Alkaloids of uncaria attenuata Korth

Abstract

Heteroyohimbine and oxindole alkaloids have been isolated from the leaves of Uncaria attenuate Korth. (Rubiaceae) by means of column chromatography. The isolated heteroyohimbines are tetrahydroalstonine, and rauniticine which has never been reported as being present in this genus before. Physical and chemical properties including chemical transformations of these two alkaloids are studied. One novel heteroyohimbine, not previously been reported elsewhere either naturally or synthetically, has been obtained. From the physical and chemical properties being studied, it is assigned as 14-hydroxy-3- isorauniticine. A detailed discussion on the elucidation of chemical structure is included. Only small quantities of two oxindoles have been obtained and traces of another oxindole is revealed. A discussion of the so far reported alkaloidal content of the genus Uncaria is presented.