New pregnane-type steroidal alkaloids from Sarcococca saligna and their cholinesterase inhibitory activity

Five new steroidal alkaloids, 5,14-dehydro-Na-demethylsaracodine [3β-Na-methyl-20S-Nb-acetyl-Nb-methylamino-pregn-5,14-diene] (1), 14-dehydro-Na-demethylsaracodine [3β-Na-methyl-20S-Nb-acetyl-Nb-methylamino-5α-pregn-14-ene] (2), 16-dehydrosarcorine [(20S)-20-(N,N-dimethylamino)-3β-(Na-acetylamido)-5α-pregn-16-ene] (3), 2,3-dehydrosarsalignone [(20S)-20-(N,N-dimethylamino)-3β-(tigloylamino)-pregn-2,5-diene-4-one] (4), and 14,15-dehydrosarcovagine-D [(20S)-20-(N,N-dimethylamino)-3β-(tigloylamino)-5α-pregn-2,14-diene-4-one] (5), were isolated from the ethanolic extract of Sarcococca saligna, along with two known bases, sarcovagenine-C (6) and salignarine-C (7). Their structures were elucidated on the basis of spectroscopic methods. All seven compounds were found to possess cholinesterase inhibitory potential in a concentration-dependent manner with the IC50 values ranging from 12.5 to 200 μM against acetylcholinesterase and from 1.25 to 32.2 μM against butyrylcholinesterase.