Nostotrebin 6, a bis(cyclopentenedione) with cholinesterase inhibitory activity isolated from Nostoc sp. str. Lukesová 27/97.

Nostotrebin 6, a new polyphenolic compound with a fully substituted 2,2'-bis(cyclopent-4-en-1,3-dione) skeleton, was isolated from a methanolic extract of the cyanobacterial strain Nostoc sp. str. Lukesová 27/97. The structure of this compound was determined using X-ray crystallography and further supported by NMR, IR spectroscopy, and MS. Nostotrebin 6 is an S-parabolic I-parabolic noncompetitive inhibitor of acetylcholinesterase (IC(50) = 5.5 microM) and an S-parabolic I-parabolic mixed inhibitor of butyrylcholinesterase (IC(50) = 6.1-7.5 microM). The inhibitory potency of nostotrebin 6 was compared with that of tacrine and galanthamine.