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Hoary Basil

Scientific Name(s): Ocimum americanum, Ocimum canum Sims
Common Name(s): American basil, Hoary basil

Medically reviewed by Last updated on Apr 13, 2022.

Clinical Overview


Animal and in vitro studies suggest anticholinesterase, anti-inflammatory, antidiabetic, antioxidant, antimicrobial, insecticidal, and anesthetic activities. However, clinical studies are lacking to recommend use of hoary basil for any indication.


Clinical studies are lacking to provide dosing recommendations.


Contraindications have not been identified.


Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking. Emmenagogue and abortifacient effects have been reported for the related species Ocimum basilicum (sweet basil).


None well documented.

Adverse Reactions

A small clinical study reported abdominal discomfort, flatulence, and constipation in hypercholesterolemic patients consuming 15 g/day of O. canum seeds.


No data.

Scientific Family

  • Lamiaceae (mint)


O. canum is commonly known as "hoary basil" or "American basil," despite being native to Africa and parts of Asia. The small annual plant grows in tropical and subtropical regions, including of the Americas, to about 0.5 m in height, and bears clusters of white or lavender flowers similar to those of O. basilicum. Small, single-seeded fruits are produced. Like other members of the basil genus, O. canum contains volatile compounds concentrated in its leaves.(Duke 2002, HSA 2003, USDA 2018)

Related plants include O. basilicum (sweet basil), Ocimum gratissimum (African basil), Ocimum tenuiflorum (holy basil), and Ocimum campechianum (Amazonian basil or Least basil). A synonym of O. canum is Ocimum americanum auct.


Hoary basil is cultivated for the young edible leaves and eaten as a side dish in some Asian cultures. Traditional medicinal uses include for cough and other respiratory conditions, rheumatism, colic, conjunctivitis, malaria, and headache, and for its analgesic and rubefacient effects. In Africa, an aqueous extract has traditionally been used to manage diabetes and liver conditions. The essential oil is used in cosmetics and soaps, and as flavoring in foods, chewing gums, sweets, teas, soft drinks, energy drinks, and milk products.(Duke 2002, HSA 2003, Ngassoum 2004, Nyarko 2002, Nyarko 2003, Sharma 2012)


Organic and amino acids and sugar content of O. americanum aerial plant parts have been described, with the amino acids asparagine, proline, glutamic acid, glycine, and gamma-aminobutyric acid being the most prevalent. Levulinic, citric, linolenic, palmitic, and oxalic acids are among the most concentrated organic acids.(Farag 2016, Shanaida 2017)

The major identified constituents of the essential oil are cineol, camphor, alpha-pinene, and trans alpha-bergamotene.(Bayala 2014, Freires 2015, Selvi 2015) Tannin and flavonoid content has also been evaluated.(Kumar 2017) Varying amounts of methyl cinnamate, citronella and citral derivatives, and eugenol as well as dipentene, terpinolene, crithmene, limonene, pinene, sabinene, camphene, and caryophyllene have been identified. Polysaccharides (including xylose, arabinose, rhamnose, and galactose) have also been described. Content varies according to geographical location and harvesting times, with resultant various chemical constituents such as methyl cinnamate, citral, eugenol, and camphor being the most prominent.(Berhow 2012, Duke 2002, Nascimento 2011, Pandey 2014, Vieira 2014, Vieira 2003, Vyry 2014, Xaasan 1981)

Uses and Pharmacology

Limited studies using extracts of hoary basil have been conducted; experiments and evaluations of uses are similar to those conducted with sweet basil and holy basil.

Anesthetic activity

Animal data

Anesthetic activity of the essential oil has been demonstrated in koi carp fish, with inhibition of sodium channels (the major cause of excitability blockade) by the chemical constituent methyl chavicol proposed as a potential mechanism of action.(Khumpirapang 2018) The chemical compound linalool from O. americanum has also been shown to have anesthetic properties in fish.(Silva 2017)

Antibacterial activity

In vitro data

Antibacterial potential of the essential oil against cariogenic Streptococci bacteria has been demonstrated, largely though in vitro studies.(Freires 2015, Vyry Wouatsa 2014)

Anticholinesterase activity

In vitro data

In an in vitro study investigating methanol extracts of 4 Ocimum species, including O. americanum, major identified phenolics (ie, rosmarinic, caftaric, and chlorogenic acids) were suggested to have a role in mediating anticholinesterase effects.(Farag 2016)

Anti-inflammatory effects

Animal and in vitro data

O. canum showed significant anti-inflammatory activity against carrageenan, prostaglandin E2, leukotriene, and arachidonic acid–induced paw edema.(Singh 1998) Anti-inflammatory activity may be associated with the essential oils and linolenic acid content, which can block both the cyclooxygenase and lipoxygenase pathways of arachidonate metabolism.(Setty 2005, Singh 1998) In vitro antioxidant activity has also been demonstrated.(George 2009, Saeio 2011)

In a study in mice evaluating effects of O. canum essential oil on induced arthritis and paw edema, reductions in cytokine expression and edema were observed; histological studies suggested a protective effect against leukocyte influx and cartilage destruction in the joints.(Yamada 2013)

Antimicrobial activity

In vitro data

Antibacterial potential of the essential oil against cariogenic Streptococci bacteria has been demonstrated, largely though in vitro studies.(Freires 2015, Vyry Wouatsa 2014) In vitro, the oil from O. canum leaves, but not the flowers, was active against some gram-positive and gram-negative bacteria(Bassole 2005, Cimanga 2002, Tajo 1999, Vyry Wouatsa 2014) and also possessed antifungal activity.(Yadav 1994)

Antioxidant activity

Animal and in vitro data

Antioxidant activity of O. canum crude methanolic extract and its fractions has been observed in vitro and supported by results in diabetic rats and nondiabetic controls.(Bayala 2014, Ononamadu 2019, Selvi 2015) O. canum methanol extract was also hepatoprotective against alcohol-induced oxidative stress in a study of rats.(George 2008)


Animal and in vitro data

In a study in mice administered aqueous leaf extracts of 5 Ocimum species, including O. canum, antimelanoma and radioprotective activity against B16F10 metastatic melanoma cell line–induced metastasis was demonstrated.(Monga 2011) In an in vitro study, essential oil isolated from leaves of O. canum demonstrated significant cytotoxicity in breast cancer cells(Selvi 2015); however, the chemical constituent estragole is considered carcinogenic.(De Vincenzi 2000)


Animal and in vitro data

In a study in diabetic mice, reductions in fasting blood glucose measures as well as improved lipid profiles were observed following administration of supplemental O. canum aqueous leaf extract for 13 weeks.(Nyarko 2003) The authors suggested that the extract promotes release of insulin from pancreatic islet cells.(Nyarko 2002) Methanolic whole extracts have demonstrated in vitro inhibition of alpha-glucosidase activity.(Smita 2018) Compared to acarbose, the methanolic crude extract of O. canum and its fractions exhibited poor inhibition of alpha-amylase and alpha-glucosidase. In contrast, the crude extract given for 28 days demonstrated a dose-dependent significant reduction in fasting blood glucose (P<0.05) that was similar to glibenclimide (ie, glyburide) in a diabetic rat model.(Ononamadu 2019)


Animal data

In a study in diabetic mice, O. canum decreased serum total cholesterol and low-density lipoprotein cholesterol and increased high-density lipoprotein cholesterol.(Nyarko 2003)

Clinical data

One small (N=30), 12-week clinical study examined the clinical outcome of nutrition counseling with O. canum seed supplementation (15 g daily) on serum lipid levels, finding no benefit to the lipid profile.(Kangsadalampai 2007)

Insecticidal activity

In vitro data

Insecticidal activity of the essential oil has been described, with methanolic extracts and powder preparations demonstrating activity against adults and larvae of Aedes aegypti and other disease vector mosquitos.(Madhiyazhagan 2014, Murugan 2016, Wangrawa 2018) The plant and essential oil are used in Africa to protect agricultural crops from insect damage(Belmain 2001, Khanom 2000, Lehman 2007, Pandey 1994) and as a mosquito repellent.(Pålsson 1999, Seyoum 2002, Seyoum 2002, Tawatsin 2001)


Clinical studies are lacking to provide dosing recommendations.

Pregnancy / Lactation

Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking. Emmenagogue and abortifacient effects have been reported for the related species O. basilicum.Duke 2002, Ernst 2002


None well documented. Case reports are lacking.

Adverse Reactions

Data are limited. A 12-week clinical trial documented abdominal discomfort, flatulence, and constipation in hypercholesterolemic patients consuming 15 g/day of O. canum seeds.(Kangsadalampai 2007) Few adverse reactions have been reported in clinical studies evaluating other members of the basil genus.


Information is limited. The chemical constituent estragole is considered carcinogenic.(De Vincenzi 2000) The median lethal dose (LD50) of O. canum ethanolic extract in rats was more than 5,000 mg/kg, which is considered nontoxic.(Ononamadu 2019)

Index Terms

  • Ocimum americanum auct.



This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.

This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.

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Further information

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