MAO-A inhibitor 2 (compound HT4) is a monoamine oxidase A ( MAO-A ) inhibitor with an IC 50 of 14.3 µM. MAO-A inhibitor 2 shows a less effect on MAO-B (IC 50 of 106 µM) and shows almost ineffective on xanthine oxidase (XO). MAO-A inhibitor 2 can be used for the neurodegenerative disorders and oxidative stress research.