SYNTHESIS, ANTI-PHYTOPATHOGENIC AND DPPH RADICAL SCAVENGING ACTIVITIES OF C-PRENYLATED ACETOPHENONES AND BENZALDEHYDES

Abstract

The syntheses of six prenylated acetophenone and benzaldehyde derivatives and their anti-phytopathogenic and antioxidant activities are reported. These com­pounds were obtained by electrophilic aromatic substitution (SEAr) of the corresponding arenes and 3-methyl-2-buten-1-ol using ZnCl2 as a Lewis acid catalyst in ethyl acetate. Reasonable to good yields were obtained based on unrecovered aromatic starting material (45-73%). All the synthesized compounds were evaluated against phytopathogenic gram-negative bacteria Agrobacterium tumefaciens , Pseudomonas syringae and Erwinia carotovora and plant fungal pathogens Botrytis cinerea , Phytophthora cinnamomi and Gibberella fujikuroi . The antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scav­enging activity assay and expressed as half maximal inhibitory concentration (IC50) values in μM concentrations. The antioxidant activity went from 27.20 μM to >100 μM. Compound 11 showed statistically significant inhibition of the growth of Botrytis cinerea , and compounds 13 and 15 showed statistically significant inhibition of the growth of Phytophthora cinnamomi , with respect to negative control fungal growth. All six compounds showed bacteriostatic effects against gram-negative plant pathogenic bacteria with IC50 values between 250 and <3.9 μM.