Preliminary screening to assess the antimicrobial activities of extracts of evergreen woody species from South Korea against Staphylococcus aureus

This study aimed to screen for plants with antimicrobial potential among the evergreen woody species of South Korea that are used for horticulture and landscaping and to provide basic information about plants with proven antimicrobial activity to underpin future research. The plant materials were extracted under various conditions, and the antimicrobial activities of the extracts were evaluated by agar diffusion assay. The screening tests demonstrated that the crude extracts of 43 species had inhibitory effects against S. aureus. The inhibitory activities of four species (Elaeocarpus sylvestris, Camellia japonica, Cleyera japonica, and Quercus salicina) were relatively higher than that of the synthetic antimicrobial agents methylparaben and phenoxyethanol. The highest inhibitory activity was observed with the leaf extracts (extracted with methanol for 30 minutes) of E. sylvestris, based on induction of the largest inhibition zone of 23.3 mm in size. In addition, solvent fractions of E. sylvestris were evaluated. The largest inhibitory zone of 23.1 mm was observed for the n-butanol fraction, which is likely to contain effective compounds that exhibit inhibitory activity against S. aureus. In contrast, n-hexane and residual aqueous fractions showed no antimicrobial activity. Overall, our findings confirm that evergreen woody plants native to South Korea have potential antimicrobial activity.