“…27) was developed back in the late 1950s; all of these drugs contained catechol groups, such as gallic acid (58), caffeic acid (59), U-0521 (60), 2-hydroxyoestrogen (61), and flavonoids like quercetin (62). However, there are numerous reports available, revealing the inhibition of COMT by some plant-derived alkaloids and phenolics (Abdel-Moty et al, 1998;Chaudhary et al, 2016Chaudhary et al, , 2018aChaudhary et al, , 2018bChaudhary et al, , 2019Chaudhary et al, , 2020El-Shorbagi et al, 2015Mohamed et al, 1993;Soliman et al, 2019;Vieira-Coelho et al, 1996). These drugs have undergone insufficient clinical trials, so they are not actually used as medicines due to unsatisfactory selectivity, toxicity, and disadvantageous pharmacokinetics (Backstrom et al, 1989;Ruottinen and Rinne, 1998).…”