Source Review: Yoshino, K., Higashi, N., & Koga, K. (2006). Antioxidant and antiinflammatory activities of oregano extract. Journal of health science, 52(2), 169-173.
Inflammatory diseases due to lifestyle changes like dietary habits can cause serious health issues like digestive ulcers, chronic gastritis, and gastric cancer.
Hydrochloric acid, digestive enzymes, and bacteria in the digestive system can cause damage to mucous membranes which can cause the production of active oxygen species like nitrogen monoxide and anion radicals.
These active oxygen species can directly injure surrounding cells and produce peroxides and other metabolites of acids that can continue to cause more damage which overall promotes inflammation.
Antioxidants are known to suppress inflammation in rat arthritis models.
They can directly scavenge for radicals and act as electron donors for peroxidases (PODs) which helps decompose hydrogen peroxide through a catalytic reaction.
Many herbs include some antioxidant components, and oregano is one such herb.
Some active components in Oregano include rosmarinic acid, caffeic acid, and various flavinoids.
All of these components can also act as substrates in the catalytic reaction for PODs.
To obtain these active components from the plant, commercial oregano leaves were ground up in a mill, added in a ethanol, and shaken at 122 degrees Fahrenheit for an hour. The mixture was then centrifuged at 5000 rpm for 10 minutes. The supernatant was separated, evaporated in vacuum, and then lyophilized (frozen). The oregano extract remains.
To measure the activity of the oregano extract active components as a POD substrate, horseradish POD was added in with oregano extract and hydrogen peroxide and the decomposition was compared to a control and a positive control (phenol, which has a known strong catalytic response).
To measure antioxidant activity, the oregano extract was added in with ferric chloride and the iron-reducing activity was tracked and compared to a standard.
To test reduction of gastric inflammation, mice were give the oregano extract and stressed. After 24 hours of starvation in cold they were killed and their stomachs were examined. The amount of bleeding points were compared to a control and hydrocortisone (a known anti inflammatory agent).
Finally contact hypersensitivity was tested with and without the oregano extract to see if the extract reduced skin swelling (a form of inflammation).
This was tested through applying a compound to make an area of the mouse sensitive, then applying a compound which actively causes swelling. The extract, hydrocortisone, and a control were then added to see which helps reduced swelling.
Oregano extract performed at 60.6 percentage of the phenol as a POD substrate, suggesting it is a good electron donor for POD. This is compared to two other herb extracts, laurel and marjoram, which are known antioxidants, which performed at 28.1 and 25.8 percentage.
It performed as an antioxidant by reducing the iron compound, but not as well as ascorbic acid (Vitamin C). Its iron-reducing ability was roughly half of ascorbic acid.
In the mice studies, oregano extract performed similarly to the hydrocortisone at lower doses where it reduced bleeding points by 30.5 to 34.0 percentage compared to hydrocortisone’s reduction of 47.5 to 49.5 percentage. However at higher doses, hydrocortisone performed much better than oregano extract (80.0 compared to 35.0 percentage).
In the testing of the inhibition of contact hypersensitivity, the oregano extract reduced swelling by up to 47.4 percentage. The hydrocortisone reduced swelling by up to 74.7 percentage.
Mouse contact hypersensitivity is known to be suppressed by antioxidants and thus the antioxidant activity of oregano extract is suggested to be what helped with the reduction in swelling.
Peroxide levels are also known to raise in mice subjected to cold and starvation, implying that the reduction in bleeding points could be from the use of the oregano extract’s active components as a substrate for POD.
While this study implies general oregano extract can reduce gastric inflammation and act as an antioxidant, it doesn’t specify which active component of the extract is promoting these activities and more studies would need to be done to confirm which are actually active.