[W4KR5]-12-oxododecanoate-curcumin conjugate significantly enhances anti-inflammatory and antinociceptive effects in vivo.

Curcumin is a natural compound known for its anti-inflammatory and analgesic properties, but its clinical utility is hampered by poor bioavailability and moderate potency. Enhancing its efficacy is crucial for broader therapeutic application. Non-steroidal anti-inflammatory drugs (NSAIDs) often target cyclooxygenase (COX) enzymes, but their non-selective inhibition of COX-1 and COX-2 can lead to adverse effects. Developing selective COX-2 inhibitors with improved potency and bioavailability is a key strategy to mitigate these issues and provide safer, more effective pain and inflammation management. Peptide conjugation offers a promising route to achieve this.

Researchers designed and synthesized three cyclopeptide-curcumin conjugates, including [W4KR5]-12-oxododecanoate-curcumin, to improve COX inhibition and anti-inflammatory/antinociceptive effects. They employed an integrated approach: molecular docking against COX-1 (PDB ID: 3N8X) and COX-2 (PDB ID: 1PXX) for binding affinity, in-vitro COX inhibition assays for enzyme selectivity, and in-vivo evaluations in animal models. The in-vivo studies included acetic acid-induced writhing, tail immersion, formalin-induced pain, and carrageenan-induced paw edema to assess antinociceptive and anti-inflammatory activities. Curcumin served as a comparator in these experiments.

All cyclopeptide-curcumin conjugates showed superior binding affinity to COX enzymes compared to curcumin alone. Specifically, [W4KR5]-12-oxododecanoate-curcumin exhibited the strongest COX-2 interaction with a binding affinity of -11.4 kcal/mol, significantly better than curcumin's -7.8 kcal/mol. This interaction was stabilized by key residues Tyr385, Ser530, and Arg120. > In-vitro, [W4KR5]-12-oxododecanoate-curcumin demonstrated marked COX-2 selectivity with an IC50 of 0.82 µM, compared to 4.65 µM for COX-1, substantially outperforming curcumin's COX-2 IC50 of 6.21 µM. In in-vivo models, this conjugate significantly reduced acetic acid-induced writhing by 72.4% (vs. 39.4% for curcumin), increased tail immersion latency by 63.1%, and suppressed both neurogenic (61.7%) and inflammatory (75.5%) phases of formalin-induced pain. Furthermore, it inhibited carrageenan-induced paw edema by 68.2%, again surpassing curcumin's 39.4% inhibition.