A Mutagenic β-Carboline Derivative in Soy Sauce

A yellow substance (YS) isolated for the first time from the soy sauce by HPLC showed weak mutagenicity in Salmonella TA100 without S9 mix. The mutagenicity of YS increased 7.5 times (His+ revertants/μg/plate) after treatment with sodium nitrite.The YS was identified as 1-(5-hydroxymethyl 2-furyl)-9H-pyrido [3, 4-b] indole (1-hydroxymethyl-furyl-β-carboline) by MS, 1H-NMR and 13C-NMR. The survey showed that the concentration of YS in Koikuchi soy sauce (regular fermented) was 2.0μg/ml. The semifermented Koikuchi soy sauce and the soy sauce supplemented with amino acid had 0.79μg/ml and 0.38μg/ml, respectively. The amount of YS in three kinds of soy sauce increased two fold by heating (120°C, 20min). The concentration of YS in soy sauce might serve as a good quality indicator for soy sauce.