Abstract:
BACKGROUND: Owing to antibiotic resistance, alternative antimicrobials from medicinal plants are receiving attention
as leads for anti-infective agents. This study aimed to investigate selected tree species and their constituents for
activity against bacterial foodborne pathogens, particularly Salmonella serovars.
METHODS: Antibacterial activity of ten plant species was determined by serial microdilution against bacteria
implicated in causing gastrointestinal ailments. Active compounds were isolated from Loxostylis alata using
bioassay-guided fractionation. Antioxidant activity was determined using free-radical scavenging assays. Cytotoxicity
and genotoxicity of the extracts was ascertained on Vero cells, and using the Ames assay respectively.
RESULTS: Extracts had low to moderate MIC values from 0.04 to 2.5 mg/mL. Protorhus longifolia and Loxostylis alata
were most active and L. alata had the highest selectivity index value (2.51) against Salmonella Typhimurium, as well
as high antioxidant activity. Cytotoxicity values ranged from 0.02 to 0.47 mg/mL, while tested extracts were not
genotoxic. Bioactive compounds isolated from L. alata included delicaflavone and a polymethoxyflavone.
CONCLUSIONS: The Loxostylis alata leaf extract had strong activity against Salmonella serovars but isolated
compounds were less active, indicating likely synergistic effects. Extracts of L. alata are promising candidates for
development of antimicrobial preparations or food additives against microbial contamination.
