Plant-Derived Hydrolates as Functional Components in Topical Gel and Emulgel Platforms: A Comparative Evaluation of Hydrolate-Based Semisolid Systems

Abstract Plant-derived hydrolates are aqueous co-products of hydrodistillation that remain underexplored despite their potential as sustainable bioactive ingredients. This study comparatively evaluated two nanostructured topical platforms for hydrolate valoriza-tion: a thermoresponsive nanogel containing Anacardium occidentale L. hydrolate and a nanostructured emulgel containing Pectis brevipedunculata hydrolate associated with babassu oil. Both systems were based on Pluronic F127 and Carbopol 974P and were characterized by physical stability assessment, Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and antimicrobial assays against Escherichia coli , Staphylococcus aureus , and Candida albicans. Hydrolate incorporation influenced the supramolecular organization and biological performance of both platforms, although in a formulation-dependent manner. The A. occidentale hydrolate-loaded nanogel showed thermoresponsive behavior, hydrolate– polymer interactions, reduced crystallinity, compact lamellar morphology, and antimi-crobial activity at the highest tested concentration. The P. brevipedunculata hydrolate-loaded emulgel preserved the structural integrity of the matrix, enhanced hydrogen bonding interactions, displayed a porous amorphous morphology, and improved anti-fungal performance at lower concentration. Overall, these findings indicate that plant-derived hydrolates can act as functional components rather than inert aqueous residues, supporting their use in sustainable nanostructured topical systems with antimicrobial potential.