Subsequent experiments were conducted to determine inhibitory concentrations of all selected plant extracts. Garcinia mangostana showed the greatest antimicrobial effect. The MIC values against both organisms were equal (0.039 mg/ml) and the MBC values were 0.039 and 0.156 mg/ml against Propionibacterium acnes and Staphylococcus epidermidis, respectively (Table 1).