Endogenous alkaloids in man--synthesis, analytics, in vivo identification, and medicinal importance.

The in vitro and in vivo condensation of endogenous (or administered) reactive amines and carbonyl compounds is reported, leading to alkaloid-type heterocycles. The spectrum of the presented "mammalian alkaloids" ranges from isoquinoline derivatives, via beta-carbolines, through to thiazolidines, arising from vitamin B6, chloral, and glyoxylic acid, respectively. Formation of these compounds may occur accidentally, but might also be induced intentionally, as a therapy for metabolic diseases.