This study adhered to the research guidelines and ethical protocols of Wageningen University in the Netherlands. Thirty respondents, ten of whom were male were interviewed from September 1996 to September 2000 . The respondents were obtained by snowball sampling, and were found in thirteen different sites, 12 in Trinidad (Paramin, Talparo, Sangre Grande, Mayaro, Carapichaima, Kernahan, Newlands, Todd's Road, Arima, Guayaguayare, Santa Cruz, Port of Spain and Siparia) and one in Tobago (Mason Hall). Snowball sampling was used because there was no other means of identifying respondents. The chief objective of the sampling method was to identify knowledgeable respondents; no priority was given to extrapolating the data to the wider population to establish prevalence of use. No statistical analysis is applied to the data since this would have required the use of a random sample thus increasing the risk of not identifying knowledgeable respondents.
Twenty respondents were interviewed once, the other ten (who were healers) were interviewed three or four times. Healers were also asked to reconstruct the circumstances and contexts of the plant uses so that the means of administration of the plants could be identified. No interview schedule of questions was used but a more qualitative, conversational technique. Plants were collected when available to verify that the common names used by each respondent were the same in each ethnic group as those recorded in the literature. The majority of the plants were identified at the Herbarium of the University of the West Indies but voucher samples were not deposited. This ethnomedicinal study was part of a larger research project on ethnoveterinary medicine [11,18].
Validation of practices
A preliminary validation of ethnomedicinal practices ensures that clinical trials are not wasted on plants that are used solely for cultural or religious reasons. The validation of the remedies was conducted with a non-experimental method [11,18,19]. This method consists of:
1. obtaining an accurate botanical identification,
2. determining whether the folk data can be understood in terms of bioscientific concepts and methods,
3. searching the chemical/pharmaceutical/pharmacological literature for the plant's known chemical constituents and to determine the known physiological effects of either the crude plant, related species, or isolated chemical compounds that the plant is known to contain. This information is used to assess whether the plant use is based on empirically verifiable principles or whether symbolic aspects of healing are of greater relevance. If ethnobotanical data, phytochemical and pharmacological information supports the folk use of a plant species it can be grouped into the validation level with the highest degree of confidence.
Four levels of validity were established :
1. If no information supports the use it indicates that the plant may be inactive; or no research has been done on the plant.
2. A plant (or closely related species of the same genus), which is used in geographically or temporally distinct areas in the treatment of similar illnesses, attains the lowest level of validity, if no further phytochemical or pharmacological information validates the popular use. Use in other areas increases the likelihood that the plant is active against the illness.
3. If in addition to the ethnobotanical data, phytochemical or pharmacological information also validates the use in Trinidad, the plant may exert a physiological action on the patient and is more likely to be effective than those at the lowest level of validity.
4. If ethnobotanical , phytochemical and pharmacological data supports the folk use of the plant, it is grouped in the highest level of validity and is most likely an effective remedy.
A comparable validation process was used to examine the plants used by traditional healers of ancient Persia to induce abortions . The authors evaluated the validity and the efficacy of the plants used by (1) comparing other reported uses of these plants in traditional medicine, (2) investigating the medical and pharmacological literature on the medicinal properties of the plant species used, and (3) investigating the reported cytotoxic effects of compounds prevalent in these plants.