Isolation, Structure, and Properties of the ?-Carboline Formed from 5-Hydroxytryptamine by the Superoxide Anion-Generating System

Publisher Website
Google Scholar
Abstract
A yellow substance was isolated by Sephadex LH-20 gel chromatography, silica gel TLC, and reversed-phase HPLC after incubation of 5-hydroxytryptamine (5-HT) with the superoxide anion (O2-)-generating system, i.e., the xanthine-xanthine oxidase system, in the presence of the Fe-EDTA complex and glycine in alkaline medium. The product gave a blue color with Ehrlich''s reagent very slowly butr no color with xanthydrol and Gibb''s reagent. Its reduced form, however, gave an immediate blue-violet color with all three reagents. No color was developed with ninhydrin, but the reduced form was orange-red. The chemical structure of the yellow substance was identified by 1H-nuclear magnetic resonance and field resorption mass spectroscopy as 4,9-dihydro-3H-pyrido[3,4-b]indol-6-ol (6-hydroxy-3,4-dihydro-.beta.-carboline, 5-hydroxy-2,3-dihydrotryptoline). The one carbon unit inserted into 5-HT came from glycine, with its 14C-2 being incorporated into C-1 of the yellow substance. The mechanism for the formation of the yellow substance from 5-HT is discussed. This compound inhibited 5-HT uptake into rat brain cortical synaptosomes with an IC50 of 1.5 .times. 10-4 M and a Ki value of 1.2 .times. 10-5 M.