Two New Oleanane-Type Saponins with Anti-Proliferative Activity from Camellia oleifera Abel. Seed Cake

Two new oleanane-type saponins, named oleiferasaponins C₄ (1) and C₅ (2), were isolated from Camellia oleifera Abel. seed cake residue. Their respective structures were identified as 16α-hydroxy-22α-O-angeloyl-23α-aldehyde-28-dihydroxymethylene-olean-12-ene-3β-O-[β-d-galacto-pyranosyl-(1→2)]-[β-d-glucopyranosyl-(1→2)-β-d-galactopyranosy-(1→3)]-β-d-glucopyranosid-uronic acid methyl ester (1) and 16α-hydroxy-22α-O-angeloyl-23α-aldehyde-28-dihydroxy-methylene-olean-12-ene-3β-O-[β-d-galactopyranosyl-(1→2)]-[β-d-galactopyranosyl-(1→3)]-β-d-glucopyranosiduronic acid methyl ester (2) through 1D- and 2D-NMR, HR-ESI-MS, and GC-MS spectroscopic methods. The two compounds exhibited potent cytotoxic activities against five human tumor cell lines (BEL-7402, BGC-823, MCF-7, HL-60 and KB).