Ethanolic leaf extract of Verbena hastata produces antidiarrhoeal and gastrointestinal motility slowing effects in albino rats

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Abstract
The antidiarrhoeal effects of ethanol leaf extract of Verbena hastata were evaluated in rat .Studies were investigated on castor oil-induced diarrhoea and gastrointestinal motility activity in rat. The extract (200 and 400 mg/kg) elicited a greater anti-motility than 5 mg/kg atropine (P < 0.05) and significantly (P < 0.05) protected rats against castor oil-induced diarrhoea. The frequency of defaecation as well as the wetness of faecal droppings was significantly (P < 0.05) reduced. The oral LD 50 of the extract was found to be greater than 5000mg/kg in mice. The result obtained shows that the ethanol leaf extract of V. hastata may contain some biologically active principles that are active against diarrhoea and this may be the basis for management of gastrointestinal disorders.
Journal of Medicinal Plants Research Vol. 4(16), pp. 1624-1627, 18 August, 2010
Available online at http://www.academicjournals.org/JMPR
DOI: 10.5897/JMPR10.013
ISSN 1996-0875 ©2010 Academic Journals
Full Length Research Paper
Ethanolic leaf extract of Verbena hastata produces
antidiarrhoeal and gastrointestinal motility slowing
effects in albino rats
G. C. Akuodor1*, M. Idris-Usman1, T. C. Ugwu1, J. L. Akpan2, L. A. Irogbeyi3, T. C.
Iwuanyanwu1 and U. A. Osunkwo2
1Department of Pharmacology and Toxicology, National Institute for Pharmaceutical Research and Development,
P. M. B. 21, Garki, Abuja, Nigeria.
2Department of Pharmacology and Therapeutics, Faculty of Clinical Medicine, Ebonyi State University, Abakiliki, Nigeria.
3Department of Pharmacology and Therapeutics, Abia State University, Uturu, Nigeria.
Accepted 28 May, 2010
The antidiarrhoeal effects of ethanol leaf extract of Verbena hastata were evaluated in rat .Studies were
investigated on castor oil- induced diarrhoea and gastrointestinal motility activity in rat. The extract
(200 and 400 mg/kg) elicited a greater anti-motility than 5 mg/kg atropine (P < 0.05) and significantly (P <
0.05) protected rats against castor oil- induced diarrhoea. The frequency of defaecation as well as the
wetness of faecal droppings was significantly (P < 0.05) reduced. The oral LD50 of the extract was found
to be greater than 5000mg/kg in mice. The result obtained shows that the ethanol leaf extract of V.
hastata may contain some biologically active principles that are active against diarrhoea and this may
be the basis for management of gastrointestinal disorders.
Key words: Verbena hastate, anti-diarrhoeal, gastrointestinal tract, castor oil.
INTRODUCTION
Diarrhoea is an important health problem especially in
developing countries and it is the cause of 5 - 8 million
deaths through out the world annually. To combat the
problems of diarrhoea, the World Health Organization
(WHO) initiated a diarrhoea disease control program to
study traditional medicine practices and other related
aspects, together with the evaluation of health education
and prevention approaches (Syder and Merson, 1982;
Mukherjee, 1995). The use of herbal drugs in the
treatment of diarrhoea disease is a common practice in
many countries of Africa. These plants, which abound in
the environment, enjoy wide acceptability by the
population and serve as cheaper alternatives to Orthodox
medicine (Sofowora, 1993; Akah and Nwabie, 1994).
Verbena hastata (Vervain), family Verbenaceae, have
broadly ovate leaves, about 2 m high. The plant is used
*Corresponding author. E-mail: goddyakuodor@yahoo.com.
Tel: +2348036725237.
traditionally in the treatment of various medical
conditions. The leaves and roots are used as tonic,
expectorant, emetic, diaphoretic and vermifuge; its leaves
are used in the treatment of depression, tension and
pain. The plant is used in parts of southern Nigeria for the
treatment of fever, dysentery and diarrhoea.
However, the plant has not been experimentally tested
for its antidiarrhoeal activity. Hence, an effort was made
to investigate the plant extract in experimentally- induced
diarrhoea in rats adopting modifications of the reported
method of Awouters et al. (1978).
MATERIALS AND METHODS
Plant materials and extraction
Fresh leaves of V. hastata were collected by Mr Joseph L. Akpan
from Nnug Ita, Akwa Ibom State, Nigeria. The plant was identified
and authenticated by Prof. J. C. Okafor of Coal City University,
Enugu, Nigeria. The leaves were cleaned, air-dried at room
temperature for 7 days and crushed into coarse power using pestle
and mortar. 220 g of the powdered materials was macerated
with ethanol f or 24 h with constant shaking. The liquid extract
obtained was c oncentrated to dryness in vacuum at 40°C. The yield
was ( 8.2% w/w). This ethanolic extract was used in all the studies
with doses expressed in grams per kilogram body weight of the
animal.
Experimental animals
Albino rats of either sex weighing between 200 - 250 g were used
for the experiments. The animals were maintained at the Animal
facility center, National Institute f or Pharmaceutical Research and
Development Idu, Abuja, Nigeria. They were fed with standard diet
and had free access to water ad libitum. The animals were
maintained under standard c onditions of humidity, temperature and
12 h light/ 12 h darkness cycle. A standard protocol was drawn up
in accordance with the good laboratory practice (G.L.P.) principles
of the OECD as adopted by the WHO (WHO Document, 1998). The
“Principles of laboratory animals care” (NIH publication No 85-23,
1985) were also followed in this study.
Acute toxicity test
The acute toxicity LD50 was estimated p.o in Swiss albino mice (20 -
25 g) following Lorke’s method (1983). Dose levels used ranged
from 100 - 5000 mg/kg of the ethanolic extract. The acute t oxicity
LD50 was c alculated as geometric mean of the dose that resulted in
100% lethality and that which caused no lethality at all. Toxicity
signs such as death, changes in physical appearance, behaviourial
changes were observed for 72 h after administration of ethanol
extract of the plant material.
Castor oil induced diarrhoea
The method described by Awouters et al. (1978) was followed.
Healthy albino r ats of either sex (200 - 250 g) were randomly
selected and divided into five groups of five animals each. They
were f asted for 18 h prior to the test, with free access to water.
Group 1 received 20 ml/kg of normal saline (negative control), while
those in group 2 receive loperamide (3 mg/kg) as positive control.
Animals in group 3, 4 and 5 received Verbena hastata extract (100 -
400 mg/kg) respectively. Extract administration was by the oral
route. The animals were housed singly in cages lined with
transparent paper. One hour after pre-treatment with the extract,
the animals were then administered with 1ml of castor oil orally.
Thereafter, they were observed for 4 h for the presence of
diarrhoea. Diarrhoea for the purpose of this study was taken to
mean watery (wet), unformed stool
Gastrointestinal motility test (Charcoal meal)
Albino rats of either s ex (200 - 250 g) were r andomly divided into 5
groups of 5 rats each. They were fasted f or 24 h prior to the test,
but were allowed free access to water. Group 1 rats were treated
with 20 ml/kg normal saline and served as control, while groups 2, 3
and 4 received different doses of the extract (100,200 and 400
mg/kg, p.o). Group 5 rats received atropine sulphate (5 mg/kg, p.o).
Thirty minutes after drug administration, 1 ml of charcoal meal (5%
deactivated charcoal in 10% aqueous tragacanth) was administered
orally to all animals in the study and 30 min later, all the rats were
sacrificed and the abdomen opened. The small intestine was
dissected out from the pylorus to the caecum and the total distance
traveled by the charcoal plug along the small intestine was
Akuodor et al. 1625
estimated for both the control and the treated groups. The percen-
tage distance traveled by the charcoal meal from the pylorus to the
caecum was noted.
Castor oil-induced enteropooling
In this method, rats were fasted for 18 h prior to the experiment.
The rats were divided into five groups of five each. Normal saline
(10 ml/kg p.o) was given to the first group. The second group
received 1 ml of castor oil, while the last three groups received
graded doses of Verbena hastata extract (100 - 400 mg/kg
p.o).Thirty minutes later, all the rats were treated with 1 ml of castor
oil. After thirty minutes, each rat was sacrificed and the whole
length of the intestine from the pylorus to the caecum was
dissected and the c ontents measured. Percentage reduction of the
intestinal secretion (volume) was calculated
Phytochemical test
The ethanol leaf extract of V .hastata was subjected to quantitative
phytochemical investigation acc ording to standard methods (Trease
and Evans, 1989).
Statistical analysis
Results were expressed as mean ± S.E.M. The significance of
difference between mean was determined using one way analysis
of variance
RESULTS
Phytochemical screening
Phytochemical analysis of the ethanolic extract gave a
positive reaction for each of the following secondary
metabolites: Saponins, Terpenes, Sterols, flavonoids and
Carbohydrates.
Acute toxicity studies
There was no mortality observed in the mice upon oral
administration, even at doses as high as 5000 mg/kg
signifying that the LD50 was greater than 5000 mg/kg.
Apart from sedation and mild weakness, V. hastata did
not produce any major clinical signs of toxicity in mice
during 4 day observation per
Effect of extract on castor oil induced diarrhoea
The ethanol leaf extract of V. hastata exhibited marked
dose dependent anti diarrhoea activity in the study. The
extract significantly inhibited both the frequency of
defaecation as well as the wetness of the faecal dropping
in rats. Four hundred milligrams per kilogram of the
extract produced 100% inhibition of castor oil induced
diarrhoea in rats and this result is similar to the effect of
standard anti diarrhoea drug, loperamide 3 mg/kg (Table
1)
1626 J. Med. Plant. Res.
Table 1. Anti -diarrhoeal effect of the extract of V. hastata (100 - 400 mg/kg p.o) on castor oil- induced diarrhoea in rats.
Group Dose (mg/kg ) Number of wet defaecation ± (SEM) % maximal inhibition of diarrhea
Control Normal saline 5.6 ± 0.25 0
Loperamide 3 0.0 100*
V. hastata 100 3.6 ± 0.24 35.71*
V. hastata 200 2.75 ± 0.43 50.89*
V. hastata 400 0.0 100*
Values are mean ± S E M, n = 5. *significant as compared to normal control P < 0.05.
Table 2. Effect of V. hastata (100 - 400 mg/kg p.o) on intestinal motility in rats
(charcoal meal study).
Group Dose (mg/kg) Mean distance traveled (%)
Control Normal saline 62.4 ± 6.25
V. hastata 100 48.4 ± 4.73*
V. hastate 200 40.8 ± 3.71*
V. hastate 400 31. 2 ± 2.70*
Atropine 5 45. 2±3.19*
Values are mean ± S E M, n = 5. *Significant as compared to normal control P < 0.05.
Table 3. Effect of V. hastata extract (100 - 400 mg/kg, p.o) on castor oil- induced
enteropooling in rats.
Group Dose Volume of intestinal content (ml).
Control Normal saline 0.72±0.20
Castor oil 1 ml 3.84±0.25
V. hastate 100 mg/kg 2.32±0.19*
V. hastate 200 mg/kg 2.2±0.14*
V. hastate 400 mg/kg 1.42±0.13*
Values are mean ±SEM, n = 5. *significant as compared to normal control P < 0.05.
Effects on intestinal transit time
The effects of extract on gastrointestinal motility revealed
that the ethanolic leaf extract of V. hastate caused a
significant decreased in gut motility in a dose dependent
manner. This observation was significantly different from
what was seen in the control group. Two hundred and
four hundred milligram per kilogram body weight of the
extract exerted greater anti-motility effects than 5 mg/k g
of atropine sulphate (Table 2).
Effect on castor oil induced enteropooling
V. hastate was found to possess an anti-enteropooling
activity. Oral administration of castor oil produced a
significant increase in the intestinal fluid when compared
to control rats that received normal saline. V. hastata
extract exerted a significant inhibitory effect against
castor oil-induced activity in a dose dependent manner
(Table 3).
DISCUSSION
In this study, preliminary phytochemical screening and
evaluation of anti-diarrhoea activity of ethanolic leaf
extract of V. hastate were carried out. Flavonoids, sapo-
nins, sterols and terpenes, which have been reported for
their antidiarroeal activity (Galvez et al., 1991; Longanga
et al., 2000), are also found in the extract studied.
The inhibition of experimental diarrhoea and the reduc-
tion in fecal output by a substance are the basis of the
pharmacological evaluation of a potential anti-diarrhoeal
agent.Castor oil causes diarrhoea due to its active
metabolite, recinolic acid (Ammon et al., 1974; Watson
and Gordon, 1962), which stimulates peristaltic activity in
the small intestine leading to changes in the electrolyte
permeability of the intestinal mucosa. The precise
mechanism of action of castor oil is through elevated
prostaglandin biosynthesis (Bruton, 1985; Galvez et al.,
1993). Prostaglandin contributes to the pathophysio-
logical functions in gastrointestinal tract (Sanders, 1984).
Inhibitors of prostaglandin biosynthesis delay castor oil
induced diarrhoea (Awouter et al., 1978). It has been
shown that E type of prostaglandins cause diarrhoea in
experimental animals as well as in human beings. The
mechanism has been associated with dual effects on
gastrointestinal motility as well as water and electrolyte
transport (Beubler and Juan, 1979). The maximal effect
produced by the extract was similar to that produced by
loperamide, which is at present one of the most
efficacious and widely employed antidiarrhoea drugs;
loperamide effectively antagonized diarrhoea induced by
castor oil (Niemegeers et al., 1974). Loperamide, apart
from regulating the gastrointestinal tract, is also reported
to slow down transit in the intestine, reduce colon flow
rate, and consequently any effect on colonic motility
(Theoderau et al., 1991). The therapeutic effect of
lopermide is believed to be due to its antimotility and
antisecretory properties (Couper, 1987).
Atropine and different doses of the extract significantly
decreased intestinal transit time. This is possible due to
its anticholinergic effect (Brown and Taylor, 1996),
atropine being less potent than the leaf extract at 200 and
400mg/kg body weight. The significant inhibition of the
castor oil- induced enteropooling in rats suggests that the
extract produced relief in diarrhoea by spasmolytic in vivo
and anti-enteropooling effects. It is also possible that
flavonoids present in the ethanolic leaf extract may be
responsible for the antidiarrhoeal activity .Flavonoids has
been ascribed to their ability to inhibit intestinal motility
and hydro-electrolytic secretion (DiCarlo et al., 1993). In
addition, flavonoids possess antioxidant properties, which
are presumed to be responsible for the inhibitory effects
exerted upon several enzymes including those involved
in the arachidonic acid metabolism.
The present study has shown that Verbena hastata
contains pharmacologically active substance(s) with
antidiarrhoea properties. Further study is to be carried out
to fractionate and purify the extract to fully investigate the
mechanisms responsible for the antidiarrhoeal activity
observed.
ACKNOWLEDGEMENTS
The authors are grateful to Mr. Sunday Dzama for his
technical assistance and Miss Ngozi Anyalewechi for her
secretarial assistance.
Akuodor et al. 1627
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