Palmatine and Berberine Isolation Artifacts

Abstract

Some 8-substituted derivatives of the protoberberine alkaloids palmatine (1a) and berberine (1b) have been prepared and investigated by 1D and 2D NMR spectroscopy (H-1, C-13, N-15). Complete NMR data for the 8-hydroxy (2), 8-methoxy (3), 8-ethoxy (4), and 8-trichloromethyl (5) 7,8-dihydro derivatives of 1a and 1b, as well as X-ray data for 8-methoxydihydroberberine (3b), 8-trichloromethyldihydropalmatine (5a), and 8-trichloromethyldihydroberberine (5b), are presented. The physicochemical data for all of these compounds are reviewed and compared with previously published values.

Quantum chemical and nuclear magnetic resonance spectral studies on molecular properties and electronic structure of berberine and berberrubine

“…The observed carbon chemical shifts and carbon-proton bond correlations are listed in Tables 2 and 3, respectively. It may be noted that the proton chemical shifts are close to those observed by Saran and Srivastava, 15 Huang et al 11 and Jeon et al 12 The difference in resonance positions in C 6 D 6 , CD 2 Cl 2 and DMSO solvents 13,14 are attributed to the effect of the solvent on the conformation of the molecules. The carbon chemical shifts are comparable to those cited in the literature.…”

Covalent bonding of azoles to quaternary protoberberine alkaloids

“…For instance, a recent publication [26] inexplicably compares NMR data obtained for quaternary berberine in several different solvents with published data for a berberine base (8-hydroxy-7,8-dihydroberberine) measured in CD 2 Cl 2 and C 6 D 6 . [20] Large differences in chemical shifts found in 1 H NMR (up to 3.44 ppm) and 13 C NMR (up to 67.67 ppm) and summarized in the tables in this paper [26] are attributed to the effects of the different solvents. However, it should be pointed out that quaternary berberine (e.g.…”

“…This observation is in accordance with the fragmentation patterns obtained for other 8-substituted 7,8-dihydroprotoberberines. [20,23] Due to the lability of the C8-N1 bond and the extraordinary stability of the quaternary form, quaternary ions and heterocyclic bases were formed spontaneously during the ionization process. The EI-MS data for individual compounds are summarized in the Experimental section.…”

“…However, recent studies have indicated that the mechanism of interaction could be different. NMR ( 1 H, 31 P, NOE) and fluorescence studies have shown berberine to be localized in a minor groove of the adenine-thymine (AT)-rich sequences. [15] Generally, it is of great importance to investigate the capacity of a QPA to form covalent bonds with nucleic acid bases, nucleic acids (cytotoxicity, mutagenic effects), [13,16] or the functional groups of proteins.…”

“…[1] Several 8-substituted adducts have been prepared, e.g. with liquid ammonia, [17] chloroform, [18 -20] cyanide, [21] sodium methoxide, and sodium ethoxide, [20,22] and characterized by NMR spectroscopy and X-ray diffraction. However, we report here the first study of the nucleophilic addition of some azoles to the protoberberine skeleton.…”