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Laxative activities of Mareya micrantha (Benth.) Müll. Arg. (Euphorbiaceae) leaf aqueous extract in rats
- Souleymane Méité1,
- Calixte Bahi1,
- Dodéhé Yéo1,
- Jacques Y Datté†2,
- Joseph A Djaman1 and
- David J N'guessan†1Email author
© Méité et al; licensee BioMed Central Ltd. 2010
Received: 6 October 2009
Accepted: 16 February 2010
Published: 16 February 2010
Mareya micrantha (Benth.) Müll. Arg. (Euphorbiaceae) is a shrub that is commonly used in Côte d'Ivoire (West Africa) for the treatment of constipation and as an ocytocic drug. The present study was carried out to investigate the laxative activity of Mareya micrantha in albino's Wistar rats.
Rats were divided in 5 groups of 5 animals each, first group as control, second group served as standard (sodium picosulfate) while group 3, 4 and 5 were treated with leaf aqueous extract of Mareya micrantha at doses of 100, 200 and 400 mg/kg body weight (b.w.), per os respectively. The laxative activity was determined based on the weight of the faeces matter. The effects of the leaves aqueous extract of Mareya micrantha and castor oil were also evaluated on intestinal transit, intestinal fluid accumulation and ions secretion.
Phytochemicals screening of the extract revealed the presence of flavonoids, alkaloids, tannins, polyphenols, sterols and polyterpenes. The aqueous extract of Mareya micrantha applied orally (100, 200 and 400 mg/kg; p.o.), produced significant laxative activity and reduced loperamide induced constipation in dose dependant manner. The effect of the extract at 200 and 400 mg/kg (p.o.) was similar to that of reference drug sodium picosulfate (5 mg/kg, p.o). The same doses of the extract (200 and 400 mg/kg, p.o.) produced a significant increase (p < 0.01) of intestinal transit in comparison with castor oil (2 mL) (p < 0.01). Moreover, the extract induced a significant enteropooling and excretion of Cl-, Na+, K+ and Ca2+ in the intestinal fluid (p < 0.01).
The results showed that the aqueous extract of Mareya micrantha has a significant laxative activity and supports its traditional use in herbal medicine.
Constipation is a highly prevalent, often chronic gastrointestinal disorder that affects adults [1–3]. The treatment with classic drugs did not cut, in one hand with the inadequate relief of bloating and other symptoms, and with the lack of efficacy in relieving constipation. So far, half of patients were not satisfied with the effect of laxatives on improving quality of life [4, 5].
Plants have long been a very important source of drugs against several diseases including constipation. Mareya micrantha is well known in the traditional medical practice of the south of Côte d'Ivoire (West Africa) where the leaves of this plant is extracted with water and the extract is taken orally for the treatment of constipation . It is commonly called "oyia" in the local language of "Attié" . Mareya micrantha (Benth.), Syn. Mareya spicata (Baill), Müll. Arg. (Euphorbiaceae) is a shrub that is found in west and central Africa. The plant flourishes in tropical climate and it is commonly used in different parts of west and central Africa to treat diseases which require drastic action, such as tapeworm infections, gonorrhea and leprosy .
Previous studies showed that the aqueous leaf extracts of M. micrantha suppressed cardiac contractility of isolated frog and rat hearts in a concentration dependent way [8, 9]. In another test, an aqueous leaf extract elicited concentration-dependent contractions of the longitudinal muscle of isolated guinea-pig ileum . Leaf extracts caused hypotension in dogs, and a root extract caused paralysis of the respiratory centre in rats. The methanol and cold aqueous extracts of the leaves showed antibacterial activity against Enterobacter aerogenes, Agrobacterium tumefaciens, Bacillus subtilis, Clostridium sporogenes, Escherichia coli and Staphylococcus aureus . Ethanolic leaf extracts showed low antiplasmodial activity against a chloroquine-resistant strain of Plasmodium falciparum .
Although quite a number of scientific investigations have been undertaken to validate the local use of this plant, there seems to be no report on the laxative activity of the leaves of the plant. The present study was planned to examine the laxative activity of the aqueous extract of Mareya micrantha leaves.
The Mareya micrantha leaves, used for the study were collected from Mareya micrantha plants located at Akoupé (south of Côte d'Ivoire, West Africa) in June 2007. The plant was identified and authenticated by Pr AKE ASSI at the Department of Botany, University of Cocody. After identification, a voucher specimen (N°18041) was deposited at the herbarium of "Centre National de Floristique" of the University of Cocody-Abidjan.
The harvested leaves were air-dried and then reduced to powder with mortar and pestles. 80 g of the powder was extracted at a temperature of 90°C (by the process of maceration) with 2 L of distilled water. The macerated mixture was filtered and the filtrate was evaporated in a carefully regulated water bath (maintained at temperature of 90°C) to yield 4.5 g of dark solid extract. The extract was stored at a temperature of - 4°C pending the time for biological investigations.
Albinos Wistar rats weighing 150-200 g were housed and bred in the animal house of UFR-Biosciences at Cocody University in Abidjan (Côte d'Ivoire). The animals were kept in standard cages with good ventilation, free access to feeds and water.
Experimental procedures and protocols used in this study were approved by ethical committee of Health Sciences, University of Cocody-Abidjan. These guidelines were in accordance with the internationally accepted principles for laboratory use and care.
The aqueous extract of Mareya micrantha was screened for phytochemical constituents using standard procedures of analysis .
Gastrointestinal motility tests
The method of Mascolo et al.  was used. Rats were divided into different groups of five rats each and fasted for 18 hours before the experiment. Three of the groups were then treated orally with three increasing doses (100, 200 and 400 mg/kg) of the extracts serving as the test groups. One group served as blank or negative control treated with saline (5 mL/kg, p.o.) and the last group was administered castor oil (2 mL/rat, p.o.), a laxative agent, as the positive control. After 30 min, the animals were given 1 mL of freshly prepared charcoal meal (distilled water suspension containing 10% gum acacia, 10% vegetable charcoal). Following 30 min of charcoal administration, the rats were sacrificed by cervical dislocation and the abdomen immediately cut open, to excise the whole small intestine (pylorus region to caecum). The length of the small intestine and the distance between the pylorus region and the front of the charcoal meal was measured for obtaining the charcoal transport ration or percentage.
Water and electrolyte secretion
The method of Robert et al.  was used. Animals of the first group received saline solution (5 mL/kg, p.o). Groups 2, 3, 4 and 5 received respectively castor oil (2 mL/rat, p.o) and increasing doses of the aqueous extract of Mareya micrantha (100, 200 and 400 mg/kg, p.o). Two hours later, the rats were sacrificed and the small intestine from the pylorus to caecum was extracted. The intestinal contents were collected by milking into a graduated tube and their volume was measured . The fluid samples were analyzed for Na+, K+, Cl- and Ca2+ contrentrations using flame photometer (Elico® CL361).
The method of Capasso et al.  was followed for this activity. Rats fasted for 12 h before the experiment were placed individually in cages lined with clean filter paper. Rats were divided in five groups with the first group acting as the control and administered saline (5 mL/kg, p.o.) that acted as the negative control. The second group received sodium picosulfate (5 mg/kg, p.o), this served as the positive control. The third, fourth and fifth groups received 100, 200 and 400 mg/kg per os of the Mareya micrantha aqueous extract. The faeces production (total number of normal as well as wet faeces) in all five groups was monitored for 16 h.
Laxative activity on loperamide induced constipation
This study was carried out, as earlier described by Takahura et al. . Rats were placed individually in cages lined with clean filter paper, allowed to fast for 18 hours and divided into five groups of five animals each. The aqueous extract of Mareya micrantha (100, 200, and 400 mg/kg, p.o.) was administered per os to the first three groups of rats. One of the two remaining other group received normal saline (5 mL/kg, p.o) and served as a control. The last group received per os the standard drug sodium picosulfate (5 mg/kg). After 1 h, all the animals received Loperamide (5 mg/kg, p.o.) by gavage. The faeces production (total number of normal as well as wet faeces) in all five groups was monitored for 8 h.
Data obtained are presented as means ± standard error of mean (S.E.M.) for the number of animals in each group (n = 5). The differences between the data obtained from 'test' animal groups and the data obtained from untreated animal groups, were subjected to one-way analysis of variance (ANOVA; 95% confidence interval), followed by Dunnett's test. Values with p < 0.05 compared with the control group were considered as being significantly different.
The phytochemical screening with the different tests described (see material and methods) revealed the presence of alkaloids, tannins, flavonoids, polyphenols, sterols and polyterpenes.
2-Effect of the aqueous extract of M. micrantha on gastrointestinal motility
Effects of M. micrantha aqueous extract (MAR) on gastrointestinal motility in rats
Percentage of distance (%)
68,78 ± 4,64
93.71 ± 2.74***
70.54 ± 5.48
87.77 ± 1.84**
91.41 ± 2.11**
3-Effect on intestinal water secretion
Effects of M. micrantha aqueous extract (MAR) on intestinal water secretion in rats
Volume of intestinal fluid(mL)
0.74 ± 0.15
3.06 ± 0.25**
1.54 ± 0.12
1.8 ± 0.70
2.92 ± 0.58**
4-Effect on intestinal ion secretion
Effects of M. micrantha aqueous extract on intestinal ion secretion in rats
2.160 ± 0.27
0.196 ± 0.01
13.96 ± 1.69
0.478 ± 0.07
3.99 ± 0.66*
0.380 ± 0.5*
29.81 ± 2.03***
0.782 ± 0.04**
2.288 ± 0.21
0.168 ± 0.02
15.68 ± 0.70
0.650 ± 0.06
2.566 ± 0.25
0.254 ± 0.03
19.86 ± 2.31
0.690 ± 0.02*
3.756 ± 0.50*
0.356 ± 0.06*
23.89 ± 2***
0.748 ± 0.04**
5-Laxative activity of aqueous extract of M. micrantha
Laxative activity of aqueous extract of M. micrantha (MAR) in rats
Faeces out put (g)
8 h-16 h
0.748 ± 0.42
1.608 ± 0.65
5.090 ± 1.11**
5.415 ± 0.61**
0.892 ± 0.17
1.190 ± 0.28
3.703 ± 0.77*
4.733 ± 0.1.10*
4.829 ± 0.92**
5.217 ± 0.59**
6-Effect of the aqueous extract of M. micrantha on loperamide induced constipation in rats
Effect of M. micrantha aqueous extract (MAR) on loperamide induced constipation in rat
Weight of faeces (g)
0.938 ± 0.45
3.84 ± 0.62**
2.602 ± 0.33
2.806 ± 0.42*
3.507 ± 0.45**
The laxative activity of Mareya micrantha was studied in rats. The results showed that an oral administration of the leaves aqueous extract of M. micrantha produced significant and dose dependant increase in faeces output of rats in regards to the accumulation of water in intestinal loop and the stimulation of gastrointestinal motility. These effects were similar with that of castor oil (standard drug) at high dose of 400 mg/kg. Castor oil affects electrolyte transport and smooth muscle contractility in the intestine . Its cathartic action is due to water accumulation in the intestine . Castor oil causes diarrhea due to its active metabolite ricinoleic acid  which stimulates peristaltic activity in the small intestine, leading to changes in the electrolyte permeability of the intestinal mucosa. Its action also stimulates the release of endogenous prostaglandin . The observed activities therefore suggest that laxative activity of the aqueous extract of M. micrantha may be mediated through this mechanism of action of ricinoleic acid.
In the other hand, our results have indicated that M. micrantha and sodium picosulfate exert respectively opposite effects with loperamide on the gastrointestinal function. It is well documented that loperamide abolishes experimental osmotic diarrhea by acting on intestinal motility, and consequently reducing the flow entering the colon [22, 23]. Sodium picosulfate is a member of the polyphenolic group of stimulant laxatives. Following oral administration, it is converted in the colon to an active form through the action of bacterial enzymes . As a result, its effects are directed principally in the colon, where it stimulates peristalsis and, in common with other laxatives, reduces water reabsorption leading to the softening of stools. These results suggest that the aqueous extract of M. micrantha contains secondary metabolites which could act by this way.
This study has also shown that M. micrantha had stimulated Na+, K+ and Cl- secretion. Most of the naturally laxative exert their effects on the colonic epithelium by stimulating Cl- secretion and/or inhibiting Na+ absorption, resulting in an accumulation of fluid and subsequent increased colonic motility .
The results showed that the aqueous extract of M. micrantha increased the propulsion of charcoal meal. This result is in concordance with the findings of Traoré et al. who have shown that the leaves aqueous extract of M. micrantha caused stimulant effects on the spontaneous motility of isolated rabbit ileum. In the other hand, Tsaï et al.  have put in evidence the presence of cholinergic active ingredients in the aqueous extract of M. micrantha using the longitudinal muscle of isolated guinea-pig ileum. The propulsion of charcoal meal is probably due to the increasing of peristaltic movement in rat gastrointestinal tract resulting from the stimulation of cholinergic receptors by M. micrantha.
The intestinal transit is controlled by both neural and myogenic mechanisms . An increase of the contractile activity of the smooth layers in general is responsible for acceleration of intestinal propulsion. Several mediators and neurotransmitters govern these motor patterns. Acethylcholine is the main excitatory neurotransmitter in the enteric nervous system . Thus the presence of cholinomimetic constituents in the plant extract can explain the usefulness of M. micrantha in constipation pointed out by the ethnobotanical informations .
The Presence of phytoconstituents like terpenoids, sterols, flavonoids, phenolic compounds, tannins and alkaloids  have been previously found to be responsible for laxative activities in plants. Phytochemical screening of the extract of M. micrantha revealed the presence of alkaloids, tannins, flavonoids, polyphenols, sterols and polyterpenes. These constituents may be responsible for the laxative activity of M. micrantha.
This study has shown that M. micrantha has laxative effects in addition to the various physiological effects earlier reported by other authors. The results of this study justify the use of the leaves of M. micrantha as laxative in traditional medicine. Further studies may be directed at characterizing the bioactive ingredients that are responsible for the observed activity in the plant.
The authors are indebted to Professor Aké-Assi Laurent (Laboratory of Botany, Unité de Formation et de Recherche -Biosciences, University of Cocody-Abidjan, Côte d'Ivoire) for botanical identification of Mareya micrantha (Benth.) Müll. Arg. (Euphorbiaceae).
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