New quinoline alkaloids from Ruta chalepensis

The roots of Ruta chalepensis, collected from the northern Saudi desert, yielded two new quinoline alkaloids, namely, 2-{6'-(2H-benzo[d]1 ",3 "-dioxolen-5 "-yl)hexyl}-hydroquinolin-4-one (1) and 2-{6'-(2H-benzo[d]1 ",3 "-dioxolen-5 "-yl)hexyl}-4-methoxy-quinoline (2). Nine previously reported alkaloids, dictamnine, pteleine, skimmianine, rutacridone, isogravacridonechlorine, maculosidine, graveoline, graveolinine, and 4-methoxy-1-methyl-2(1H)-quinolinone, and coumarins, chalepensin, and umbelliferone were also isolated. Structure elucidations were based primarily on 1D and 2D NMR analyses and chemical transformations. Antimicrobial activity of these compounds is discussed.