Nature's Pharmacopeia: A World of Medicinal Plants
Black cohosh is a perennial herbaceous plant that grows in the understory of deciduous forests in the eastern part of North America, from southern Ontario through southern New England, Appalachia, and the Midwest.115 The plant’s leaves consist of three leaflets, each further divided into several pointed lobes, and grow both close to the ground and on upright stems 1 to 2.5 meters in height.116 Flowers occur on wand-like stems, each one producing dozens of whitish flowers about 2 centimeters in diameter (figure 14.13). Fruits are small, with eight to ten seeds each.117 The part of the plant commonly used in medicine is the root and underground stem, or rhizome.
FIGURE 14.13 Black cohosh.
Diverse ethnobotanic accounts describe black cohosh root in the medical practices of indigenous eastern North American groups. For example, the Iroquois of the modern-day northeastern United States and Canada are said to have used it to promote the flow of milk in nursing women and in a bath to treat joint pain.118 Among the Cherokee of the southeastern United States, black cohosh root was described to address a suite of health concerns—including colds and cough, constipation, backache, hives, and fatigue—as well as to help a baby sleep.119 When the eclectic physicians of nineteenth-century America began compiling their list of herbal drugs, they included black cohosh, a “very active, powerful, and useful remedy.”120
FIGURE 14.14 A package of Zoa-Phora, a patent medicine that contained black cohosh, early twentieth century. The label for this “woman’s friend” indicates: “For all forms of female weakness, painful, scanty, delayed or declining periods, spasms at month, local discharges or whites, impaired complexion, sick headache, neuralgia, debility, goneness, falling of the womb, arising from want of tone in the system, preparatory treatment for confinement, after-pains, change of life, hot flushes, wakefulness, bloating, etc.” (Smithsonian Institution, National Museum of American History, 1980.0698.068)
American physicians used black cohosh root for dozens of ailments, from syphilis to asthma to fevers. An extract of black cohosh root in alcohol was deemed to be effective against rheumatism and scrofula (generally a bacterial disease), among other ailments, and to have “an especial affinity for the uterus.”121 According to testimonials from the mid-nineteenth century, doctors employed black cohosh root, or its extract, to treat gynecological concerns such as sterility, irregular menstruation, vaginal discharge, prolapse of the uterus, and heavy menstrual bleeding.122 By the late nineteenth century, black cohosh declined in use among mainstream medical practitioners in the United States but persisted in certain patent medicines (figure 14.14). It was also taken up to some degree by doctors in Germany.123 Today, black cohosh is usually associated with treatments for the symptoms of menopause, such as hot flashes, depression, and discomfort.124
An assortment of chemicals has been isolated from black cohosh root, including various triterpenoids and some polyphenolic compounds (figure 14.15).125 It is an ongoing challenge for biochemists and physiologists to determine whether an extract of black cohosh root has biological activities in the laboratory and clinic consistent with its perceived effects in menopause. One hypothesis is that black cohosh root compounds have estrogenic properties and therefore offset in some way the reduced estrogen hormone levels occurring at menopause. However, this estrogenic activity has not been consistently observed in the laboratory, and many recent reports show no such effect.126 A more recent hypothesis posits that certain chemicals present in the black cohosh root extract are psychoactive, producing effects in the brain’s perception of pain.127
In support of this notion, investigations have uncovered evidence that black cohosh extract can act on the opioid receptors in the brain, possibly contributing to a calming and pain-reducing capacity of the herbal treatment.128 Furthermore, it has chemicals that appear to be able to modulate the serotonin neurotransmitter signaling system, which may influence thermoregulation and mood in people taking black cohosh.129 Taken together, the identification of components active in the central nervous system along with the paucity of evidence for estrogenic effects may help explain black cohosh’s various cultural uses in treating many types of pain and discomfort, along with some of its uses in menopause.130 While these observations might help address some long-standing questions of black cohosh’s utility in therapy, the mechanisms of action are still not completely understood, and its entire chemical repertoire is not yet fully characterized.
FIGURE 14.15 Acteol, one of the prospective active principles of black cohosh.
The standard by which biomedical efficacy is judged is the well-designed clinical trial, and those testing black cohosh’s utility against menopause symptoms have generated conflicting data. Recent clinical trials have used various preparations of black cohosh root extract, usually processed with ethanol or isopropanol as a solvent.131 A review of clinical trials failed to show a positive effect of black cohosh extract on a series of menopausal symptoms but recommended further efforts to produce high-quality controlled studies to address this research question.132 Ultimately, biomedical studies may shed further light on this plant of many virtues, so esteemed by indigenous Americans, eclectic physicians, and patients around the world.