August 2010-- An overview of the potential health benefits of oregano, funded by the McCormick Science Institute. An evaluation of the research is presented. Read the entire study (PDF)
MSI Funded Paper:
Potential Health Benefits of Oregano
Singletary, K
Oregano is an herb that has been cultivated for centuries in the Mediterranean area, although it now can be found on most continents. Actually, there is not simply one ‘‘oregano,’’ but rather several species that may contribute to the oregano used for culinary purposes. Origanum vulgare (also referred to as Spanish thyme and wild marjoram), a member of the plant family Lamiaceae, is generally the spice variety sold as oregano in Europe and the United States.
Medicinal uses for oregano date back to the ancient Greek and Roman empires where applications of the leaves were used to treat such maladies as skin sores and relieve aching muscles and as an antiseptic. Oregano also has been used in traditional medicines for such ailments as asthma, cramping, diarrhea, and indigestion. In Greece, an oregano infusion is still used as a folk remedy against colds and upset stomach and to maintain general health. Based on the current scientific literature, oregano extracts and individual constituents consistently have demonstrated antimicrobial actions in vitro toward food-borne pathogens, although the capacity to counter human infections is not well studied.
Oregano contains several potent antioxidants that may contribute to the findings in preliminary studies that oregano exhibits benefits toward the cardiovascular and nervous systems, relieves symptoms of inflammation, and modulates blood sugar and lipids. Well-controlled human studies substantiating these health effects are lacking.
| An evaluation of the quality of the scientific research is presented below: | Rating[1] |
|---|---|
| Antimicrobial actions Oregano and some of its constituents are reported in in vitro models to suppress microbes that cause food spoilage and those that contribute to human and animal disease. Both the essential oil and other extracts of oregano can suppress the growth of gram-positive and gram-negative bacteria, yeast, and some fungi.(20-29) Depending on the test system and microorganism evaluated in these assays, the effective concentrations of oregano ranged from 0.4 to 4000 µg/mL. Oregano oil added at 4% wt/wt has been used to fortify flexible polypropylene film as an antimicrobial strategy.(30) Oregano oil tested in a range of concentrations from 0.1 to 2.0% wt/wt was effective in suppressing microbial growth in beef and sausage products.(31,32) However, in another study, oregano did not suppress growth of Yersinia enterocolitica or Listeria monocytogenes in barbequed chicken.(33) Oregano was reported to inhibit Helicobacter pylori, the bacterium associated with gastritis in humans, to kill human intestinal parasites in vitro (at ~175 µg/mL concentration), and at a dose of 10 mg oregano oil/kg body weight to effectively treat colibacillosis of newborn calves.(34-37) In a short-term study in humans infested with enteric parasites, daily intake of 600mg of emulsified oregano oil resulted in noticeable decreases in occurrence of some of the parasites.(38) Individual components of oregano, such as carvacrol and thymol, also have antimicrobial actions.(39-43) The effective doses of thymol or carvacrol may range from 20 to 50 µg/mL.(20) Of interest is the observation that oregano phytochemicals can suppress microorganisms associated with oral disease and ear infections.(44-47) Although the antiviral efficacy of spice phytochemicals can vary,(24) rosmarinic acid was reported to reduce the mortality of mice infected with an encephalitis virus (48) and has been identified as an inhibitor of HIVE type 1 reverse transcriptase.(49) | P |
| Effects on inflammation and immunity Several investigators have provided evidence that oregano extracts or constituents thereof can suppress inflammation in vitro and in vivo. Thymol (at doses of 2.5-20 µg/mL) inhibited the release of elastase, a marker of inflammatory disease, from human neutrophils induced by a chemotactic peptide,(50) an action in part mediated through inactivation of calcium-channel machinery. Likewise, rosmarinic acid inhibited neutrophil elastase release and weakly suppressed thrombin activity.(51) On the other hand, neither an essential oil of oregano nor the phytochemicals thymol, carvacrol, p-cymene, or y-terpinene possessed anti-inflammatory actions in a chorioallantoic membrane assay, and in fact, thymol, at the dose used (10 µg), was shown to be an irritant.(52) Rosmarinic acid induced apoptosis of lymphocytes and was able to kill T and natural killer cells, which are means by which harmful immune responses can be mitigated.(53,54) Oregano essential oil, administered intrarectally (0.1-1.0 mg/kg body weight) or in the diet (0.05%-2.0%) had a significant protective effect in rodents against chemically induced colonic damage, inflammatory cell infiltration, and vascular dilation along with suppressing production of proinflammatory cytokines IL-1ß and IL-6.(55,56) In several mouse studies of inflammation rosmarinic acid (50 mg/kg body weight intraperitoneally or 1.5 mg/d orally) dramatically decreased inflammatory autoimmunoarthritis and allergic asthma and markedly reduced inflammatory markers and cyclooxygenase 2 expression.(57-59) In human patients with seasonal allergic rhinoconjunctivitis who were treated with 50 or 200 mg/d of rosmarinic acid, there was a significant decrease in seasonal allergic rhinoconjunctivitis symptoms compared with controls.(60) In activated T cells obtained from patients with rheumatoid arthritis, rosmarinic acid induced apoptosis, which was suggested by the authors as a potential strategy to inhibit pathogenic T cell-mediated progression of rheumatoid arthritis.(61-63) | P |
| Antioxidant properties The antioxidant properties of the volatile oils are not as robust as that of water-soluble constituents. However, because of variability in composition and origin of different Origanum spp, the antioxidant capacity reported can vary substantially. In one study,(5) oregano had the highest total antioxidant capacity and phenolic content compared with 5 other Labiatae herbs, thyme, sage, rosemary, mint, and sweet basil. Oregano extracts have demonstrated radical scavenging action, suppression of lipid peroxidation, inhibition of nitric oxide activity, and protection of DNA against H2O2-induced oxidant damage.(64-67) The constituents reported to be responsible for the antioxidant strength of oregano have been variously attributed to carvacrol, y-terpinene, rosmarinic acid, ursolic acid, protocatechuate-glycosides, and thymol.(67-77) Oregano also contains homologs of the nutrient antioxidant tocopherol.(78) In rats, oregano or constituents (42.5 mg/kg body weight) increased aging brain antioxidant activity and total antioxidant status.(79) Dietary oregano leaf (1% wt/wt) alleviated carbon tetrachloride-induced oxidative stress in rats.(80) Rosmarinic acid, given to rats orally at 100 mg/kg body weight, suppressed mesangioproliferative glomerulonephritis apparently due to its fibrinolytic and antioxidative properties.(81) However, in healthy nonsmoking males, oregano extract administered at a dose up to 600 mg/d total phenolics in a fruit drink had no effect on markers of lipid peroxidation.(14) | P |
| Nervous system benefits Oregano and some constituents (such as carvacrol, thymol, and y-terpinene) have been reported in preliminary studies to influence nervous system chemistry and diverse functions, including responses to olfactory stimulation.(82-85) Intriguing evidence from animal studies suggests that rosmarinic acid (2 mg/kg body weight intraperitoneally) produces antidepressive activity and may inhibit an emotional abnormality produced by stress.(86-88) | P |
| Blood glucose and lipid regulation There is limited evidence that oregano extracts or constituents have the potential to benefit the management of diabetes and cardiovascular disease. For example, water extracts of oregano and rosmarinic acid exhibited considerable a-glucosidase inhibitory activity in vitro.(89) Rosmarinic acid-containing oregano extracts also inhibited porcine pancreatic amylase activity.(90) In 2 animal studies using diabetic rats, a water extract of Origanum vulgare administered orally at 20 mg/kg body weight demonstrated antihyperglycemic activity.(91,92) In rats, the tissue injury resulting from treatment with the diabetes-inducing drug streptozotocin was substantially lessened by long-term administration of the essential oil of O onites L.(93) In several assay systems, extracts of Origanum spp and individual constituents such as y-terpinene and carvacrol have been shown to inhibit blood platelet aggregation and adhesion, decrease cholesterol biosynthesis, and reduce serum total cholesterol and triglyceride levels.(89,94-97) In normotensive rats, administration of carvacrol (100 µg/kg intraperitoneally) decreased systolic and diastolic blood pressures.(94) In cockerels, dietary supplementation with thymol and carvacrol (1 mmol/kg diet) suppressed serum cholesterol levels, which in part could be due to increased activity of geranyl pyrophosphate pyrophosphatase.(95) | P |
| Anticancer actions Oregano constituents have antimutagenic, antigenotoxic, and antiproliferative properties. For example, in cell culture studies, oregano extracts protected cells from oxidative stress-, mitogen- and radiation-induced DNA damage.(98,99) Likewise, carvacrol and rosmarinic acid have each been reported to protect DNA from a variety of damaging agents and to suppress proliferation of cancer cells or cells with active oncogenes.(100-107) Carvacrol and thymol, for example, suppressed the in vitro growth of melanoma cells, demonstrating IC50 values of (120-150) µmol/L.(104) Furthermore, an extract of oregano was capable of upregulating the activity of the DNA repair enzyme MGMT (O6-methylguanine-DNA methyltransferase) as well as the phase II detoxification enzyme glutathione-S-transferase.(108) It also induced levels of MGMT protein and activity and thus may have beneficial chemoprevention activity in inhibiting alkylating agent-induced DNA lesions. Mice treated orally with thymol and carvacrol (200 mg/kg body weight) evidenced significant increases in liver activities of glutathione-S-transferase, NAD(P)H-quinone reductase, and 7-ethoxycoumarin-O-deethylase.(101) Rosmarinic acid blocked processes associated with cancer invasion and metastasis.(109,110) Also, rosmarinic acid administered topically (1.3 mg per mouse) inhibited epidermal inflammatory responses in a murine 2-stage model of skin cancer.(111) | P |
| Miscellaneous Oregano oil, rosmarinic acid, or carvacrol (73 mg/kg body weight) has been shown to protect liver cells in rodents from lead toxicity and to stimulate liver regeneration following partial hepatectomy.(112,113) Carvacrol (73mg/kg body weight) also protected rat liver from defects caused by ischemia and reperfusion and was not hepatotoxic.(114) Rosmarinicacid (100-200 µM) can protect cardiomyocytes in culture from doxorubicin and adriamycin-induced toxicity and thus was suggested as a potential chemotherapeutic agent to inhibit cardiotoxicity in patients undergoing drug treatments.(115,116) | P |
S: Strong, convincing evidence
E: Emerging, suggestive evidence
P: Preliminary, inconclusive evidence
No comments:
Post a Comment