Flavonoids at the crossroads of plant defence: a multifunctional shield against insect pests

Flavonoids are a diverse group of secondary metabolites or specialized metabolites that play crucial roles in plant defence against insect herbivores, linking biochemical, physiological, and ecological processes. This review provides a comprehensive overview of flavonoid biosynthesis, classification, and regulatory mechanisms, emphasizing their direct and indirect roles in deterring insect attacks. Also, the structural modifications in flavonoid classes can strongly alter their bioactivity across insect orders. We explore how insect-derived cues dynamically influence flavonoid production, highlighting their importance in signal transduction and the co-evolution of plant-insect interactions. In addition, we discuss the multifunctional nature of flavonoids in responding to both biotic and abiotic stresses, and how these defence layers interact to shape complex plant responses. The review also examines emerging genetic and molecular approaches that harness flavonoid pathways for enhanced pest resistance, with consideration of recent biotechnological advances, environmental impacts, and their potential applications as biopesticides and biostimulants. By integrating these perspectives, we highlight the promise of flavonoid-based strategies in developing sustainable, ecosystem-specific pest management solutions.