Ethnobotany in the Forests of Belize
While the world scrambles in the race against time to grapple with the enigmatic HIV virus, an aging traditional healer in Belize is guiding western scientists through the forest, sharing his knowledge of plants with medicinal value, and proving to be a contributor in the search for a cure. Traditional healer Don Eligio Panti has shown that he and his colleagues possess the knowledge that could expedite the search for plant compounds with anti-AIDS and anticancer activity.
In preliminary, small-scale trials, ethnobiologists from the Institute of Economic Botany of the New York Botanical Garden (IEB), and the Ix Chel Tropical Research Center, Ltd, collaborating with Don Eligio Panti, and the National Cancer Institute (NCI), experienced a 25% success rate in identifying a sample of plant collections with marked biological activity. This compares to a 6% success rate from plant samples randomly collected without the assistance of the traditional herbalist. These small-scale trials are included in The Belize Ethnobotany Project, a collaborative effort to conduct a country-wide survey of plants used by traditional healers and others who have indigenous knowledge of native Belizean flora. In 1986 the NCI contracted the IEB to collect 1500 plant samples annually from the neotropics for its anticancer and anti-AIDS screening program. The Belize Ethnobotany Project has been a part of this endeavor. Drs Rosita Arvigo and Gregory Shropshire are the Primary collaborators in the Belize effort.
Researchers sought to identify the most effective collection method to generate the highest proportion of leads in the in-vitro screening process. Three collection strategies commonly used are the random method, the target method, and the ethnobotanical approach.
The random method entails complete collection of plant samples found in a forest area, with major emphasis given to fruiting or flowering species. The second strategy, the target method, is to collect plants from families known to be high in biologically active compounds, such as alkaloids, glycosides, steroids or flavonoids. The ethnobotanical approach uses knowledge possessed by traditional healers about the medicinal uses of plants and their environment. This strategy is challenging in that it requires researchers to identify those people who possess knowledge of medicinal plants, and to secure their cooperation. Both the ethnobotanical and the random approach are used by the IEB.
The hypothesis behind this research is that indigenous knowledge about medicinal plants, combined with collection and documentation of this knowledge by ethnobotanists, will yield a higher number of biologically active compounds from the screening program on a per sample basis, as compared to plants collected at random.
In-vitro HIV screening
The first priority of the NCI sponsored program is screening plant materials for their effectiveness against the human immunodeficiency virus (HIV), the causative agent of AIDS. Plants are collected, dried in the field, and packaged in 0.5 and 1.0 kg samples. These samples are used for extraction and study at The Frederick Cancer Research Facility, Natural Products Repository in Maryland. Some samples are sent to the US for international distribution and study by botanists, while others are kept in the host country.Upon arrival in the U.S., the samples are frozen, labeled and recorded in a database. The samples are then sent to the Natural Products Extraction Laboratory for processing, whereby organic and water extracts are obtained.
In the HIV screen, human T lymphoblastic cells infected with AIDS are incubated for six days with varying concentrations of the plant extracts. Infected cells not treated with the extracts die quickly after failing to proliferate. Some infected cells treated with extracts containing effective antiviral agents will proliferate and survive at moderate extract concentrations. In general, high concentrations of extract will kill infected cells. The degree of biological activity is measured in terms of the level of protection provided by extracts at sub-toxic concentrations.
Random versus ethnobotanical collection
In this comparative study of methodologies, two groups of plants were collected, one using random collection, the other using the ethnobotanical method. The plants were sent to the NCI for screening against HIV. The random collection included plants from Belize and Honduras. The ethnobotanical collection comprised plants of substantial therapeutic value as selected and used by Don Eligio, the master traditional healer.Of the 20 plants tested from the ethnobotanical collection, five were found to be active against HIV cells. Of the 18 randomly collected plants, only 1 was found to be biologically active against HIV. Although these were small samples, the study’s results suggest a valid hypothesis regarding the relative efficiency of ethnobotanical versus random collection.
For this study, the collection period is scheduled to continue for five years. At the end of that period much more information will be available about medicinal and non-medicinal uses, anticancer and anti-AIDS effectiveness, and trends among plant families. Broader uses of this methodology could streamline the discovery and development of drugs from plant compounds. Conservation of these species is essential to the survival of existing healthcare networks in tropical countries that rely on the cornucopia of medicinal treatments provided by the forest.
Balick, Michael J. Ethnobotany and the identification of therapeutic agents from the rainforest. Bioactive compounds from plants, Chadwick, D.J. and J. Marsh (eds), 1990, Ciba Foundation Symposium No. 154, J. Wiley and Sons, Chichester.
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