Studies on the pharmaceutical quality evaluation of crude drug preparations used in orient medicine "Kampoo". III. Precipitation reaction of glycyrrhizin with alkaloids or alkaloidal crude drugs in aqueous solution.
Precipitation reaction of glycyrrhizin (I) with 32 kinds of alkaloids including synthetic bases and 10 kinds of crude drugs which contain various types of alkaloids in an aqueous solution was investigated. Tertiary alkaloids which had heterocyclic aromatic rings or N atoms neighboring in the aromatic ring or conjugated olefine systems in the structure, i.e., papaverine, noscapine, emetine, O-methyl domesticine, domesticine, nornuciferine, dl-tetrahydroberberine, l-corydaline, quinine, reserpine and sinoactine gave precipitate, while other types of alkaloids, i.e., l-ephedrine, N-methylephedrine, l-phenylalaninol, atropine, l-scopolamine, cocaine, morphine, ethylmorphine, codeine, hydrocodeine, thebaine, sinomenine, aconitine, physostigmine, caffeine and pethidine did not. Tertiary alkaloids which had pKa values smaller than 7.5 were likely to precipitate with I, while those which had pKa values larger than 7.5 did not. Among quaternary alkaloids, berberine and coptisine produced precipitate, while menisperine, N-methyl scopolamine and neostigmine did not. Among crude drugs which contained various alkaloids, Coptis rhizome, Corydalis roots, Phellodendron cortex and Evodia fruits gave precipitate with I in an aqueous solution, while Aconitum roots, Areca seeds, Ephedra herb, Magnolia cortex, Nuphar rhizome and Sinomenium roots did not.