Antimicrobial Evaluation of the Extract/Fractions of the Millettia aboensis (Leguminosae) Stem against Streptococcus mutans

Aims: Millettia aboensis (Hook.f.) Baker belongs to the Leguminosae family, known locally as nduezi in Igbo, erurumesi in Edo, and Òdúdū in Efik. Millettia aboensis stem is a rich source of flavonoids, phenolic acid, alkaloids, and steroids, hence with medicinal and physiological potentials. It is used in traditional medicine for general healing of diseases including ulcers and laxatives. The present study was aimed at evaluating the antibacterial potential of the extract/fractions of the stem of M. aboensis against Streptococcus mutans – dental caries causative organism and detection of its principles. Methodology: Cold maceration in methanol and liquid-liquid fractionation techniques using hexane, ethyl acetate, and butanol as solvents were utilized for the extraction and fractionation processes respectively. Some phytochemicals from the fractions were suspected using High Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD). The crude methanol stem extract/fractions were screened to analyze its antibacterial activity against Streptococcus mutans. Results: The results showed for the fractions that aqueous fraction extract had the highest percentage yield (57.73%), followed by ethyl acetate (16.79%), butanol (12.17%), hexane (9.48%), while the percentage yield of the methanol extract is 2.98%. The HPLC-DAD analysis detected the following phytochemical constituents from the stem fractions: pestalotioprolide C - 1, corynesidone D - 2, enniatin B - 3, dipiperamide E - 4, isopranetin 8-C-glucoside - 5, genistein 8-C-glucoside - 6, genistein 6-C-glucoside - 7, and peniciaculin B - 8. In relatively low and high concentrations (6.25 – 50 mg/ml), the extract/fractions of M. aboensis were found ineffective against Streptococcus mutans. Conclusion: The plant – M. aboensis with its phytochemicals present could be an excellent source of novel biologically active compounds with pharmaceutical and industrial importance.