Current worldwide research is focused in finding new and safe antioxidants to prevent oxidative deterioration of fatty foodstuffs and to minimize damage of biological membranes of living cells caused by oxidative reactions. Many studies have concentrated upon spice and herb constituents.
Already in the 1950s Chipault et al. (1952) measured antioxidative activities of different spices and found that oregano was among those spices, which have an ability to retard oxidation of lard. Later on Chipault et al. (1955) found that oregano was effective also in oil-in-water emulsion and when it was added as ground into different types of foods, its antioxidant capacity was best in mayonnaise and in french dressing (Chipault et al., 1956). Nakatani and Kikuzaki (1987) and Kikuzaki and Nakatani (1989) reported that antioxidative activity of water soluble fraction of methanol extraction of oregano leaves was due to two new compounds and it was comparable to BHA (butylated hydroxy anisol). Tsimidou and Boskou (1994) have written a whole chapter by name "Antioxidant Activity of Essential Oils from the Plants of the Lamiaceae Family" in the book Spices, Herbs and Edible Fungi edited by Charalambous (1994). Carvacrol is one of the compounds responsible for antioxidant capacity of various herbs, and according to Tsimidou and Boskou (1994) "oregano plants" are rich in carvacrol according to which the various taxa could be differentiated.
Recent research has confirmed that oregano indeed is an effective antioxidant. In studies done by Baratta et al. (1998) oregano oil showed highest antioxidative activity compared with laurel, sage, rosemary and coriander oils. The antioxidant activity was measured by the modified thiobarbituric acid reactive species (TBARS) assay, using egg yolk and rat liver as oxidable substrates. Dorman et al. (1995) made measurements of antioxidant capacity of oregano oil among other herb oils finding it one of the most antioxidative ones, and suggested that feeding trials in vivo upon polyunsaturated fatty acid metabolism during vital periods of life span, in particular fetal/neonate and aging periods, ought to be done. Chung et al. (1997) have detected that oregano as well as brown mustard, thyme, clove and allspice exhibit strong hydroxy-radical scavenging effects. In chromatographic and spectorophotometric analyzes by Vekiari et al. (1993), oregano contains flavonoids (apigenin, eriodictyol, dihydrokaempferol and dihydro-quercetin), which were effective lipid antioxidants in lard and in vegetable oils under storage and during frying.
Madsen et al. (1996) report that total phenol content of oregano extract correlates linearly with the antioxidant activity as measured by oxygen depletion, but not with free radical scavenging effect. They conclude that extracts of the investigated spices (Labiateae family spices) contain components with at least two different antioxidative mechanisms. In their experiments Turkish oregano and Chilean oregano showed the highest activity, while marjoram as well as basil had the lowest one.
Lagouri and Boskou (1996) did, indeed, publish a study, in which they showed that also a non-polar fraction of oregano is responsible for its antioxidant capacity due to its contents of tocopherol homologs. They also reported that the non-polar fraction was able to suppress the mutagenity of Trp-P-2, a dietary carcinogen. In this work four different species of oregano, O. vulgare subsp. hirtum, Satureja thymbram, O. dictamnus and Origanum onites were investigated.
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