Diterpenoids with anti-inflammatory activities from Isodon rubescens

Nine previously undescribed diterpenoids, namely, Henanabinins A-I (1-9), and 14 known analogues (10-23), were isolated from the aerial part of Isodon rubescens. Henanabinins A-C (1-3) were classified as ent-abietane diterpenoids, whereas Henanabinins DI (4-9) as ent-kaurane diterpenoids. Their structures were elucidated through extensive and mass spectrometric analyses. The structure of compound 1 was further confirmed by single- crystal X-ray diffraction, enabling the determination of its absolute configuration. The anti-inflammatory activities of all isolated diterpenes were evaluated using a lipopolysaccharide stimulated RAW264.7 cell model. Compound 10 (rubescensin B) inhibited NF-κB nuclear translocation with an IC₅₀ value of 3.073 μM. Additionally, it showed no cytotoxicity at a concentration of 12.5 μM.