Antimicrobial activity and chemical characterization Fractions Derived from Aqueous and Ethanolic Extracts from Pteleopsis suberosa (Combretaceae) and Acalypha wilkesiana (Euphorbiaceae)

Résumé

Infectious diseases are a global public health issue, exacerbated by the rise of antimicrobial resistance. One possible solution lies in the search for new therapeutic substances in plants. This study aimed to evaluate the antimicrobial activity and chemical characterization of fractions from the extracts of Pteleopsis suberosa and Acalypha wilkesiana used in traditional Beninese medicine. Aqueous and ethanolic extracts from stem bark of Pteleopsis suberosa and the leaves of Acalypha wilkesiana were separately fractionated using a liquid-liquid method. Four types of fractions were tested against several pathogens, and their minimum inhibitory concentrations (MIC) were determined. The main phytochemical groups present in these fractions were identified by thin-layer chromatography, flavonoid and total phenol concentrations were measured using spectrophotometric methods. The results revealed that the fractions exhibited varied inhibitory effects, with MIC ranging from 3.12 mg/mL to 100 mg/mL. Most fractions were active on Candida albicans ATCC 90028, with the exception of the dichloromethane (DCM) fractions. Only the ethyl acetate (ACE) fraction of the ethanolic extract of Pteleopsis suberosa was effective on all tested bacterial strains. The intermediate (INT) fraction of the ethanolic extract of Pteleopsis suberosa showed notable efficacy on Staphylococcus aureus (MIC = 3.12 mg/mL), while Escherichia coli was resistant. Phytochemical analysis identified the presence of tannins, flavonoids, and polyphenols in the fractions, with no significant variation in their concentrations. These compounds may be responsible for their antibacterial and antifungal activities.

Keywords: Pteleopsis suberosa, Acalypha wilkesiana, Extract fractions, Antimicrobial activity, Benin.