Supplementary Observations on the Chemistry of the Alkaloids of Berberine Series. II. The Ultraviolet Absorption Spectra of Berberines and Related Compounds

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AbstractThe ultraviolet absorption spectra of berbines and ϕ‐berbines consist of a single, weak and narrow band in which λmax position dependeds on the kind of auxochrome group i. e., methylenedioxy‐or dimethoxy group attached to 2–3 position. The effect of the auxochrome group at 11–12 position or 12–13 position is very small.The shape of the band of oxyberberine, oxy‐ϕ‐berberine and oxyprotoberberine are similar, especially those of the latter two substances resemble closely.Comparing with isoquinoline, the bands (b), (c) and (d) of G‐berberines and protoberberine are considered as characteristic of isoquinoline structure, while the band (a) in visible region is of berberinium structure, however, the absorption curve of ϕ‐berberines does not show any characteristic of isoquinoline or berberinium structure.