Structural diversity of ecdysteroids of Lychnis flos-cuculi

摘要

Eleven ecdysteroids have been isolated from Lychnis floscuculi; we are the first who report eight ecdysteroids of the eleven compounds in this plant. Two of these ecdysteroids, dihydrorubrosterone and 20-hydroxyecdysone 3-acetate are newly discovered natural products. The success of isolation of these new ecdysteroids has been based on the use of separation methods in a proper order; these separation procedures were completing each others. At the beginning steps of isolation simple separation methods were used, such a solvent-solvent distribution and fractionated precipitation. Two third of the contaminants were removed thereby. High capacity low resolution methods were used then, such as classical adsorption column chromatography and preparative thin-layer chromatography. The major component (20-hydroxyecdyssone) and certain minor ecdysteroids (polypodine B and rubrosterone) were isolated in pure form here. Purification of the further minor components (poststerone, 2-deoxy-20-hydroxyecdysone, vitikosterone E, dihydrorubrosterone, makisterone A, taxisterone, 20-hydroxyecdysone 2-acetate, 20-hydroxyecdysone 3-acetate) required HPLC and other absorption chromatographic methods. Our recent separation scheme means a generally applicable guiding principle for isolation of any plant ecdysteroid, major and minor alike. Structural identification of the known ecdysteroids was based on their spectral data and that of their literature information. Structural elucidation of 20-hydroxyecdysone 3-acetate was done by the help of a standard component prepared by acetylation of 20-hydroxyecdysone. From the mixture of seven acetates the corresponding compound (20-hydroxyecdysone 3-acetate) was isolated, and used for identification. Structural diversity of ecdysteroids of Lychnis flos-cuculi is evaluated, and a tentative explanation is introduced for the formation and biosynthesis of the versatility of phytoecdysteroids.