Studies on the Spectra of Protoberberine Alkaloids. I. Absorption Spectrum of Berberine

Measurements have been made of the visible and UV absorption spectra of berberine chloride in pure aqueous, methanol, ethanol and propanol solutions and in the presence of various concentrations of either hydrochloric acid or potassium hydroxide. In all solutions, potassium hydroxide considerably influences both the form of the absorption curves and the values of the extinction coefficients. Bathochromic shifts (red s hift s) of the ab sorption maxima were observed in the ultra-violet spectrum and the disappearence of the absorption maxima in the visible. It has been suggested that the addition of potassium hydroxide causes the formation of the carbinolic form of berberine in all but the aqueous solutions. The open carbinol form is probably formed in the presence of l arge concentrations of KOH. It was found that the shapes of the absorption curves of berberine in the presence of KOH differ widely in different solvents