The current study was aimed to evaluate the prolyl endopeptidase (PEP) inhibitory activity of glutinol (1), azadiradione (2), quercetin 3-O-β-d-glactopyranoside (3), catechin (4), quercetin (5), naringenin (6) isolated from Parrotia persica C. A. Mey. Naringenin (6) was further derivatized into