Synthesis, bioactivity and structure-activity relationships of new 2-aryl-8-OR-3,4-dihydroisoquinolin-2-iums salts as potential antifungal agents

Abstract

As our continuing research on antifungal dihydroisoquinolin-2-ium salts, forty 2-aryl-8-OR-3,4-dihydroisoquinolin-2-ium bromides were synthesized and characterized by spectroscopic analysis. By using the mycelium growth rate method, the compounds were evaluated for antifungal activity against three plant pathogenic fungi and structure-activity relationships (SAR) were derived. The vast majority of the compounds displayed the medium to high activity with inhibition rates of 50-100% at 150μM. About half of the compounds were more active than their natural model compounds sanguinarine and chelerythrine for all the fungi, and part or most of them were more active than positive drugs thiabendazole and azoxystrobin. SAR analysis showed that both substitution patterns of the C-ring and the type of 8-OR group significantly influenced the activity. Thus, a series of new title compounds with excellent antifungal potency emerged.

Keywords: 2-Aryl-8-methoxy-3,4-dihydroisoquinolin-2-ium; Antifungal activity; Isoquinoline; Plant pathogenic fungi; Structure–activity relationship.