Occurrence of stereoisomers of 1-(2'-pyrrolidinethione-3'-yl)- 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in fermented radish roots and their different mutagenic properties.

Stereoisomers of the tetrahydro-beta-carboline derivative, 1-(2-pyrrolidinethione)-3-yl)-1,2,3,4-tetrahydro-beta-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*, 3R*)- and (1R*, 3S*, 3R*)-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*, 3R*)- and (1R*, 3S*, 3R*)-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.