Origanum syriacum, Origanum compactum, Origanum onites.
Fungal, bacterial, and parasitic infections.
Mechanism of Action
Origanum vulgare has potent antibacterial, antifungal, antioxidant, and anti-inflammatory properties. The composition of the dried leaves of Origanum vulgare (excluding the essential oil component) includes a large amount of triterpene phenolic acids including rosmarinic, ursolic, oleanolic, caffeic, and lithospermic,1,2 with unique components known as origanol A and origanol B),3 which have demonstrated in vitro and in vivo anti-inflammatory and antioxidant activity.4, 5 Other bioactive secondary metabolites with prominent effects include β-caryophyllene oxide,6 β-sitosterol and flavonoids: eriocitrin, apigenin, luteolin, chrysoeriol, diosmetin, quercetin, and eriodictyol.7,8
Major active components of Origanum vulgare are phenolic monoterpenes, which constitute approximately 90% of the total composition of Origanum vulgare essential oil. Carvacrol is considered the predominant compound, followed by thymol (an isomer of carvacrol), p-cymene, and γ-terpinene.9
Origanum vulgare essential oil extracts of thymol and carvacrol have shown significant antioxidant and antimicrobial activity in vitro, leading to the destruction or growth inhibition of a broad spectrum of microorganisms such as Escherichia coli, Staphylococcus aureus,10,11 Listeria innocua and L. monocytogenes,12 Saccharomyces cerevisiae, Aspergillus niger,13 Bacillus cereus,14 Bacillus subtilis, Candida albicans, and Eimeria tenella.15,16
The comparative efficacy of Origanum vulgare oil, carvacrol, nystatin and amphotericin B were examined in vitro, and Origanum vulgare oil was found to completely inhibit the growth of C. albicans in culture, as well as the germination and mycelial growth of C. albicans in a dose-dependent manner.17
Antibacterial properties are thought to be primarily tied to carvacrol, which is active on its own, but has also demonstrated synergistic effects when combined with thymol.18,19 Carvacrol has been used for many generations as a food preservative, and it is speculated that these compounds are able to inhibit biofilm formation,20 disrupt the cell membrane of bacteria, and in particular, sensitize the phospholipid bilayer of the cell membrane, increasing the permeability and leakage of vital intracellular constituents. In addition, efflux pump inhibition is another proposed intracellular mechanism of action which can boost antimicrobial activity.21
An in vivo study performed serial extractions of the aerial parts of Origanum compactum using either ethyl acetate, essential oil, or water. The parts were then screened for their antioxidant and antimalarial activity, and cytotoxic activity against human breast cancer cells. Among the extracts, the aqueous extract showed the highest antioxidant activity while the ethyl acetate and ethanol extracts showed activity against human breast cancer cells. The essential oil showed the greatest results concerning anti-malarial activity, and was also considered to be nontoxic.22
Thymol and carvacrol have also demonstrated antispasmodic activity in vitro. The mechanism of action seems to be both musculotropic and neurotropic, indicating an inhibition of smooth muscle responsiveness, and interference with Ca2+ availability to the contractile apparatus by acting as Ca2+ antagonists.23,24
Origanum vulgare has been shown to possess antioxidant and antimicrobial activity in both in vitro and in vivo models, and is thus considered potentially beneficial to human health. Human studies that use the leaf or oil extracts are, however, lacking. The oil of Origanum vulgare has been used to hinder bacterial replication in the food25 and cosmetic26 industries and thus prolong product shelf life.
Human Studies: Adults (N=14) with chronic fatigue and gastrointestinal complaints who tested positive for fecal parasites Blastocytis hominis, Entamoeba hartmanni, or Endolimax nana, were given 600 mg oil of Origanum vulgare daily by mouth for 6 weeks. After 6 weeks of supplementation there was complete disappearance of Entamoeba hartmanni (four cases), Endolimax nana (one case), and Blastocystis hominis in eight cases. Also, Blastocystis hominis scores declined in three additional cases, and gastrointestinal symptoms improved in 7 of the 11 patients who had tested positive for Blastocystis hominis.27
A randomized, double-blind study was performed to determine the effects of 3% Origanum vulgare ointment vs. petrolatum on bacterial contamination, subsequent infection on post-surgical wounds, and overall wound healing (i.e., scar appearance) in 40 patients who underwent surgical excision. Cultures were obtained on day 12 and scars were evaluated using the Patient and Observer Scar Assessment tool on days 12, 45, and 90. In the Origanum vulgare ointment group, 19% of cultures tested positive for Staphylococcus aureus compared with 41% in the petrolatum group. Only one patient in the Origanum vulgare group developed cellulitis compared with three patients in the petrolatum group. The Origanum vulgare group also had a statistically significant improvement in scar color, pigmentation, and pliability when compared with the petrolatum group.28
Animal Studies: In a murine model of systemic candidiasis, infected mice were fed varying amounts of Origanum vulgare oil in 0.1 mL of olive oil. The daily administration of 8.6 mg of Origanum vulgare oil in 100 µL of olive oil/kg body weight for 30 days resulted in 80% survivability, with no renal burden of C. albicans as opposed to the group of mice fed olive oil alone, who died within 10 days. Similar results were obtained with carvacrol; however, the mice fed Origanum vulgare oil exhibited cosmetically better clinical appearance compared with those cured with carvacrol.17
Another study in mice examined the efficacy of the antimicrobial properties of volatile aromatic oils and medium-chain fatty acids derived from edible plants. Groups of mice (six and eight, respectively) infected with Staphylococcus aureus were given Origanum vulgare oil, carvacrol, monolaurin, or combined Origanum vulgare oil/monolaurin in 0.2 mL of olive oil for 30 days. Control mice received daily either olive oil alone (negative control) or olive oil orally plus vancomycin (positive control). In the first experiment, the daily dose of Origanum vulgare oil was either 2.0 µL (1.6 mg) or 4.0 µL (3.2 mg), and the mice gavaged with carvacrol received doses comparable to the phenol content in the two doses of Origanum vulgare oil. In the second study, the daily dose of Origanum vulgare oil was the same as the higher dose used before, that is, 4.0 µL (3.2 mg). Monolaurin was given at the same dose, and when both agents were combined, the same individual doses were used, that is, 3.2 mg of each. Both experiments were terminated at the end of 30 days. The body weight, disease status, and overall health of the mice during the experiments were recorded. Injected Staphylococcus aureus killed all 14 mice in the control group within a 1-week period. In treated mice, over one third survived for 30 days when given oral Origanum vulgare oil daily for 30 days. Interestingly, carvacrol given in a dose equivalent to the phenol content in the Origanum vulgare oil, delayed death beyond the control group (21 days compared with 3 days) but did not cure the mice. Thus, carvacrol alone could not duplicate, to the same extent, the beneficial effects of Origanum vulgare oil, suggesting that either the addition of thymol and/or other phenols is necessary for full synergistic effect. The authors concluded that the daily oral administration of the studied natural products alone or combined may be highly effective in preventing and treating Staphylococcus aureus infections and theoretically may even be effective against antibiotic-resistant strains.10
In another experiment, 13 sheep affected by ringworm from Trichophyton mentagrophytes infection were treated twice daily for 15 days with a topical mixture of essential oils consisting of Thymus serpillum 2%, Origanum vulgare 5%, and Rosmarinus officinalis 5% in sweet almond (Prunus dulcis) oil. The major components of the mixture were identified as thymol, carvacrol, 1,8 cineole, α-pinene, p-cymene, and c-terpinene. Seven other sheep were given conventional treatment, and two sheep were left untreated. A clinical and etiological cure was obtained at the end of each treatment regimen in only the treated animals. The study concluded that topical treatment with the essential oils was practical and effective, and showed a better result than conventional treatment with regard to the speed of resolution.29
Another study looked at the effect of 5% Origanum vulgare, 5% Rosmarinus officinalis, and 2% Thymus serpillum in sweet almond oil administered topically, twice a day for a month on cats infected with dermatophytoses due to Microsporum canis. Five out of seven cats treated with the herbal mixture recovered clinically, with four of them showing negative cultures. Two animals healed partially and still yielded positive cultures. No adverse effects were reported for any of these animals.30
Safety in Pregnancy and Breastfeeding
There is no information on the safety of Origanum vulgare in pregnancy or lactation in the scientific or traditional literature; however, traditional use as an emmenagogue suggests that is best avoided in higher than culinary amounts. It is also recommended to avoid the internal use of essential oils during pregnancy.
The only clinical study using Origanum vulgare oil for oral supplementation in humans used a dose of 600 mg daily for 6 weeks. No adverse effects or side effects were reported.27
Exposure of gastrointestinal mucosa to concentrated essential oils can cause localized irritation, especially with prolonged usage, and could theoretically cause dysbiosis because of the strong antibacterial effects.
This herb may be considered safe at doses up to 600 mg/day, for up to 6 weeks.
The genus Origanum includes 39 species of perennial plants widely distributed throughout the world whose composition of essential oils and other constituents varies with the geographical location, climate, and other ecological factors. The essential oils obtained from aromatic plants such as Origanum have been widely used since the Middle Ages for numerous applications.
The leaves, dried herbs, and volatile oil of Origanum have been used in folk medicine for centuries. Origanum also has a highly developed culinary use as a flavoring and food preservative. Aqueous infusion of Origanum is traditionally used to treat dysentery, colitis, bronchopulmonary, gastric acidity, and gastrointestinal diseases.
A major traditional use is as a carminative and stomachic (taken with meals to reduce gastrointestinal distress), and as an antispasmodic, often in the form of a tea but also as aromatherapy in the form of a bath, steam inhalation, and vaporization. Other uses include diuretic, emmenagogue, and aphrodisiac. A warm infusion would be used to produce diaphoresis or promote menstruation, and to reduce general pain and inflammation.
In traditional Chinese medicine Origanum spp. are used for the treatment of heat stroke, fever, vomiting, acute gastroenteritis, and respiratory disorders. Origanum spp. are also widely used in the treatment of respiratory and cutaneous infections and would often be administered externally as a fomentation. In addition, the herb would be used in a gargling preparation to treat earache and oral infections such as blisters, ulcers, gingivitis, and toothache.
1 J Agric Food Chem. 2006;54(15):5388–92. Polar constituents from the aerial parts of Origanum vulgare L. Ssp. hirtum growing wild in Greece. Koukoulitsa C, et al.
2 Acta Pol Pharm. 2013;70(3):413–8. HPTLC-densitometry determination of triterpenic acids in Origanum vulgare, Rosmarinus officinalis and Syzygium aromaticum. Nowak R, et al.
3 Biol Pharm Bull. 2003;26(12):1725–9. Screening chemical composition and in vitro antioxidant and antimicrobial activities of the essential oils from Origanum syriacum L. growing in Turkey. Alma M, et al.
4 J Zhejiang Univ Sci B. 2017;18(1):79–84. Chemical composition and antioxidant activities of essential oils from different parts of the oregano. Han F, et al.
5 J Agric Food Chem. 2010;58(12):7119–25. LC-MS method for the simultaneous quantitation of the anti-inflammatory constituents in oregano (Origanum species). Shen D, et al.
6 Mol Carcinog. 2014;53(10):793–806. β-Caryophyllene oxide inhibits constitutive and inducible STAT3 signaling pathway through induction of the SHP-1 protein tyrosine phosphatase. Kim C, et al.
7 Pharmacognosy Res. 2011;3(2):143–5. Chemical constituents and biological studies of Origanum vulgare Linn. Venkateswara R, et al.
8 Int J Food Sci Nutr. 2007;58(2):87–93. The effects of essential oils and aqueous tea infusions of oregano (Origanum vulgare L. spp. hirtum), thyme (Thymus vulgaris L.) and wild thyme (Thymus serpyllum L.) on the copper-induced oxidation of human low-density lipoproteins. Kulisic T, et al.
9 Res Vet Sci. 2016;104:77–82. Larvicidal potential of carvacrol and terpinen-4-ol from the essential oil of Origanum vulgare (Lamiaceae) against Anopheles stephensi, Anopheles subpictus, Culex quinquefasciatus and Culex tritaeniorhynchus (Diptera: Culicidae). Govindarajan M, et al.
10 Toxicol Mech Methods. 2005;15(4):279–85. Effects of essential oils and monolaurin on Staphylococcus aureus: in vitro and in vivo studies. Preuss H, et al.
11 Braz J Microbiol. 2012;43(3):1120–7. Combination of Origanum vulgare L. essential oil and lactic acid to inhibit Staphylococcus aureus in meat broth and meat model. De Barros J, et al.
12 J Sci Food Agric. 2013;93(11):2707–14. Chemical composition and bioactivity of different oregano (Origanum vulgare) extracts and essential oil. Teixeira B, et al.
13 Nat Prod Res. 2011;25(20):1993–8. Terpenoid composition and antifungal activity of three commercially important essential oils against Aspergillus flavus and Aspergillus niger. Bisht D, et al.
14 Molecules. 2013;18(12):14948–60. Chemical composition and biological activity of essential oils of Origanum vulgare L. subsp. vulgare L. under different growth conditions. De Falco E, et al.
15 J Egypt Soc Parasitol. 2012;42(1):245–50. The efficacy of Origanum vulgare on Eimeria tenella. Toulah F, et al.
16 Medicines (Basel). 2017;4(2). Antibacterial and antifungal activity of essential oils against pathogens responsible for otitis externa in dogs and cats. Ebani V, et al.
17 Mol Cell Biochem. 2001;228(1–2):111–7. Antifungal activities of origanum oil against Candida albicans. Manohar V, et al.
18 Int J Food Microbiol. 2011;146(2):144–50. The antimicrobial activity of microencapsulated thymol and carvacrol. Guarda A, et al.
19 Recent Pat Antiinfect Drug Discov. 2012;7(1):28–35. Antimicrobial activity of carvacrol: current progress and future prospectives. Nostro A, et al.
20 Plant Biol (Stuttg). 2017;19(4):599–607. Inhibitory effect of Thymus vulgaris and Origanum vulgare essential oils on virulence factors of phytopathogenic Pseudomonas syringae strains. Carezzano M, et al.
21 Future Microbiol. 2018;13:59–67. Antimicrobial activity of six essential oils against Burkholderia cepacia complex: insights into mechanism(s) of action. Perrin E, et al.
22 J Food Sci. 2011;76(3):C512–8. Oregano: chemical analysis and evaluation of its antimalarial, antioxidant, and cytotoxic activities. El Babili F, et al.
23 Planta Med. 1980;38(4):317–31. Antispasmodic activity of Origanum compactum. Van Den Broucke C, et al.
24 Planta Med. 1982;45(3):188–90. Antispasmodic activity of Origanum compactum. Part 2: Antagonistic effect of thymol and carvacrol. Van den Broucke CO, Lemli JA.
25 Int J Food Microbiol. 2004;94:223–53. Essential oils: their antibacterial properties and potential applications in foods—a review. Burt S, et al.
26 Int J Pharmaceut. 2012:434:360–5. Thymol nanospheres as an effective anti-bacterial agent. Wattanasatchaa A, et al.
27 Phytother Res. 2000;14(3):213–4. Inhibition of enteric parasites by emulsified oil of oregano in vivo. Force M,
28 J Drugs Dermatol. 2011;10(10):1168–72. Oregano extract ointment for wound healing: a randomized, double-blind, petrolatum-controlled study evaluating efficacy. Ragi J, et al.
29 Mycoses. 2013;56(3):333–7. A herbal antifungal formulation of Thymus serpillum, Origanum vulgare and Rosmarinus officinalis for treating ovine dermatophytosis due to Trichophyton mentagrophytes. Mugnaini L, et al.
30 J Mycol Med. 2012;22(2):179–84. In vitro and in vivo antifungal activity of some essential oils against feline isolates of Microsporum canis. Mugnaini L, et al.