Effect of oxindole alkaloids from the hooks of Uncaria macrophylla on thiopental-induced hypnosis.

Four tetracyclic oxindole alkaloids, rhynchophylline, isorhynchophylline, corynoxine and corynoxine B were isolated from the hooks of Uncaria macrophylla Wall. (Rubiaceae), that is a dominant plant widely distributed in Yunnan province. These compounds exhibited prolongation of the thiopental-induced hypnosis on oral administration in mice.