Six samples of Uncaria elliptica leaves from Thailand were investigated for their alkaloid content. Seven diastereoisomers of the pentacyclic heteroyohimbine series of alkaloids, 14-β-hydroxy-3-isorauniticine and tetrahydroalstonine N-oxide were isolated. Rauniticine oxindole A, rauniticine pseudoindoxyl, 3-isorauniticine pseudoindoxyl and akuammigine pseudoindoxyl were isolated for the first time as natural products. The roxburghine alkaloids, previously isolated from U. elliptica, were not detected and the species is more varied chemically than was hitherto supposed. The 1H NMR spectra of the eight diastereoisomeric pentacyclic heteroyohimbine alkaloids have been compared. © 1983.