Occurrence of Stereoisomers of 1-(2'-Pyrrolidinethione-3'-yl)-1,2,3,4-tetrahydro-β-carboline-3-carboxylic Acid in Fermented Radish Roots and Their Different Mutagenic Properties

Stereoisomers of the tetrahydro-β-carboline derivative, 1-(2′-pyrrolidinethione-3′-yl)-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (PTCC), were formed from L-tryptophan with 4-methylthio-3-butenyl isothiocyanate, and their mutagenic properties and contents in different types of the radish products were studied. The isomers were identified as (1S *, 3S *, 3′R *)- and (1R *, 3S *, 3′R *)-PTCCs; the former was found as the major compound but had no mutagenic activity, while the latter was mutagenic toward Salmonella typhimurium TA 98 in the presence of a rat microsomal fraction. Both (1S *, 3S *, 3′R *)- and (1R *, 3S *, 3′R *)-PTCC were detected in a ratio of about 4:1 in a product fermented for 8 months, but only a trace was apparent in products manufactured within a few weeks.