Abstract
Background: Curcumin is well recognized as a natural anti-inflammatory and analgesic compound; however, its application in clinical conditions is hindered by its poor bioavailability and moderate potency. Peptide conjugation modification is a promising approach to enhance its potency. Objectives: The purpose of this study was to design, synthesize and evaluate new cyclopeptide-curcumin conjugates to enhance cyclooxygenase inhibition, anti-inflammatory efficacy and antinociceptive effects. Methods: Three cyclopeptide–curcumin conjugates—[W4KR5]-5-oxopentanoate-curcumin, [W4KR5]-3,5-dioxopentanoate-curcumin and [W4KR5]-12-oxododecanoate-curcumin—were investigated using integrated in-silico, in-vitro and in-vivo approaches. Molecular docking was performed against COX-1 (PDB ID: 3N8X) and COX-2 (PDB ID: 1PXX). In-vitro COX inhibition assays assessed enzyme selectivity. At the same time, in-vivo antinociceptive and anti-inflammatory activities were evaluated using acetic acid–induced writhing, tail immersion, formalin-induced pain and carrageenan-induced paw edema. Results: All conjugates demonstrated superior binding affinity to COX enzymes compared to curcumin, with [W4KR5]-12-oxododecanoate-curcumin exhibiting the strongest COX-2 interaction (?11.4 kcal/mol vs. ?7.8 kcal/mol for curcumin), stabilized by key residues Tyr385, Ser530 and Arg120. This compound showed marked COX-2 selectivity in-vitro (IC50 = 0.82 µM) relative to COX-1 (IC50 = 4.65 µM), outperforming curcumin (COX-2 IC50 = 6.21 µM). In-vivo, it significantly reduced acetic acid–induced writhing (72.4%), increased tail immersion latency (63.1%), suppressed formalin-induced neurogenic (61.7%) and inflammatory (75.5%) pain phases and inhibited carrageenan-induced paw edema by 68.2%, compared to 39.4% for curcumin. Conclusion: The conjugation of cyclopeptide significantly increases the anti-inflammatory and antinociceptive potency of curcumin. Of the tested analogs, [W4KR5]-12-oxododecanoate-curcumin is particularly noteworthy as a lead compound worthy of further studies.