Pain plays no favorites. It affects rich and poor alike, old and young, members of every culture and ethnic group. No one is exempt, but some seem to suffer more than their share of it. Whether it’s a momentary sharp twinge or a dull, throbbing ache, however, pain does serve the useful purpose of warning us of actual or potential damage to our body. Having attended to the medical problem, though, we’d just as soon the pain disappeared. Sometimes, it doesn’t, and sometimes it’s so severe that it’s difficult to function. Today, drugs, surgery, acupuncture, electrical stimuli, and biofeedback all are available for combating pain, but in times past, people often turned to plants for relief from their suffering. One group of plants, the willows (Salix spp.), not only have a long history as pain relievers but are indirectly the 'parents' of America’s most popular over-the-counter analgesic.
When we cut a hand or sprain an ankle, the pain we experience seems instantaneous, but actually a split-second delay occurs before we register it. Pain receptors (free nerve endings found in most body tissues except the brain, especially in skin and connective tissue) at the site of the injury transmit pain impulses to the spinal cord, where chemical pain messengers proceed both to the brain and back to the pain source, thus causing pain sensations.
The pain of our cut hand or injured ankle is acute pain, also called fast, sharp, pricking, or electric pain. It is sudden in its onset but doesn’t last long. This kind of pain is usually not felt in deeper tissues. Chronic pain, also called slow, aching, throbbing, or nauseous pain, is the long-term or recurrent pain experienced in arthritis or certain cancers. It is usually associated with tissue destruction, and it may occur either in the skin or in deep tissues or organs.
Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, and acetaminophen reduce the transmission of pain impulses to the brain by inhibiting the production of prostaglandins, hormonelike substances associated with pain and inflammation. Most bathroom cabinets in America probably hold a stash of these drugs for relieving minor aches and pains and the discomfort of colds or flu. In the past five years, their use in the United States has increased by more than 50 percent. Although quite effective in many situations, these drugs can have serious side effects: gastrointestinal irritation and bleeding in the case of aspirin and ibuprofen, liver damage with acetaminophen.
When pain is severe and unrelenting, however, stronger painkillers are called for. Opiates (including opium, heroin, methadone, morphine, and codeine, all derived from opium poppies, Papaver somniferum) work by binding to pain receptors and inhibiting the release of chemical pain messengers to the brain. They relieve chronic pain that NSAIDs can’t touch, but because they can be addictive, they must be dispensed by a physician.
Fighting pain with willow
In ancient Greece, arthritis sufferers steeped willow bark or leaves in olive oil in special clay pots, then immersed the ailing joint in the mix. Native Americans throughout North America from Florida to California and Alaska used the bark or leaves to relieve pain, inflammation, and fever. The Houma used black willow root bark as a blood thinner. The Creek used the root tea as an anti-inflammatory for rheumatism and to reduce fevers. The Kiowa rubbed the leaves on their bodies to treat rheumatic pains and chewed the leaves to relieve toothaches. The Chickasaw used a root decoction to treat headaches. The Montagnais poulticed the leaves on the forehead to relieve headaches. In American folk medicine, the bark was used as a blood thinner and to treat fevers.
The willow family (Salicaceae) contains two genera, Salix (willows) and Populus (poplars, cottonwoods, and aspens). Of the 300 or so species of Salix, those recognized as sources of medicinal bark include the European white willow (S. alba), crack willow (S. fragilis), purple willow (S. purpurea), violet willow (S. daphnoides), and bay willow (S. pentandra), and the native black willow (S. nigra). All the European species but violet willow are naturalized in eastern North America. White willow is the “classic” willow used medicinally since ancient times, whereas black willow is probably the species most widely used among Native American groups.
How it works
The inner bark of both willows and poplars contains compounds called phenolic glycoside esters. Intestinal microorganisms transform these compounds to saligenin, which is oxidized in the liver and blood, producing salicylic acid. Salicylic acid reduces pain by inhibiting the synthesis of prostaglandins in sensory nerves, but it can sometimes upset the stomach.
While S. alba contains only small amounts of the phenolic glycoside salicin (0.5 to 1.0 percent), S. purpurea contains 6.1 to 8.5 percent salicin, S. daphnoides contains 4.9 to 6.4 percent, and S. fragilis contains 3.9 to 10.2 percent, depending on the season: the total content of salicin is higher in spring or summer and lowest in winter.
The German Commission E permits taking the equivalent of 60 to 120 mg of salicin daily to relieve headaches or rheumatic complaints or to reduce fever. In the United States, 270-mg capsules of willow-bark extract standardized to 41 mg of salicin are available. The powdered willow bark sold in health-food stores for making teas is too weak to be effective: you’d need to drink between three pints and five quarts of the tea a day to equal the 4.5 g of aspirin typically taken to treat arthritis pain. Willow-bark products should not be given to children with chicken pox or the flu because of the risk of Reye’s syndrome.
Aspirin: An herbal medicine?
Aspirin, though not derived directly from willow, was developed as a result of research on a compound found in willow.
In 1830, salicin (named for the genus Salix) was first isolated from willow bark. In 1838, salicylic acid was synthesized from salicin and a year later was isolated from the flower buds of queen-of-the-meadow (Filipendula ulmaria, formerly Spiraea ulmaria). (Another name for salicylic acid was spiraeic acid.)
By 1874, salicylic acid was being manufactured in large quantities to preserve meats and milk. During the next twenty-five years, sodium salicylate, a salt of salicylic acid which was easier and less expensive to manufacture, was promoted for reducing the pain and fever of rheumatic fever, as well as for rheumatic pains, lumbago, sciatica, and as a diuretic. However, its numerous side effects included roaring in the ears, vertigo, profuse sweating, and stomach irritation. In 1899, researchers at the Bayer company in Germany, seeking a less irritating alternative to salicylic acid, synthesized acetylsalicylic acid, which they called “aspirin” (from acetyl + spiraeic acid). Though long-term use of large doses can cause gastrointestinal bleeding, aspirin has proven safe enough to have become America’s most widely used drug.
Steven Foster is an author, photographer and consultant specializing in medicinal plants