# Citrus Flavonoids-Coated Biogenic Nanoparticles for Controlling Xanthomonas axonopodis pv. citri: Antimicrobial Efficacy and NMR-Based Investigation of Bacterial Metabolic Reprogramming

## TL;DR

This study explores using citrus flavonoid-coated silver nanoparticles to control citrus canker, showing they are more effective than traditional antibiotics.

## Contribution

The novel approach combines green-synthesized silver nanoparticles with citrus flavonoids to combat citrus canker effectively.

## Key findings

- Flavonoid-coated nanoparticles outperformed streptomycin in inhibiting X. axonopodis pv. citri.
- AgNP@HSD caused membrane damage and metabolic adaptation, while AgNP@HST induced oxidative stress and cellular collapse.
- Hesperetin's higher bioactivity explains the differential antimicrobial effects observed.

## Abstract

Citrus canker, caused by the Gram-negative bacterium Xanthomonas axonopodis pv. citri poses a major threat to global citrus production, with increasing
resistance to copper-based pesticides and antibiotics. This study
presents a sustainable approach for bacterial control using biogenic
silver nanoparticles (AgNPs) synthesized via green methods and functionalized
with citrus peel-derived flavonoids, hesperidin and hesperetin. These
flavonoid-coated nanoparticlesAgNP@HSD and AgNP@HST, respectivelywere
structurally characterized, confirming successful biofunctionalization
and providing insight into flavonoid–nanoparticle interactions.
Antimicrobial assays demonstrated potent inhibitory effects against X. axonopodis pv. citri, with both
formulations outperforming streptomycin in terms of minimum inhibitory
concentrations. Mechanistic investigations revealed distinct antimicrobial
pathways: AgNP@HSD induced a broad stress response marked by elevated
amino acid levels and extensive membrane damage, while maintaining
intracellular ATP and NAD­(P)H levels, suggesting a metabolic adaptation
strategy. In contrast, AgNP@HST triggered targeted oxidative stress,
leading to significant depletion of energy and redox metabolites,
indicating collapse of cellular homeostasis. This differential behavior
is attributed to the higher intrinsic bioactivity of hesperetin, the
aglycone form of hesperidin. Our findings underscore the potential
of citrus flavonoid-coated biogenic nanoparticles as eco-friendly
biomaterials for plant disease management. The integration of green
nanotechnology with plant-derived metabolites offers a promising alternative
to conventional agrochemicals for the control of citrus canker and
other phytopathogenic threats.