saturated acids in sunflower oil was also studied by measuring their concen trations after heating of the oil (180 degrees C, 2 h) with and without mac erated Lepechinia plant.