Figure 1: Seeds of Guaiacum sanctum
by
Eric Ribbens, Barbra Burdett, and Angela Green
Department of Biological Science
Western Illinois University
Figure 1: Seeds of Guaiacum sanctum
Dr. Beth Tonoany is a tropical population ecologist who has been studying an unusual tree, Guaiacum sanctum, which once grew throughout the dry tropical forests of Central America as well as on some of the Caribbean islands. Guaiacum sanctum produces a wood called lignum vitae, and is known in Costa Rica and other Spanish-speaking countries as guayacan reál. The wood is extremely heavy because it contains extensive deposits of resin (Howes, 1949) and it will sink if placed in water (Wilson and Eisner, 1968). During World War I and II it was extensively harvested for use in the ship-building industry because the wood, which does not split easily, is self-lubricating due to its high resin content. The wood is very durable, and was in high demand for constructing bearing sleeves to support ship propellor shafts (Scurlock, 1987). It has also been used for making railroad ties (Woods, 1951).
Dr. Tonoany has been studying one of the last remaining populations of lignum vitae in the Palo Verde Nature Preserve in northwestern Costa Rica. Probably fewer than 100 trees remain in Costa Rica, most in the Palo Verde Nature Preserve. Her research has included tracking seedlings and saplings, locating and measuring adult trees, and interviewing some of the local Ticos to learn about the tree’s past history in Costa Rica. The tree, while rare now due to the dramatic conversion of tropical deciduous forest in Costa Rica into pasturelands and to selective logging of the tree for its valuable wood, was once more common, and many of the older Ticos remember that the saplings were used to make cattle switches because of the strong flexible wood in the saplings.
Interestingly, Dr. Tonoany has also heard from several Ticos that the tree also was used medicinally. Señora Milena Gonzalez, an elderly woman now living in Bagaces, told Dr. Tonoany that she remembered her grandmother “suffered from aches and pains in her legs” and would boil guayacan leaves in water to make an herbal tea she claimed made her aches go away. Señora Milena added that her grandmother said you had to keep drinking the tea for it to be effective, and that it was also necessary to have a pure heart. Señor Jorge Carrera, a retired cattle herder, remembered that Señor Lopez, who owned the ranch where he worked, would sometimes experience painful swellings of his big toe. He would apply a poultice of straw and cow manure to his foot, and drink a tea made by boiling guayacan wood in water. Señor Carrera insisted that in a day or two the swelling would disappear.
Figure 2: Flowers of Guaiacum sanctum
Dr. Tonoany became interested in these medicinal uses of lignum vitae. She spent some time in the library and discovered several references discussing medicinal uses of Guaiacum sanctum. Harrar and Harrar (1962) stated that the “resin has medical value as a diaphoretic in treating rheumatism.” Morton (1981) wrote that Guaiacum sanctum “has been used in medicine as a laxative, for gonorrhea, and in Haiti resin dissolved in alcohol is used for gout and as a dentifrice.” Sargent (1890) and Gill (1988) both mentioned that the wood of Guaiacum sanctum and Guaiacum officinale, a closely related species, was once used to treat syphilis. Dr. Tonoany also discovered that the leaves of Guaiacum officinale contain several unique saponins (see Ahmad et al. publications), and that Dan Janzen found that a captive tapir refused to eat the leaves every time they were offered (Janzen, 1982).
Dr. Tonoany encouraged her graduate student, Mabel Gailke, to determine if Guaiacum sanctum produces a chemical that has anti-inflammatory properties: “We have lots of anecdotal evidence that lignum vitae is useful in treating rheumatism, arthritis, and gout, but it’s frustrating that there is absolutely no data to support these claims. I want you to design and implement a study that we can use to support or reject the idea that this species might be medically valuable.”
Figure 3: Scientists measure a specimen of Guaiacum sanctum in Costa Rica
Image Credits:
Figures 1, 2—Photos of flowers and seeds of lignum vitae by Suzanne Kores, provided courtesy of © Fairchild Tropical Garden (http://www.fairchildgarden.org).
Figure 3—Photo of scientists by © Eric Ribbens.
Date Posted: 01/16/04 nas
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