Novel bisthiolane polysulfides from lachrymatory factor synthase-suppressed onion and their in vitro cyclooxygenase-1 inhibitory activity.

Two novel bisthiolane polysulfides (compounds 1 and 2), trivially named thiolanotrisulfide and thiolanotetrasulfide, were isolated from a reaction model of tearless onion (in which lachrymatory factor synthase is suppressed), and the presence of another novel bisthiolane polysulfide (3), trivially named thiolanopentasulfide, was confirmed. On the basis of spectroscopic and mass spectrometric analyses, it was found that these bisthiolane polysulfides were bis(5-hydroxy-3,4-dimethylthiolan-2-yl)-tri/tetra/pentasulfide with the general formulas of C12H22O2S5 (tri-), C12H22O2S6 (tetra-) and C12H22O2S7 (penta-), and they were confirmed to exist in authentic tearless onion juice. Thiolanotrisulfide (1) and thiolanotetrasulfide (2) inhibited cyclooxygenase-1 activity with IC50 values of 720 ± 78 and 464 ± 48 μM respectively, compared with 3282 ± 188 μM for aspirin.