Alain Bertrand Dongmo

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-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.

Anti-hypertensive effects of the methanol/methylene chloride stem bark extract of Mammea africana in L-NAME-induced hypertensive rats

AIM OF THE STUDY The methanol/methylene chloride (CH(3)OH/CH(2)Cl(2)) extract from the stem bark of Mammea africana was showed to possess vasodilating effect in the presence and the absence of N(omega)-nitro-l-arginine methyl ester (l-NAME). The present study was designed to evaluate the effects of the methanol/methylene chloride from the stem bark of Mammea africana. MATERIALS AND METHODS The extract (200 mg/(kg day)) was administered orally in rats treated concurrently with l-NAME (40 mg/(kg day)). l-Arginine (100 mg/(kg day)) and captopril (20 mg/(kg day))were used as positive controls. Bodyweight, systolic arterial blood pressure and heart rate were measured weekly throughout the experiment period (28 days). At the end of treatment, animals were killed and the cardiac mass index evaluated. The aorta was used to evaluate the endothelium-dependant relaxation to carbachol. The aorta contraction induced by noradrenalin was also examined and expressed as a percentage of that induced by KCl. RESULTS The extract neither affected the body weight nor the heart rate. The extract as captopril completely prevented the development of arterial hypertension. Both the substances failed to restore the endothelium-dependent vascular relaxation and increased the vascular contraction to norepinephrine in relation to KCl contraction. They also significantly reduced the left ventricular hypertrophy induced by l-NAME. CONCLUSION These findings are in agreement with the traditional use of Mammea africana in the treatment of arterial hypertension and indicate that it may have a beneficial effect in patients with NO deficiency but will be unable to improve their endothelium-dependent vasorelaxation.

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.

Pentacyclic triterpenoids and ceramide mediate the vasorelaxant activity of Vitex cienkowskii via involvement of NO/cGMP pathway in isolated rat aortic rings.

ETHNOPHARMACOLOGICAL RELEVANCE Vitex cienkowskii Kotschy & Peyritsch is a deciduous tree, prescribed by Cameroonian traditional healers as one of the most popular plant widely used in many disorders including cardiovascular diseases. The preliminary pharmacological studies carried out on Vitex cienkowskii showed its vasorelaxant activities on guinea-pig aortic rings. AIM OF THE STUDY The present work evaluated the vasorelaxant activity of extract and isolated compounds from Vitex cienkowskii. MATERIALS AND METHODS Rat aortic rings were used to evaluate the in vitro vascular effect of the extract. The antioxidant activity was determined by measuring the reduction of the free radical 1,1-diphenyl-1-picryl-hydrazyl (DPPH). RESULTS Vitex cienkowskii induced significant relaxation in a concentration- and endothelium-dependent manner (EC(50)=12.12 μg/ml, CH(2)Cl(2)-MeOH, 1:1) and did not produce a vasorelaxant effect on contraction evoked by KCl (60 mM). In order to determine its mode of action, Vitex cienkowskii-induced relaxant effect was evaluated in the presence of indomethacin (10 μM), L-NAME (100 μM), ODQ (1 μM) and SQ22356 (100 μM). Relaxation was significantly blocked by L-NAME and ODQ. These results indicate that Vitex cienkowskii-mediated relaxation is endothelium dependent, probably due to NO release, and the consequent activation of vascular smooth muscle soluble guanylate cyclase (sGC), a signal transduction enzyme that forms the second messenger cGMP. Bio-guided study of Vitex cienkowskii allowed the isolation of the known pentacyclic triterpenoids and a ceramide. It is the first report of salvin A, maslinic acid and a ceramide from Vitex cienkowskii. The activity induced by these compounds indicated that they may be partly responsible for the vasorelaxant effect of the plant extract. A dose of 40 mg/kg of CH(2)Cl(2)-MeOH (1:1) extract administered intravenously induced a decrease of mean arterial pressure but did not affect the heart rate. Moreover the plant extracts were found to be highly active in the DPPH radical scavenging assay. CONCLUSION Vitex cienkowskii extract possesses antioxidant property, vasorelaxing, and hypotensive effect linked to the endothelium related factors, where nitric oxide is involved.

Antihypertensive and vasorelaxant effects of Cinnamomum zeylanicum stem bark aqueous extract in rats.

The present study was undertaken to evaluate the antihypertensive and vasorelaxant effects of Cinnamomum zeylanicum Blume stem bark aqueous extract in rats. The in vivo activities of the extract were evaluated on normotensive and three rat models of hypertension while the in vitro tests were assayed on rat isolated aorta rings. Acute intravenous injection of the extract (5, 10 and 20mg/kg) induced a significant reduction in mean arterial blood pressure in anaesthetised normotensive Wistar rats, salt-loaded hypertensive, L-NAME hypertensive and spontaneously hypertensive rats. Pre-treatment of rats with either propranolol or atropine significantly inhibited the hypotensive effects of the plant extract suggesting its possible action through the interferences with both cholinergic and sympathetic transmissions. Moreover, pre-treatment of rats with L-NAME inhibited the sustained plant antihypertensive effects, suggesting a possible active vasodilatation, which might be partly mediated by an endothelial l-arginine/nitric oxide pathway. In isolated rat aortic rings pre-contracted with KCl (60mM), the extract exhibited cumulative vasodilating effects, which were attenuated with either L-NAME, vascular endothelium removal or both tetraethylammonium and glibenclamide pre-treatments. The vasorelaxant effects may be involved in the extract antihypertensive mechanism, partially by increasing the endothelial nitric oxide and by activating the KATP channels in vascular smooth muscle.

Antimalarial and vasorelaxant constituents of the leaves of Allanblackia monticola (Guttiferae)

Abstract Phytochemical investigation of the leaves of Allanblackia monticola led to the isolation and characterisation of five prenylated xanthones [1,6-dihydroxy-3,7-dimethoxy-2-(3-methylbut-2-enyl)xanthone 1, α-mangostin 2, tovophyllin A 3, allanxanthone C 4 and 1,7-dihydroxy-3-methoxy-2-(3-methylbut-2-enyl)xanthone 5], two biflavonoid derivatives (amentoflavone 6 and podocarpusflavone A 7) and one pentacyclic triterpene (friedelan-3-one 8). The structures of these compounds were established on the basis of homo- and hetero-nuclear, one- and two-dimensional, nuclear magnetic resonance. Compounds 2–8 and a crude methanolic extract of A. monticola leaves were each tested for antimalarial activity in vitro, using the chloroquine-sensitive F32 and chloroquine-resistant FcM29 strains of Plasmodium falciparum; the median inhibitory concentrations (IC50) recorded varied from 0.7 to 83.5 μg/ml. The cytotoxicities of the compounds and crude extract, against cultures of human melanoma cells (A375), were then investigated, and cytotoxicity/antimalarial IC50 ratios of 0.6–16.75 were recorded. In tests involving aortic rings from guinea pigs, a crude extract of the leaves of A. monticola was found to induce concentration-dependent vasorelaxation, causing up to 82% and 42% inhibition of noradrenaline- and KCl-induced contractions, respectively. The corresponding values for compounds 2 and 6 when tested against noradrenaline-induced contractions were approximately 18% and 35%, respectively.

Antinociceptive and anti-inflammatory effects of the methanolic stem bark extract of Antrocaryon klaineanum Pierre (Anacardiaceae) in mice and rat

ETHNOPHARMACOLOGICAL RELEVANCE Antrocaryon klaineanum is used by traditional healers to treat many disorders including pain and inflammatory diseases. This study aimed to evaluate the analgesic and antiinflammatory activities of methanol extract of A. klaineanum in mice and rats. MATERIALS AND METHODS Reverse phase high-performance liquid chromatography (RP-HPLC) was performed to establish the chromatographic fingerprint and to identify various chemical components of the plant extract. The anti-nociceptive activity of methanol extract of A. klaineanum was assessed using the acetic acid-induced abdominal constriction model, formalin test, capsaicin and cinnamaldehyde induced-neurogenic pain and hot plate test. Anti-inflammatory activity was assessed on carrageenan-induced inflammation. Extract was administrated orally at 200, 400 and 600mg/kg. RESULTS Phytochemical analysis indicated the presence of proanthocyanidins, phenolic acids and flavonoids. The results of anti-nociceptive and anti-inflammatory activities showed that methanol extract significantly (p<0.01) reduced the pain induced by acetic acid with an inhibition percentage of 45.49% (600mg/kg). In the formalin test, the extract also significantly (p<0.01) reduced linking time in both phase (neurogenic and inflammatory) of the test with inhibition percentage of 56.28% and 60.73% respectively at the dose of 600mg/kg. The methanol extract of A. klaineanum significantly (P<0.001) reduced neurogenic pain linking time induced by capsaicin and cinnamaldehyde by 82.54% and 75.94% at the highest dose (600mg/kg) respectively. More over the extract significantly increase the reaction time in hot plate test. In the inflammatory test, the plant extract significantly reduced the carrageen induced rat paw oedema from 30min to 6h with a maximum percentage inhibition of 89.88% (6h) at the dose of 600mg/kg. CONCLUSION These results demonstrate that the methanol extract of A. klaineanum may possess analgesic and anti-inflammatory effects and provide support of the traditional use of this plant in the treatment of different pain and inflammatory conditions. Further investigation could reveal metabolites of the extract responsible for the observed effects.

Antiplasmodial activity of some phenolic compounds from Cameroonians Allanblackia

BACKGROUND Plasmodium falciparum, one of the causative agents of malaria, has high adaptability through mutation and is resistant to many types of anti-malarial drugs. This study presents an in vitro assessment of the antiplasmodial activity of some phenolic compounds isolated from plants of the genus Allanblackia. METHODS Tests were performed on well plates filled with a fixed parasitized erythrocytes volume. Compounds to be tested were then added in wells. After incubation, tritiated hypoxanthine is added and the plates were returned to the incubator. After thawing, the nucleic acids are collected. Inhibitory Concentration 50 (IC50) was determined by linear interpolation. RESULTS From Allanblackia floribunda, have been isolated and characterized 1,7-dihydroxyxanthone 1, macluraxanthone 4, morelloflavone 9, Volkensiflavone 10 and morelloflavone 7-O-glucoside 11; from Allanblackia monticola, α-mangosine 2, rubraxanthone 3, allaxanthone C 5, norcowanine 6, tovophiline A 7, allaxanthone B 8 and from Allanblackia gabonensis, 1,7-dihydroxyxanthone 1. Six of them were evaluated for their antimalarial properties. The most active compound, macluraxanthone, presented a very interesting activity, with an IC50 of 0.36 and 0.27 µg/mL with the F32 and FcM29 strains respectively. CONCLUSION This work confirms that species of Allanblackia genus are medicinally important plants containing many biologically active compounds that can be used effectively as antiplasmodial.