The growing need for processing natural lipophilic and often volatile substances such as thymol, a promising candidate for topical treatment of intestinal mucosa, led us to the utilization of solid-state nuclear magnetic resonance (ss-NMR) spectroscopy for the rational design of enteric pellets with a thymol self-emulsifying system (SES). The SES (triacylglycerol, Labrasol®, and propylene glycol) provided a stable o/w emulsion with particle size between 1 and 7 μm. The ex vivo experiment confirmed the SES mucosal permeation and thymol delivery to enterocytes. Pellets W90 (MCC, Neusilin®US2, chitosan) were prepared using distilled water (90 g) by the M1-M3 extrusion/spheronisation methods varying in steps number and/or cumulative time. The pellets (705-740 μm) showed mostly comparable properties-zero friability, low intraparticular porosity (0-0.71%), and relatively high density (1.43-1.45%). They exhibited similar thymol release for 6 h (burst effect in 15th min ca. 60%), but its content increased (30-39.6 mg/g) with a shorter process time. The M3-W90 fluid-bed coated pellets (Eudragit®L) prevented undesirable thymol release in stomach conditions (<10% for 3 h). A detailed, ss-NMR investigation revealed structural differences across samples prepared by M1-M3 methods concerning system stability and internal interactions. The suggested formulation and methodology are promising for other lipophilic volatiles in treating intestinal diseases.

Department of NMR Spectroscopy Institute of Macromolecular Chemistry Czech Academy of Sciences 162 06 Prague Czech Republic

Department of Pharmaceutical Technology Faculty of Pharmacy Masaryk University Brno 612 00 Brno Czech Republic

Department of Pharmacology and Toxicology Veterinary Research Institute 621 00 Brno Czech Republic

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