*2.6. Determination of Antibacterial Activity*

The inhibitory effects of 67 spices were estimated according to the agar diffusion method as previously reported with slight modification [24]. The freeze-dried extracts were dissolved in DMSO to a final concentration of 100 mg/mL and filtered through 0.22 μm sterilizing filters. Briefly, all bacteria were diluted to about 1 <sup>×</sup> 106 CFU/mL with sterile LB medium, and then 100 <sup>μ</sup>L of each bacterial suspension was evenly spread onto the surface of LB agar plate by sterile glass beads (6 mm in diameter). Oxford cups (sterilized hollow cylinder with an inner diameter of 6 mm, outer diameter of 7.8 mm, and height of 10 mm) were placed lightly on the agar surface, and then 60 μL of the prepared samples (100 mg/mL) were delivered into the cups. DMSO (60 μL/cup) was used as a negative control. The plates were incubated at 37 ◦C for 24 h for bacterial growth in an incubator (BI-150A, Shanghai Stik Co., Ltd., Shanghai, China). The diameters of the inhibitory zones (DIZs) formed around the Oxford cups were measured to evaluate the antibacterial activity and expressed in millimeter (mm). All experiments were performed in triplicate. DIZ values less than 8 mm were considered as "no inhibition zone (NIZ)".
