Friday, October 21, 2005
Recent studies indicate that extract of bitter leaf exerts antibiotic action against drug resistant micro-organisms and can prevent or delay the onset of breast cancer and diabetes. CHUKWUMA MUANYA reports.
COMMONLY called Bitter Leaf, Vernonia amygdalina belongs to the plant family Compositae. In Nigeria, the Edo calls it oriwo, Hausa, chusar doki (a horse tonic food containing the leaves), fatefate/mayemaye (a food prepared from the leaves), Ibibio atidot, Igbo, onugbu, Tiv, ityuna and Yoruba, ewuro.
A Professor of Botany and Head of the Department of Botany and Microbiology, University of Lagos, Oluwatoyin Ogundipe, describes Bitter Leaf as a shrub or tree which grows to about five meters high especially around forest-margins and is widely distributed throughout tropical Africa.
"The leaves are very bitter. Bitterness can be abated by boiling or in the young leaves by soaking in several changes of water. They are held to be anti-scorbutic and are added to soups or eaten as spinach."
An extract of Bitter Leaf has been shown to be an active anticancer agent. Physiologically relevant concentrations of extract from Bitter Leaf (Vernonia amygdalina) inhibit DNA synthesis in a breast cancer cell line.
According to recent research, "Discovery of water-soluble anticancer agents (Edotides) from a vegetable found in Benin City, Nigeria," published in the journal Experimental Biology and Medicine, Bitter Leaf may prevent the onset of breast cancer.
The objective of this study was to evaluate the effect(s) of a novel water-soluble leaf extract of Vernonia amygdalina (VA) on human breast cancer cell DNA synthesis. The MCF-7 cell line, considered a suitable model, was used in this study.
The reseachers led by E.B. Izevbigie write: " Treatment of cells with physiologically relevant concentrations of water-soluble VA extract potently inhibited DNA synthesis in a concentration dependent fashion, both in the absence and presence of serum. Fractions of VA extract separated using preparative reverse-phase chromatography also inhibited DNA synthesis (p is less than 0.005)."
The researchers conclude: "These results suggest that the vegetable VA, if incorporated in the diet, may prevent or delay the onset of breast cancer."
They write: "Current treatment approaches have yielded significant progress in the fight against cancer, but the incidence of certain types of cancer continues to rise.
"This is especially true in the African-American communities. African Americans are about 33 per cent more likely to die of cancer than are whites and more than twice as likely to die of cancer as are Asian-Islander, American-Indians, and Hispanics.
"This increase, coupled with the harsh side effects of some of the cancer chemotherapy, have led to the search for more natural biological products, especially those derived from plant products, currently known as herbal medicine. There is a need for a continued search for novel natural products that may be used as cancer chemopreventive and/or chemotherapeutic agents."
According to a study carried out by researchers at the University of Jos, Bitter Leaf has an anti-diabetic effect in diabetes mellitus (Type 2 diabetes).
The researchers include: Steven S. Gyang of the Department of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, Davou D. Nyam of the Department of Botany, Faculty of Natural Sciences and Elijah N. Sokomba, Department of Pharmacology, Faculty of Pharmaceutical Sciences.
The study published in the Journal of Pharmacy & Bioresources was carried out to evaluate the hypoglycaemic effect of the crude chloroform extract of Vernonia amygdalina (leaves) on blood glucose concentration (BGC) of normoglycaemic and alloxan-induced hyperglycaemic rats. The study is titled " Hypoglycaemic activity of Vernonia amygdalina (chloroform extract) in normoglycaemic and alloxan-induced hyperglycaemic rats."
Adult male albino rats were randomly allocated into four groups. Group I animals served as untreated controls to normoglycaemic group II animals. Alloxan-induced hyperglycaemic rats of group III served as untreated controls to hyperglycaemic rats of group IV. Groups II and IV animals were treated with a single intraperitoneal (IP) dose of 750 mg/kg of crude chloroform extract of Bitter Leaf. Control animals of groups I and III were administered equi-volume (per kilogram of bod y weight) of normal saline IP. The BGCs of all animals in each group were determined at 0, 0.5, one, four, eight and 24 hours post-treatment with normal saline (controls) or the crude chloroform extract (treated groups).
There was significant (P is less than 0.05) lowering of BGCs between one - four hours (for normoglycaemic rats) and one - eight hours (for hyperglycaemic rats). Thus the crude chloroform extract of the leaves of Vernonia amygdalina has a hypoglycaemic activity in both normoglycaemic and alloxan induced hyperglycaemic rats. This study lends support to the claim by herbalists of Plateau and Nassarawa States that Vernonia amygdalina may have an antidiabetic effect in diabetes mellitus.
According to a study published in the West African Journal of Pharmacology Drug Res., Bitter Leaf could be effectively used against drug resistant microorganisms.
The study was carried out to determine antibacterial potential of Vernonia amygdalina using a panel multi-drug resistant gram-negative and gram-positive bacteria and standard strains: Eschericia coli ATCC 25922 and Staphylococcus aureus ATCC 25923.
Using agar-well and disc-diffusion assays, aqueous extract of Bitter Leaf was found to produce growth inhibitory zones of 15.6-16.1mm for Eschericia coli, 15.5-16.6mm for Salmonella typhi, 10.3-15.6mm for Shigella spp, 12.1-12.3 mm for MSSA and MRSA, 15.8-16.7 mm for Bacillus spp and 11.9-12.6mm for Streptococcus spp. Two out of the eight Pseudomonas aeruginosa isolates tested showed susceptibility (inhibitory zone diameter = 6.7 + 0.2mm) to bitter leaf by agar well diffusion only. Macro broth dilution assay further revealed antibacterial potency of the active extract with MICs of 22.5-26.0mg/mL and 19.8-26.4mg/mL and MBCs of 30-34.5mg/mL and 28.3-34.3mg/mL for the gram-negative and gram-positive isolates tested.
The bactericidal activity of the active extract resulted in a decline in viable cells of gram-negatives and gram-positives at a rate of 1.6-6.2 x 103 cfu/h and 6.3-7.9 x 103 cfu/h, respectively. Specifically, the active extract challenge resulted in a decline in the number of viable cells of E.coli, Bacillus and Salmonella by 4logcfu and Shigella, Streptococcus spp and Staphylococcus aureus isolates by 3log cfu within four hours of incubation in the time-kill assay.
The results of this study have scientifically demonstrated the antibacterial activity of Vernonia amygdalina and further suggest its possible exploitation as a source of natural product for future use in the management of multi-drug resistant bacterial infections in Nigeria.
According to the West African Encyclopedia of Medicinal Plants, "the leaves of bitter leaf are widely used for fevers and are known as a quinine-substitute. A leaf-decoction is taken as a laxative. A purgative enema is made by macerating the leaves through a cloth and adding peppers and spices. A cough medicine is made as an expectorant. The leaves are rubbed directly onto the skin for itch, parasitic affections, ringworm, among others. Cold infusion is applied as a wash. During the puerperium, a mother may take a decoction of the leaves to affect her milk so as to act as a prophylactic against worms in the baby. The leaves are added to horse-feed as a vermifuge and to treat internal disorders symptomised by mucal discharge from the nose. Leaves are rubbed onto the breast for weaning infants.
" The wood, most usually from the root after the bark has been removed by scorching, provides one of the common chewsticks in Nigeria. It is valued as a tooth-cleaner and more especially as a stomachic and appetiser. It has an alleged beneficial effect on dental caries, but no antibiotic activity has been found in material from Ibadan. In Northern Nigeria, the Hausa use these chewsticks with natron for gastro-intestinal troubles. A root-infusion is taken in Nigeria as a worm expeller as well as for intestinal parasitic infections.
" The bark of stem and roots is particularly bitter and is more or less astringent. Infusions are commonly taken for fever and diarrhoea. In Nigeria an infusion is used for rheumatism. Dried flowers are used to treat stomach-disorders. The fruit is used as an aphrodisiac, and powdered seeds as worm expeller."