Dioxygenation of Long-Chain Alkadien(trien)ylphenols by Soybean Lipoxygenase

Long-chain alkadien(trien)ylphenols, i.e., cardanols, cardols, and anacardic acids, as well as their acetylated and methylated derivatives were used in enzymatic dioxygenation catalyzed by soybean lipoxygenase-1 (LOX-1). Kinetic studies revealed the influence of functional groups, chain length, number of double bonds, and the distance of the double bonds from the terminal end. Free functional groups were found to be a structural prerequisite for high affinity and turnover number; exceptional kinetic parameters were obtained for ω-6 compounds possessing the same chain length as linoleic acid. The regioselectivity and enantioselectivity of LOX-1 catalysis were investigated with 3-[(Z,Z)-8‘,11‘-pentadecadienyl]phenol as the representative substrate, yielding 3-[12‘-(S)-hydroperoxy-(Z,E)-8‘,10‘-pentadecadienyl]phenol as the main product. Our extensive chromatographic and spectroscopic studies comprised HPLC−MS/MS for differentiation of the regioisomers, 1H NMR spectroscopy for determination of the double-bond configuration, GC−MS to evaluate the enantiomeric excess, and exciton-coupled circular dichroism for determination of the absolute configuration. Keywords: Lipoxygenase; dioxygenation; cardanols; cardols; anacardic acids; exciton-coupled circular dichroism (ECCD)