Diverse epoxy grayanane diterpenoids with analgesic activity from the roots of Pieris formosa.

Abstract In our on-going study to investigate components with analgesic activity, eight new grayanane diterpenoids, epoxypieristoxins A–H (1 – 8), along with one known compound (9) were isolated from the roots of Pieris formosa. Their structures with absolute configurations were characterized by a series of spectroscopic methods and X-ray diffraction. Notably, compounds 1 – 5 represented the first example of natural grayanane diterpenoids possessed a 10,14-epoxy group. Whereas, compounds 6 – 7 were the first example of grayanane diterpenoid with a 7,10-epoxy group. Biological assays showed that compounds 1 – 3 and 5 – 8 displayed significant analgesic activity at a dose of 5.0 mg/kg (ip) compared to the vehicle tests (p <.05). Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]