Synthesis, antimicrobial and antioxidant evaluations of allyloxy chalcone derivatives

Abstract

Objectives: Chalcones, a class of natural products, have different biological activities. The aim of this research was synthesis and evaluation of antimicrobial effects of three chalcones bearing allyloxy moiety similar to some natural flavanoids. Methods: Chalcones (3a-c) were prepared in two steps. First, vanillin, isovanillin and salicylaldehyde were reacted with allyl bromide to afford allyloxy aldehydes. Then, allyloxy aldehydes were reacted with 2-hydroxyacetophenone in the alkaline media to afford final products. Standard disc diffusion and Agar dilution methods were used for analyzing antimicrobial activities on three gram-positive and two gram-negative bacterial species and also three fungi species. Antioxidant activity of the compounds was determined by DPPH using brand-Williams method. Results: Chalcones 3a-c were synthesized as yellow-orange crystals in 60-70% yield. Chalcone 3c with concentration about 4 mg/disc had 11.7 mm inhibition zone on P. aeruginosa and Chalcone 3b with MIC value about 0.5 mg/ml, exhibited 8.8 and 16.5 mm inhibition zone in 2 and 4 mg/disc for S. epidermidis, respectively. Mean while MIC value of the Chalcones 3a and 3c was more than 2 mg/ml. Chalcones 3a-c had no antifungal activities. Antioxidant activities of chalcones 3a, 3b and 3c were determined to be 31, 28 and 27 percent respectively. Conclusion: Chalcones 3a-c were synthesized in two steps. Their antimicrobial and antioxidant activities were evaluated. The two 3b and 3c regioisomers showed selective and weak antibacterial activities. Chalcone 3b and 3c affected on gram positive and gram negative bacteria, respectively. Chalcone 3a did not show any antibacterial activity.