Bioactive triterpenoids from the leaves of <i>Eriobotrya japonica</i> as the natural PDE4 inhibitors

<p>The ethanolic extract of the leaves of <i>Eriobotrya japonica</i> exhibited inhibitory activity against phosphodiesterase-4D (PDE4D), which is a therapeutic target of inflammatory disease. Subsequent bioassay-guided fractionation led to the isolation of a new triterpene (<b>1</b>), together with seven known triterpenoids, methyl corosolate (<b>2</b>), ursolic acid (<b>3</b>), oleanolic acid (<b>4</b>), methyl maslinate (<b>5</b>), <i>α</i>-amyin (<b>6</b>), 3<i>β</i>,19<i>α</i>,23-trihydroxy-urs-12-ene (<b>7</b>) and uvaol (<b>8</b>). The structure of compound <b>1</b> was established as 3<i>β</i>-hydroxyl-21<i>β</i>-acetoxyl-urs-12-en-28-carboxylate on the basis of interpretation of its 1D and 2D NMR and HR-ESI-MS spectroscopic data. The bioassay results verified compounds <b>2</b>, <b>3</b> and <b>8</b> inhibited PDE4D2 effectively with the IC₅₀ values of 3.06, 2.18 and 5.17 μM, respectively, which may provide a novel mechanism for the anti-inflammatory activity of the leaves of <i>E.</i> <i>japonica.</i></p