<p>Two new sesquineolignans, hawthornsesquinins K and L (<b>1</b> and <b>2</b>), were isolated from the seeds of <i>Crataegus pinnatifida</i>. Their structures were determined by spectroscopic analyses, including 1D, 2D NMR and HRESIMS data. All isolated compounds were tested for their <i>β</i>-amyloid aggregation inhibitory activity and neuroprotective effects against H<sub>2</sub>O<sub>2</sub>-induced damage in SH-SY5Y cells. The results indicated that compound <b>1</b> showed prominent inhibition of A<i>β</i><sub>1–42</sub> aggregation and significant neuroprotective effect on H<sub>2</sub>O<sub>2</sub>-induced cellular damage in SH-SY5Y cells.</p
