Inhibitory Effect of Verbascoside Isolated from Buddleja Brasiliensis Jacq. Ex Spreng on Prolyl Oligopeptidase Activity

The phenylpropanoid glycoside verbascoside [2‐(3,4‐dihydroxyphenylethyl)‐1‐O‐α‐l‐rhamnopyranosyl‐(1→3)‐β‐d‐(4‐O‐caffeyl)‐glucopyranoside] (1) has been isolated as the main constituent of the crude extract of Buddleja brasiliensis Jacq. ex Spreng from Southern Brazil. The crude extract, main fractions and the compound 1 were evaluated for inhibition of the enzymes acetylcholinesterase (AChE), dipeptidyl peptidase‐IV (DPP‐IV) and prolyl oligopeptidase (POP). Compound 1 showed weak activity against DPP‐IV with an IC50 >> 150 µm and was inactive against AChE, with a pMIQ determined by bioautography of 9.6. In contrast, 1 displayed significant inhibition of POP in a dose‐dependent manner with an IC50 value of 1.3 ± 0.2 µm, similar to the positive control, baicalin, with a POP IC50 of 12 ± 3 µm. Copyright © 2012 John Wiley & Sons, Ltd.