The minimal inhibitory concentration (MIC) was determined by
broth macrodilution method [19]. One hundred microliter of the
ethanol extract and rhodomyrtone were diluted to final concentrations
ranging from 0.5 to 1024 mg/mL and 0.06e32 mg/mL,
respectively. Five hundred microliter of the bacterial suspension
(2 106 colony forming unit/ml, CFU/mL) and 400 ml of supplemented
BHI broth were added and incubated at 37 C for 72 h under
anaerobic condition. The MIC is defined as the lowest concentration
that produced a completely inhibition of bacterial growth. Minimal
bactericidal concentration (MBC) is performed with the extract that
gave significant MIC values using a sterile loop streaking on supplemented
BHI agar. Experiments were done in triplicate. Bacterial
culture with 1% DMSO was used as negative control. In addition,
erythromycin, a common antibiotic used in acne treatment was
included as a positive control. The MIC break point (mg/mL) of