Antibacterial and antifungal activities of Quassia undulata and Quassia amara extracts in vitro.

Extracts of Quassia undulata and Quassia amara (Simaroubaceae) were screened for in vitro antibacterial and antifungal properties respectively. A total of eight extracts, comprising hexane and methanol extracts of the leaves and stems of each of the two plants were investigated. At a concentration of 5 mg/ml all eight extracts exhibited marked antibacterial and antifungal activities in most cases higher than the standard reference drugs included in the study. The extracts inhibited the growth of Escherichia coli, Streptococcus faecalis, Stapylococcus aureus and Aspergillus niger, even when the standard reference drugs utilized in the study did not. Quassia amara leaf methanol extract singularly exhibited the highest activities in both assays, which included the use of six clinical strains of bacteria and five fungi. The agar cup (10 mm diameter) diffussion and broth dilution techniques were used in both assays, utilising eleven human pathogenic microorganisms. Ampicillin and tioconazole were also included in the assay as reference compounds, while methanol was used as control. Diameter of zones of inhibition ranged between 11.0-29.0 mm for the tested extracts/drugs. All the extracts have shown impressive activities against the commonly encountered microorganisms and have thus confirmed the folklore uses of the plants in the African ethnomedicine.