Acute diarrheal diseases caused by food poisoning consitute serious public health problem in developing countries where they are the leading cause of death. WHO recommends research towards discovery of new anti-infective molecules that could be used in the treatment of bacterial and fungal infections such food poisoning, diarrhea. Literature reports that tannins are a very effective natural treatment. For example, in Democratic Republic of Congo, MEYAMICINE® was developed as very effective drug against food poisoning and diarrhea. The antimicrobial activity of condensed tannins from Erythrophleum guineensis
stem barks (Caesalpiniaceae) was evaluated using the micro-dilution method in a liquid medium on seven reference strains, notably Staphylococcus aureus
CIP 7625, Salmonella enterica
NR 13555, Shigella flexneri
NR 518, Escherichia coli
ATCC 25922, Candida albicans
NR 29450, Candida krusei
ATCC 6258 and Candida parapsilosis
The hydro-ethanolic crude extract of stem bark contains several classes of secondary metabolites such as polyphenols, tannins, flavonoids, terpenoids, alkaloids, saponins mucilage, coumarin, cardiac glycosides, etc. The partition of this crude extract with ethyl acetate resulted into the isolation of condensed tannins. The determination of condensed tannins via total proanthocyanidin assay yielded a concentration of 0.865 mg EC / mL with an optical density of 0.558. The minimum inhibitory concentrations (MIC) ranged from 1.25 to 2.5 mg / mL while the minimum bactericidal or fungicidal concentrations (MBC or MFC) ranged from 1.25 mg / mL to 5 mg / mL. The best bactericidal and absolute fungicidal activities were respectively recorded on Staphylococcus aureus and Candida krusei and Candida parapsilosis with results (MBC/ MIC or MFC / MIC = 1). A relatively bactericidal activity good was also recorded againat Shigella flexneri (MBC / MIC = 2). On the other hand, condensed tannins exhibited bacteriostatic or fungistatic activitities on Salmonella enterica, Shigella flexneri, Escherichia coli and Candida albicans with (MBC / MIC = 4).
This study has also led to isolation of a proanthocyanidol. On the basis of the antimicrobial activities of condensed tannins in this study, it can be concluded that condensed tannins from Erytrhophleum guineensis effectively exhibit antimicrobial properties and this may justify the use of this plant in the treatment of diarrhea caused by food poisoning.