Isolation and structural characterization of an iridoid glycoside and a pyridine derivative, both previously undescribed, from the flowers of <i>Rhododendron decorum</i>

An iridoid glycoside, rhododeoside C (<b>1</b>), and a pyridine derivative, rhododeodine A (<b>2</b>), both previously undescribed, were isolated from the flowers of <i>Rhododendron decorum</i>. The structures were elucidated using 1D and 2D NMR spectroscopy, along with high-resolution electrospray ionization mass spectrometry (HRESIMS). The absolute configurations of both compounds were unambiguously assigned using electronic circular dichroism (ECD) computational methods. Furthermore, all isolated compounds were assessed for their cytotoxic activities against HepG2 and HeLa cell lines.