From the trunk bark of Balfourodendron riedelianum (Engler) Engler (Rutaceae) the chloride and the perchlorate of the new quaternary alkaloid ribalinium (I) have been isolated. According to functional groups analyses and UV absorption, I contains a 2,4-dialkoxy-1-methyl-quinolinium moiety (A), and the presence of a linerly fused oxygenated ring is indicated by the 4-quinolone nature of the nor-base (V) obtained by dequaternization of O-methylribalinium (IV). Coupled mass and NMR spectrometry established the oxygenated ring as 20-substituted-dihydro-furane; the side chain, an α-hydroxylated isopropyl fragment was proved by combined chemical, IR and NMR data. Finally, location of the phenolic function at position-6 by NMR measurements of I and V have led to the complete structure of the ribalinium cation. © 1965.