Pannorin isolated from marine Penicillium sp. SG-W3: a selective monoamine oxidase A inhibitor

Six compounds were isolated from Penicillium sp. SG-W3, a marine-derived fungus, and their inhibitory activities against target enzymes relating to neurological diseases were evaluated. Compound 1 (pannorin) was a potent and selective monoamine oxidase (MAO)-A inhibitor with a 50% inhibitory concentration (IC₅₀) of 1.734 μM and a selectivity index (SI) of > 23.07 versus MAO-B, and it showed an efficient antioxidant activity. All compounds showed weak inhibitory activities against acetylcholinesterase, butyrylcholinesterase, and β-secretase. The inhibition constant (K_i) of 1 for MAO-A was 1.049 ± 0.030 μM with competitive inhibition. Molecular docking simulation predicted that compound 1 forms hydrogen bonds with MAO-A, and binds more tightly to MAO-A than to MAO-B (− 25.02 and − 24.06 kcal/mol, respectively). These results suggest that compound 1 is a selective, reversible, and competitive MAO-A inhibitor that can be a therapeutic candidate for treating neurological diseases.