The alkaloid adifoline, from the heartwood of Adina cordifolia (m.p. > 350°), was previously shown by Cross et al. to be a β-carboline derivative with the suggested formula C₁₂H₁₀N₂O₄. We have now determined its structure (1) based on chemical and spectroscopic evidence, of which the main points are outlined. Adifoline has the molecular formula C₂₂H₂₄N₂O₇, containing one C-methyl group, one O-methyl group (present in a methoxycarbonyl group, removable by hydrolysis), a carboxy-group, and two phenolic and/or enolic functions, as indicated by methylation, acetylation, and reduction reactions. Reduction of adifoline with sodium borohydride lost a UV chromophore at 236 mμ and IR bands at 1640 and 1613 cm⁻¹, while trimethyladifoline was unaffected, consistent with a β-alkoxy-α,β-unsaturated ester chromophore in adifoline (enol form protected as methyl ether in trimethyladifoline). UV spectra of adifoline [λmax (log ε): 234(4.61), 283(4.29), 362(3.68) mμ] and its derivatives showed a bathochromic shift in acid, suggesting a substituted 3-carboxy-β-carboline chromophore, supported by a mass spectral peak at m/e 242 (C₁₄H₁₀N₂O₂) attributed to ion (IIa). NMR spectra indicated four aromatic protons consistent with the β-carboline moiety; the hydroxy-group at C-10 was confirmed by reducing trimethyladifoline to a compound with a UV spectrum practically superimposable on that of 7-methoxyharman. Adifoline was readily dehydrated to anhydroadifoline (IIIa, C₂₂H₂₂N₂O₆), an enol ether (unaffected by sodium borohydride) with a methoxycarbonyl pyran system, supported by UV, NMR, and mass spectra (major ion at m/e 165, C₉H₉O₃, pyrylium ion IV). NMR data (chemical shifts, multiplicities, coupling constants) allowed assignment of the relative configuration shown for adifoline. The structure (1) is further substantiated by additional chemical and spectroscopic data to be reported in detail in our full paper.