Utilization of the By-Product of Corn: Guided Identification of Bioactive Terpenoids from <i>Stigma Maydis</i> (Corn Silk)

Abstract

<i>Stigma maydis</i> (corn silk) (<i>S. maydis</i>) is a food-based by-product of maize and possesses great nutritional and pharmaceutical value. This study aimed to explore bioactive components from <i>S. maydis</i>. By the guidance of bioactivity-guided approach and Global Natural Products Social (GNPS) molecular networking, 12 terpenoids were discovered from <i>S. maydis</i>. The structures of 11 undescribed compounds (<b>1</b>-<b>11</b>) were determined by detailed spectroscopic analyses, single-crystal X-ray diffraction analysis, specific rotation calculations, electronic circular dichroism (ECD) calculations, and NMR calculations. The neuroprotective and acetylcholinesterase (AChE) inhibitory effects of <b>1</b>-<b>12</b> were examined, and most of them showed significant or moderate activities. The underlying neuroprotective mechanism of <b>4</b> and <b>5</b> was revealed by Hoechst 33258, AO-EB, and JC-1 staining assays. This work illustrated the potential of <i>S. maydis</i> as a prospective natural source of bioactive compounds in food and pharmaceutical industries.