Novel triterpene saponins from Zizyphus joazeiro

Two dammarane-type saponins with a novel aglycone derived from the parent 1 6,22-epoxy-24-methylidenedammarane and lotoside A, a new lotogenin derivati ve, were isolated from the MeOH extract of the stem bark of the Brazilian m edicinal plant Zizyphus joazeiro, in addition to the known saponin 3 beta-( (O-[O-[alpha-L-arabinofuranosyl-(1 --> 2)]-O-[beta-D-glucopyranosyl-(1 --> 3)]]-alpha-L-arabinopyranosyl)oxy))ujubogenin (1). The structures of the ne w compounds were determined as 16,22-epoxy-3 beta-[(beta l-D-glucopyranosyl )oxy]-24-methylidenedammarane-15 alpha,16 alpha,20 beta-triol (2), 16,22-ep oxy-3 beta-((O-[O-[beta-D-glucopyranosyl-(1 --> 2)]-O-[beta-D-apiofuranosyl -(1 --> 3)]]-beta-D-glucopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl)oxy)- 24-methylidenedammarane-15 alpha,16 alpha,20 beta-triol (3), and 3 beta-((O -[O-[beta-D-glucopyranosyl-(1 --> 2)]-O-]beta-D-apiofuranosyl-(1 --> 3)]]-b eta-D-glucopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl)oxy)lotogenin (4) b y means of 1D- and 2D-NMR spectroscopy, as well as FAB mass spectrometry. F or the novel aglycone, we propose the name joazeirogenin and, for the new s aponins, joazeiroside A (2) and B (3). Joazeirogenin was found to be 16,22- epoxy-24-methylidenedammarane-3 beta,15 alpha,16 alpha,20 beta-tetrol.