Separation and NMR studies on lignans of Raulinoa echinata.

Investigation of the leaves of Raulinoa echinata Cowan (Rutaceae) has led to the isolation of several furofuran (2,6-diaryl-3,7-dioxabicyclo[3.3.0]-octane) lignan derivatives, namely (+)-sesamin, (+)-eudesmin, (+)-methylpiperitol (= kobusin), (+)-piperitol-gamma,gamma-dimethylallylether and the corresponding epi compounds: (+)-asarinin, (+)-epieudesmin, (+)-methylxanthoxylol, (+)-methylpluviatilol, (+)-xanthoxylol-gamma,gamma-dimethylallylether and (+)-pluviatilol-gamma,gamma-dimethylallylether. This is the first report of the chromatographic separation of the epimers (+)-methylxanthoxylol/(+)-methylpluviatilol and (+)-xanthoxylol-gamma,gamma-dimethylallylether/(+)-pluviatilol-gamma,gamma- dimethylallylether and of their NMR nOe difference studies.