Chemical Constituents of Gentianaceae XX: Natural Occurrence of (—)-Loliolide in Canscora Decussata

(—)-Loliolide was isolated as a native compound from Canscora decussata Schult (Gentianaceae). Physical and spectral (UV, IR, PMR, CMR, and mass spectra) properties of the compound and its acetate derivative established its identity. The significance of the cooccurrence of loliolide with a number of carotenoids in C. decussata and the facile transformation of violaxanthin into loliolide and violoxin are discussed in the light of the biogenesis of the degraded carotenoid.