Isolation and structure assignment of an iminotetrasaccharide from a cultured filamentous cyanobacterium Anabaena sp

In search of bioactive metabolites in cultured microalgae, a novel acylated iminopseudotetrasaccharide was isolated from a filamentous cyanobacterium Anabaena sp., and its structure was established by NMR, chemical degradation, and X-ray crystallography. The compound consists of glucose, glucuronic acid, arabinose, and 1,4,6-trideoxy-1,4-imino-D-allitol, which is closely related to potent glucosidase inhibitors such as nojirimycin. The tetrasaccharide itself showed moderate inhibitory activity against beta-D-glucuronidase.