Scuregeliolides a–C: new <i>neo</i> -clerodane diterpenoids from <i>Scutellaria regeliana</i> and their anti-inflammatory activities

Three new <i>neo</i>-clerodane diterpenoids, named scuregeliolides A<b>-</b>C (<b>1</b>-<b>3</b>), were isolated from the whole plant of <i>Scutellaria regeliana</i>. Their chemical structures, including absolute stereochemical configurations, were fully elucidated by means of integrated spectroscopic techniques and Electronic Circular Dichroism (ECD) calculations. <i>In vitro</i>, three undescribed <i>neo</i>-clerodane diterpenoids showed significant anti-inflammatory activities due to inhibiting the release of TNF-<i>α</i>, IL-6 and IL-1<i>β</i> in the LPS-induced RAW264.7 cells, as well as preventing the release of <i>β</i>-glucuronidase from the PAF-stimulated PMNs.