“Plant allelochemicals as inhibitors of insect digestive enzymes: Mechanisms, insect responses and applications in sustainable pest management”

Insect pests rely heavily on digestive enzymes such as proteases, α-amylases, lipases and glycosidases to hydrolyse dietary macromolecules into absorbable nutrients essential for growth and reproduction. Plants, in turn, have evolved a wide array of allelochemicals that specifically inhibit these enzymes, thereby reducing nutrient utilization and impairing insect development. Proteinase inhibitors (e.g., Kunitz, Bowman-Birk, Potato I and II types), α-amylase inhibitors, lectins, flavonoids and tannins are pivotal in disrupting insect digestion. These inhibitors act through diverse mechanisms, including competitive, non-competitive, allosteric and irreversible binding to enzyme active sites. While highly effective, insects counteract these defenses via enzyme overproduction, isoform variation, detoxification pathways and symbiotic assistance, posing challenges to long-term efficacy. Recent advances such as genetic engineering, RNAi, nano-encapsulation and molecular docking provide new avenues to enhance allelochemical-based inhibitors stability, delivery and specificity. This review highlights the diversity of insect digestive enzymes, the inhibitory potential of plant allelochemicals, insect counter-adaptations and emerging strategies to exploit these natural compounds for sustainable pest management.