| As the usage of synthetic antioxidants (e.g. butylated hydroxytoluene) is not approved in several developed countries, thus natural antioxidants have gained popularity in recent years. Among Lamiaceae plants many contain phenolic compounds which may lead the strong antioxidant activity. In this study, the antioxidant properties of marjoram (Origanum majorana L.) herb and extracts obtained by ethanol, n-hexane and supercritical CO2 extraction are presented. Individual antioxidants (ursolic acid, carnosic acid and carnosol) were identified with high performance liquid chromatography. The effects of the parameters (temperature and pressure) of high pressure extraction on the yields of carnosol and ursolic acid were analysed. The effects of fractionation of extracts were followed at different extraction pressure. For screening the antioxidant activities of the herb aqueous and solvent extracts widely used analytical methods were applied. The free radical scavenging activities with 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the total scavenger activity by chemiluminometric method were compared. From solvent extracts the antioxidant activity was performed using Rancimat method.
Marjoram (Origanum majorana L.) is widely known and used Mediterrian spice, which contains up to 3% of volatile oil. Other compounds like flavonoid glycosides (luteolin- 7-diglucoside, apigenin-7-glucoside), arbutin, tannins, caffeic acid, labiatic acid, rosmarinic acid, steroids (e.g., b-sitosterol), triterpenoids (ursolic acid, etc.), paraffins and others can be found in the herb. Sweet marjoram is considered to have carminative, antispasmodic, diaphoretic, and diuretic properties. Marjoram used locally to relieve the symptoms of the common cold, such as nasal congestion and in mouthwashes for oral hygiene. Besides its antimicrobial activity, lately further examination has been carried out to map all the possible effects of marjoram extracts. One purified compound from methanolic extract of O. majorana was shown to possess oxigene anion scavenging activity in vitro tests. Ursolic acid isolated from marjoram herb seemed to be efficient acetylcholinesterase inhibitor (key compound in Alzheimer’s disease) and this compound also showed strong antioxidant activity on Abeta-induced neurotoxicity.
The ursolic acid and carnosol contents of marjoram were revealed and the effects of the parameters (pressure and temperature) of supercritical CO2 extraction on the yields of them were determined. Compounds with low polarity can be extracted with supercritical CO2 therefore conventional solvent extractions (with n-hexane and ethanol) were carried out for comparison of their antioxidant properties.
In conclusion the Origanum majorana L. herbs and their extracts whether are originating from Hungary or Egypt possess relatively strong antioxidant activities which can adequately be measured by several methods. Concerning the hydrogen donating abilities and the total scavenging capacities of aqueous solutions the Egyptian herb showed stronger antioxidant properties. The products obtained by conventional solvent extraction and supercritical CO2 extraction still exhibited strong antioxidant activities, that were significantly higher using polar solvent (ethanol) for extraction. Natural antioxidant compounds were quantified from the herbs and extracts, marjoram contained high amount of ursolic acid and carnosol, while the highly labile carnosic acid was absent from the extracts. The amount of carnosol can be enhanced with the optimization of the extraction conditions (pressure and temperature). The usage of certain extractable compounds and / or the whole herb and its extracts are highly reasonable within food-, cosmetic or pharmaceutical industries. |