2.10 BOTANY OF PLANTS USED IN THIS STUDY
2.10.9 Combretum molle (COMBRETACEAE)
The Combretum moUe (Figure 10) is common in the tropics especially in Africa. The tree produces fruits that have four or more wings on it.
Figure 10. Combretum moUe tree (www.images.google.com)
Fresh or dry leaves are used for dressing wounds, snakebites, fever and anthelmintics, and as abortifacients (Watt and Breyer-Brandwijk, 1962). Roots are used for constipation, swelling of the abdomen, infertility, diarrhoea, bleeding after birth, convulsions, and as an aphrodisiac (Gelfand et al., 1985).
Chemical constituents that have been isolated from the plant include mollie acid, xyloside, arabinoside and large amounts of triterpenoids (Rogers and Thevan, 1986; Lawton and Rogers, 1993). The relative abundance of triterpenoids might explain the anti- inflammatory, ant-microbial and molluscicidal activities associated with this plant.
2.10.10 Eugeniajamholana (MYRTACEAE)
The plant is found in the tropics and some parts of North America. The tree produces green unripe berries that become purple when ripe (Figure 11).
Figure 11 Eugeniajambolana (www.images.google.com)
The pulp extract as well as the seed extract of E. jambolana fruits display hypoglycaemic activity although the action is said to be speedy (Achrekar, et al., 1991; Wang and Ng, 1999; Grover, et al., 2000). Oral administration of the extract in normoglycemic and streptozotocin-induced diabetic rats causes the serum insulin levels to rise. It has also been shown that incubation of the extracts with isolated islets of Langerhans from normal and diabetic rats augments insulin secretion from the islets. These extracts inhibited insulinase activity from liver and kidney (Achrekar, et al., 1991; Wang and Ng, 1999; Vikrant, et al., 2001). Although many studies have shown the hypoglycaemic activity of this plant, one study reported that the plant does not exhibit this activity. Pepato et aI., (2001) reported that Eugenia jambolana leaf decoction had no antidiabetic activity in Streptozotocin- diabetic rats treated for 17 days. This discrepancy might only be explained as being due to differences in the extraction process between the groups. It is my view that extraction processes can result in losses of active compounds
The various plants belonging to Eugenia uniflora L. (Myrtaceae) are used in North-eastern Argentina as a treatment for hypertension. Intraperitoneal administration of the aqueous crude extract (ACE) decreased blood pressure of normotensive rats (Consolini, et at., 1999). The results from this work suggest that the empirical use of Eugenia uniflora L.
(Myrtaceae) is mostly due to a hypotensive effect mediated by a direct vasodilating activity, and to a weak diuretic effect that could be related to an increase in renal blood flow. Although, the authors do not specify the species of Eugenia used in their study, one can postulate that Eugenia jambutana might also have its hypotensive through the above- mentioned mechanism.
Various terpenoids including monoterpenoids, sesquiterpenoids, and triterpenoids have been isolated from the plant. The plant also produces saponin. Oleanolic acid isolated from its flowers has been reported to have strong anti-fertility effect in male albino rats (Rajasekaran et at., 1988).
Ethanol extracts of the plant showed significant inhibitory activity against castor oil induced diarrhoea and PGE2 induced enteropooling in rats. The extracts also showed a significant reduction in gastrointestinal motility in charcoal meal tests in rats Thus, the results obtained establish the efficacy of the plant materials as anti-diarrhoeal agents (Mukherjee, et at., 1998)
2.10.11 Clerodendrum trichotomum (VERBENACEAE)
The plant is found in the warm tropical areas. It is a shrub that produces light to dark-pink flowers (Figure 12).
The plant has been reported to be used to reduce blood pressure. In addition to the blood lowering effect, plants belonging to this genus have been shown to have anthelminitic properties, sedative effects and muscle stimulating action (Gupta et a!., 1994)
Figure 12. Clerodendrum trichotomum (www.images.google.com)
The chemical constituents that have been isolated from the plant might include saponins.
Intravenous administration of extracts from the dried leaves elicited renal vasodilatation and increased urine flow and urinary sodium excretion in dogs and rats (Lu et al., 1994).
Oral administration reduced blood pressure of spontaneously hypertensive rats but not normotensive control rats. Chronic administration also prevented increases in blood pressure of spontaneously hypertensive rats.
2.10.12 Psychotria serpens (RUBIACEAE)
The plant is found in the tropical areas. P. serpens is a shrub that has succulent leaves and stems. It has its inflorescence at the terminal and the flowers bud green and turn white (Figure 13). It produces green bellies that turn yellow to orange in colour.
Whole herbs of Psychotria serpens are used a lot in folklore medicine. In Taiwanese folklore, the whole herb is used as an antirheumatic, analgesic, muscles relaxing, and circulation promoting drug (Chung, 1979).
Ursolic acid was found to be one of the active principles of cytotoxic anti-leukaemic extracts from dried whole plants (Lee et al., 1988). The authors clearly indicated that ursolic acid showed significant cytotoxicity against the growth of lymphocytic leukaemia cell lines as well as a human lung carcinoma cell line. It also showed marginal cytotoxicity in the human colon and mammary tumour cells.
Figure 13. Psycho tria serpens (www.images.google.com)