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Potential uses of Tetrapleura tetraptera Taub.
(Mimosaceae)
Prof C. O. Adewunmi
Drug Research and Production Unit
Faculty of Pharmacy
Obafemi Awolowo University
Ile-Ife, Nigeria. E-mail: cadewumi@oauife.edu.ng
Introduction
 Tetrapleura tetraptera, locally known as Aridan in Southwest Nigeria is a medicinal plant with many folkloric uses. Some of the folkloric uses of this popular west African plant have been authenticated in laboratory and field experiments. The plant is claimed to be therapeutically useful in the management of convulsion, leprosy, inflammation and/ or rheumatoid pains (Dalziel, 1948). Ghanians use the fruit as multivitamins while the fruit is used as spice in Nigeria and some other west African countries. Some of the authenticated biological activities of this plant are presented in this paper.
Efficacy of Tetrapleura tetraptera as a molluscicide
Molluscicides are used to kill snails that serve as intermediate hosts for schistosomes and other trematodes. The molluscicidal activity of the methanolic extracts of the leaf, leaf-stalk, stem-bark, root-bark and fruit of
T. tetraptera varied between 1.50 and 3.16 mg/L indicating the presence of molluscicidal activity in all parts of the plant. The methanolic extract of
T. tetraptera is effective against a variety of freshwater snails such as
Bulinus globosus, Lymnaea natalensis, L. columella, and Physa waterlotti
with LC50 of 2.03 to 4.56 mg/L (Adewunmi and Marquis, 1981; Adewunmi et al., 1982; Adewunmi et al., 1989). Water extract of
T. tetraptera (10 - 25.0 mg/L) is also active against Bulinus globosus (Adewunmi and Marquis, 1987). Saponins from
T. tetraptera are among the most powerful natural molluscicides (Maillard et al., 1989) and have similar potencies to those isolated from
Phytolacca dodecandra (Dorzas and Hostettmann, 1986) and Swartzia madagascariensis
(Borel and Hostettmann, 1987). 10.0 mg/L of the methanolic extract of the fruit evaluated at water contact sites at Fasina and Edun-Abon during the months of February and March, 1980 produced a significant reduction in the number of snails
(B. globosus, Lanistes spp. and B. forskalii) in their natural habitats after molluscicidal application compared with untreated sites. We also found that the water extract (50.0 - 100.0 mg/L) produced 100% mortality to the snails within a period of 24 hours (Adewunmi et al., 1982). The water extract of
T. tetraptera reduced field snail population and kept the transmission sites free from schistosome cercariae production for about 28 days (Adewunmi, 1984). This is due to the ability of the extracts and saponin glycosides isolated from the plant to interrupt schistosome transmission at two other points in the life cycle of the schistosome (Adewunmi and Furu, 1989). This interruption is possible at the infecting stage of snails by miracidia and the infection stage of man by cercariae. The cercaricidal effect of aridanin and the water extracts of
T. tetraptera has not been evaluated under field conditions. The effective utilization of this product as a cercaricidal agent will be highly useful in the control of fascioliasis which is the cause of economic loss to farmers and in the control of dermatitis caused by cercariae of
Trichobliharzia ocellata. Dermatitis caused by T. ocellata cercariae is the cause of economic loss in the recreation industry in Europe.
The calculated IC50s of aridanin on freshly laid to one-day-old eggs, 3-day-old eggs and 5-day-old eggs of
B. glabrata are 5.81 mg/L, 7.30 mg/L and 16.24 mg/L respectively (Adewunmi, 1991b). This indicates the poor ovicidal action of aridanin. This poor ovicidal activity could be overcome by multiple treatments timed to kill the adult and juvenile snails in the control of schistosomiasis (Adewunmi, 1984).
A joint schistosomiasis research project, carried out by our group and the Danish Bilharziasis Laboratory between 1988 and 1989 in southwestern Nigeria provided data by which it was possible to relate snail recovery from potential transmission sites to the presence or absence of
T. tetraptera. The presence of T. tetraptera around transmission sites appeared to be the most important limiting factor for the presence of snails. Water extracts of
T. tetraptera (40.0 - 120.0 mg/L) produced molluscicidal activity against
B. globosus and L. natalensis at Esinmirin and Fasina (Adewunmi et al., 1990). The results indicate that the planting of
T. tetraptera along water courses has potential for the local control of schistosomiasis. Molluscicides are crucial for controlling schistosomiasis (Adewunmi, 1991a). Therefore, plant derived molluscicides such as
T. tetrapterawhich is easily biodegraded in the environment can be substituted for chemical molluscicides in endemic poor nations of Africa.
Anti-ulcer activity
Extracts obtained from T. tetraptera exhibited significant anti-ulcer activity confirming its ethnomedical use in the management of gastro-intestinal disorders especially stomach ulceration (Noamesi et al., 1992).
Anti-microbial activity
Alcoholic and water extracts of T. tetraptera inhibited the growth of Staphylococcus aureus (Salako et al., 1990). The anti-microbial activity of this plant has been exploited in the formulation of the dried powdered fruits of the plant. Thus, dried powdered herbs have been formulated into soap bases using palm kernel oil, shea butter and mixtures of the two bases. The formulated soaps were evaluated for organoleptic properties and foaming ability. Soaps with the mixture of the two bases were of better qualities than those with the individual base. Incorporation of powdered plant materials influenced both the foaming property and the hardness of the soaps. Except for the
T. tetraptera fruit powder which improved the foaming ability of the soaps (Adebayo et al. 2000), all other herbs including
Acalypha wilkesiana, Harugana madagascariensis and Ficus exasperata depressed the foaming ability of the soaps.
Anticonvulsant activity
The extracts from T. tetraptera exhibited anticonvulsant activity which could be linked to their ability to depress the central nervous system (Akah and Nwambie, 1993).
Emulsifying property
The emulsifying property of the extracts from T. tetraptera has been demonstrated (Olaifa et al., 1993).
Birth control
The ethanol extracts and saponins from the stem-bark of T. tetraptera exerted an inhibitory effect on luteinizing hormone released by pituitary cells (El Izzi et al., 1990) suggesting its use as a contraceptive agent.
Nutritive activity
The nutritional quality of the dry fruit of T. tetraptera used as spice, was assessed. The fruit shell, fruit pulp and seed contained varying amounts of nutrients such as protein, lipids and minerals, which were comparable and some were even higher than popular spices such as red pepper, onion, curry and ginger (Essien et al., 1994). In eastern parts of Nigeria, fruits are used to
prepare soups for mothers from the first day of delivery to prevent postpartum contraction (Nwawu and Akah, 1986). It is used in the preparation of pepper soup in southern parts of Nigeria. The fruits also contain cinnamic acids, caffeic acid and carbohydrates (Adesina , 1982). The latter two of these components are common in most spices.
Pharmacological examination of an aqueous extract of T. tetraptera showed that it had little or no hypotensive effect on anaesthetized cats, dogs, and rabbits, but significantly depressed the blood pressure of anaesthetized rats (Adewunmi at al., 1987). The implication of this finding in rats is that this cardiovascular effect may be species specific. Aridanin and water extract of
T. tetraptera had no influence on cell proliferation and neither induced chromosomal aberrations nor sister chromatid exchanges in Chinese hamster ovary cells (i.e. no genotoxic effect) cultured in vitro and no mutagenic effects occurred in Salmonella typhimurium TA 97, TA 98 and TA 100 (Adewunmi et al., 1991). An MeoH extract of the fruit exhibited weak mutagenic activity only in the presence of S-9. The stem-bark saponin isolates, aridanin and other saponins were not mutagenic, either with or without metabolising activation (Ngassapa et al., 1993).
Experiments were also conducted on mice with 3H-Aridanin by whole-body autoradiography and liquid scintillation (Adewunmi and Appelgren, 1989). No specific retention in any tissue was observed after 24 hours and aridanin did not pass the placenta barrier in pregnant mice. After oral administration to mice, most of the labelled aridanin was found in the intestinal contents indicating a very poor absorption. The results showed that a rapid uptake and disappearance and low oral uptake of aridanin in a non-target mammal make this molluscicide a suitable candidate to be tested in field studies and that safe use of the plant extract could be encouraged.
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