Fungicidal activity of indole derivatives against some plant pathogenic fungi

Fungicidal activity of six prepared indole derivatives in addition to indole-3-acetic acid and indole-3-butyric acid was in vitro evaluated against Fusarium calmorum, Pythium debarianum, Rhizoctonia solani and Macrofomina phaseoli fungi. The toxicity appeared to be a function of both the treated fungus and the tested concentration. IC50 values were calculated and the structure activity relationship (SAR) was illustrated. 2-Phenylindole and 1-acetylindole-3-butyric acid exhibited persuasive fungicidal activities, so their effects were examined in vivo against polyphenoloxidase (PPO), peroxidase (PO), DNA, RNA and sugar contents. Polyphenoloxidase in R. solani systematically responded to 2-phenylindole concentrations with IC50 value of 80.3 μg/ml. 1-Acetylindole-3-butyric acid was more effective than 2-phenylindole with IC50 values of 41.5 and 80.2 μg/ml comparing with 87.6 and 117.1 μg/ml on F. calmorum and M. phaseoli, respectively. While against P. debarianum, the enzyme was inhibited by 1-acetylindole-3-butyric acid with IC50 equaled 45.6 μg/ml. Effect of the tested compounds on peroxidase was differed among the tested fungi. The peroxidase extracted from P. deparianum was less inhibited. Changing in sugar, DNA and RNA contents of the tested fungi were exhibited that explains the disturbance of the fungal cell physiology and developing deformed and dead cells.