|
|
|
|
Research Article
|
|
Hypotensive Effects and Acute Toxicity Property of Methanol Extract of Baissea axillaris Hau. Leaf on Animal Models
|
|
M. Idu,
O. Timothy,
E.K.I. Omogbai
and
F. Amaechina
|
|
|
ABSTRACT
|
The hypotensive and acute toxicity activities of methanol
extract of B. axillaris leaves, obtained by soxhlet extraction,
were analyzed using animal models. The extract exhibited a dose-dependent
reduction in rabbit blood pressure. Basal mean arterial pressure of 115.67
± 3.60 mm Hg was progressively reduced to 106.22 ± 3.13
and 69.3 ± 2.59 mm Hg by 2.5 and 20 mg kg-1 doses of
extract, respectively. Hematological parameters in Wister rats treated
with 1, 2 and 4 g kg-1 of extract showed no significant difference,
p>0.05. However, lethal dosage was obtained at 8 g kg-1.
The need for further evaluation and prospect of the plant in health care
was also discussed.
|
|
|
|
|
INTRODUCTION
Plants serve various purposes in this world. Their usefulness can
be in form of food, shelter, textile, religious, medicines etc. (Fabeku,
2006). Over 40,0000 species of tropical flowering plants have medicinal
properties (Aibinu, 2006). The use of medicinal plants for both preventive
and curative therapies is not new as records of indigenous knowledge from
various parts of the world illustrate an age long tradition of plants
being a major bioresource base for health care (Stepp and Moerman, 2001;
Yesilada, 2005).
High blood pressure is a major risk factor for the development of cardiovascular
complications including stroke congestive heart failure, peripheral vascular
disorder and renal failure (Lloyd-Jones et al., 2000). It is of
relatively high prevalence in Nigeria where about 11% of the population
was reported to have the disease condition (Mabadeje, 2002). Of the several
pharmaceutical drugs presently used in its management today, none promise
a permanent cure and there are often various complications arising from
side effects of their use (Ayinde and Amaechina, 2005). Certain indigenous
plants have been reported to possess blood pressure lowering activities
in animal models (Amos et al., 2003; Takahashi and Smithies, 2004;
Kim et al., 2006).
There is however, the need for proper scientific investigation of both
beneficial and harmful effects of any medicinal plant (Olatunji-Bello
and Awobajo, 2006; Idu et al., 2006a). Toxicity testing of new
drugs on animal models can be extrapolated to identify the relative potential
hazard it may have on man (Fabricant and Farnsworth, 2001). It helps to
determine the upper limits of administration of effective therapy. If
the toxicity is low then there is a chance of possible introduction of
such a drug for therapeutic use (Ataman et al., 2006). Most toxic
effects of drugs occur at a predictable (usually short) time after administration:
a basis for acute toxicity testing (Curtis, 2001).
The Urhobos (in the Niger Delta region of Nigeria) administer decoction
of Baissea axillaris Hau. orally for the treatment of hypertension.
Little has been done scientifically to justify the efficacy of this treatment,
although Ayinde and Amaechina (2005) reported that the hypotensive property
of the plant can be influenced by the solvent used in its extraction.
Although no harmful or contraindication has been reported about its use
among the natives, it is important to substantiate this with standard
scientific trials.
B. axillaris belongs to the family Apocynaceae. It is a climbing
perennial shrub. The leaves are 2.5-4 cm by 1.2-2.7 cm broad, glabrous
on both surfaces, arranged in opposite pairs with short stipules. It exudes
milky latex when plucked or cut. The apical and young stems are tender
and brittle, becoming more ligneous and tough towards the base and with
age.
The plant is often found interwoven with hedges, other woody supports
(dead or alive) and fences (especially mesh-like iron fences) where it
forms a thick evergreen mass of twisted stems and leaves above the ground.
It thrives better in water-rich soil and ample supply of sunlight.
MATERIALS AND METHODS
B. axillaris was harvested in the month of March around Ugbowo
axis, Benin City, Nigeria. The leaves were plucked off with bare fingers,
cleaned off debris and dried in a Gallenkhamp laboratory oven set at 40 °C
for 18-24 h. The dried, brittle leaves were pulverized in an electric
mill.
Methanol was used to extract 3.5 kg of the powered leaves by soxhlet
extraction. A rotary evaporator was used to concentrate the extract into
a viscous paste (Somchit et al., 2003). This was preserved in a
properly covered bottle container and kept in a refrigerator till used
for experiments.
For the hypotensive experiment, a total of 10 male rabbit weighing between
1.4-2.4 kg were purchased from Aduwawa market in Benin City and kept in
the Animal house of Department of Pharmacology, University of Benin, feed
with rabbit pellets and provided with water ad libitum and acclimatized
for two weeks. Under general anaesthesia (urethane), the marginal ear
vein was canulated with a 21-G scalp vein canula fixed to a three way
stop tap. Subsequent intravenous administrations of doses saline were
via this route.
The carotid artery was similarly canulated with a butterfly canula connected
to a DC powered Ugo Basile double or 2-channel recorder via a transducer.
The animal was then left undisturbed and observed for about 20 min and
basal blood pressure was noted Graded doses of the extract (2.5, 5.0,
10 and 20 mg kg-1) from a stock preparation of 50 mg mL-1
were administered at regular time interval for drug effects to be observed.
This procedure was repeated for five replicates.
A possible mechanism of hypotensive activity was investigated by the
prior administration of 1 mg kg-1 atropine and after 20 min,
administered graded doses of the extract. A similar test was conducted
using 1 mg kg-1 of chlorpheniramine in place of atropine.
To determine the acute toxicity, fifteen male Wistar rats were purchased
from animal unit of the Department of Microbiology, University of Benin,
Benin City. They were distributed equally in 5 groups. Average weight
per group ranged between 200-250 g. Each rat in groups 2, 3, 4 and 5 were
administered the extract, intraperitoneally, in doses of 1, 2, 4 and 8
g kg-1 body weight respectively while the control (group 1)
received 2 mL normal saline. All 5 groups were allowed unrestricted access
to feed and observed for 48 h. Blood samples were collected by cardiac
puncture from each of the surviving rats and analysed for haematological
parameters using a hema-auto-analyser and the results subjected to Duncan
multiple comparison test.
RESULTS AND DISCUSSION
Table 1 reveals that the Mean Arterial Pressure
(MAP) of rabbit was significantly and progressively reduced from a basal
level of 115.67 ± 3.60 to as low as 69.33 ± 2.59 at the highest
dose of extract, 20 mg kg-1. While Fig. 1 accentuates the level
of Fall in Mean Arterial Pressure (FMAP) resulting from each treatment.
Table 2 shows that only the rats treated with 8 g kg-1
of extract died whereas lower dosage did not confer mortality. From
Table 3, except for the MXD count of group 4, there were
no significant differences (at 95% confidence level) in hematological
parameters of the variously treated surviving rats.
Idu et al. (2006b) reported that aqueous extract of Stachytarpheta
jamaicensis dose-dependently reduced MAP in rabbits from a basal level
of 102.8 ± 4.2 mm Hg to 96.6 ± 7.3 and 74.7 ± 8.7
mm Hg by doses of 2.5 and 20 mg kg-1, respectively. Equivalent
doses of methanol extract of B. axillaris reduced rabbit`s MAP
from a basal level of 115.67 ± 3.6 to 106.22 ± 3.13 and
69.33 ± 2.59,
Table 1: |
The effect of methanol extract of B.
axillaris leaf on the mean arterial pressure of rabbit |
 |
Mean ± SEM, MAP: Mean Arterial Pressure |
Table 2: |
Lethal effect of various dosage of methanol
extract of B. axillaris leaf on Wistar rats |
 |
Control = Normal Saline |
 |
Fig. 1: |
Fall in MAP (FMAP) with methanol extract
of B. axillaris leaf |
Table 3: |
Effect of methanol extract of B. axillaris
leaf on some hematological parameters of wistar rats |
 |
Means ± SEM
with similar superscript within a column are not significantly different
p>0.05, Means ± SEM with different superscripts within a
column are significantly different p<0.05, WBC: White Blood Corpuscle,
HGB: Hemoglobin, HCT: Hematocrit, RBC: Red Blood Corpuscle, PLT:
Platelets, LYM: Lymphocyte, MXD: Eosinophyll and Basophyll, NEUT:
Neutrophyll counts, Control: Normal saline |
respectively (Table 1). Similarly, Ayinde and Amaechina
(2005) reported FMAP values of 12.9 ± 0.58, 26.6 ± 1.8 and 34.43 ± 0.59
mm Hg after administration of 2.5, 10 and 20 mg kg-1 doses
of aqueous extract of B. axillaris. However, the present
study revealed similar doses of methanol extract resulted in (FMAP) of
9.44 ± 1.54, 28.44 ± 1.28 and 46.33 ± 1.96 mm Hg, respectively
(Fig. 1).
The prior administration of atropine or chlorpheniramine (antagonists)
did not inhibit the hypotensive effect of the extract and there was no
obvious effect on the heart rate. This suggests that the extract may not
be acting through histamine release, but possibly through the stimulation
of endothelia muscarinic receptors which can lead to the release of vaso-relaxant
nitric oxide (Idu et al., 2006b).
The observation of either hematological, behavioural, biochemical or
histological changes have been employed in toxicological studies (Jaouhari
et al., 1999; Mutalik et al., 2003; Basu and Arivukkarasu,
2006). The extracts of Jatropha curcas and Phyllanthus amarus
leaves had drastic effects on some hematological parameters (Oluwole
and Bolarinwa, 1997; Oyedapo, 2001).
The rats in this research showed high tolerance for the methanol extract
of B. axillaris leaf (Table 2). A zero
percent mortality was still recorded for a relatively high dose of 4 g
kg-1 and their agility appeared undisturbed. However, after
about 30 min of 8 g kg-1 dose administration, rats in this
group went into episode of intense general muscular spasm and died shortly
after. Hematological parameters were not significantly different (p>0.05)
except in the differential blood count (MXD) of group 3 (Table
3). Such an isolated observation could be considered to be of little
or no toxicological significance (Moto et al., 2004).
CONCLUSION
This study has further strengthened the ethnomedicinal claim as
well as earlier report on the hypotensive property of B. axillaris.
The activity of this extract in reducing systolic blood pressure may prove
to be of significance in the prevention of hemorrhagic stroke, as this
would mean a lowered force at which blood is pumped out of the heart into
the systemic circulation and thus the reduction of risk of rupture of
tender blood vessels in the brain, which is a predisposing factor to stroke
conditions in high blood pressure patients.
The therapeutic index of this plant is also impressive as the acute toxicity
dosage is high. However, the efficacy as well as the chronic toxicity
effect of the plant still requires further elucidation.
|
REFERENCES |
1: Aibinu, I., 2006. Medicinal Plants as Antimicrobials. In: Outlines and Pictures of Medicinal Plants from Nigeria, Odugbemi, T. (Ed.). University of Lagos Press, Lagos, Nigeria, pp: 53-64.
2: Amos, S., P.A. Akah, L. Binda, N.M. Enwerem, A. Ogundaini, C. Wambebe, I.M. Hussaini and K.S. Gamaniel, 2003. Hypotensive activity of the ethanol extract of Pavetta crassipes leaves. Biol. Pharm. Bull., 26: 1676-1680. CrossRef | PubMed | Direct Link |
3: Ataman, J.E., M. Idu, E.A. Odia, E.K.I. Omogbai, F. Amaechina, A.O. Akhigbe and L.E. Ebite, 2006. Histopathologic effects of Stachytarpheta jamaicensis (L.) vahl. on wistar rats. Pak. J. Biol. Sci., 9: 477-482. CrossRef | Direct Link |
4: Ayinde, B.A. and F.C. Amaechina, 2005. Hypotensive effect of Baissea axillaris (Apocynaceae) leaves in normotensive rabbits. J. Pharm. Bioresour., 2: 84-88. Direct Link |
5: Basu, S.K. and R. Arivukkarasu., 2006. Acute toxicity and diuretic studies of Rungia repens aerial parts in rats. Fitoterapia, 77: 83-85. CrossRef |
6: Curtis, D.K., 2001. Principles of Toxicology and Treatment of Poisoning. In: The Pharmacological Basis of Therapeutics, Good and Gilnan (Eds.). 10th Edn., McGraw Hills, UK., pp: 67-71.
7: Fabeku, O., 2006. Traditional Med: The Arts, Ways and Practice. In: Outlines and Pictures of Medicinal Plants from Nigeria, Odugbemi, T. (Ed.). University of Lagos Press, Nigeria, pp: 13-20.
8: Fabricant, D.S. and N.R. Farnsworth, 2001. The value of plants used in traditional medicine for drug discovery. Environ. Health Perspect., 109: 69-75. PubMed | Direct Link |
9: Idu, M., J.E. Ataman, A.O. Akhigbe, E.K.I. Omogbai, F. Amaechina and E.A. Odia, 2006. Effect of Stachytarpheta jamaicensis (L.) Vahl. on Wistar rats: Serum biochemistry and ultrasonography. J. Medical Sci., 6: 646-649. Direct Link |
10: Idu, M., E.K.I. Omogbai, F. Amaechina and J.E. Ataman, 2006. Some cardiovascular effects of aqueous extract of the leaves of Stachytarpheta jamaicensis L. vahl. Int. J. Pharmacol., 2: 163-165. CrossRef | Direct Link |
11: Jaouhari, J.T., H.B. Lazrek and M. Jana, 1999. Acute toxicity of 10 Moroccan plants reported to be hypoglycemic agents. Therapie, 54: 701-706. PubMed |
12: Kim, M., H.J. Lee, S. Wiryowidagdo and H.K. Kim, 2006. Antiphypertensive effects of Gynura procumbens extracts in spontaneously hypertensive rats. J. Med. Food, 9: 587-590. PubMed |
13: Lloyd-Jones, D.M., J.C. Evans, M.G. Larson, C.J. O’Donnell, E.J. Roccella and D. Levy, 2000. Differential control of systolic and diastolic blood pressure. Factors associated with lack of blood pressure control in the community. Hypertension, 36: 594-599. Direct Link |
14: Mabadeje, A.F.B., 2002. National survey of hypertension and obesity in Nigeria. World Hypertension League, 1: 19-20.
15: Moto, M., M. Okamura, T. Watanabe, Y. Kashida and K. Mitsumori, 2004. 13th week repeated dose toxicity of rice bran glycosplingolipid in Wistar Hannover (Galas) rats. J. Toxicol. Sci., 29: 73-80. Direct Link |
16: Mutalik, S., B. Sulochana, M. Chetana, N. Udupa and D.P. Uma, 2003. Preliminary studies on acute and sub-acute toxicity of an anti-diabetic herbal preparation, Dianex. Ind. J. Exp. Biol., 41: 316-320. Direct Link |
17: Olatunji-Bello, I.I. and F.O. Awobajo, 2006. Methods of Investigating Physiological Actions of Medicinal Plants. In: Outlines and Pictures of Medicinal Plants from Nigeria, Odugbemi, T. (Ed.). University of Lagos Press, Nigeria, pp: 65-71.
18: Oluwole, F.S. and A.F. Bolarinwa, 1997. Jatropha curcas causes anaemia in rats. Phytother. Res., 11: 538-539. CrossRef |
19: Oyedapo, O.O., 2001. Biological activities of Phyllanthus amarus extracts on Spraque Dawley Rats. Nig. J. Biochem. Mol. Biol., 16: 83-86.
20: Somchit, M.N., I. Reezal, E.I. Nur and A.R. Mutalib, 2003. . In vitro antimicrobial activity of ethanol and water extract of Cassia alata. J. Ethnopharmacol., 84: 1-4. Direct Link |
21: Stepp, J.R. and D.E. Moerman, 2001. The importance of weeds in ethnopharmacology. J. Ethnopharmacol., 75: 19-23. CrossRef | Direct Link |
22: Takahashi, N. and O. Smithies, 2004. Human genetics, animal models and computer simulations for studying hypertension. Trends Genet., 59: 347-379. Direct Link |
23: Yesilada, E., 2005. Past and future contributions of traditional medicine in the health care system of the Middle-East. J. Ethnopharmacol., 100: 135-137. CrossRef | PubMed | Direct Link |
|
|
|
 |