Achillea wilhelmsii (A. wilhelmsii) contains several therapeutic
phytochemicals, proposing a protective effect on inflammatory responses in
autoimmune diseases such as
ulcerative colitis (UC). However, its activities against UC encounter multiple obstacles. The current study aimed to formulate a colon-specific delivery of A. wilhelmsii for treating UC using
chitosan nanoparticles (NPs) and
Eudragit S100 as a mucoadhesive and pH-sensitive
polymer, respectively. Core
chitosan NP was loaded with A. wilhelmsii extract, followed by coating with
Eudragit S100. Then, physicochemical characterizations of prepared NPs were conducted, and the anti-UC activity in the rat model was evaluated. The relevant physicochemical characterizations indicated the spherical NPs with an average particle size of 305 ± 34 nm and high encapsulation efficiency (88.6 ± 7.3%). The FTIR (Fourier transform infrared) analysis revealed the
Eudragit coating and the extract loading, as well as the high radical scavenging ability of A. wilhelmsii was confirmed. The loaded NPs prevented the extract release in an acidic pH-mimicking medium and presented a complete release thereafter at a colonic pH. The loaded NPs markedly mitigated the induced UC lesions in rats, reflected by reducing
inflammation,
ulcer severity, and UC-related symptoms. Further, histopathological analysis exhibited reducing the extent of the
inflammation and damage to colon tissue, and the determination of the involved pro-inflammatory
cytokines in serum showed a significant reduction relative to free extract. The present results show that
chitosan NPs containing A. wilhelmsii extract coated with
Eudragit having proper physicochemical properties and substantial anti-inflammatory activity can significantly improve colonic lesions caused by UC.