Effect of extraction methods on the chemical composition and antioxidant activity of Egyptian marjoram (Majorana hortensis Moench)

The volatile extract compositions of marjoram (Majorana hortensis Moench) leaves obtained by hydrodistillation (HD) and supercritical fluid extraction (SFE) were estimated by gas chromatography-mass spectrometry (GC-MS); 26 components were identified. The major compounds in both extracts were terpinen-4-ol (20.39% and 10.96%), gamma-terpinene (14.13% and 8.14%), trans-sabinene hydrate (5.25% and 20.54%), linalool (3.72% and 4.06%), trans-sabinene hydrate acetate (0% and 13.01%), thujanol (4.00% and 4.12%), terpinolene (4.57% and 3.70%) and thymol (0.33% and 1.18%) in HD and SFE extracts, respectively. The total monoterpene hydrocarbons are higher in HD oil (42.57%) than that of SFE extract (22.80%). However, the SFE extract possessed higher concentrations of light oxygenated compounds, which give the oil a superior aroma. Both extracts effectively inhibited the peroxide formation of linoleic acid. The antioxidant property of the SFE extract is markedly higher than that of butylated hydroxyanisol (BHA) and HD extract, which might be due to the presence of higher contents of gamma-terpinene, terpinolene and thymol. At higher concentrations, both extracts showed higher antioxidant activity compared to BHA. In order to enhance the activity of the natural extracts examined and decrease the applicability of synthetic antioxidants, the synergistic effect was also studied by adding BHA to either extracts. The mixture of either extracts and BHA results in an additive effect of their antioxidant capacities in comparison to their individual activity. Copyright (C) 2003 John Wiley Sons, Ltd.