TB5 is a potent, selective and reversible inhibitor of hMAO-B.

TB5 and TB8 interacts with the catalytic site of hMAO-B and hMAO-A with a competitive mode of inhibition. TB5 exhibits the best inhibitory activity and higher selectivity toward hMAO-B, with Ki and SI values of 0.11±0.01 μM and 13.18, respectively. hMAO-B inhibition by compound TB5 and hMAO-A inhibition by compound TB8 are completely reversed after 24 h of dialysis. Cytotoxicity studies show TB5 is nontoxic at 5 and 25 μM with cell viabilities of 95.75% and 84.59 %, respectively[1].

Compounds are initially dissolved in DMSO (5 mg/mL), then further diluted with a PBS/EtOH mixture (70:30). To elucidate the critical interactions dictating selectivity and potency, kinetic analyses of TB5 and TB8 are conducted. Lineweaver–Burk plots, a total of five, are created to compare the catalytic rates of MAO-B and MAO-A at various substrate concentrations (0.1-1 μM) in both the absence and presence of TB5 and TB8 at differing concentrations. The initial plot reveals the baseline enzyme activity without inhibitors, while the subsequent four plots show the impact of varying concentrations of TB5 and TB8[1].

Compounds are dissolved in DMSO (5 mg/mL) and diluted with PBS/EtOH (70:30).Kinetic analyses are carried out for TB5 and TB8. A set of Lineweaver–Burk plots are constructed in the absence and presence of various concentrations of compounds TB5 and TC8. The set consists of five graphs, each constructed by measuring MAO-B and MAO-A catalytic rates at different substrate concentrations (0.1-1 μM). The first Lineweaver–Burk plot is constructed in the absence of inhibitor, while the remaining four graphs are constructed in the presence of different concentrations of TB5 and TB8[1].

In vitro cytotoxicity of brominated thiophene chalcones and standard MAO inhibitors are tested in human HepG2 hepatic cancer cells at three different concentrations (1, 5 and 25 μM)[1].