Use different concentrations of the compound (e.g. two fold serial dilution) to determine either MIC or MIC90 (or whatever percentage that is of interest to you). Perhaps the easiest first approach would be the microdilution method (in liquid) to see the efficacy of the compound - you will monitor optical density of the cells.

N-Bromosuccinimide (NBS) is a strong oxidizing and brominating agent widely used in organic chemistry, and because of its high reactivity it is toxic to living cells including bacteria. When added to a culture containing E. coli, Staphylococcus aureus, and Bacillus subtilis, NBS generates bromine radicals that damage DNA, proteins, and membranes, causing broad-spectrum toxicity that affects both Gram-negative and Gram-positive bacteria. At typical concentrations, NBS is expected to reduce colony forming units (CFU) by far more than 90%, essentially destroying or inactivating most of the culture. In microbiology, halogen-containing compounds such as chlorine, iodine, and bromine are well-known disinfectants, and NBS behaves similarly, meaning it is unsuitable for maintaining viable bacterial colonies but effective for sterilization or strong inhibition.