Isolation and Identification of 1-Furyl-β-carboline Derivatives That are Mutagenic after Nitrite Treatment

Abstract

When a mixture of 2-furaldehyde (I) and L-tryptophan dissolved in 0.1 M phosphate buffer (pH 7.0) was kept at 37°C for 4 weeks, a browning reaction gradually occurred. The reaction mixture after treatment with nitrite at pH 4.0, was mutagenic to S. typhimurium TA100 in the absence of S9 mix. The browning solution was fractionated by applying high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC), and two 1-furyl-β-carboline derivatives were isolated. They were compound A, (1R, 3S)-1-(2-furyl)-1, 2, 3, 4-tetrahydro-9H-pyrido [3, 4-b] indole-3-carboxylic acid, and compound B, (1S, 3S)-1-(2-furyl)-1, 2, 3, 4-tetrahydro-9H-pyrido [3, 4-b] indole-3-carboxylic acid. These compounds had similar mutagenic potency toward S. typhimurium TA 100 without metabolic activation after treatment with nitrite.