Design, Synthesis, and Antifungal Evaluation of 8-Hydroxyquinoline Metal Complexes against Phytopathogenic Fungi

Abstract

Phytopathogenic fungal infections have become a major threat to agricultural production, food security, and human health globally, and novel antifungal agents with simple chemical scaffolds and high efficiency are needed. In this study, we designed and synthesized 38 8-hydroxyquinoline metal complexes and evaluated their antifungal activities. The results showed that most of the tested compounds possessed remarkable <i>in vitro</i> antifungal activity. Especially, compound <b>1e</b> exhibited the highest antifungal potency among all target compounds, with EC₅₀ values of 0.0940, 0.125, 2.95, and 5.96 μg/mL, respectively, against <i>Sclerotinia sclerotiorum</i>, <i>Botrytis cinerea</i>, <i>Fusarium graminearum</i>, and <i>Magnaporthe oryzae</i>. Preliminary mechanistic studies had shown that compound <b>1e</b> might cause mycelial abnormalities of <i>S. sclerotiorum</i>, cell membrane permeability changes, leakage of cell contents, and inhibition of sclerotia formation and germination. Moreover, the results of <i>in vivo</i> antifungal activity of compound <b>1e</b> against <i>S. sclerotiorum</i> showed that <b>1e</b> possessed higher curative effects than that of the positive control azoxystrobin. Therefore, compound <b>1e</b> is expected to be a novel leading structure for the development of new antifungal agents.