Heterocyclic-Based Fungicides: Emerging Strategies for Viable Plant Disease Control

Fungal infections in plants cause significant agricultural losses worldwide, while increasing fungicide resistance and growing environmental concerns have created an urgent need for safer and more effective antifungal agents. Heterocyclic compounds have attracted considerable attention because of their structural diversity, potent antifungal activity, and ability to interact with multiple fungal targets, offering broad-spectrum protection against phytopathogens. This review summarizes the classification of heterocyclic fungicides, their mechanisms of action targeting fungal cells and enzymes, and their potential for controlling major plant fungal diseases. It also highlights recent advances in the rational design, synthesis, molecular docking, and SAR studies of heterocyclic scaffolds, along with molecular optimization strategies to overcome resistance and improve efficacy and bioavailability. Furthermore, the review emphasizes the potential of heterocyclic moieties for the development of environmentally sustainable plant protection agents. Synthetic and semisynthetic/part-natural scaffolds, particularly azole, quinoline, indole, cyclotryptamine, and phenazine derivatives, demonstrated promising antifungal activity, with structural optimization further enhancing their efficacy and identifying them as valuable lead candidates for next-generation sustainable fungicides.