ZVONIMIR GASPAREC, SEBOJKA KOMORSKY-LOVRI~, and MILIVOJ LOVRIC. Can. J. Chem. 60, 970 (1982).The absorption spectra of berberrubine in the visible and uv spectral range were recorded. The measurements were made in four different solvents (water, absolute methanol, absolute ethanol, and absolute propanol) changing the acidity and the alkalinity of the solutions in the wide range from pH 2 to pH 13 by the addition of HC1 and KOH. The experimental and theoretical results, derived by simple Hiickel MO calculations, were compared and discussed.ZVONIMIR GASPAREC, SEBOJKA KOMORSKY-LOVRI~ et MILIVOJ LOVRIC. Can. J. Chem. 60, 970 (1982).On a enregistre les spectres d'absorbtion de la berberrubine dans le visible et l'uv. On a effectue ces mesures dans quatre solvants differents (eau, methanol, ethanol et propanol) et on a fait varier le pH de 2 a 13 par addition de HC1 ou de KOH aux solutions. On compare et on discute des resultats experimentaux et des valeurs theoriques obtenues par des calculs simples OM de Hiickel.[Traduit par le journal]Berberrubine belongs to the group of protoberberinic alkaloids (Fig. 1). It has been, so far, isolated only from Berberis vulgaris L . , family Berberidaceae (I), but as early as 1903 Berkurst and Frerichs (2) had synthesized it from berberine chloride by pyrolysis at 200°C with urea.The alkaloids of the berberine group are known to form complexes with biologically important macromolecules, such as alcohol dehydrogenase from horse liver (3) and some nucleic acids (4). In the spectrophotometric study of these interactions it was first necessary to determine the absorption properties of the alkaloids. Recently, Pavelka and co-workers have published several papers dealing with the ultraviolet and visible absorption (5,6) and fluorescence (7) spectra of protoberberinic alkaloids. The authors have paid much attention to berberrubine because of some of its special properties. Unfortunately, their measurements were done only in 96% ethanol solution at undefined pH.The aim of this work is to report the results of the measurements of the absorption spectra of berberrubine in four different solvents with pH of the solutions changing in the range between 2 and 13. Besides, some simple Hiickel MO calculations were performed for berberine and its derivatives jatrorhizine, berberrubine, and jatrorubine and the results will be compared with present and previously published (9,10) data. The calculations were made for all three possible ionic forms of these alkaloids (quaternary amine cation, carbinolic, and open amino-aldehydic forms) in order to gain a better understanding of the possible ionic transformation of berbermbine under the influence of acid or base.