(2'R,3a'R,4'S,7a'R)-4'-羟基-2',4',6'-三甲基-3'-氧代-2',3',3a',4'-四氢螺[环丙烷-1,5'-茚]-7a'(1'H)-基beta-D-吡喃葡萄糖苷

Ptaquiloside is the major toxin of bracken, and was first isolated in 1983. Its chemical stereostructure was determined to be norsesquiterpene glucoside of illudane type by Yamada and co-workers.