Xanthones and flavonoids from Leiothrix curvifolia and Leiothrix flavescens.

8-Carboxymethyl-1,6-dihydroxy-3,5-dimethoxyxanthone, 8-carboxymethyl-1,5,6-trihydroxy-3-methoxyxanthone and 8-carboxymethyl-1,3,5,6-tetrahydroxyxanthone were isolated from the capitula of Leiothrix curvifolia and Leiothrix flavescens and characterized by spectroscopic methods, mainly 1D and 2D NMR experiments, as well as by electrospray mass spectrometry. Eight known flavonoids were also isolated and they were identified by 1D and 2D NMR experiments and comparison with literature data.

Starfish saponins, 52. Chemical constituents from the starfish Echinaster brasiliensis.

This paper reports an analysis of the chemical constituents from the Caribbean starfish Echinaster brasiliensis collected at Grand Bahama Island. This species is completely devoid of cyclic steroidal glycosides, previously isolated from two species of the genus Echinaster in place of the more common penta- and hexa-glycoside steroidal sulfates ("asterosaponins"). Two typical "asterosaponins" and ten glycosides of polyhydroxysteroids were instead isolated in relatively large amounts from E. brasiliensis. The asterosaponins include the known marthasteroside A1 [1] and the new brasiliensoside [2], while the glycosides of polyhydroxysteroids include seven new compounds (six monoglycosides and one diglycoside). The known echinasteroside A, previously found in Echinaster sepositus and in the related Henricia laeviuscula (both belonging to the family Echinasteridae), and laeviusculosides C and I from H. laeviuscula were also isolated. Most of the glycosides from E. brasiliensis are 3-O-beta-xylopyranosides of delta 4-3 beta,6 beta,8,15 alpha,16 beta pentahydroxysteroid aglycones, having different side chains and sometimes a sulfate group at C-15, structural features which are typical of steroidal glycosides from starfishes of the family Echinasteridae. Continuing the analysis of the constituents of E. brasiliensis, we have also isolated a series of anthraquinones, known animal pigments found only in echinoderms and particularly in Crinoidea and in the Echinasteridae family of Asteroidea.