Jusbetonin, the first indolo[3,2-b]quinoline alkaloid glycoside, from Justicia betonica

A new indolo[3,2-b]quinoline alkaloid glycoside, jusbetonin (1), and three known alkaloids, namely, 10H-quindoline (2), 6H-quinindoline (3), and 5H,6H-quinindolin-11-one (4), have been isolated from the leaves of Justicia betonica. The structure of 1 was established on the basis of 1D and 2D NMR ((1)H-(1)H COSY, HMQC, and HMBC) and HRFABMS data. Compound 1 is the first example of a glycosylated indolo[3,2-b]quinoline alkaloid, while compound 4 was isolated for the first time from a natural source.