Antibacterial activity of Quercus salicina, Mallotus japonicus, Euscaphis japonica and Castanopsis sieboldii against skin harmful bacteria

The objective of this study was to analyze the antibacterial and physiological activities of etanol (EtOH) extracts of four indigenous tree species Quercus salicina, Mallotus japonicus, Euscaphis japonica and Castanopsis sieboldii traditionally used as folk remedies in the Korea. The antibacterial activity against six skin pathogen, including Corynebacterium diphtheriae, and Staphylococcus aureus was evaluated using the disk diffusion method, and the minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) were measured. The results indicated that extracts from all four species exhibited antibacterial activity with E. japonica showing the highest activity among them. The antioxidant activity of the extract was evaluated through DPPH and ABTS assays, while their anti-inflammatory activity of the extract was measured by Griess assay. TAmong four species, C. sieboldii exhibited the best free radical scavenging activities and nitric oxide (NO) inhibitory activities. DPPH assay results revealed that 75.19±0.78% of free radicals were eliminated at a concentration of 9.8 μg/mL , while ABTS analysis results showed that 84.97±1.45% of free radicals were removed at a concentraton of 3.91 μg/mL. Although further research is required to identify the specific compounds responsible for the obsered antibacterial and physiological activities, these results suggest that extracts of Q. salicina, M. japonicus, E. japonica and C. sieboldii could be useful as cosmetic ingredients.