Isolation of glycosidase-inhibiting hyacinthacines and related alkaloids from Scilla socialis

An examination of the bulbs of Scilla socialis has resulted in the isolation of 11 hyacinthacines, two pyrrolidines, and three piperidines. The structures of the new alkaloids were elucidated by spectroscopic methods as β-1-C-ethyldeoxymannojirimycin (5), hyacinthacines B₇ (10), C₂ (11), C₃ (12), C₄ (13), and C₅ (14), and α-5-C-(3-hydroxybutyl)-hyacinthacine A₂ (15). Although, β-L-homofuconojirimycin (3) and α-7-deoxyhomonojirimycin (α-7-deoxy-HNJ, 4) are previously known alkaloids, this is the first report of their occurrence in the plant family Hyacinthaceae. Alkaloid 11 was found to be a good inhibitor of bacterial β-glucosidase and human placenta α-L-fucosidase, with IC₅₀ values of 13 and 17 μM, respectively, while alkaloid 12 showed no inhibitory activity toward α-L-fucosidase but was a more potent inhibitor of bovine liver β-galactosidase (IC₅₀ = 52 μM) than 11. Alkaloids 13 and 14 were shown to be inhibitory toward mammalian α-glucosidase (IC ₅₀ = 45 and 77 μM, respectively), and alkaloid 14 was demonstrated as a moderate inhibitor of bacterial β-glucosidase (IC₅₀ = 48 μM).