ent-Kaurane diterpenoids from Isodon henryi and their anti-inflammatory activities

Phytochemical investigation of the 70% ethanol extract of Isodon henryi Kudo afforded fifteen ent-kaurane diterpenoids, including nine previously undescribed compounds, named isohenolides C-K (1-9). 1 - 9 ). Compounds 1 - 6 featured an unusual 6,7;8,15-diseco-7,20-olide ent-kaurane diterpenoid scaffold, in which 1 also possessed an 11,15-lactone ring while 2 - 6 all contained a free alpha-methylene-gamma-carboxylic acid. Compound 6 was also a rare 6,8cyclo-7,20-olide ent-kauranoid. Their structures were elucidated primarily by HRESIMS, 1D and 2D NMR spectroscopy, electronic circular dichroism and X-ray diffraction (Cu K alpha) methods. Additionally, most compounds were also screened for anti-inflammatory actions against lipopolysaccharide-induced RAW 264.7 cells, and compounds 9 and 13 exhibited stronger nitric oxide inhibition, with IC50 50 values of 15.99 +/- 0.75 and 18.19 +/- 0.42 mu M, respectively.