Six insecticidal isoryanodane diterpenoids from the bark and twigs of Itoa orientalis

Four rare isoryanodane diterpenoids namely itols A–D (1–4) and two isoryanodane glucosides (5 and 6) were isolated from the bark and twigs of Itoa orientalis. Their structures were determined by NMR and MS techniques and the structure of 1 was confirmed by a single-crystal X-ray diffraction. These six diterpenoids obviously showed insecticidal activity against Spodoptera exigua, with LC50 28.62 ppm for 1 and 52.76 ppm for 2, respectively. In anti-inflammatory assay, compounds 1 and 4–6 showed anti-COX-2 activity, with inhibitory rates of 54.7–78.3% at 10 μM.