UV-Photolysis of S-(cis-l-Propenyl)-L-cysteine in Oxygen-free Aqueous Solution

From the comparisons of mass spectral fragmentations and gas chromatographic retention times with reference compounds, volatile flavor products from UV-photolysis of S-(cis-l-propenyl)-L-cysteine in oxygen-free aqueous solutions were identical with propanal, 2-methyl-2-pentenal, n-propyl mercaptan, allyl mercaptan, 1-propenyl mercaptan, 2-methylthiophene, 3-methylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, 2,5-dimethylthiophene, 3,4-dimethylthiophene, n-propyl 1-propenyl sulfide and di- 1-propenyl sulfide. Moreover, from the comparison of two-dimentional thin-layer chromatograms with reference compounds, ninhydrin-positive products with interest in terms of the degradation mechanism were identical with alanine and cystine. It seems that above-mentioned thiophene derivatives are produced via 1-propenyl thiyl radicals.