On the Constituents of Picrorhiza kurrooa. (1). The Structure of Picroside I, a Bitter Principle of the Subterranean Part

A new bitter iridoid glucoside named picroside I has been isolated from the subterranean part of Picrorhiza kurrooa ROYLE ex BENTH. (Scrophulariaceae) in addition to mannitol and vanillic acid, and the structure of picroside I has now been established as II (6'-O-t-cinnamoyl-catalpol) on the basis of chemical and physicochemical evidences. In addition, the re-examination concerning the stereostructure of catalpol has been performed and the correctness of the proposed structure (IV) has been re-confirmed.