Phytochemical and Antibacterial Evaluations of the Stem Bark of Newbouldia laevis against Isolates from Infected Wounds and Eyes

Purpose: To examine the phytochemical constituents and verify the ethnomedical claim of Newbouldia laevis (P.Beauv.) Seeman ex Bureau Bignoniaceae in treating septic wounds and eye problems. Methods: Applying standard methods, the phytochemical constituents of the stem bark were examined while the antibacterial potentials of the methanol extract of the stem bark and its organic solvent fractions were tested on clinical bacterial isolates from infected wounds and eyes using the agar - well diffusion method. Ciprofloxacin and gentamicin were used as standard controls. The time-kill kinetics of the methanol stem bark extract and ciprofloxacin were determined using isolates of Staphyloccocus aureus. Results: Phytochemical screening of the stem bark revealed the presence of flavonoids, tannins, saponins and alkaloids with no traces of cyanogenic glycosides. The 65 bacterial pathogens isolated included Proteus mirabilis (26.0 %) and Pseudomonas aeurginosa (17.4 %) from non-diabetic patients’ wounds; Staphylococcus aureus (32.0 %) and Escherichia coli (16.0%) from diabetic patients’ wounds; Staphylococcus aureus (35.3%) and Pseudomonas aeruginosa (35.3 %) from infected eyes. The chloroform fraction was observed to be more active on Gram- negative organisms while the aqueous fraction was more active on Gram-positive organisms. Time-kill kinetics of Staphylococcus aureus showed that the extract was bactericidal (99.9 % killing) at MIC and 2 x MIC after 24 and 3 hours, respectively. Conclusion: The study has established that the stem bark of Newbouldia laevis has antibacterial activities against bacterial isolates from infected wounds and eyes as claimed in ethnomedicinal practice.