Synthesis of Imidazole and Indole Hybrid Molecules and Antifungal Activity against Rice Blast

Abstract

Azole and indole are parent substances of many natural and synthetic compounds with significant biological activity. However, the biological activity of the indole and azole conjugates are lack of investigation. In the present work, a series of hybrid molecules with imidazole and indole moiety were designed by using camalexin as a molecular scaffold. Compounds with different length of the carboxylic acid (4a-4f) were prepared. The antifungal activity of this synthetic series together with the ethyl esters analogues (3a-3f) against Magnaporthe oryzae were determined by using agar cup plate assay. Data obtained from the structure-activity relationship studies indicated that the ester analogues displayed antifungal activity against Magnaporthe oryzae while the carboxylic acid derivatives did not. This result indicated that the carboxylic acid ethyl ester moiety is important to antifungal activity. Among all the synthesized compounds, we found that, at a concentration of 100 µM, compound 3c displays the most potent inhibition activity with 38.8±2.5% on the inhibition of the diameter of the mycelial mat of Magnaporthe oryzae while the positive control of propiconazole (10 µM) was found 39.3±2.9%.