A Sunday ham would be incomplete without a neat array of cloves studding its surface and giving it a spicy flavor. Years ago, however, people used cloves—the dried flower buds of the tropical tree Syzygium aromaticum—more to preserve food than to season it. Clove oil is made up of between 80 to 95 percent eugenol, which is largely responsible for cloves’ ability to keep food from spoiling. Research shows that it offers health benefits to the human body as well.
You may already be familiar with eugenol’s medicinal capacity. Oil of cloves or eugenol is commonly used by dentists because it is antiseptic and anti-inflammatory. They often apply it to the gums to kill germs and relieve the pain of dental surgery such as tooth extractions, fillings, and root canals. Moreover, clove oil, as well as cinnamon, basil, and nutmeg oils—each of which also contain eugenol—are a common ingredient in mouthwashes, toothpastes, soaps, insect repellents, perfumes, foods, and various veterinary medications.
Preliminary research is showing that eugenol may possess additional, more far-reaching medicinal value. For example, some studies show that eugenol fights bacteria and inhibits the growth of many fungi, including Candida albicans, the pathogen responsible for most human yeast infections. In cell cultures, eugenol has been between 1.4 and 2.3 times as effective against C. albicans and C. tropicalis, respectively, as equivalent doses of the antifungal pharmaceutical nystatin. Eugenol or oil of clove is already used to fight fungal infections of the skin, ears, and vagina in some non-Western countries, but this treatment can cause irritation and dermatitis so shouldn’t be tried without the guidance of a health-care practitioner.
Preliminary research also shows that eugenol is a very powerful fat-soluble antioxidant, inhibiting the accumulation of fat peroxide products in red blood cells and maintaining the activities of the body’s antioxidant enzymes at normal levels. Overall results of laboratory studies using animals indicate that only small amounts of eugenol are required for a significant protective effect because eugenol can be directly incorporated into cell membranes, which prevents lipid peroxidation right in place. In one study, rats were poisoned with carbon tetrachloride, which strongly damages tissues by oxidation. Rats who were given eugenol along with the carbon tetrachloride were strongly protected from its toxic effects, according to the researchers.
Finally, preliminary studies show that eugenol protects against cardiovascular disease by inhibiting the aggregation (abnormal clotting) of platelets. In rabbit tests, eugenol prevented aggregation nearly as well as the pharmaceutical indomethacin.
Although cloves are the richest plant source of eugenol, it is also found in significant amounts in allspice, bay rum, greater galangal, basil, nutmeg, turmeric, bay leaf, hyssop, oregano, marjoram, and many other culinary and medicinal plants. Like most essential oils and their major constituents, oil of cloves and eugenol can be toxic at relatively low concentrations when taken internally or when absorbed through the skin (never apply essential oils directly to the skin). Eugenol requires professional supervision to be used internally. Judicious use of fresh or dried herbs and spices containing eugenol is a safer way to consume eugenol, and even small amounts can provide valuable antioxidants.
James Duke, a member of the Herbs for Health Editorial Advisory Board, spent thirty years with the U. S. Department of Agriculture. C. Leigh Broadhurst holds a doctorate in geochemistry and is a nutrition consultant in Clovery, Maryland.
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