Fig. 4

Measurements of antibacterial activity by MTS assay. a Dose dependent antibacterial activity of two antibiotics measured by MTS assay. b Antibacterial activities measured by MTS assay using four representative accessions in each solvent used for the disk diffusion method. c–e Dose dependent antibacterial activities measured by MTS assay using extracts from accessions which showed strong antibacterial activities in b. x axis in a indicates concentration of antibiotics. x axis in b indicates the name of the extracts. x axis in c indicates concentration of specific extracts. y axis indicates relative growth rate of E. coli, which represents the antibacterial activity of the sample extracts. DMSO and antibiotics (ampicillin and kanamycin) are negative and positive controls of antibacterial activity. Values indicate means. Error bars indicate standard deviations. N.D. indicates undetectable level of antibacterial activity. IC50 indicates 50% of maximum inhibitory concentration of ampicillin, which is a positive control. Measurements were triplicated except for diethyl ether extracts