Susceptibilité antidiarrhéique de Dichrocephala integrifolia, Dioscorea preussii, Melenis munitiflora, Tricalysia okelensis et propriétés antidiarrhéiques de Dichrocephala integrifolia.

Abstract

Diarrhoeal diseases are one of the major causes of morbidity and mortality in the world and constitute a real public health problem. Dichrocephala integrifolia, Dioscorea preussii, Melenis minutiflora and Tricalysia okelensis are empirically used in the West Cameroon Region for the treatment of gastrointestinal disorders and intoxication. In order to develop an improved traditional medicine (ITM) for the treatment of diarrhoeal diseases, the anti-diarrhoeal properties of these four plants were evaluated to determine the plant, its extract and its effective fraction. The antimicrobial properties of the hydroethanolic extracts of D. preussii, D. integrifolia, M. minutiflora and T. okelensis, the aqueous, ethanolic and hydroethanolic extracts of D. integrifolia, and the dichloromethane, ethyl acetate and ethanol fractions of the hydroethanolic extract of D. integrifolia were evaluated in vitro by the disc diffusion and agar dilution methods. The effects of the different extracts and fractions of D. integrifolia on intestinal motility were evaluated in vivo on castor oil-accelerated intestinal transit and in vitro on spontaneous contractions of isolated rat duodenum. Also, the anti-secretory activity of these extracts and fractions of D. integrifolia was evaluated in vivo on castor oil-induced secretory diarrhoea by measuring the volume and mass of luminal contents. Similarly, the mechanism of anti-secretory action of the dichloromethane fraction of D. integrifolia (FDDi) was determined on prostaglandin E2 (PGE2 induced intestinal secretions. On the other hand, typhoid fever was induced by oral administration of 1.5 x 108 CFU of S. typhi in rats and for 16 days they were treated with FDDi. Salmonella faecal density, rectal temperature, faecal emission frequency, food and water intake of each rat were recorded daily. After sacrifice, biochemical parameters of liver and kidney function (ALT, AST and creatinine), oxidative stress (SOD, CAT, MDA, GSH and NO) and histology were assessed. The acute toxicity of FDDi was performed according to OECD guideline 423. D. integrifolia showed the highest efficacy with the inhibition of all bacterial strains tested and the inhibition of castor oil-induced acceleration of intestinal transit. Among the different extracts of D. integrifolia, the hydroethanolic extract was the most effective with bactericidal activity on E. coli, S. typhi, S. choleraesuis, S. aureus, S. flexneri, fungicidal activity on C. albicans; and significantly (p< 0.01) better than the other extracts inhibited in vitro and in vivo contractions and intestinal secretions. The hydroethanolic extract was fractionated for a bioguided study of antidiarrhoeal activity. The dichloromethane fraction (FDDi) compared to the ethyl acetate (FEADi) and ethanol (FEDi) fraction was found to be the most effective against the tested microbial strains with the respective MBC/MIC ratios of 1, 2, 2, 4 and 4 on S. choleresuis, S. typhi, S. flexneri, S. dysenteriae A 1 and S. aureus. In vitro, FDDi at concentrations between 0.005 and 1 mg/mL, in normal physiological conditions, showed a significant (P<0.01) concentration-dependent decrease in contraction amplitude and tone. In vivo, on intestinal transit, FAEDi and FDDi (12.5, 25 and 50 mg/kg) significantly (P<0.01) and in a dose-dependent manner inhibited intestinal transit. In contrast, FEDi inhibited transit in a dose-dependent manner. On intestinal secretions, FAEDi and FDDi significantly (P<0.01) and in dose-dependent manner inhibited the volume and mass of intestinal secretions induced by castor oil. In contrast, FEDi inhibited the volume and mass of intestinal secretions in a dose-dependent manner. Based on these results, FDDi was used to determine the mechanisms of action of the anti-diarrhoeal activity. FDDi significantly (P<0.01) inhibited acetylcholine, KCl and BaCl2 induced phasic contractions. Pretreatment of animals with yohimbine and Naloxone did not significantly alter the spasmolytic activity of FDDi (50 mg/kg). In contrast, atropine pre-treatment increased (p<0.05) the spasmolytic activity of FDDi, while glibenclamide reduced (p<0.01) the spasmolytic activity of FDDi. FDDi significantly (p<0.01) inhibited PGE2-induced intestinal secretions. In S. typhi-infected rats, FDDi significantly (P<0.01), and in a dose-dependent manner, reduced S. typhi density, the number of diarrhoeal stools and body temperature. FDDi significantly (P<0.01) reduced serum ALT, AST and creatinine levels. FDDi significantly (P <0.01) increased CAT, SOD and GSH levels and significantly decreased MDA and NO levels in the different tissues investigated. FDDi did not improve the architecture of liver tissue but restored the morphology of kidney tissue in Salmonella-infected rats. The median lethal dose LD50 of the dichloromethane fraction was reported to be over 5000 mg/kg body weight. Dichrocephala integrifolia, through its hydroethanolic extract and its dichloromethane fraction, would be effective on motor, secretory and infectious diarrhoea. These results would justify the use of D. integrifolia in traditional medicine.