Oregano

INTRODUCTION

Oregano

Scientific Name: Coleus aromaticus Benth.

Common Name: Country Borage^[1], Suganda ^[2]

Indian borage is an aromatic, perennial succulennt which grows to about 1metre in height. The leaves, which put forth a strong sweet smelling odour, is heart-shaped and fleshy in nature. Flowers are small, and occur in distant whorls. Calyx is bell-shaped; the throat is smooth inside, with two lips, the upper lip being ovate and thin, the lower lip having four narrow teeth. Corolla is pale purplish and 5 times longer than the calyx, with a short tube, inflated throat, and short lips. ^[1]

Parts Used:

Leaves

  ^[3]

The oregano leaves come in an oval shape and look dark green in color. ^[3] A common way to use oregano leaves is by steeping a tea. The tea can be made with fresh or dried oregano. Approximately 1 to 2 teaspoons, which is 5 to 10 grams, should be steeped in hot water for approximately 10 minutes. The recommended dosage of this tea is up to three times daily. ^[7]

ACTIVE CONSTITUENTS

Oregano leaves extract yielded two protocatechuic acid ester derivatives, (1)origanol A and (2) origanol B along with (3)ursolic acid , (4) oleanolic acid , (5)β-sitosterol , and (6)triacontanol.^[4]

It has essential oil c. 2% (incl. phenols up to 63% including carvacrol, thymol, borneol), monoterpenes 7-10% which include (paracymene, terpinenes, cymene, caryophyllene, pinene), linalyle/geranyl acetate, 1.8 cineol, bitters, tannins, coffeic/urslic/rosmarinic acids, resins, gum. Its effective qualities are pungent, bitter, warm, relaxing, stimulating, dispersin. ^[5]

 Phytochemical screening yielded carbohydrates, proteins, phenols, tannins, flavanoids, saponins, glycosides.Aerial parts yielded essential oil with 28 constituents, 16 of which were identified. Thymol (83.39%) was the major compound, while 1-octen-3-ol, terpine-4-ol, eugenol, trans-caryophyllene, caryophyllene oxide and α-cadinol were present as minor constituents. ^[6]

TRADITIONAL USE

Oregano leaves and flowers are used as antiseptic for cuts and burns. Oregano oil extracts help treat cold, mild fever, and indigestion. Oil derived from oregano leaves offers relief from toothaches and reducing of bad breath. Oregano oil when rubbed on the chest and inhaled as vapors directly from the bottle several times in a day, helps clear the passage in cases of asthma. A few drops of oregano oil rubbed on the scalp at night help control dandruff. Oregano tea is believed to have a soothing effect and helps in getting restful sleep. The tea made with oregano is also used to relieve flatulence and menstrual pain.

Oregano is a relatively good source of calcium, iron, manganese, Vitamin A, C and K. It is used as a steam inhalant, oregano helps clear sinuses. Externally crushed oregano leaves are mixed with oats and hot water and pounded into a paste. When applied over swelling, itching and aching muscles, eases pain. It also provides relief when rubbed on affected joints in case of arthritis. ^[7]

PHARMACOLOGICAL ACTIVITY

Some of oregano's pharmacologic actions may be connected to activation of the transient receptor potential (TRP) channel V3, which mediates warm sensations, by carvacrol and thymol. In addition, carvacrol and thymol rapidly activate and desensitize TRPA1, another similar receptor. These are distinct from the action of capsaicin, the pungent principle of chili pepper, which activates TRPV1, and menthol, the cooling principle of mint, which activates TRPM8. There are few clinical studies on the medicinal effects of oregano, despite its widespread culinary use.

Antioxidant activity

Many experiments have demonstrated that in vitro antioxidant activity of oregano essential oil and its constituent compounds rosmarinic acid, carvacrol, and thymol are similar to or better than alpha tocopherol. Accelerated solvent extraction was proposed to yield higher antioxidant activity than room temperature extraction. Vanillin, vanillic acid, and protocatechuic acid from C. aromaticus showed both antioxidant activity and inhibition of cellular melanogenesis, while a novel phenolic glycoside from oregano also inhibited melanogenesis. Long-term dietary administration of oregano to rats reduced carbon tetrachloride-induced oxidative stress.  The clinical importance of these effects is not yet established. In a double-blind, placebo-controlled trial among healthy adult men, no differences in biomarkers of lipid peroxidation were found with oregano extract supplementation.

Antifungal activity

Oregano inhibited aflatoxin production and prevented growth of Aspergillus at concentrations as low as 0.1%.Further studies have compared the effects of oregano essential oil, thymol, and carvacrol, which all completely inhibited fungal growth of Aspergillus and Penicillium species. Oregano oil has exhibited some antifungal activity against Candida species, possibly because of its carvacrol content. Synergism of oregano oil antifungal effects with nystatin has been observed in vitro.

Antibacterial activity

The volatile oil of oregano has demonstrated in vitro antibacterial activity against a wide range of gram-positive and gram-negative microorganisms, including Listeria , Pseudomonas , Proteus , Salmonella , and Clostridium species, as well as some methicillin-resistant Staphyloacocci. An ointment formulation targeting methicillin-resistant Staphylococcus aureus  has been developed. 61 Low to moderate activity against Helicobacter pylori has been demonstrated. Oregano oil appears to inhibit organisms at relatively low concentrations, and its activity is primarily due to the phenolic components thymol and carvacrol. Functional changes in bacterial cell membrane potential and permeability have been linked to oregano oil treatment. The effect of oregano oil on foodborne bacterial pathogens has been widely studied. Some methods of essential oil extraction appear to yield oil with poor antibacterial properties.

Antiparasitic action

In one study, 14 patients with known parasites were administered 200 mg emulsified C. aromaticus oil for 6 weeks.Entamoeba harmanni, Endolimax nana and Blastocystis hominis were eradicated from 13 patients. Several oils, including oregano, were shown to inhibit Giardia trophozoite growth and viability. The oil of C.aromaticus has been shown to eradicate common parasites in chickens and pheasants. In vitro experiments showed activity against Trypanosoma cruzi.

Antispasmodic effects

Coleus aromaticus has been as a spasmolytic, prepared as a tea from flowers and leaves of the plant. The rapid spasmolytic action of C. aromaticus was demonstrated in in vitro experiments after using acetylcholine on smooth muscle preparations to produce contractions. It is suspected that the herb stabilizes the muscle membrane by interfering with the influx of calcium and its regulatory proteins. The active components in the C. aromaticus essential oil appear to be thymol and carvacrol.

Diabetes

Researchers have demonstrated a hypoglycemic effect of oregano in rats with induced diabetes, providing some supportive evidence for the use of oregano leaves in diabetic patients. The effect was independent of insulin and occurred after a single dose, as well as with repeated daily dosing.

Other researchers have demonstrated an aldose reductase inhibitory effect by lithospermic and rosmarinic acid extracted from oregano. Some researchers have suggested that inhibiting the accumulation of sorbitol may contribute to the prevention of chronic complications, such as retinopathy and peripheral neuropathy in diabetic patients.

Another group reported constituents with both antagonistic and agonist effects at the peroxisome proliferator-activated receptor gamma, which could be of use in metabolic syndrome.

Anti-inflammatory effects

A supercritical fluid extract of C. aromaticus reduced proinflammatory cytokines, while increasing anti-inflammatory interleukin, Rosmarinic acid, oleanolic acid, and ursolic acid were identified as the anti-inflammatory constituents. A combination of thyme and oregano oils were found to reduce the expression of pro-inflammatory cytokines in a mouse model of colitis. Protein levels of IL-1beta and IL-6 were also reduced.

Other

Both oregano essential oil and aqueous infusions showed inhibitory activity against low-density lipoprotein (LDL) oxidation, with different constituents responsible for the activity in the 2 preparations. 76 In hyperlipidemic patients, 25 mL of an aqueous distillate of oregano watertaken daily enhanced the effects of altered lifestyle and low-fat diet interventions in modulating mild hyperlipidemia.

Monoamine reuptake inhibition in the rat brain by an oregano extract was observed, and serotonin levels, as measured by microdialysis, were elevated by the same extract.

Essential oils of C. aromaticus inhibited growth of breast cancer cells in vitro; however, they were not cytotoxic. Oregano ethanolic extract induced apoptosis in human colon cancer cells. In rats, whole oregano given orally markedly inhibited dimethylhydrazine-induced colon cancer at 40 mg/kg. Galangin and quercetin from oregano were shown to be antimutagenic in an Ames test with Salmonella typhimurium TA98.Thymol had genotoxic activity in a Drosophila model; however, this activity was antagonized by carvacrol. ^[8]

TOXICITY

In a study investigating the effect of oregano on growth and development of mouse embryos, an increase in the proportion of dead cells in pre-implantation embryos was observed. ^[10] There are some reports of gastrointestinal upset with oil of oregano. There are also reports of allergic reactions. There is no evidence to suggest that oil of oregano, used at high (medicinal) amounts, may be used safely in pregnant or breast feeding women. However, when used in cooking, and as part of a regular diet, there is also no evidence that causes harm in pregnancy or breastfeeding. Animal studies show that if you give enough carvacrol (one of oregano’s constituents), it can cause death. ^[9]  

^[1]JC Kurian, 2010, Amazing Healing Plants

^[2]Suganda, 2011; http://stuartxchange.com/Oregano.html

^[3]Troy Nelson, 2011;  http://www.amillionlives.net/growing-oregano-tips-for-cultivating-the-perennial-herb.html

^[4]Chemical constituents and biological studies of Origanum vulgare Linn. April 2011, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3129025/

^[5]Oregano by Charlotte Branca, http://www.herballegacy.com/Branca_Chemical.html

^[6]Phytochemical study of essential oil from the aerial parts of Coleus aromaticus Benth. / Tewari G1, Pande C, Kharkwal G, Singh S, Singh C. / Nat Prod Res. 2012; 26(2):182-5. / doi: 10.1080/14786419.2011.574135.

^[7]Oregano Herbal Medicine Uses, Health Benefits and Side Effects,2011; http://www.medicalhealthguide.com/articles/oregano.htm

^[8]Oregano, 2000-2014; http://www.drugs.com/npp/oregano.html#ref30

^[9] Oil of Oregano, May 26, 2011; http://www.sciencebasedmedicine.org/oil-of-oregano/

^[10] Domaracký M, Rehák P, Juhás S, Koppel J. Effects of selected plant essential oils on the growth and development of mouse preimplantation embryos in vivo. Physiol Res . 2007;56(1):97-104.

Compiled by:

Ianna N. Fuentes