Norlignans and Phenolics from Curculigo capitulata and Their Neuroprotection Against Glutamate-Induced Oxidative Injury in SH-SY5Y Cells

The herb <i>Curculigo capitulata</i> (Lour.) Ktze is widely distributed in southern and southwestern China. The <i>Curculigo</i> genus and its primary chemical constituents exhibit remarkable antidepressant activities. To investigate the chemical constituents and potential health benefits of <i>C. capitulata</i>, a phytochemical study was conducted. In this study, seven new compounds (capitugenin A-G), including three new norlignans (<b>1</b>-<b>3</b>), a new chalcone dimer (<b>4</b>), a new hemiacetal (<b>5</b>), two novel pyrrolidine-based compounds (<b>6</b> and <b>7</b>), including one identified as a natural product (<b>7</b>), and nineteen known compounds (<b>8</b>-<b>26</b>), were isolated from <i>C</i>. <i>capitulata.</i> The chemical structures and absolute configurations of Compounds <b>1</b>-<b>7</b> were elucidated via comprehensive spectroscopic data analyses. The neuroprotective effects of Compounds <b>1</b>-<b>26</b> against glutamate-induced cell death were tested in the human neuroblastoma cell line SH-SY5Y. Compounds <b>1</b>, <b>3</b>, <b>6</b>, <b>8</b>, <b>11,</b> and <b>17</b> showed significant neuroprotective effects, with protection rates ranging from 29.4 to 52.8% at concentrations ranging from 5 to 40 μM. Western blot analysis indicated that Compound <b>3</b> exerted a protective effect by regulating the expression of Nrf2/HO-1.