Inhibitory effect of phenolic compounds on lipoxygenase activity in reverse micellar systems

Lipoxygenases catalyze the oxidation reaction of fatty acids that have 1,4-Z, Z-pentadiene systems, forming conjugated hydroperoxides as primary products. These enzymes are present in foods participating in oxidative processes that can lead to organoleptic and nutritional quality spoilage. Therefore, different technological processes have been developed that modulate its pro-oxidant activity by antioxidant addition. As LOX substrates are insoluble in water, its reactions in reversed micelles offer numerous advantages, including the solubilization of both hydrophilic and hydrophobic substrates or products, minimized reaction volumes, a substantial hydrophilic/hydrophobic interfacial area, and control over enzyme activity and stability. The main aims of this work were to evaluate the inhibitory effect of synthetic and natural antioxidants on lipid oxidation catalyzed by lipoxygenase and to determine the kinetic parameters and type of inhibition in reverse micelles for the first time. This biomimetic system water in oil was designed using AOT as the surfactant and linoleic acid as a substrate to measure the enzyme inhibition of a series of phenolic compounds. All these compounds assayed have behavior as mixed non-competitive inhibitors according to linear and non-linear regression methods. The reductions of the catalytic activity of lipoxygenase were between 50% and 70%; besides, the kinetic parameters were also affected by decreasing the V_max from 266 μMs⁻¹ to 217, 215, and 101 μMs⁻¹ for sinapic acid, propyl gallate, and quercetin, respectively, as the most active inhibitors of the series. Selecting phenolic compounds with strong LOX inhibitory activity maximizes the prevention of lipid oxidation in various food matrices.