Antibacterial potential of the flavonoids from the fruits of Voacanga africana Stapf and Tabernaemontana contorta Stapf on diarrheagenic bacteria: A Comparative study between the crude extracts and their fractions

Diarrhea, ranked second cause of death in children under five years globally, is one of the main causes of death in these children in Cameroon. The development phenomena of resistant strains, the side effects, and the costs of often restrictive drugs have motivated populations to look towards phytotherapy. The objective of this study was to carry out a comparative of the antibacterial activity of flavonoids of crude extracts and fractions of the fruit of Voacanga africana Stapf and Tabernaemontana contorta Stapf on the germs responsible for diarrhea. The fruits have been macerated in a hydro-ethanolic solution followed by the extraction of flavonoids by differential fractionation with solvents of increasing polarity. The polyphenols and flavonoids content of the crude extracts and the fractions have been determined by colorimetric methods and the antibacterial activity by the macro-dilution using Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli strains. Finally, a comparison of the results was obtained. Phytochemical screening highlighted classes of compounds common to the two species, such as flavonoids and alkaloids and differences; the assay showed that the crude extract of Voacanga africana contains many more polyphenols with a value of 143.10 ± 1.01 mg EAT / g of dry extract, but Tabernaemontana contorta contains more flavonoids, including its extract ethyl acetate has the highest value, 40.65 ± 0.02 mg EQ / g of dry extract. For the antibacterial activity, the flavonoids of the ethyl acetate fraction of T. contorta have greater antibacterial activity against the strains tested with MICs ranging from 6.25 to 12.5 mg / mL followed by the raw extract of V. africana. This contribution could offer applications in the medical field for the fight against diarrhea.