At first glance, bee propolis may seem out of place in a column on herbal chemistry. But tests show that propolis retains the therapeutic compounds of tree resins, which bees use to make propolis, so calling it a medicinal plant product makes sense.
Bees collect and manufacture propolis resins from tree buds, twigs, and barks, using it as putty to seal cracks in the hive and strengthen and repair honeycombs. They also use it to “mummify” larger animals that have invaded the hive. Researchers believe propolis inhibits microbes that constantly threaten the humid, close quarters of a beehive.
Most propolis research focuses on resins from forests where bees collect mainly from the poplar (Populus) genus, and, to a lesser extent, beech, chestnut, birch, and conifer trees. Chemical analyses indicate that the bees’ propolis is almost chemically identical to these tree resins and is similar to medicinal gums such as boswellia and myrrh (for more about boswellia, see “Inside plants” on page 20 of the January/February 1998 issue of Herbs for Health). The biblical Balm of Gilead is nearly indistinguishable from propolis; Balm of Gilead is made of resin from various poplars, including P. balsamifera, P. nigra, and P. gileadensis.
Propolis is useful medicine
Propolis has been used to clean wounds, kill microbes, and fight inflammation for more than 2,000 years. European, Asian, and Middle Eastern cultures have used it to heal festering wounds, such as bedsores, diabetic ulcers, and battlefield slashes from jagged bayonets.
Modern researchers have confirmed these traditional uses and found support for more modern ones. Propolis compounds are making a strong showing as antioxidants and cancer preventives. The effectiveness of antibiotics such as tetracycline and penicillin has been increased ten to 100 times when combined with propolis extract. Propolis is also used in antibacterial mouthwashes, and evidence shows that it combats staph and strep infections.
Many compounds in propolis are antioxidants, but in cell culture studies conducted in 1995 and 1996, caffeic acid phenethyl ester (CAPE) came out as its strongest antioxidant overall. CAPE also inhibits two enzymes that are involved in the creation of eicosanoids, a family of hormones and “signaling” biochemicals. Eicosanoids are vital to health, but if their production is excessive or unbalanced, they make certain conditions worse, including tendinitis, arthritis, asthma, psoriasis, and allergies.
Animal research indicates that CAPE may relieve other types of inflammation as well. In a small study conducted in 1996, mice were injected with a chemical that causes acute inflammation, then treated with various components of propolis, commonly used pharmaceuticals, or nothing. Of all the propolis components, CAPE reduced inflammation the most, and it worked as well as the pharmaceuticals.
CAPE’s enzyme inhibition has led researchers to consider whether it (and propolis) might be effective against some cancers. Some inflammation-causing eicosanoids also stimulate the growth of cancerous cells and help tumors “stick” to healthy tissues. In cell cultures, CAPE selectively killed precancerous cells that were mutated by viral infection, but left healthy cells alone.
Animal studies carried the cancer research a step further. In a 1993 study, researchers injected rats with a chemical that causes abnormal growth of colon cells. When they measured the levels of enzymes that stimulate abnormal cell growth, they found that rats fed food containing various caffeic acid derivatives such as CAPE had fewer of these enzymes than rats given only the abnormal-growth chemical.
Broadhurst, C. L. “Benefits of bee propolis.” Health Supplement Retailer July 1996: 46–48.
Chiao, C., et al. “Apoptosis and altered redox state induced by caffeic acid phenethyl ester (CAPE) in transformed rat fibroblast cells.” Cancer Research 1995, 55: 3576–3583.
Krol, W., et al. “Inhibition of neutrophils’ chemiluminescence by ethanol extracts of propolis (EEP) and its phenolic components.” Journal of Ethnopharmacology 1996, 55:19–25.
Mirzoeva, O. K., and P. C. Calder. “The effect of propolis and its components on eicosanoid production during the inflammatory response.” Prostaglandins, Leukotrienes, and Essential Fatty Acids 1996, 55:441–449.
C. Leigh Broadhurst holds a doctorate in geochemistry and is a nutrition consultant in Clovery, Maryland.
James Duke spent thirty years working for the U.S. Department of Agriculture and is a member of the Herbs for Health Editorial Advisory Board. His most recent book, The Green Pharmacy, (Rodale, 1997) was released last fall.