Novel Triterpene Saponins from Zizyphus joazeiro

Two dammarane-type saponins with a novel aglycone derived from the parent 16,22-epoxy-24-methylidenedammarane and lotoside A, a new lotogenin derivative, were isolated from the MeOH extract of the stem bark of the Brazilian medicinal plant Zizyphus joazeiro, in addition to the known saponin 3β-{{O-[O-[α-L-arabinofuranosyl-(1→2)]-O-[β-D-glucopyranosyl-(1→3)]]-α-L-arabinopyranosyl}oxy}jujubogenin (1). The structures of the new compounds were determined as 16,22-epoxy-3β-[(β-D-glucopyranosyl)oxy]-24-methylidenedammarane-15α,16α,20β-triol (2), 16,22-epoxy-3β-{{O-[O-[β-D-glucopyranosyl-(1→2)]-O-[β-D-apiofuranosyl-(1→3)]]-β-D-glucopyranosyl-(1→2)-α-L-arabinopyranosyl}oxy}-24-methylidenedammarane-15α,16α,20β-triol (3), and 3β-{{O-[O-[β-D-glucopyranosyl-(1→2)]-O-[β-D-apiofuranosyl-(1→3)]]-β-D-glucopyranosyl-(1→2)-α-L-arabinopyranosyl}oxy}lotogenin (4) by means of 1D- and 2D-NMR spectroscopy, as well as FAB mass spectrometry. For the novel aglycone, we propose the name joazeirogenin and, for the new saponins, joazeiroside A (2) and B (3). Joazeirogenin was found to be 16,22-epoxy-24-methylidenedammarane-3β,15α,16α,20β-tetrol.