New Sugar-Mimic Alkaloids from the Pods of Angylocalyx pynaertii

Chromatographic separation of the pod extract of Angylocalyx pynaertii resulted in the isolation of 13 sugar-mimic alkaloids (1−13). The structures of the new alkaloids were elucidated by spectroscopic methods as the 6-O-β-d-glucoside (10) and N-hydroxyethyl derivative (11) of 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) (1), 1,6-dideoxynojirimycin (12), and 1,3,4-trideoxynojirimycin (13). 2,5-Imino-1,2,5-trideoxy-l-glucitol (7), 2,5-dideoxy-2,5-imino-d-fucitol (8), and β-homofuconojirimycin (9), isolated from the pods as well as the bark, were very specific inhibitors of α-l-fucosidase with no significant inhibitory activity toward other glycosidases. In this work, 1,4-dideoxy-1,4-imino-d-ribitol (6) was found to be a better inhibitor of lysosomal β-mannosidase than 2,5-imino-1,2,5-trideoxy-d-mannitol (2). N-Hydroxyethyl-1-deoxynojirimycin (miglitol), which is commercially available for the treatment of diabetes, retained its inhibitory potential toward rat intestinal maltase and sucrase, whereas 11 and the synthetic N-hydroxyethyl derivative of 2,5-dideoxy-2,5-imino-d-mannitol markedly lowered or abolished their inhibition toward all enzymes tested.