Two Novel Norwithasteroids with Unusual Six- and Seven-Membered Ether Rings in Side Chain from Flos Daturae

Chemical investigation of 50% ethanol eluate fraction of macroporous resin for the flower of Datura metel L. collected in Jiangsu province of China resulted in the isolation of two novel naturally occurring norwithasteroids, baimantuoluoline I (1) and baimantuoluoside J (2). Their structures were elucidated as 5α, 6β, 12β-trihydroxy-1-oxo-2-en-ergosta-21,24;22,29-diepoxy-26-carboxylic acid (1) and 5α, 6β, 12β, 25-tetrahydroxy-1-oxo-2-en-ergosta-21,24;22,29-diepoxy-26-carboxylic acid (2) on the basis of extensive spectroscopic analysis, including 1D, 2D-NMR, and HR-ESI-MS. According to the literatures, this study represents the first report of the norwithasteroids in the side chain with unusual six- and seven-membered ether rings instead of those with an unmodified skeleton (δ-lactone or δ-lactol side chain) and a modified skeleton (γ-lactone or γ-lactol side chain) in the family of withanolides. Meanwhile, compounds 1 and 2 were evaluated for their immunosuppressive activity against mice splenocyte proliferation in vitro.