Investigations On Tremulane Sesquiterpenoids From The Fungus Conocybe Siliginea:Structures And Biological Activities

Conocybe siliginea is a fungus of the genus Conocybe in the family Bolbitiaceae.It mainly grows in the forest land in Sichuan and other places in China on Summer and Autumn.Previous chemical investigations on this fungus have led to the identification of a series of tremulane-type sesquiterpenes,like conocenols A–D and 5,6-seco-tremulane sesquiterpenoids.Some of them were found to possess vascular-relaxing and 11β-hydroxysteroid dehydro-genase inhibitory activities(11β-HSD).In addition,a novel sesquiterpene,conosilane A,was isolated from the scale-up fermentation of C.siligine.Conosilane A was a tremulane sesquiterpene with highly oxygenated tetracyclic ring system,which had significant 11β-hydroxysteroid dehydrogenase inhibitory activity(11β-HSD).At present,there have been studies on the total synthesis of conosilane A and synthesis of both enantiomers of conosilane A.Our research group has long been focused on the secondary metabolites from higher fungi and their bioactivities.In order to search for more new and bioactive compounds from higher fungi,53 compounds,including 31 new ones,were isolated from the fermentation broths(80L)of Conocybe siliginea by varied chromatographic methods,and their structures were established on the basis of extensive spectroscopic analysis(including 1D and 2D NMR,MS,UV,IR,and single crystal X-ray diffraction analyses).The compounds isolated are tremulane sesquiterpenes,furan derivatives,steroids,cyclic dipeptides,benzene ring derivatives,etc.Some Tremulane sesquiterpenes were screened for their cytotoxic activity and lymphocyte toxicity and proliferation inhibitory activity.It was found that compound 22 had a significant inhibitory activity on T cell proliferation,and the selection coefficient was ideal and the toxicity was low.