This work was carried out in collaboration between all authors. Author OLA designed the project, managed the protocol for qualitative screening, antimicrobial analysis, performed the statistical analysis and wrote the first draft of manuscript. Author AJ designed and wrote protocol for quantitative analysis of phytochemicals and managed the literature searches. Authors SBK and OPJ searched for samples, prepared samples for analysis and managed parts of laboratory works. All authors read and approved the final manuscript.

Bacterial resistance to conventional antibiotics justifies the need to explore alternative remedies from medicinal plants since they represent a rich source of antimicrobial agents. We present a comparative evaluation of in vitro antibacterial activities of different solvent extracts of seven medicinal plants used to treat bacterial infections amongst the tribes of Northern Ghana. In the present study, extracts of the plants were obtained using solvents of different polarities and their growth inhibitory activity against Salmonella typhi and Escherichia coli evaluated in vitro. Phytochemical screening revealed the presence of alkaloids, saponins, tannins, coumarins and flavonoids in most of the extracts. These secondary metabolites have been implicated as antibacterial agents in several reports. The extracts from the seven plants showed varied antibacterial activity against the test organisms. Of the bacteria tested, Salmonella typhi was the least susceptible to most of the extracts. The ethanol extracts of the plants generally demonstrated superior growth inhibitory activity at 100 and 200mg/ml concentrations while the aqueous extracts were the least active at similar concentrations. The maximum antibacterial activity was recorded for Khaya senegalensis ethanol stem bark extract against Escherichia coli (zone of inhibition = 20.10mm) and Salmonella typhi (zone of inhibition = 17.10mm) at 200mg/ml. The result presents the basis for which these plants have been used for treatment of bacterial infections in folkloric medicine. The results further reveal that ethanol stem bark extract of K. senegalensis demonstrated the greatest activity and thus can be very useful in the search for novel antibacterial agents.

Vernonia colorata has been used in traditional medicine for the treatment of diseases related to certain bacteria. Crude leaf extracts of the plant have also been reported to contain antibacterial agents in previous in vitro studies. Fractionation of crude solvent extracts may lead to isolation and subsequent characterization of the active compound(s). In the current research, crude aqueous and ethanolic leaf extracts of V. colorata were evaluated for antibacterial activity against five human pathogenic bacteria. The crude extracts were further fractionated by solvent-solvent partitioning using petroleum ether, chloroform and diethyl ether. The various fractions were tested against selected bacteria using the agar-well diffusion method. Crude ethanolic extract showed MIC ranging between 5-6 mg/ml while aqueous extract showed MIC between 6-7.5 mg/ml. All fractions from the aqueous extract at 10 mg/ml did not show zone of inhibition against the bacteria tested. However, the chloroform fraction of the ethanolic extract showed activity only against S. aureus at 10 mg/ml with zone of inhibition of 15.00 ± 0.20 mm. The antibacterial activity of the chloroform fraction of the ethanolic extract was significant in comparison with control (P < 0.05). The results suggested that the crude ethanolic leaf extract of V. colorata possess superior antibacterial activity as compared with aqueous extract. The result further suggests that chloroform fraction of the ethanolic leaf extract possesses antibacterial activity hence turn out to be a good candidate for further isolation and characterization of antibacterial agents.