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Health aspects of peppermint
Peppermint (Mentha piperita L.) is a perennial herb best known for its fragrance and flavoring properties. Its leaves and essential oil have found many uses in food, cosmetic, and pharmaceutical products. Many studies have evaluated the properties of peppermint, and some of these findings are indicated here, to serve as information on the many health uses of this plant.
The maturity of the peppermint plant, the plant variety, geographical region, and processing conditions are factors that affect the chemical components to be found in the leaves and essential oil of peppermint. Generally, the fatty acids present in the peppermint leaves are palmitic, linoleic, and linolenic acids. In peppermint essential oil, the volatile components usually found are menthol, menthone, isomenthone, eucalyptol, menthyl acetate, methofuran, and several others.
Some studies have also reported the presence of beta-carotenes, other carotenoids, and chlorophylls. There also are several minerals present in peppermint, the major ones being potassium, calcium, magnesium, and some sodium; smaller amounts of iron, manganese, zinc and copper; and traces of chromium, iodine, and selenium.
A research team studied 120 edible plants for antitumor activity against okadaic acid, which affects formation of tumors. Of these plants, only eight plants, including peppermint, showed strong ability to suppress the effects of okadaic acid. The menthol from peppermint appeared to inhibit the activity of an enzyme in a tumor cell found in human liver. A flavonoid (luteolin) found in an aqueous extract of peppermint strongly suppressed the ability to mutate of a human carcinogen.
Anti-allergen activity. A study on mast cells found in rat peritoneum observed that flavonoid glycosides derived from peppermint exhibited antiallergenic activity, particularly luteolin-7-0-rutinoside. Menthol from peppermint had significant suppressant effect on the production of compounds involved in inflammatory mediation, such as leukotriene B4 and prostaglandin E2. Another peppermint constituent, eucalyptol, inhibited the production of several inflammatory mediating compounds.
A research study in 1967 observed that aqueous extracts from peppermint leaves had significant antiviral activity against several viruses: influenza A, Newcastle disease, herpes simplex, and vaccinia. These were observed in egg and cell-culture systems. Combined with four other herbs, an alcohol extracted from peppermint effectively inhibited influenza viruses from reproducing, in embryonated eggs and tissue cultures.
In 1998, a research team found that an aqueous extract of peppermint had potent activity against human immunodeficiency virus-1 (HIV-1). Other researchers in 2003 reported a suppressant effect of peppermint essential oil on the ability to replicate of herpes simplex virus (HSV-1); this was related to another 2003 report that peppermint oil inhibited the action of HSV-1 and HSV-2 when the viruses were treated with the oil before (but not after) they penetrated the host cell.
There have been many research studies detailing the antibacterial activity of peppermint. One study showed that peppermint oil, and components menthol and methone, had moderate inhibitory effect on human pathogens, including Staphylococcus aureus, S. epidermi, and Listeria monocytogenes. A 1996 research study reported peppermint oil potent against 22 different bacteria. Menthol from peppermint is very useful against respiratory tract bacteria such as Streptococcus pneumoniae, Staphylococcus aureus, Legionella pneumophila, and Haemophilus influenzae.
Peppermint oil showed potent fungicidal activity against 11 of 12 fungi tested in 1996, including the common Candida albicans and Aspergillus fumigatus. Many other studies have documented the moderate ability of peppermint extracts to fight pathological fungi. Peppermint oil is a proven antimicrobial agent in various food crops and foodstuffs.