Objective: To investigate the phytochemical test and selected pharmacological activities (antidiarrhoeal and antibacterial activity) of the aqueous and methanolic leaves extracts of Dissotis thollonii Cogn. (Melastomataceae) (D. thollonii).
Methods:The aqueous and methanolic extracts were evaluated for their antibacterial activities on the in vitro growth of 2 clinical isolates (Staphylococcus aureus and Shigella flexneri), and 5 reference bacteria strains [Escherichia coli ATCC 8739 (E. coli), E. coli ATCC 10536, Salmonella typhi ATCC 6539, Enterobacter aerogenes ATCC 13048 and E. coli ATCC 11775] by determining the minimum inhibitory concentrations (MICs) and bactericidal concentrations using broth microdilution method as well as on the infectious, secretory and osmotic induced diarrhoea models in rats.
Results:The aqueous extract inhibited the in vitro growth of all bacteria tested (the 05 reference bacteria strains and the 02 clinical isolates), with MICs values comprised between 32 and 512 μg/mL, whereas the methanolic extract has done the same with the MICs values located between 128 and 512 μg/mL. In vivo, the methanolic and aqueous extracts provoqued at all doses, a significant decrease (P<0.001) in the bacterial load in the faeces of rats, 6 and 7 d of treatment respectively. Infected animals relatively lost weight when treated with the aqueous extract but it remained constant for those treated with the methanolic extract. The results also showed that, the aqueous and methanolic leaves extracts of D. thollonii had, after 6 h of observation, significantly (P<0.001) inhibited in vivo, diarrhoea induced experimentally by castor oil and magnesium sulphate, particularly by prolonging the latency time, reducing the water content of faeces, the frequency of defecation and the number of wet defecation as compared to the negative control which received distilled water and the animals having received 2.5 mg/kg of loperamide used as reference substance. The phytochemical assay revealed the presence of flavonoids, phenols and polyphenols in the leaves extracts of D. thollonii, which are compounds with antidiarrhoeal and antibacterial activities.
Conclusions:The leaves of D. thollonii thus have antibacterial and antidiarrhoeal effects, which could result from their activities on blocking the inhibiting effects of the bacterial enzymes, inhibiting the bacterial protein synthesis, allowing the rupture of the lipopolysaccharidic membrane, as well as on inhibiting prostaglandins-E2 synthesis or increasing the hydroelectrolytic reabsorption. These results attestted the ethnopharmacological use of D. thollonii leaves in the treatment of diarrhoea and gastro-intestinal infections.

Objective: To evaluate spasmolytic mechanisms of aqueous and methanolic extracts from Distemonanthus benthamianus trunk-bark. Methods: Spasmolytic activities of extracts were evaluated in vitro on spontaneous and potassium chloride-induced jejunum contractions, or against cholinergic [acetylcholine (0.3μmol/L)] stimulations. High performance liquid chromatography analysis of both extracts was performed in reference to standard compounds. Results: Extracts developed concentration-dependent inhibitory activities. The methanolic extract, which revealed better activity, produced spasmolytic and myorelaxant effects at concentrations of 0.01-0.30 mg/mL with EC50 of 0.06 and 0.09 mg/mL (95％ CI: 0.03-0.3 mg/mL), respectively. Its anticholinergic effect was obtained at the same concentrations with EC50 of 0.11 mg/mL (95％ CI:0.03-0.3 mg/mL). Chromatograms showed the presence of gallic acid in both extracts, rutin being only detected in the aqueous extract. Conclusions: Distemonanthus benthamianus extracts exhibit verapamil and atropine-like activities, thus highlighting calcium channels and muscarinic receptors blocking potentials, which may be conveyed by some phenolic compounds. These results confirm the antidiarrheal activity of Distemonanthus benthamianus extracts.

Objective: To evaluate the anti-arthritic effect of aqueous and methanolic extracts of Distemonanthus benthamianus. Methods: Monoarthritis was induced by an injection of 0.3 mL zymosan A (0.9% NaCl, v/v) in the right posterior knee joints of rats. Then, joint diameter and pain threshold were determined. Polyarthritis was induced by an intracaudal injection of complete Freund’s adjuvant and rats were treated from day 14 post 1st complete Freund’s adjuvant injection until 28 day. The clinical, hematological, biochemical and oxidative stress parameters were evaluated. In addition, histological analysis of the knee joint was perfomed in both tests. Results: The aqueous and methanolic extracts of Distemonanthus benthamianus at a dose of 500 mg/kg ameliorated zymosan A-induced monoarthritis, as evidenced by reduced joint diameter, increased pain threshold, as well as improved joint architecture. In addition, both extracts of Distemonanthus benthamianus markedly increased body weight and pain threshold, while reducing paw edema in polyarthritic rats. They also led to a marked decrease in platelets and white blood cells (P<0.05), as well as a significant increase in red blood cells, hemoglobin and hematocrit (P<0.05). The aqueous and methanolic extracts of Distemonanthus benthamianus significantly reduced alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase activities, while increasing serum protein levels (P<0.05) with no significant variation in creatinine level. Moreover, both extracts increased catalase and glutathione activities (P<0.05), and inhibited malondialdehyde and nitric oxide production (P<0.01 and P<0.001) in the liver and kidneys. Histological analysis of the joints showed that both extracts triggered tissue reparation. Conclusions: Distemonanthus benthamianus could be used as a potential candidate in the treatment of rheumatoid arthritis.