An Alternative Method for the Synthesis of Tetraketones and their Lipoxygenase Inhibiting and Antioxidant Properties

A new method for the preparation of tetraketones 2-22 has been developed by using tetraethyl ammonium bromide (Et4N+Br¯) as a new reagent for condensation of dimedone (5,5-dimethyl cyclohexane-1,3- dione) and aldehydes. These compounds showed varying degrees of lipoxygenase inhibitory and antioxidant activities ranging between 7.8-198.0 and 33.6-248.0 μM, respectively. Compound 19 proved to be most active lipoxygenase inhibitor with IC50 value 7.8 μM in the present series. Out of twenty two tetraketones, four other compounds i.e. 3 (IC50 = 16.3 μM), 8 (IC50 = 21.3 μM), 11 (IC50 = 17.5 μM), 22 (IC50 = 12.5 μM) were also found to have excellent lipoxygenase inhibition, if compared to baicalein (IC50 = 22.4 μM) used as standard. On the other hand only compound 19 (IC50 = 33.6 μM) was found to be most antioxidant, if compared to standard t-butyl-4-hydroxyanisole (IC50 = 44.7 μM).