This study reports the antioxidant activity against singlet oxygen (O-1(2)) of five newly synthesized furanyl chalcones (FCs) (E)-3 (5-(4 chlorophenyl)furan-2-yl)-1-arylprop-2-en-1-ones (3a-e). Their structural difference is based on the aryl substituent as follows (Ar): 3a = -C6H4-OCH3, 3b = -C6H3-(1,2-OCH3), 3c = -C6H4OC6H4, 3d = - C10H6-(OCH3) and 3e = -C4H3O. We used a Claisen-Schmidt condensation involving a 5-(4-chlorophenyl)furan-2-carbaldehyde and the corresponding ketones under ultrasonic irradiation. Their property to O-1(2) quenching was analyzed in terms of the rate constant for the process (k(Q) at 25 degrees C) determined by the Stern-Volmer model in ethanol. For the compounds 3c, 3d and 3e, the k(Q) values are slightly larger respect to 3a and 3b. The FCs 3c behaves as the best quencher (k(Q )of 8.44 (+/- 0.09) x 10(7) M-1 s(-1)). Geometry analysis and electronic structure calculations have been performed in the framework of Density Functional Theory (DFT) and DFT/Multi-Reference Configuration Interaction (DFT/MRCI) methods. According to DFT/MRCI, a physical quenching of O-1(2) from the ground states of the FCs may not likely induce a spontaneous energy transfer processes but a chemical quenching mechanism may dominate the kinetics. (C) 2020 Elsevier Ltd. All rights reserved.
Furanyl chalcone derivatives as efficient singlet oxygen quenchers. An experimental and DFT/MRCI study
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