An ethnobotanical survey of medicinal plants in Trinidad

Background An ethnobotanical survey was conducted on the Caribbean island of Trinidad to identify medicinal plants commonly used in traditional medicine to treat a variety of medical conditions. Methods A pilot survey was conducted to identify the top ten most common ailments where medicinal plants were used. The results of the foregoing study guided a wider national survey conducted between October 2007 and July 2008. A total of 450 households from 50 rural communities were interviewed using the TRAMIL (Traditional Medicine in the Islands) questionnaire for data collection. Details of plants, part(s) used, and remedy formulations were elicited from informants and voucher specimens collected for identification at the National Herbarium of Trinidad and Tobago. The TRAMIL methodology set a limit of a plant with 20 % or more citations for any particular ailment as having significant or popular use. Results At the end of the survey 917 single plant remedies were identified. The majority of species were from the following families; Asteraceae, Lamiaceae, Leguminosae, Verbenaceae and Poaceae. Applying the TRAMIL 20 % citation of a plant for popular use as significant, Leonotis nepetifolia (for cough/common cold), Gomphrena globosa (for “stoppage-of-water”), Curcuma longa and Senna occidentalis (for “afterbirth”), Cymbopogon citratus and Neurolaena lobata (for fever), and Citrus limon (for kidney stones) qualified in our study. Those not reaching the TRAMIL 20 % significant (popular) use were Stachytarpheta jamaicensis (L.) Vahl, Senna alata (L.) Roxb.and Momordica charantia L. which were widely used as “‘cooling/cleanser’” in our survey. Conclusions Our survey showed significant retention of traditional knowledge of medicinal plants in rural Trinidad. More interestingly, a large remnant of medico-cultural concepts such as “cooling/cleanser”, “afterbirth”, “stoppage-of-water” and “womb infection” persist in the rural population. Although the scientific literature show that some of the cited plants possessed antimicrobial, anti-inflammatory and related pharmacological activities in laboratory studies, these results must be taken with caution until clinical trials are conducted to establish safety and efficacy.


Background
The island of Trinidad which lies approximately 13 km off the coast of the Paria Peninsula of Venezuela is the larger of the twin-island state of the Republic of Trinidad and Tobago. The island has a population of approximately 1.3 million people with about 77 % being either of African or Asian Indian ancestry or an admixture of these major ethnic groups [1]. Unlike other Caribbean islands, Trinidad is a continental island sharing its geology, flora and fauna, with South America having recently separated from the mainland ca. 10,000 years ago [2]. This gives Trinidad a unique mix of Antillean and South American elements in its flora and fauna. However, the natural vegetation has been significantly transformed in the post-Columbian era with the arrival of the Europeans, West Africans and the East Indians [3]. Today, approximately one-third of the flora is made up of exotic species which are fully incooperated into the modern herbal medicine repertoire, for example, ginger (Zingiber officinale Roscoe) (Baksh-Comeau YS, Maharaj SS, Harris SA, Filer DL, Hawthorne WD: An annotated checklist to the vascular plants of Trinidad and Tobago, unpublished).
The Caribbean region has a long history of using herbal medicine for disease management and maintenance of health. The native Amerindians incorporated indigenous ]species of medicinal plants in their rituals as part of their healthcare system. These First Nation people were gradually replaced by the sequential arrivals of European settlers, enslaved Africans, indentured Asian Indians and other minority ethnic groups. By and large the peoples who came to the region brought with them inherent knowledge of the use of medicinal plants, substituting with the local flora, which over time has led to the development of herbal pharmacopeias in the region [4][5][6]. There has been a significant loss of this folkloric knowledge, which depended on the oral tradition, for its transmission to successive generations. The main causes of this loss were due to migration, urbanization, modernization and the acceptance of western medicine strongly rooted over the last century. Therefore it is imperative that a concerted effort be made to document and preserve this residual knowledge [7].
Earlier ethnobotanical surveys in Trinidad were mostly qualitative in nature, and restricted in scope with regard to health conditions and localities. One of the first published works on the island described an ethnobotanical survey conducted by Wong [6] over 40 years ago in Blanchisseuse, a small remote village, in north Trinidad. This was followed by a more extensive survey of medicinal plants undertaken between 1979 and 1980 conducted by Seaforth and colleagues across 18 localities on the island. The findings of this survey resulted in the publication of A guide to the medicinal plants of Trinidad & Tobago by the Commonwealth Secretariat [8]. Over the last decade, a survey by Lans used a small sample size of 30 persons across 13 sites [9]. During that period, and a group led by Clement [10][11][12] focused on complementary use of herbal remedies in a few hundred patients attending over 20 modern primary public healthcare facilities spread across the island, who were being managed with the chronic diseases namely, hypertension, diabetes mellitus and asthma.
Overall, the global trend indicates that knowledge of traditional folkloric medicine is fast disappearing, especially in the urban communities. Similarly, in Trinidad which is relatively industrialized most of the population reside in urban communities and have access to modern healthcare and medicines. We therefore assumed that people living in rural agricultural communities, with restricted access to transportation and healthcare facilities, would retain more traditional knowledge and more likely to use herbal remedies rather than those in urban areas. This assumption is supported by other studies [13][14][15], and hence the rationale for focusing our survey in these communities.
The objectives of our survey were to; i) determine the most common ailments treated with herbal remedies, ii) identify the plants used to treat these common ailments, plant part(s) used, and their mode of preparation, iii) determine which of these plants met the 20 % criteria for popular (significant) use according to TRAMIL criterion and iv) assess the literature regarding the pharmacological evidence that could support the traditional use of these popular (significant) plants.

Materials and methods
An ethnobotanical survey was conducted in 450 households across 50 randomly selected rural communities on the island of Trinidad between October 2007 and July 2008 (Fig. 1). We used the TRAMIL (Traditional Medicine in the Islands) questionnaire to collect data regarding medicinal plant use Appendix 1. (See http://www.tramil. net/english/TramilModelo.html).
TRAMIL is a non-governmental network established in the Caribbean Basin since 1982 whose goals include the documentation of Caribbean folkloric knowledge of herbal medicine for the preservation of such 'home remedy' knowledge [16]. The network is administrated from Santo Domingo in the Dominican Republic.

Survey instrument
The structured TRAMIL questionnaire required participants to provide information about the herbal remedies used as first treatment for the most common ailments. This instrument was used as the primary data collection tool in face-to-face interviews with respondents, following their verbal consent. The questionnaire is very simple in design and respondents were asked to describe the complaint, the plant(s) used, the preparation description, precautions and contraindications in children. The questionnaire, however, does not collect demographic details, such as sex, age, income, etc. TRAMIL defines a remedy with significant (popular) use as the combination of plant species, plant part and form of preparation that is identified by 20 % or more of the study population as a primary treatment resource for a given ailment.

Pilot study
The pilot survey was undertaken to validate the use of the TRAMIL survey instrument in the island to determine the top ten aliments most commonly treated with 'herbal remedies'.
Using data provided by the Central Statistical Office [1] and the Elections and Boundaries Commission [17] in Trinidad and Tobago regarding the population distribution, and the locations of healthcare facilities (provided by the Ministry of Health), we identified over 200 communities that satisfied the inclusion criteria for selection as a rural community. The criteria were (1) having a population of less than 1500 inhabitants and (2) limited access to amenities, particularly healthcare services. The name of each community was written on equally sized pieces of paper, folded uniformly, placed in a pot and the five communities were randomly selected for the pilot study. For each community ten randomly selected households were interviewed. From each household the individual with the most knowledge about herbal medicine was interviewed. The top ten ailments most commonly treated with herbal remedies were then selected from the full range of ailments recorded from all the informants.

Site selection and plant collection
The selection of the 50 rural communities for the wider national survey were randomly chosen using the same method as for the pilot study, and the distribution of communities across the island is given in Fig. 1. Using the detailed maps (including house location) provided by the Elections and Boundaries Commission for each randomly selected community, a house at the start of the main street was purposefully chosen to initiate the survey. At that house, field officers introduced themselves and explained the nature of the study and asked for the person (this could have been either male or female) in that household with the most knowledge about medicinal plant use. Subsequently, we used a snowball approach to obtain the sample size from each community; with this approach the preceding interviewee would identify someone else in the community whom they regarded as having had good knowledge of medicinal plant use.
The unmodified TRAMIL questionnaire was used in both the pilot and wider national survey; TRAMIL assumed that the eldest woman in the household had the most knowledge about herbal medicine use and would be the person of interest. However, the field officers asked for the person (which could be either male or female) with the most knowledge about herbal medicine. Although our field officers noted the names and ages of some of the respondents, this was not consistently collected and we therefore could not include any demographic details in our results. Respondents provided vernacular names for plants and the field interviewers collected specimens which were subsequently taken to the National Herbarium of Trinidad and Tobago for identification by a plant taxonomist. The website www.theplantlist.org was accessed to verify the accepted nomenclature for each species.

Results
From the pilot survey the top ten ailments emerging from the informants were cough/common cold, asthma, "stoppage-of-water", "womb infection", kidney stones, "afterbirth", diabetes, hypertension, "cooling/cleanser" and fever, where herbal remedies were frequently used in rural communities in Trinidad. In the wider national survey, 1590 questionnaires were completed from 450 interviews in 50 randomly selected rural communities. These included mixtures, but we present the data for only single plant remedies. Most of the mixtures contained two or more plants, and in some cases up to eight plants with additional ingredients, such as, olive oil, "soft candle" (local name for a paraffin mixture), salt and honey. A major objective of the study was to link the individual plants with relevant pharmacological evidence to support their traditional use. Hence dealing with mixtures would prove almost impossible to determine which plant was responsible for producing the biological activity to correlate with its traditional use.

Herbal remedies for ailments affecting the upper respiratory tract
A total of 279 persons identified herbal remedies for the treatment and management of cough/common cold. While 37 different plant species were identified, Leonotis nepetifolia turned out to be the most common with 85           citations out of 279 or 30.5 % thus applying the TRAMIL criteria it is a plant with popular use for the treatment of cough/common cold. The remedy was prepared as an aqueous infusion or decoction using fresh leaves, or the juice extracted by pounding the leaves and a teaspoon full mixed with a pinch of salt and taken orally. It was recommended that the remedy be taken for up to three days until symptomatic relief. Only 13 respondents indicated the use of herbal remedies prepared from 11 different plant species in the treatment of asthmatic symptoms. However, the most commonly used plants were Sambucus canadensis and Bryophyllum pinnatum (2 each out of 13 citations; 15.4 %), which did not reach popular use level according to TRAMIL.

Herbal remedies for ailments affecting the genitourinary tract
Four common ailments that affected the genitourinary tract were "stoppage of water", "womb infection", kidney stones and "afterbirth". "Stoppage-of-water" refers to the condition commonly known as urinary retention. This condition may arise from neurological complications or due to obstructive causes, the most common being benign prostatic hypertrophy in men and uterine fibroids in women. In our survey, 39 persons indicated the use of 17 different plant species for the treatment of "stoppage-of-water". The most common plant used was Gomphrena globosa (17 out of 39 citations, 43.6 %) and had popular use according to TRAMIL. The remedy was made using a few flowers of the plants to make an aqueous infusion or decoction.
Sexually transmitted infections, such as Chlamydia and gonorrhea, are the most common causes of uterine or "womb" infection. Uterine infections are also more likely to occur following childbirth. In our survey, 43 persons cited the use of herbal remedies for "womb infection" with plants from 24 species; Momordica charantia was the most commonly cited plant with seven persons indicating its use (or 16.3 % of respondents). The remedy is made using a handful of leaves, attached to the vine, to make a decoction which is consumed for up to three days until the infection clears. However, none of the plants cited for use in the treatment of "womb infection" reached popular use status according to TRAMIL.
A total of 46 persons indicated the use of herbal remedies from 15 different plant species for the treatment of kidney stones. The juice of the fruit of Citrus limon was cited by 9 persons (or 19.6 %) for the treatment of kidney stones and reached popular use according to TRAMIL.
The natural expulsion of the placenta following childbirth is referred to as the "afterbirth". However, there is a prevailing cultural belief in Trinidad that in some women the whole "afterbirth" may not be fully expelled; a similar belief held by many cultures throughout the developing world [18][19][20][21]. Therefore, herbal remedies are used to ensure the complete expulsion of the placenta and blood clots in the few days following childbirth. Postnatal vaginal bleeding and discharge containing blood clots and uterine tissue (also called lochia) occurs naturally for a few weeks following childbirth, and this may have been traditionally interpreted to mean that the whole placenta was not delivered following childbirth.
In our survey, 38 respondents cited the use of herbal remedies made from eight different plant species for the treatment of "afterbirth". These remedies were usually taken within one week of childbirth. The most commonly used plants were Curcuma longa (17 out of 38 citations, or 44.7 %) and Senna occidentalis (8 out of 38 citations, 21.1 %) and both reached popular use status according to TRAMIL criterion. For Curcuma longa the       herbal remedy was prepared using the rhizome or underground stem of the plant to make either a decoction or by pounding and extracting the juice for oral consumption. The roots of Senna occidentalis are used to make a decoction for oral administration.

Herbal remedies for chronic diseases
Diabetes mellitus and hypertension were the two common chronic diseases identified in the survey. For diabetes, there were 67 citations with plants being derived from 30 different species; Catharanthus roseus, Momordica charantia and Azadirachta indica were the most commonly cited plants for the treatment of diabetes, and were cited equally by 7 persons (10.5 % each). However, none of these plants reached significant use by TRAMIL standards. There were 100 citations for hypertension treatment from 28 different plant species. The most commonly used plants for the treatment of hypertension were Artocarpus altilis (11 citations, or 11.0 %) and Tamarindus indica (11 citations, or 11.0 %). The yellow leaves of Artocarpus altilis were used to make either an infusion or decoction and an infusion or decoction was made using the fruit and leaves of Tamarindus indica. The remedies for diabetes and hypertension were used irregularly for symptomatic control of high blood pressure.
Herbal remedies used for 'cooling/cleanser" and treatment of fever The humoral medicine concept, with the "hot-cold" dichotomy, is probably one of the oldest universally held traditional beliefs of health and disease, which has been infused into traditional cultures in Latin America and the Caribbean [22,23]. This classical humoral concept was used to describe good health as the maintenance of equilibrium between 'hot' and 'cold' elements in the body. A disruption in this balance would result in excessively 'hot' or excessively 'cold' diseases [24]. Diseases ascribed to excessive heat were treated with 'cold' remedies while "cold" diseases were treated with 'hot' remedies [25]. It was suggested by Lans [9] that in the Trinidadian context of "hotcold" system, traditional herbal preparations were administered in accordance with the correlation between cause and effect, with "cooling/cleanser"being used as both treatment for "hot" conditions, as well as prophylaxis to bring the body "back into balance".
Although the "hot-cold" concept of disease has long been abandoned by mainstream Western biomedical science, it remains relevant in the folkloric concept of health and disease throughout the Americas. In our survey we found a large percentage of respondents indicated the use of herbal remedies for "cooling". Most likely the use of traditional herbal remedies as "cooling/ cleanser to treat certain "hot" ailments persists in presentday Trinidad as a relic of this historical "hot-cold" dichotomy of disease. In Trinidad, as in the Americas, "hot" aliments refer to conditions such as fever, constipation, rash and skin ailments, and general malaise.
We found that 38 different plant species were used as "cooling/cleanser" by 194 persons in the survey. For most of the remedies a few fresh leaves were used to make either an infusion or decoction which was consumed for a few days up to one week. There were 98 citations for the treatment of fever with 21 plant species being identified. Two plants, Cymbopogon citratus (30 out of 98 citations, 30.6 %) and Neurolaena lobata (46 out of 98 citations, 46.9 %) accounted for most of the citations. Most of the herbal remedies for fever were made using a few leaves of the plant to prepare either an infusion or decoction, which was consumed for a few days until the fever subsided.

Discussion
To our knowledge this is the first systematic ethnobotanical study done in Trinidad to determine the extent of traditional use of medicinal plants throughout several rural communities on the island. This study is significant in that it covered fifty remote communities with a sufficiently large sample size to assess the distribution of medicinal plant use for common ailments. We used the validated TRAMIL survey instrument which allowed us to determine herbal 'home remedies' use among these rural communities. Although we limited the number of ailments, for practical considerations, we were able to gather a wealth of information on several plants, including methods of preparation and mode and frequency of administration.
There were notable differences between our findings and that obtained in earlier surveys. Almost 40 years ago, Wong [6] identified 186 different medicinal plants from his interviews with 70 villagers at a remote community for a wide range of ailments, but only 52 of these plants had similar traditional use compared to our survey; and none were used for kidney stones or asthma. In the more extensive survey by Seaforth and colleagues across 18 rural communities [8], although 78 plants were identified, only 28 of these plants had similar traditional use compared to our survey; and none were used for kidney stones, "stoppage-of-water" or "afterbirth". The more recent survey by Lans cited 24 plants used for "cooling/cleanser" [9], but just 11 of these plants had similar use compared to our survey.
The surveys by Clement and colleagues [10][11][12] focused on the complementary use of herbal remedies in patients with chronic diseases attending modern primary public healthcare facilities. Although some commonly cited plants such as Leonotis nepetifolia, Zingiber officinale, Cymbopogon citratus and Aloe vera were also found in our survey, the use of herbal remedies for culture-bound health issues such as "afterbirth", "stoppage-of-water" and "womb infection" was notably absent. In our setting, this observation partly supports our initial assumption that there are rural-urban differences in retention of traditional knowledge and use of herbal remedies.
Although medico-cultural concepts such as "stoppage-of-water", "womb infection" and "afterbirth" could be explained by modern medicine, and conventional therapies are available for treatment, people in remote communities may still prefer to rely on generations-old traditions as their preferred mode of treatment. The cultural interpretation of these aliments and conditions may differ from that proposed by modern medicine, and generations of anecdotal evidence would be having a significant impact on the continuation of these rural traditions.
It would be problematic to conceptualize the use of "cooling/cleanser" as prophylaxis in modern medicine, as the "hot-cold" dichotomy of health and disease has long been abandoned. But, surprisingly, "cooling" was among the most popular indications for medicinal plant use in rural Trinidad. The maintenance and restoration of the "hot-cold" balance in the body seems to resonate among rural communities across the developing world, and point to similarities in the origin of cultural beliefs regarding health and disease.
A major objective of our survey was to determine whether relevant pharmacological evidence existed that would support the traditional use of medicinal plants with significant (popular) use in our setting. A preliminary review of the literature shows that there was very sparse clinical evidence. However, we provide in the rest of this discussion the limited evidence from studies conducted in cell cultures (in vitro), isolated tissues (ex vivo) and laboratory animals (in vivo) which may lend support to their traditional use.
Leonotis nepetifolia was the most commonly cited plant being used to treat an array of conditions, including fever, common cold/cough, "cooling", diabetes and asthma; and, the literature is sparse regarding its biological activity. In an ex vivo model the aqueous extract of the leaves of L. nepetifolia produced relaxation of pre-contracted guinea-pig tracheal rings but only at relatively high concentrations of 1000 μg/mL and this may lend support for its traditional use in the treatment of asthma [26].
Neurolaena lobata was the second most commonly cited plant in our survey, and was used to treat fever, the common cold/cough, diabetes and "womb infection". The infusion, made from the leaves, is very bitter-tasting and is commonly used throughout the Caribbean and Latin America for fever, colds, malaria, 'painful belly pains' , painful menstruation and even diabetes [27]. Toxicity studies in mice have demonstrated safety in an animal model at aqueous oral doses up to 5,000 mg/kg [28].
The literature provides pre-clinical evidence to support the biological activity for several extracts of Neurolaena lobata against infectious organisms, including protozoa, malaria parasite, fungi and filarial worms. The aqueous and lipophilic extracts, and isolated sesquiterpene lactones were active in vitro against Plasmodium falciparium (the parasite responsible for malaria) [29]. The methanol extract significantly reduced parasitemias in Plasmodium berghei-infected mice and was active against both chloroquine-susceptible and resistant P. falciparum strains [30]. Crude, hexane and ethanol extracts significantly inhibited both trypomastigote and epimastigote developmental forms of Trypanosoma cruzi [31,32]. Extracts, fractions and isolated sesquiterpenes lactones significantly inhibited parasite growth of Leishmania mexicana, L. cruzi and L. vaginalis [33]. The ethanol extract exhibited a significant macrofilaricidal effect against Brugia pahangi (a lymphatic dwelling filiarial worm) in a concentrationand time-dependent manner [34]. Bioassay-guided fractionation of N. lobata demonstrated its weak to moderately active antifungal activity [35]. Additionally, the leaf extracts possessed anti-inflammatory properties in an in vitro LPS-stimulated monocyte model [36,37] and analgesic properties in in vivo models for pain [28]. However, there is no clinical data to support the use of this plant for any of the traditional uses in Trinidad.
Cymbopogon citratus was the most frequently cited plant for fever, and was used to a lesser extent for the treatment of common cold/cough and as "cooling". The essential oils of Cymbopogon citratus demonstrated significant analgesic and anti-inflammatory properties [38]. Other pre-clinical studies show that the aqueous extract and the essential oils of C. citratus possess considerable anti-inflammatory properties [39][40][41][42]. Although Carlini and colleagues [42] reported that an aqueous extract of C. citratus was not effective in reducing body temperature in hyperthermic mice at a dose 40 times higher than that normally used in traditional preparations, a more recent study by a group led by Ghenou [43] showed that the essential oils demonstrated strong antipyretic effects similar to a conventional analgesic agent.
Curcuma longa was the most commonly cited herb in our survey for the treatment of "afterbirth". Although thousands of papers have been published regarding the biological properties of Curcuma longa, and its purified (contraindications and directions for use) Available at: http://www.tramil.net/english/TramilMo delo.html