African Journal of Traditional, Complementary and Alternative Medicines, Vol. 3, No. 3, 2006, pp. 48-58
EVALUATION OF ETHNOMEDICAL CLAIMS AND BRINE SHRIMP TOXICITY OF SOME PLANTS USED IN TANZANIA AS TRADITIONAL MEDICINES.
Mainen J.Moshia*, Zakaria H.Mbwamboa, Ramadhani S.O.Nondoa, Pax J.Masimbaa, Appolinary Kamuhabwab, Modest C.Kapingua, Pascal Thomasb, Marco Richardb.
Institute of Traditional Medicinea, and School of Pharmacyb, Muhimbili University College of Health Sciences, P.O.Box 65001, Dar es Salaam, Tanzania. E-mail: *firstname.lastname@example.org Tel: 255 22 2150096; Fax 255 22 2150465
Code Number: tc06036
Using information from the literature it has been demonstrated that twenty one (21) plants out of 60 (35%) which are used in traditional medicine, in Tabora region (Western Tanzania), are used elsewhere for the treatment of similar conditions or their claims have proven biological results. Ethanol extracts of some of the plants exhibited low, some intermediate, and some high toxicity against brine shrimps. The brine shrimp assay results for Psorospermum febrifugum Spach (Guttiferae) [LC50 12.7µg/ml], agreed with previous reports of established anticancer activity, while for Phyllanthus engleri Pax. (Euphorbiaceae) [LC50 0.47µg/ml]they supported literature reports that it is toxic to rabbits and fish. Despite the therapeutic claims, literature reports, and brine shrimp assay results, more rigorous studies are needed to confirm the therapeutic utility of the plants.
Key words: Ethnomedical claims, Drug discovery approaches, Toxicity.
A good number of Tanzanians use traditional medicines for their day to day health care needs. The use of traditional medicines has a strong cultural influence to the extent that, even in urban settings where many modern health care facilities are available, people still consult traditional healers. In Dar es Salaam, for example, it was previously reported that 21% of the people consult a traditional healer as their first referral point before going to a modern health care facility (Kilima et al., 1993). This is supported by the number of traditional healers who are practicing in towns. A survey of traditional healers treating epilepsy alone, in Dar es Salaam, was able to identify over 100 healers in one district who were managing epileptic patients (Moshi et al., 2005), indicating the importance and acceptability of their services. The challenge ahead is to authenticate the therapeutic efficacy and safety of the plants and other matiria medica that are being used.
This study evaluated the strength of therapeutic claims on some of plants collected from an ethnomedical survey in 3 districts of Tabora region (Western Tanzania), and also employed the brine shrimp lethality test as a preliminary tool to evaluate other potential biological activities that have not been reported by the traditional healers.
Materials and Methods
Ethanol was bought from Fisher Scientific UK Ltd. (Loughborough, Leicestershire, UK). Dimethyl sulphoxide (DMSO) was purchased from Sigma (Poole, Dorset, UK), and ethanol from Fisher Scientific UK Ltd (Bishop Meadow Road, Loughborough, Leicestershire, LE 11 5RG, UK). Brine shrimp eggs were bought from O.S.I. Marine Lab. Inc., Hayward, CA 94545, USA. Sea salt was prepared by evaporating water collected from the Indian Ocean along the Dar es Salaam coast.
Collection of Plant materials
The plants used in this study were collected from three districts of Tabora region, i.e. TaboraMunicipality, Tabora Rural, and Urambo districts. Sixty (60) plants were selected from the list (Table 1a, b, c, d) for inclusion in this study. The plants were identified by a botanist at the Department of Botany, Faculty of Science, University of Dar es Salaam, and voucher specimens are kept at the Herbarium of the Institute of Traditional Medicine, Muhimbili University College of Health Sciences. The Tabora Regional Branch of Traditional Healers Association was fully involved in the interviews and all national guidelines for working with traditional healers were followed.
Evaluation of the therapeutic claims based on the literature.
The literature was consulted to identify reports of similar uses elsewhere or proven biological results, as a basis to establish the value of the claims. The NAPRALERT data base of the University of Illinois, at Chicago, was used to download the literature cited in this work.
Preparation of plant extracts
Air-dried powdered plant materials (200g) were extracted with 80% ethanol (1L), concentrated under reduced pressure, in vacuo, followed by removal of residual water by freeze-drying. Extract yields of between 0.25-7.5% were obtained. The extracts were stored in a freezer, at -20°C, until needed for testing. On test day the extracts were dissolved in DMSO to appropriate working concentrations.Brine shrimp lethality test
The brine shrimp lethality test (BST) was used to assay cytotoxic activity (Meyer et al., 1982). Assay procedures and analysis of results was done as reported earlier (Moshi and Mbwambo, 2005).
Evaluation of the therapeutic claims based on the literature.
Using a symptom guided interview, plants that are used to treat or manage bronchial asthma, diabetes mellitus, epilepsy, psychosis, malaria, bacterial infections, fungal infections, impotence, HIV/AIDS, bilharzia, cancer, yellow fever, skin conditions, and hypertension were identified (Table 1a, b, c, d). Literature based evaluation of the claimed uses (Table 1a, b, c, d, column 5) agree with 35% of the claims, which included uses of Boscia salicifolia Oliv (Capparidaceae) for the treatment of impotence (Haerdi, 1964), Combretum molleG.Don (Combretaceae)(Asres et al., 2001), and Cassia abbreviata Oliv (Caesalpiniaceae) (Khan et al., 1980; Connely et al., 1996) for the treatment of malaria, and Discorea dumetorum Pax (Discoreaceae)for treatment of mental disorders (Bevan et al., 1956; Schlag et al., 1959).
The Brine shrimps lethality test
The plants exhibited varying degrees of toxicity against brine shrimp larvae, with some having very low and some very high toxicity (Table 2a, b). Six out of the 60 plants (10%) gave LC50 values greater than 100µg/ml, 21(35.0%) plants gave LC50 values between 51-100µg/ml, 23 (38.3%) plants gave LC50 values between 20-50µg/ml, and 10 (16.7%) plants gave LC50 values below 20µg/ml. Afzelia quanzensis (LC50 2.95µg/ml), Dalbergia melanoxylon (LC50 8.64µg/ml), Ekebergia benguelensis (LC50 2.14µg/ml), Euclea natalensis (LC50 19.33µg/ml), Lonchocarpus capassa (LC50 17.79µg/ml), Psorospermum febrifugum (LC50 12.69µg/ml), Phyllanthus engleri (LC50 0.46µg/ml), Neurotaenia mitis (LC50 0.34 µg/ml), Sansevieria conspicua (LC50 13.98µg/ml), and Terminalia kaiserana (LC50 15.74µg/ml) were the most toxic extracts to the brine shrimps. Cyclophosphamide, a standard anticancer drug, gave an LC50 value of 16.30µg/ml.
Approximately 35% of plants used by traditional healers in Tabora were, on the basis of literature, supported to have therapeutic value. This figure is consistent with data that have been reported previously for diseases like diabetes mellitus and epilepsy (Moshi and Mbwambo, 2002; Moshi et al., 2005). The results confirmed the supportive role of traditional healers in offering health care services to local communities. The majority of areas in Tabora region are remote and, therefore, likely that its people would depend on the service offered by traditional healers. The claims on Psorospermum febrifugum have a special merit. The plant is used for the treatment of cancerous wounds, which agreed with results of tests carried out using cancer cell lines and the subsequent isolation of an active compound (Abou-shoer et. al., 1988). This was supported by brine shrimp results which are sometimes used to predict anticancer activity (Meyer et al., 1982). Despite the low predictive capability of brine shrimp assay results, there was a remote possibility that some other plants in this study might have anticancer activity. The 10 plants (Table 2a, b) which exhibited high toxicity with LC50 values below 20μg/ml were likely candidates. The results may suggest that some of these plants are toxic. This was true for Phyllanthus engleri, which was reported to be toxic to fish (Breyer Brandwijik, 1934), and rabbits (Watt and BreyerBrandwijik, 1929; BreyerBrandwijik, 1934). While some of the therapeutic claims have been supported by literature reports, and some by brine shrimp assay results, more rigorous studies are needed to confirm the therapeutic utility of the plants.
Literature reports have supported the therapeutic claims of some plants that are used in traditional medicine, thus supporting the ethnomedical method as a viable tool for drug discovery. However, while brine shrimps assay results have supported a few of the claims, they remain inconclusive and hence the need for more rigorous studies to confirm the therapeutic utility of the plants.
We thank the Management of the NAPRALERT Data Base at the University of Illinois, Chicago, for allowing us access to literature. We are also grateful to the collaborating traditional healers in Tabora region for availing information on the plants.
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