The root bark of Evodia grauca Miq. (Rutaceae) has yielded a series of new bitter limonoids, graucin A, B and C, with limonin and rutaevin. Extensive ^1H NMR studies including Homonuclear J-correlation techniques allowed us to assign all of the peaks in the complex spectra and derive the structures: graucin A; 12α-hydroxylrutaevin, graucin B; 6α-acetoxyllimonin and graucin C; limonin diosphenol. NOE difference spectra of limonin exhibited that irradiation of the axial 8β-Me peak induced 13.5% NOE in 15α-H signal. Similar NOE in 15-H signal was also observed in another limonin-type compounds.
