Structure and Bioactivity of Thiosulfinates Resulting from Suppression of Lachrymatory Factor Synthase in Onion

摘要

In normal onion (Allium cepa), trans-S-1-propenyI-L-cysteine sulfoxide is transformed via 1-propenesulfenic acid into propanethial S-oxide, a lachrymatory factor, through successive reactions catalyzed by alliinase and lachrymatory factor synthase (LFS). A recent report showed that suppression of the LFS activity caused a dramatic increase in thiosulfinates previously reported as "zwiebelane isomers". After purification by recycle high-performance liquid chromatography and subsequent analyses, we established the planar structure of the putative "zwiebelane isomers" as S-3,4~dimethyl-S-hydroxythiolane-2-yl 1-propenethiosulfi-nate, in which two of the three molecules of 1-propenesulfenic acid involved in the formation gave the thiolane backbone, and the third molecule gave the thiosulfinate structure. Of at least three stereoisomers observed, one in the (2'R,3'jR,4'.R,$'.R)-configuration was collected as an isolated fraction, and the other isomers were collected as a combined fraction because spontaneous tautomerization prevented further purification. Both fractions showed inhibitory activities against cyclooxygenase-1 and oglucosidase in vitro.