Phytochemical investigation on the aerial parts of Uncaria perrottetii led to the isolation of three pentacyclic oxindole alkaloids uncarine A or isoformosanine (1), uncarine E or isopteropodine (2), and rauniticine-allo-oxindole A (3). Five oxindole alkaloids, isomitraphylline (4), mitraphylline (5), uncarine B or formosanine (6), uncarine F (7), corynoxine (8), and uncarine D or speciophylline (9), were isolated from the leaves of Uncaria lanosa f. philippinensis. Their structures were determined by spectroscopic techniques and in comparison with the literature data. These compounds proved to be important chemotaxonomic markers in the genus Uncaria. Keywords: Rubiaceae, Uncaria, Oxindole alkaloids, Chemotaxonomy, Uncarine