Nimbandiolactone-21 and nimbandioloxyfuran, two new 28-norlimonoids from the leaves of <i>Azadirachta indica</i> (Meliaceae)

<p>From an EtOAc-soluble fraction of the leaves of <i>Azadirachta indica</i>, two new 28-norlimonoids named nimbandiolactone-21 (<b>1</b>) and nimbandioloxyfuran (<b>2</b>), together with nimbandiolactone-23 (<b>3</b>), were isolated. Their relative structures were elucidated based on NMR spectroscopic interpretation and biosynthetic consideration. Nimbandioloxyfuran (<b>2</b>) and nimbandiolactone-23 (<b>3</b>) showed potent <i>α</i>-glucosidase inhibitory activity, with the IC₅₀ values of 46.2 and 38.7 <i>μ</i>M, respectively.</p