According to our previous NMR study, trehalose forms an intermolecular complex with the cis-type double bond of diene compounds in aqueous solution. To elucidate the main driving force of such an intriguing complex formation, we calculated the potential of mean force (PMF) as a function of the distance (R) between the center of mass of trehalose and one double-bond of heptadiene. PMF exhibited the single minimum at a value of R=5-6Å, where the heptadiene molecule was located around the C3 (C3') methine groups and the exocyclic methylene groups of the trehalose, consistent with the results from the NMR study. Ab initio quantum chemical calculations indicated that the multiple interactions through weak hydrogen bonds such as CH/π and OH/π interactions play an important role in stabilizing the intermolecular complex. Furthermore, a significant increase in the activation energy was found for hydrogen abstraction reaction from the activated methylene group of heptadiene. On the basis of these results, we propose a novel mechanism for the antioxidant function of trehalose.
