Activités antioxydantes de dix plantes medicinales de la pharmacopée ivoirienne.

Le stress oxydant, cause de plusieurs maladies, suscite la recherche de nouveaux remèdes antioxydants. Dans cette optique, l’étude de l’activité antioxydante des extraits méthanoliques de dix (10) plantes utilisées dans la pharmacopée ivoirienne a été réalisée. Ces plantes sont issues de la région forestière de la Côte d’Ivoire et précisément du département d’ISSIA (région du haut Sassandra). Les extraits des dix plantes sont obtenus après macération dans le méthanol 96 %, pendant 48 H, à la température ambiante (25°C), suivie d’une double filtration sur coton puis sur papier wattman 3 mm et évaporé au rotavapor. La poudre ainsi obtenue, nous a permis de réaliser nos tests phytochimiques et antioxydants. Le tri phytochimique, l’activité antiradicalaire par le DPPH et l’inhibition de la peroxydation lipidique par la méthode au thiocyanate ferrique et la méthode des TBARS ont été utilisées. Le tri phytochimique a permis de révéler que ces plantes contiennent des stérols, des polyterpènes, des polyphénols, des flavonoïdes des alcaloïdes et des saponines. Celles qui présentent l’activité antioxydante et antiradicalaire avérée sont: Mitragyna ciliata (CI50 = 10,5 ± 0,288 μg/mL), Trichilia prieuriana (CI50 = 7,5 ± 0,288 μg/mL), Chrysophyllum perpulchrum (CI50 = 4,00 ± 0,288 μg/mL) et Disthemonanthus benthamianus (CI50 = 4,50 ± 0,288 μg/ ml). Ces plantes contiennent des flavonoïdes et des polyphénols qui sont en général de très bons antioxydants. Ainsi, elles sont, au vu de notre étude, considérées comme des plantes antioxydantes et antiradicalaires parmi les 10 plantes sélectionnées.Mots clés : antioxydante, antiradicalaires, Screening, phytochimi

Acute and Subacute Toxic Study of Aqueous Leaf Extract of Combretum Molle

Purpose: The purpose of the present study was to evaluate the acute and subacute toxicity of the aqueous leaf extract of Combretum molle.Methods: The acute toxicity of the extract was evaluated in rats. The animals were orally administered with doses ranging from 2000 to 8000 mg/kg and observed continuously for the first 4 h, then hourly for the next 24 h, and finally, 6-hourly for 72 h. Control animals received orally normal saline. The rats were observed carefully for mortality, pain as well as respiratory movements. For subacute toxicity, 6 groups of 6 rats (3 male and 3 female) each received intraperitoneally, normal saline (control), 400, 600, 800, 1000 and 1200 mg/kg of the extract, respectively, thrice daily for 15 days. At the end of the treatment period, the animals were sacrificed and their organs (liver, heart and kidney) removed for macroscopic examination.Results: For the acute toxicit test, no death and signs of poisoning were observed in the treated groups. In the subacute tstudy, LD50 in the rats after intraperitoneal administration was 700 mg/kg (456 - 896, 95 % confidence interval). The clinical signs of poisoning (motor difficulties, decreased respiratory rate, and tremor preceding death) were observed, suggesting overt toxicity throughout the neuromuscular system. However, histological examination of vital organs showed normal architecture suggesting no morphological abnormalities in the heart, kidney and liver.Conclusion: The results show that the aqueous leaf extract of C. molle is moderately toxic when given intraperitoneally.Keywords: Combretum molle, Acute/subacute toxicity, Histopathology, Rat

In vitro anticholinestarase and cholinergic effect of the aqueous extract of Trema guineensis on rabbit duodenum

Purpose: In previous studies, the aqueous extract of Trema guineensis (Ulmaceae) was shown to increase rabbit duodenal contractions. The aim of this study was to evaluate the mechanism of the stimulation of the rabbit duodenum by the aqueous extract of Trema guineensis (Ulmaceae). Methods: The in vitro organ bath method was used in our experiments. The enzyme was extracted from rabbit duodenum. The acetylcholinesterase (AChE) activity was determined by Ellman\'s assay using acethylthiocholine iodide as substrate. The rate of hydrolysis of acetylcholinesterase was monitored at 412 nm using a spectrophotometer. Results: The effective concentration which induces 50% effect of Hypo+ (EC50) was obtained with 8 x 10-2 mg/ml of Hypo+. The tests carried out in the presence of atropine showed a considerable reduction in the amplitudes of intestinal contractions. Hypo+ exerted mixed competitive inhibition on acetylcholinesterase (Vmax = 8.33 μM/min and KM= 6.25 x 10-4 M). These results indicate that the crude extract of Trema guineensis contains anti-AChE and cholinomimetic substances. These two properties can explain the increase of duodenal contraction by Hypo+. Conclusion:These results support the use of Trema guineensis as a laxative due to its stimulating effects on duodenal contractility. Keywords: Trema guineensis, Myostimulation, Acetylcholinesterase, Hypo+, Duodenal contractionTropical Journal of Pharmaceutical Research Vol. 8 (1) 2009: pp. 11-1

In vitro assays for bioactivity-guided isolation of antisalmonella and antioxidant compounds in Thonningia sanguinea flowers

Bioguided fractionation of the aqueous extract of Thonningia sanguinea flowers, used traditionally in the treatment of microbial diseases, led to the isolation of two phenolic compounds. The structure of these compounds was elucidated by 1H, 13C 1D NMR and mass spectrometry experiments. The antibacterial activity against Salmonella strains and antioxidant activity of the crude extract, fractions and isolated compounds was evaluated using the DPPH method. The isolated compounds identified asbrevifolin carboxylic acid and gallic acid demonstrates moderate antibacterial activity against Salmonella enteritidis, Salmonella typhimurium, and Salmonella abony. The results indicated that thetwo isolated compounds, gallic acid (IC50 = 13.5 ìM) and brevifolin carboxylic acid (IC50 = 18.0 ìM) were mainly responsible for the good scavenging activity of the aqueous extract

Entomological Surveillance of Behavioural Resilience and Resistance in Residual Malaria Vector Populations.

The most potent malaria vectors rely heavily upon human blood so they are vulnerable to attack with insecticide-treated nets (ITNs) and indoor residual spraying (IRS) within houses. Mosquito taxa that can avoid feeding or resting indoors, or by obtaining blood from animals, mediate a growing proportion of the dwindling transmission that persists as ITNs and IRS are scaled up. Increasing frequency of behavioural evasion traits within persisting residual vector systems usually reflect the successful suppression of the most potent and vulnerable vector taxa by IRS or ITNs, rather than their failure. Many of the commonly observed changes in mosquito behavioural patterns following intervention scale-up may well be explained by modified taxonomic composition and expression of phenotypically plastic behavioural preferences, rather than altered innate preferences of individuals or populations. Detailed review of the contemporary evidence base does not yet provide any clear-cut example of true behavioural resistance and is, therefore, consistent with the hypothesis presented. Caution should be exercised before over-interpreting most existing reports of increased frequency of behavioural traits which enable mosquitoes to evade fatal contact with insecticides: this may simply be the result of suppressing the most behaviourally vulnerable of the vector taxa that constituted the original transmission system. Mosquito taxa which have always exhibited such evasive traits may be more accurately described as behaviourally resilient, rather than resistant. Ongoing national or regional entomological monitoring surveys of physiological susceptibility to insecticides should be supplemented with biologically and epidemiologically meaningfully estimates of malaria vector population dynamics and the behavioural phenotypes that determine intervention impact, in order to design, select, evaluate and optimize the implementation of vector control measures

Negative Cross Resistance Mediated by Co-treated bed nets: A Potential Means of Restoring Pyrethroid-susceptibility to Malaria Vectors.

Insecticide-treated nets and indoor residual spray programs for malaria control are entirely dependent on pyrethroid insecticides. The ubiquitous exposure of Anopheles mosquitoes to this chemistry has selected for resistance in a number of populations. This threatens the sustainability of our most effective interventions but no operationally practicable way of resolving the problem currently exists. One innovative solution involves the co-application of a powerful chemosterilant (pyriproxyfen or PPF) to bed nets that are usually treated only with pyrethroids. Resistant mosquitoes that are unaffected by the pyrethroid component of a PPF/pyrethroid co-treatment remain vulnerable to PPF. There is a differential impact of PPF on pyrethroid-resistant and susceptible mosquitoes that is modulated by the mosquito's behavioural response at co-treated surfaces. This imposes a specific fitness cost on pyrethroid-resistant phenotypes and can reverse selection. The concept is demonstrated using a mathematical model

Semi-field evaluation of the cumulative effects of a "lethal House Lure" on malaria mosquito mortality

Background: There is growing interest in the potential to modify houses to target mosquitoes with insecticides or repellents as they search for human hosts. One version of this 'Lethal House Lure' approach is the In2Care® EaveTube, which consists of a section of polyvinyl chloride (PVC) pipe fitted into a closed eave, with an insert comprising electrostatic netting treated with insecticide powder placed inside the tube. Preliminary evidence suggests that when combined with screening of doors and windows, there is a reduction in entry of mosquitoes and an increase in mortality. However, the rate of overnight mortality remains unclear. The current study used a field enclosure built around experimental huts to investigate the mortality of cohorts of mosquitoes over multiple nights. Methods: Anopheles gambiae sensu lato mosquitoes were collected from the field as larvae and reared through to adult. Three-to-five days old adult females were released inside an enclosure housing two modified West African style experimental huts at a field site in M'be, Côte d'Ivoire. Huts were either equipped with insecticide-treated tubes at eave height and had closed windows (treatment) or had open windows and open tubes (controls). The number of host-seeking mosquitoes entering the huts and cumulative mortality were monitored over 2 or 4 days. Results: Very few (0-0.4%) mosquitoes were able to enter huts fitted with insecticide-treated tubes and closed windows. In contrast, mosquitoes continually entered the control huts, with a cumulative mean of 50-80% over 2 to 4 days. Baseline mortality with control huts was approximately 2-4% per day, but the addition of insecticide-treated tubes increased mortality to around 25% per day. Overall cumulative mortality was estimated to be up to 87% over 4 days when huts were fitted with tubes. Conclusion: Only 20-25% of mosquitoes contacted insecticide-treated tubes or entered control huts in a given night. However, mosquitoes continue to host search over sequential nights, and this can lead to high cumulative mortality over 2 to 4 days. This mortality should contribute to community-level reduction in transmission assuming sufficient coverage of the intervention