Impact of chemical derivatization on drug release properties of Euryale ferox Salisb polysaccharide matrices.

The present study investigates the chemical modification of Euryale ferox Salisb. starch via acetylation (ACT), oxidation (OST), carboxymethylation (CMT), and citric acid crosslinking (CST) to enhance its efficacy as a colon-targeted drug delivery excipient. Modified starches exhibited improved swelling, solubility, water retention, and amylose levels, attributed to crystalline disruption, hydrophilic site introduction, and structural reorganization. FTIR confirmed derivatization with distinct functional groups: CMT (3650-3200, 1740 cm-1), CST (1353, 1366 cm-1), OST (1740, 1639 cm-1), and ACT (1740, 1005-1148 cm-1). XRD revealed varied crystalline phases: CMT showed the highest crystallinity (56.46 %, A-type), CST displayed a hybrid C-type, ACT retained A-type (49.26 %), and OST exhibited moderate crystallinity (50.42 %) with peak shifts. TGA indicated a three-stage degradation: moisture loss (30-200 °C), decomposition (200-400 °C), and carbonization (400-800 °C). ACT showed the greatest mass loss (61.49 %) due to acetyl group degradation, whereas CST demonstrated enhanced thermal stability (23.08 % loss). Rheological analysis confirmed non-Newtonian shear-thinning, with ACT showing the highest viscosity (K = 1.6025 Pa·sⁿ). In vitro drug release studies revealed distinct pH-responsive behaviors. CMT emerged as the optimal candidate for colon-targeted delivery, demonstrating superior gastric protection with minimal release (10.78 % at 4 h, pH 1.2) coupled with enhanced intestinal delivery (25.48 % at 4 h, pH 6.8) through a unique super-Case II mechanistic transition (n = 1.22), while ACT provided excellent sustained-release characteristics with distinct pharmaceutical advantages for site-specific delivery applications.