In normal onion (Allium cepa), trans-S-1-propenyl-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-5-hydroxythiolane-2-yl 1-propenethiosulfinate, 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'R,4'R,5'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 α-glucosidase in vitro.
Turmeric (Curcuma longa) is used as a food ingredient, coloring agent, and traditional medicine. While various medicinal properties of turmeric have long been known, scientific reports on its prevention and alleviation of alcohol hangover are scarce. In this study, we employed an assay system for the preventive effect of a turmeric extract against ethanol-induced hepatocyte injury, a presumed cause of alcohol hangover, and screened for its active compounds. The preventive effect of the turmeric extract and its fractions was assessed using primary hepatocytes isolated from Sprague-Dawley rats. The turmeric extract containing 6 μM curcuminoids showed stronger cytoprotective activity than the purified curcuminoids at 6 μM. The structures of additional active compounds were determined as ar-turmerone and bisacurone by NMR and mass spectrometry. Among curcumin, ar-turmerone, and bisacurone, bisacurone appeared to be most effective and showed preventive effects at concentrations as low as 1 μM.
Folic acid (FA) is an essential compound involved in important biochemical processes and is used to fortify various food products. FA in fortified acidic beverages decomposes during storage due to H+ attack. FA stability in acidic beverages is a serious problem as food fortification should guarantee labeled FA concentrations until the expiry date. In this study, we investigated the influence of ethanol (EtOH) on FA depletion using a model acidic beverage and observed that small amounts of EtOH, derived from added flavor, promoted FA depletion. FA depletion was promoted by only small amounts of EtOH, but not by acetonitrile. This suggested that FA decomposition might be accelerated by EtOH, which surrounds FA molecules in solution due to selective solvation. In the development of FA‐fortified beverages, EtOH content should be decreased or removed altogether, to prevent accelerating FA decomposition.
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