Spray dried inulin–sodium carboxymethylcellulose microcarriers with solid-to-colloidal transition: Development for foliar delivery of polyphenol-rich extract

This study reports on the development of a carbohydrate-based spray-dried microparticulate system (F-CHES) conceived for the stabilization and foliar delivery of polyphenol-rich plant extracts for sustainable phyto defense applications. Chestnut spiny bur (CHES) extract, with demonstrated anti-fungal activity against phytopathogens, was micro-encapsulated via spray-drying in a polysaccharide matrix, composed primarily of inulin (INU DP ∼15), sodium carboxymethylcellulose (CMC) and low amount of sodium lauryl sulfate (SLS 0.05 % w/v), engineered to improve extract processability, water compatibility, stability and functional performance. Structural characterization by semi-solid (HRMAS) and solid-state (CPMAS) NMR revealed polysaccharide matrix–extract interactions that influenced the internal organization and component distribution within microparticles. The integration of high-resolution analytical techniques was also essential for standardizing the production process. The optimized F-CHES 0.8 micropowder, containing 1.5 % w/v of CHES extract, 5 % INU, 0.8 % Na-CMC, showed a process yield (70.42 ± 2.42 %) and high encapsulation efficiency (98.58 %). The formulation ensured chemical stability over 12 weeks (active compound retention ≥94.86 %), and displayed favorable morphological and physicochemical properties, including hydrodynamic diameter of 0.55 µm and ζ-potential of –37.2 mV. Interestingly, upon dispersion in water, the microparticles converted into a colloidal state and the resulting dispersion can form stable transparent coating on leaf surface suited for foliar delivery.