Today, the most common form of medicinal oregano is essential oil extract. Oil of oregano can be applied externally, either directly to the skin, teeth and gums, or as a compound of soaps (Wild Oil of Oregano, 2010). Furthermore, it can be ingested orally, either direct drops under the tongue or diluted in water.
The main active compounds in oregano extract are two phenols, carvacrol and thymol (Rivera, Bocanegra-García and Monge, 2010). These are derived from rosmarinic acid and caffeic acid other, other important components of the herb (Rivera, Bocanegra-García and Monge, 2010). It is important to note that although rosmarinic acid is present in both the leaves and the plant itself, caffeic acid is only present in the plant. This is important because rosmarinic and caffeic are responsible for the antioxidant properties of oregano (Rivera, Bocanegra-García and Monge, 2010). The phenolic structure of carvacrol and thymol are responsible for their antimicrobial activity (Rivera, Bocanegra-García and Monge, 2010). Both carvacol and thymol inhibit bacterial growth by disrupting the bacterial membrane, specifically Gram-negative microorganisms (Rivera, Bocanegra-García and Monge, 2010). What’s more, carvacrol is also the compound that gives oregano its warm, pungent aroma and flavor (Tonk et al, 2009). On the other hand, thymol also has potent antiseptic properties. Interestingly, thymol is the active compound in another common culinary herb, thyme.
FUN FACT: Thymol is the active ingredient in Listerine® mouthwash.