Novel ceramides and a new glucoceramide from the roots of Incarvillea arguta

Novel ceramides, rel‐(3S,4S,5S)‐3‐[(2R)‐2‐hydroxycosanoyl‐hexacosanoylamino]‐4‐hydroxy‐5‐[(4Z)‐tetradecane‐4‐ene]‐2,3,4,5‐tetrahydrofuran (1a‐g), and a new glucoceramide, 1‐O‐β‐d‐glucopyranosyl‐(2S,3S,4R,8E)‐2‐[(2R)‐2‐hydroxytetracosanoylamino]‐1,3,4‐octodecanetriol‐8‐ene (2) were isolated from the aqueous ethanolic extract of the roots of Incarvillea arguta, together with eight known compounds: β‐sitosterol (3), oleanolic acid (4), ursolic acid (5), piperin (6), maslinic acid (7), β‐sitosterol 6′‐O‐acyl‐β‐d‐glucopyranoside (8), 8‐epideoxyloganic acid (9), and plantarenaloside (10). Their structures were elucidated on the basis of spectral data including IR, MS, NMR [1H NMR, 13C NMR (distortionless enhancement by polarization transfer), 1H−1H COSY, heteronuclear multiplequantum coherence, and heteronuclear multiple‐bond coherence correlations]. The relative configurations were established by nuclear Overhauser effect spectroscopy experiments and by comparison of the NMR spectral data and coupling constants with those already reported in the literature.