Phytomedicine Research Centre, Department of Botany, University of Fort Hare, Alice 5700, South Africa
Olajuyigbe, O.O., Phytomedicine Research Centre, Department of Botany, University of Fort Hare, Alice 5700, South Africa; Afolayan, A.J., Phytomedicine Research Centre, Department of Botany, University of Fort Hare, Alice 5700, South Africa
The antibacterial activities of stem bark ethanolic extract of Erythrina caffra Thunb. against bacteria in diarrhoea was determined in vitro by the agar diffusion and dilution, macrobroth dilution, and time-kill assay methods. The result showed that the extract produced inhibition zones ranging between 15 ± 1.0 mm and 23 ± 1.0 mm, and the bacteria were susceptible at concentrations ranging between ≤100 and ≤1000 g/mL. While the MICs of the extract ranged between 39.1 and 625 g/mL, and the MBCs ranged between 78.1 and 625 g/mL, the MICs of Micrococcus luteus, Proteus vulgaris CSIR 0030, Enterococcus faecalis KZN, and Staphylococcus aureus OK3 were less than 100 g/mL, and the mechanisms of antibiosis indicated that the crude ethanolic extract was highly bactericidal against the entire test bacteria isolates. In the time-kill assay, the average log reduction of the viable cell count ranged between 0.916 log 10 and 1.851 log 10 cfu/mL on incubating the bacteria for 4 h at the MICs, while the reduction ranged between 0.183 log 10 and 1.105 log 10 cfu/mL after 8 h of incubation. Incubating the bacteria for 4 h at 2 × MICs resulted in the reduction of the viable cell count to between - 0.264 log 10 and 0.961 log 10 cfu/mL, while the average log reduction ranged between - 3.968 log 10 and - 0.425 log 10 cfu/mL after 8 h of incubation with Micrococcus luteus, Proteus vulgaris CSIR 0030, and Staphylococcus aureus OK3 being the most highly affected bacteria. The result showed that the extract exhibited broader-spectrum antibacterial activity and justifies the use of Erythrina caffra in the folkloric medicine for treating gastrointestinal infections in South Africa. © 2012 Olufunmiso Olusola Olajuyigbe and Anthony Jide Afolayan.
antiinfective agent; Erythrina caffra extract; plant extract; unclassified drug; antiinfective agent; plant extract; agar diffusion; antibacterial activity; antibiosis; article; bactericidal activity; cell count; diarrhea; dilution; Enterococcus faecalis; Erythrina caffra; in vitro study; incubation time; inhibition kinetics; medicinal plant; Micrococcus luteus; nonhuman; Proteus vulgaris; Staphylococcus aureus; bacterial phenomena and functions; chemistry; dose response; drug effect; dysentery; Erythrina; human; LD 50; microbiology; Enterococcus faecalis; Erythrina caffra; Micrococcus luteus; Proteus vulgaris; Staphylococcus aureus; Anti-Bacterial Agents; Bacterial Physiological Phenomena; Dose-Response Relationship, Drug; Dysentery; Erythrina; Humans; Lethal Dose 50; Plant Extracts