Six naphthylisoquinoline alkaloids and a related benzopyranone from a Congolese Ancistrocladus species related to Ancistrocladus congolensis

Two 5,1′- and four 5,8′-coupled naphthylisoquinoline alkaloids were isolated from a recently discovered Ancistrocladus species related to Ancistrocladus congolensis, along with a yet unknown benzopyranone. From the roots of a recently discovered Ancistrocladus taxon, with close affinities to Ancistrocladus congolensis regarding molecular ITS sequence data, six naphthylisoquinoline alkaloids, 5′- O-demethylhamatine ( 2), 5′- O-demethylhamatinine ( 3), 6- O-demethylancistroealaine A ( 4), 6,5′- O, O-didemethylancistroealaine A ( 5), 5- epi-6- O-methylancistrobertsonine A ( 6), and 5- epi-4′- O-demethylancistrobertsonine C ( 7), have been isolated, along with a likewise benzopyranone carboxylic acid, 8. The structural elucidation succeeded by chemical, spectroscopic, and chiroptical methods. Their bioactivities were tested against protozoan parasites causing severe tropical diseases. Furthermore, eight known related alkaloids were identified.