Two new steroidal saponins from Selaginella uncinata (Desv.) Spring and their protective effect against anoxia

Four steroidal saponins were isolated from the anti-anoxic fraction of the 60% EtOH extract of Selaginella uncinata, including two new compounds, (3β, 7β, 12β, 25R)-spirost-5-ene-3, 7, 12-triol-3-O-α-L-rhamnopyranosyl-(1→2)-O-[α-L-rhamnopyranosyl-(1→4)]-O-β-D-glucopyranoside (1), (2α, 3β, 12β, 25R)-spirost-5-ene-2, 3, 12-triol-3-O-α-L-rhamnopyranosyl-(1→2)-O-[α-L-rhamnopyranosyl-(1→4)]-O-β-D-glucopyranoside (2) and two known compounds, (3β, 12β, 25R)-spirost-5-ene-3,12-diol-3-O-α-L-rhamnopyranosyl-(1→2)-O-[α-L-rhamnopyranosyl-(1→4)]-O-β-D-glucopyranoside, (3), (1α, 3β, 25R)-spirost-5-ene-2-diol-3-O-α-L-rhamnopyranosyl-(1→2)-O-[α-L-rhamnopyranosyl(1→4)]-O-β-D-glucopyranoside (4). The four compounds showed potent protective effect against anoxia in the anoxic PC12 cells assay, among which compounds 1 and 2 were the most active. To our knowledge, this is the first study to report the steroidal saponins in the plant S. uncinata and demonstrate their protective effect against anoxia in PC12 cell assay.