Clove (Syzygium aromaticum) is a spice that has attracted the attention of researchers due to its potent antioxidant and antimicrobial activities.
It appears to have some traditional usage as an aphrodisiac as well as for the medicinal purposes of dental disorders, respiratory disorders, headache and sore throat (1).
The clove plant has a rich source of phenolic compounds such as eugenol, eugenol acetate and gallic acid, and are what researchers believe give it its range of pharmacological effects (2).
Clove is an effective antioxidant. Antioxidants are disease-fighting compounds naturally found in various foods, especially fruits and vegetables, that help to neutralize harmful free radicals, preventing them from damaging the body. As free radicals interact with other molecules in the body, they cause oxidative damage that can result in the development of a wide range of illnesses and diseases.
It is becoming increasingly evident that natural antioxidants, which have phenolic structures, play an important role in protecting the tissues against free radical damage. Eugenol is one such naturally occurring phenolic compound.
In a 2018 issue of the International Journal of Molecular Sciences, researchers discuss the effects of Syzygium aromaticum and argan essential oils on hydrogen peroxide-induced liver, brain and kidney tissue toxicity in rats (hydrogen peroxide is often used as an experimental source of oxygen-derived free radicals). The results show that the content of antioxidant compounds in Syzygium aromaticum essential oil is higher than that found in argan oil.
It was concluded that the mixture of argan oil with Syzygium aromaticum essential oil can reduce oxidative damage (3).
In another study, the antioxidant activity of water and ethanol extracts of clove buds and lavender (Lavandula stoechas L.) was studied. Both extracts of clove and lavender exhibited strong total antioxidant activity.
At concentrations of 20, 40, and 60 μg/ml, water extract of clove and lavender had an almost 95 percent inhibition on lipid peroxidation. The powerful antioxidant activity of both extracts may be attributed to metal chelating ability and scavenging of free radicals — hydrogen peroxide and superoxide (4).
Clove has been shown to have antibacterial activity. The antimicrobial activities of clove have been proven against several bacterial and fungal strains. In one study, researchers tested the antimicrobial activity of different Indian spice plants, including mint, cinnamon, mustard, ginger, garlic and clove.
The only spice that showed complete bactericidal effect against all the food-borne pathogens tested — Escherichia coli (E. coli), Staphylococcus aureus and Bacillus cereus — was the aqueous extract of clove at 3 percent. Even at the concentration of 1 percent, clove extract also showed good inhibitory action (5).
In another study, the antibacterial activity of black pepper, geranium, nutmeg, oregano, thyme and clove was tested against 25 strains of Gram-positive and Gram-negative bacteria. The oils with the widest spectrum of activity were thyme, oregano and clove respectively (6).
Clove has libido-boosting ability. In an experimental study, researchers administered extracts (50% ethanolic) of nutmeg and clove to different groups of male mice. The extracts of the nutmeg and clove were found to stimulate the mounting behavior of male mice, and also significantly increased their mating performance (7).
In another study, oral administration of 50 percent ethanolic extract of clove (500 mg/kg) produced a significant and sustained increase in the sexual activity of normal male rats. Specifically, it significantly increased the mounting frequency and erections and caused significant reduction in the mounting latency and post ejaculatory interval (8).
There were no adverse effects noted.
Clove has anticancer potential. According to the results of an in vitro study published in Oncology Research, clove extract displays potent cytotoxic activity against several human cancer cell lines. The extract displays cell growth inhibition against breast, ovarian, cervical, liver, pancreatic and colon cells (9).
Oleanolic acid is one of the main components of clove extract identified as being responsible for its antitumor activity.
Clove may help treat cirrhosis of the liver. Cirrhosis of the liver is a late stage of scarring (fibrosis) of the liver caused by many forms of liver diseases and conditions, such as hepatitis and chronic alcoholism. Advanced cirrhosis is life-threatening and predisposes one to liver cancer. (10).
To test the liver protective effects of clove, researchers treated cirrhotic animals with eugenol-rich fraction (ERF) of clove for 9 weeks. A second group received normal saline.
Treatment with ERF (as determined by histopathology and through a battery of biochemical markers of hepatic injury, oxidative stress and drug metabolizing enzymes) significantly improved the signs of liver cirrhosis (11).
Research on the liver protective effects of clove in humans is limited; further research is necessary to evaluate its efficacy in humans with liver cirrhosis.
Clove may promote bone health. Osteoporosis is a bone disease that occurs when the body loses too much bone, makes too little bone, or both. As a result, those with this condition are at greater risk for broken bones.
According to the National Osteoporosis Foundation, approximately one in two women and up to one in four men age 50 and older will break a bone due to osteoporosis (12).
Studies show that hydroalcoholic extract of dried clove buds has bone-preserving efficacy against osteoporosis. The results of a recent female osteoporosis rat study found that bone density, bone mineral content, bone tensile strength and histological analysis improved after 4 weeks of treatment with 50 percent hydroalcoholic extract of dried clove buds (13).
There have been some reports of eugenol being toxic in large amounts and ingestion of oil of cloves may cause liver damage, especially in children (14).
While several animal studies showed no adverse reactions with supplementation, not enough is known about the safety of clove supplementation in humans.
Clove is safe when consumed in amounts commonly found in foods. More research is needed to determine the safest and most effective supplementation dosage in humans.
Clove (Syzygium aromaticum) is a spice that has been shown to have antioxidant and antimicrobial properties. It has traditionally been used as an aphrodisiac. Clove contains a wide range of bioactive compounds, such as eugenol, eugenol acetate and gallic acid, and are what researchers believe give it its therapeutic potential.
Growing studies show that it may be a novel treatment for a range of conditions and diseases, including osteoporosis, certain cancers and cirrhosis of the liver.
Most of the research has been limited to in vitro and animal studies; more human studies are needed to learn exactly how clove supplementation benefits humans, as well as the safest and efficacious dosage.