Eleven highly oxygenated and anti-inflammatory guaian-8,12-olides from Hedyosmum orientale

Eleven previously undescribed guaian-8,12-olides, hedyolides A‒K (1−11) featuring a characteristic 5,7,5-fused tricyclic and possessing different degrees of unsaturation and oxygen substitution patterns, were isolated from the leaves and twigs of Hedyosmum orientale. In particular, compounds 6 and 10 are rare chlorinated guaianolides of plant origin. Their structures and absolute configurations were elucidated by a combination of spectroscopic analysis, quantum chemical calculations, DP4+ probability, and single-crystal X-ray diffraction. All compounds exhibited inhibitory effects on nitric oxide production in lipopolysaccharide-induced RAW 264.7 macrophages with IC50 values ranging from 1.22 to 6.51 μM.