Albert Kamanyi

Acute and subchronic oral toxicity assessment of the aqueous extract from the stem bark of Erythrina senegalensis DC (Fabaceae) in rodents

AIM OF THE STUDY The decoction of the stem bark of Erythrina senegalensis (EAES) is traditionally used in the Western region of Cameroon against liver disorders. The present study evaluated the potential toxicity of this decoction after acute and sub-chronic administration in rodents. MATERIALS AND METHODS In acute study, a single administration of EAES was given orally to mice at doses ranging from 1.25 to 12.5 g/kg. General behaviour, adverse effects and mortality were determined for up to 14 days post treatment. In the sub-chronic study, EAES was given orally as a single administration to Wistar rats at doses of 300, 600 and 1,200 mg/kg/day for 28 days. Animal body weight was observed throughout the experimental period while haematological and biochemical parameters of blood and urine, as well as kidney and liver tissues histology were evaluated at the end of the experiment. RESULTS In the acute study in mice, none of the doses used induced mortality or significant behavioural changes. In the sub-chronic study in rats, daily oral administration of EAES at the dose of 600 mg/kg resulted in a significant increase in the relative body weight at the last week of treatment. The relative weights of organs were not affected by the treatment. No haematological changes were observed a part of a significant increase in WBC count at the dose of 600 mg/kg. Serum AST, ALT, ALP, total protein, total cholesterol and triglycerides decreased significantly while total and conjugated bilirubin significantly increased. Renal function indices assay in blood showed significant modification in all the treated groups compared to control while, in urine, only urea excretion markedly reduced at a dose of 1,200 mg/kg. Histological analysis did no show any liver or kidney alteration. CONCLUSION These results demonstrated that there is a wide margin of safety for the therapeutic use of EAES and further corroborated the traditional use of this extract as a hepatoprotective agent.

Analgesic and Anti-Inflammatory Properties of Extracts from the Bulbils of Dioscorea bulbifera L. var sativa (Dioscoreaceae) in Mice and Rats

The aqueous and methanol extracts from the dry bulbils of Dioscorea bulbifera L. var sativa (Dioscoreaceae)—evaluated orally at the doses of 300 and 600 mg/kg against pain induced by acetic acid, formalin, pressure and against inflammation induced by carrageenan, histamine, serotonin and formalin in mice and rats, showed a dose dependant inhibition of pain and inflammation with a maximum effect of 56.38%, 73.06% and 42.79% produced by the aqueous extract, respectively on pain induced by acetic acid, formalin and pressure while the methanol extract at the same dose respectively inhibited these models of pain by 62.70%, 84.54% and 47.70%. The oral administration of aqueous and methanol extracts caused significant anti-inflammatory activity on paw oedema induced by histamine, serotonin and formalin. The present results show that the bulbils of Dioscorea bulbifera var sativa possess potent analgesic and anti-inflammatory activities. These activities may results from the inhibition of inflammatory mediators such as histamine, serotonin and prostaglandins. Thus, the analgesic activity of the bulbils of Dioscorea bulbifera may be at least partially linked to its anti-inflammatory activity.

Anti-inflammatory and analgesic properties of the stem bark extracts of Erythrophleum suaveolens (Caesalpiniaceae), Guillemin & Perrottet.

The MeOH stem bark extract of Erythrophleum suaveolens dissolved in water and shaken up with ethylacetate (EtOAc) and fractionated on a polyamide column with methanol as eluent produced five principal fractions. These fractions were designated as fraction A (74.8 mg yield and rich in alkaloids), fraction B (36.6 mg), fraction C (7.8 mg yield, monomeric procyanidin), fraction D (26.6 mg yield, rich in monomeric and oligomeric procyanidin), and fraction E (18.1 mg yield, rich in polymeric procyanidin). The original MeOH extract administered (100 mg/kg po) produced about 47% inhibition of carrageenin-induced paw oedema 1 h after administration. Fraction D, obtained from the ethylacetate extract and rich in procyanidins produced over 33% inhibition of carrageenan-induced paw oedema while a dose of 19.2 microg/ml produced 100% inhibitory effect on 5-lipoxygenase. A dose of 100 mg/kg of the MeOH extract also produced over 30% reduction of the sensitivity to pain while 50 mg/kg of fraction D rich in procyanidins produced over 45% analgesic effects. These results were judged significant compared to those obtained with indomethacin and acetylsalicylic acid. These findings suggest that extracts of the bark of Erythrophleum suaveolens possess potent anti-inflammatory and analgesic property and that the procyanidins lead to the observable pharmacological effects.

Anti-ulcerogenic properties of the aqueous and methanol extracts from the leaves of Solanum torvum Swartz (Solanaceae) in rats.

ETHNOPHARMACOLOGICAL RELEVANCE Solanum torvum (Solanaceae) is a plant currently used in Cameroon ethnomedicine for the treatment of stomach ailments. AIM OF THE STUDY The present study was undertaken to determine the anti-ulcer potential of the aqueous and methanol extracts from the leaves of Solanum torvum. MATERIALS AND METHODS The aqueous and methanol extracts from the leaves of Solanum torvum were tested orally at the doses of 250, 500 and 750 mg/kg, on gastric ulcerations experimentally induced by HCl/ethanol, indomethacin, pylorus ligation and stress. The fractionation of the methanol extract through silica gel column chromatography produced seven different fractions (A-G) which were tested orally at the dose of 100mg/kg against HCl/ethanol-induced ulceration. RESULTS The methanol extract at the dose of 750 mg/kg produced 98.12, 99.16, 98.70 and 96.03% inhibition when gastric ulcerations were induced by HCl/ethanol, indomethacin, pylorus ligation and stress, respectively. The aqueous extract at the same dose produced 96.55, 96.86, 98.63 and 98.63% inhibition on ulcerations induced respectively by HCl/ethanol, indomethacin, pylorus ligation and stress. All the fractions of the methanol extract significantly inhibited ulcer formation. Fraction F which contains flavonoids and triterpens was the most active and exhibited an inhibitory percentage of 84.74. Both extracts significantly increased mucus production and reduced gastric acid secretion. CONCLUSIONS The aqueous and methanol extracts of the leaves of Solanum turvum possess anti-ulcerogenic properties that may be due to cytoprotective mechanism. These results support the ethnomedical uses of the plant in the treatment of gastric ulcer.

Anti-inflammatory and Analgesic Effects of Drypemolundein A, a Sesquiterpene Lactone from Drypetes molunduana

Previous pharmacological screening in our laboratory showed analgesic and anti-inflammatory effects of a crude stem bark extract of Drypetes molunduana. Phytochemical studies of this plant led to the isolation an structural elucidation of seven pentacylic triterpenes and one lignan, which were already known compounds, and a new furanosesquiterpene lactone, Drypemolundein A. The purpose of this study was to examine the anti-inflammatory and analgesic activities of drypemolundein A. The compound was studied against carrageenan-induced acute edema. At doses of 10 and 20 mg/kg, orally administered, it significantly reduced (57.57 and 66.66% inhibition at 1 h intervals, respectively) paw edema. At the same doses, this sesquiterpene lactone also exhibited significant analgesic action in force-induced pain in rat paw. These results indicate that drypemolundein A functions as an effective anti-inflammatory and analgesic agent.

Anti-inflammatory and analgesic properties of the stem bark extract of Mitragyna ciliata (Rubiaceae) Aubrév. & Pellegr.

Mitragyna ciliata is widely used in traditional medicine for the treatment of inflammation, hypertension, headache, rheumatism, gonorrhoea and broncho-pulmonary diseases. In the present study, the anti-inflammatory and analgesic properties of the stem bark extract of M. ciliata were investigated. The stem bark of this plant was extracted over Soxhlet with hexane followed by another extraction with methanol. The resulting methanol extract was used for the pharmacological test. Anti-inflammatory activity was evaluated on the basis of the inhibitory effect of the extract on 5-lipoxygenase, and carrageenin-induced hind paw oedema in the rat. The methanol extract, at a dose of 19.2 microg/ml, exhibited no inhibition on 5-lipoxygenase. However, this extract administered per os (50 mg/kg) produced about 70% inhibition of carrageenin-induced paw oedema 1 h after administration. This inhibition was maintained to about 50% 2 h after administration. The dose of 50 mg/kg of MeOH extract significantly decreased sensitivity to pain from 78.75 to 107.5 g These findings suggest that extracts of the bark of M. ciliata, possess potent anti-inflammatory and analgesic effects. Chemical analysis of the extract showed the presence of alkaloids and kaempferol derivative which may be responsible for the anti-inflammatory properties.

Hypertensive effects of oral administration of the aqueous extract of Solanum torvum fruits in L-NAME treated rats: evidence from in vivo and in vitro studies.

ETHNOPHARMACOLOGICAL RELEVANCE Solanum torvum fruits are commonly used in Cameroonian traditional medicine for treatment of arterial hypertension. It has been previously shown that intravenous administration of aqueous extract from dried fruits (AEST) reduced blood pressure. AIM The present work evaluates acute toxicity and effects of oral administration of AEST in chronic arterial hypertension induced by L-NAME. Effects of AEST were also evaluated on isolated aorta. MATERIALS AND METHODS AEST (200 mg/kg/day, p.o.) was given solely or concomitantly with L-NAME (40 mg/kg/day, p.o.) for 30 consecutive days. Animal body weight, systolic blood pressure and heart rate were measured before stating the treatment and at the end of each week. Urinary volume and urinary sodium and potassium contents were quantified before and at days 1, 15 and 30 of the treatment. Aorta from treated animals was tested for their sensitivity to noradrenaline and carbachol. Aorta from normal untreated rats was used to evaluate the in vitro vascular effect of AEST. RESULTS The results showed that AEST did induce neither mortality nor visible signs of toxicity. When given solely or in co-administration with L-NAME, AEST significantly reduced animals body weight. It amplified the hypertensive and cardiac hypertrophy effect of L-NAME and did not affect these parameters in normotensive animals. AEST increased the sensitivity to noradrenaline in normotensive and significantly reduced it in hypertensive animals. AEST significantly increased urinary volume and sodium excretion in L-NAME treated animals while reducing the sodium excretion in normotensive. In vitro, AEST induced a potent partial endothelium-dependent contraction of aortic ring; contractions that were partially antagonized by prazosin and verapamil and were not relaxed by carbachol. CONCLUSION These results suggest that oral chronic administration of AEST induced potentiation of arterial hypertension and cardiac hypertrophy in L-NAME treated rats. These effects may result from a reduction in sensitivity to vasorelaxant agents and increase in hypersensitivity to contractile factors. AEST possess potent in vitro vasocontractile activity that may result from activation of both alpha(1)-adrenergic pathway and calcium influx.

A dimeric triterpenoid glycoside and flavonoid glycosides with free radical-scavenging activity isolated from Rubus rigidus var. camerunensis.

The aerial part of Rubus rigidus var. camerunensis (Rosaceae) is used to treat respiratory and cardiovascular disorders in the Cameroonian traditional medicine. The ethanol extract exhibited more potent antioxidant activity (Emaxs of 119% and 229% activity on DPPH and β-carotene test) than aqueous extract. Bioactivity-guided fractionation of the ethanol extract based on free radical-scavenging assay (DPPH assay) afforded five flavonoid glycosides (four flavonol glycosides and an anthocyanin) and three glucosides of 19α-hydroxyursane-type triterpenoid (two monomeric and one dimeric triterpenoids). The flavonoids were identified as kaempferol 3-O-(2″-O-E-p-coumaroyl)-β-D-glucopyranoside (1), kaempferol-3-O-β-D-glucopyranoside (astragalin, 2), kaempferol-3-O-α-L-arabinofuranoside (juglanin, 3), quercetin-3-O-β-D-glucopyranoside (isoquercitrin, 4), pelargonidin-3-O-β-D-glucopyranoside (callistephin, 5). The three triterpenoids were 2α, 3β, 19α, 23-tetrahydroxyurs-12-ene-28-O-β-D-glucopyranosyl ester (nigaichigoside F1, 6), 2α, 3β, 19α-trihydroxyurs-12-ene-23-carboxyl-28-O-β-D-glucopyranosyl ester (suavissimoside R1, 7) as monomeric triterpenoids and coreanoside F1 (8) as a dimeric triterpenoid. The flavonoids exhibited potent antioxidant activities (66 to 93.56% against DPPH radical) and they were also active on β-carotene test. Coreanoside F1 exhibited a 63% antioxidant activity, meanwhile the other two triterpenoids showed a weak activity. Three important facts on structure-activity relationship were observed: Compound 8, a dimeric triterpenoid glycoside, strongly enhanced antioxidant activity of its monomers, compound 3 with 3-O-α-L-arabinofuranyl has much more potent activity than compound 2 with 3-O-β-D-glucopyranosyl, and antocyanin (5) is more potent than its corresponding flavonol glycosides.

Effects of leaf aqueous extract of Bidens pilosa (Asteraceae) on KCl- and norepinephrine-induced contractions of rat aorta

The effect of leaf aqueous extract of Bidens pilosa Linn. on KCl- and norepinephrine-induced contractions of rat aortic strips was studied. In aortic strips with endothelium intact, contractions induced using 60 mM KCl and 10(-5) M norepinephrine were dose-dependently relaxed by the extract, a more significant effect being seen with norepinephrine-induced contractions. Following mechanical damage to the aortic endothelium, inhibition of contractions was more prominent (105%) with the norepinephrine-induced contractions compared with KCl-induced contractions (15%) when the maximal dose (8 mg/ml) of the extract was used. The results suggest that the relaxation effect of the extract may be due to the blockade of the influx of extracellular Ca2+ into the cell.

Acute and chronic antihypertensive effects of Cinnamomum zeylanicum stem bark methanol extract in L-NAME-induced hypertensive rats

BackgroundPrevious study showed that the aqueous extract of the stem bark of Cinnamomum zeylanicum possesses antihypertensive and vasodilatory properties. The present work investigates the acute and chronic antihypertensive effects of the methanol extract of Cinnamomum zeylanicum stem bark (MECZ) in L-NAME-induced hypertensive rats.MethodsThe acute antihypertensive effects of MECZ (5, 10 and 20 mg/kg) administered intravenously were evaluated in rats in which acute arterial hypertension has been induced by intravenous administration of L-NAME (20 mg/kg). For chronic antihypertensive effects, animals were treated with L-NAME (40 mg/kg/day) plus the vehicle or L-NAME (40 mg/kg/day) in combination with captopril (20 mg/kg/day) or MECZ (300 mg/kg/day) and compared with control group receiving only distilled water. All drugs were administered per os and at the end of the experiment that lasted for four consecutive weeks, blood pressure was measured by invasive method and blood samples were collected for the determination of the lipid profile. The heart and aorta were collected, weighed and used for both histological analysis and determination of NO tissue content.ResultsAcute intravenous administration of C. zeylanicum extract (5, 10 and 20 mg/kg) to L-NAME-induced hypertensive rats provoked a long-lasting decrease in blood pressure. Mean arterial blood pressure decreased by 12.5%, 26.6% and 30.6% at the doses of 5, 10 and 20 mg/kg, respectively. In chronic administration, MECZ and captopril significantly prevented the increase in blood pressure and organs’ weights, as well as tissue histological damages and were able to reverse the depletion in NO tissue’s concentration. The MECZ also significantly lower the plasma level of triglycerides (38.1%), total cholesterol (32.1%) and LDL-cholesterol (75.3%) while increasing that of HDL-cholesterol (58.4%) with a significant low atherogenic index (1.4 versus 5.3 for L-NAME group).ConclusionMECZ possesses antihypertensive and organ protective effects that may result from its ability to increase the production of the endogenous NO and/or to regulate dyslipidemia.