Some flavonoids are synergistic in their anti-inflammatory effects when combined. In particular chrysin and kaempferol significantly synergised in their inhibitory effect upon NO, PGE(2) and TNF-alpha secretion. These findings open further avenues of research into combinatorial therapeutics of inflammatory-related diseases and the pharmacology of flavonoid synergy.

Curcumin is a highly pleiotropic molecule with significant regulatory effects upon inflammation and inflammatory related diseases. However curcumin has one major important limitation in which it has poor bioavailability. Design of synthetic structural derivatives of curcumin is but one approach that has been used to overcome its poor bioavailability while retaining, or further enhancing, its drug-like effects. We have synthesized a series of curcumin analogues and describe the effects of 2,6-bis-4-(hydroxyl-3-methoxy-benzylidine)-cyclohexanone or BHMC upon nitric oxide and cytokine synthesis in cellular models of inflammation. BHMC showed a significant dose-response inhibitory action upon the synthesis of NO and we have shown that this effect was due to suppression of both iNOS gene and enzyme expression without any effects upon scavenging of nitrite. We also demonstrated that BHMC has a very minimal effect upon iNOS activity with no effect at all upon the secretion of PGE(2) but has a strong inhibitory effect upon MCP-1 and IL-10 secretion and gene expression. Secretion and gene expression of TNF-alpha and IL-6 were moderately inhibited whereas IL-8 and IL-1beta were not altered. We conclude that BHMC selectively inhibits the synthesis of several inflammatory mediators. BHMC should be considered a promising drug lead for preclinical and further pharmacological studies.

A series of thirty three 2,6-bisbenzylidenecyclohexanone and pyrazoline derivatives were synthesized and evaluated for inhibitory activities on IFN-c/LPS-activated RAW 264.7 cells and DPPH radical scavenging activity. Compounds 8, 9, and 11a demonstrated significant NO inhibitory activity as compared to L-NAME and curcumin with IC 50 values of 6.68 ± 0.16, 6.09 ± 0.46, and 6.84 ± 0.12 lM, respectively. Apparently the suppression upon NO secretion was not due to cell death since the active compounds did not reduce the cell viability in close proximity to the IC 50 of NO inhibition. Overall, incorporation of pyrazoline ring as part of the linker chain improved cell viability compared to the 2,6-bisbenzylidenecyclohexanone derivatives. Meanwhile, compound 11 (IC 50 = 13.27 ± 1.78 lM) bearing ortho hydroxyls on the aromatic rings recorded the highest radical scavenging activity as compared with quercetin (IC 50 = 21.46 ± 0.85 lM).

HMP [3-(2-hydroxyphenyl)-1-(5-methyl-furan-2-y-l) propenone] was evaluated for its ability to inhibit the synthesis of major proinflammatory mediators and cytokines in interferon-gamma (IFN-gamma)- and lipopolysaccharide (LPS)-induced RAW 264.7 cells and phorbol myristate acetate (PMA)-differentiated/LPS-induced U937 cells. HMP suppressed the production of nitric oxide (NO) with significant inhibitory effects at doses as low as 0.78 microM (P < 0.05). Prostaglandin E2 (PGE2) secretion was also inhibited at doses of 12.5 microM and above (P < 0.01). The secretion of both TNF-alpha and IL-6 were only inhibited at the highest dose used (25 microM; P < 0.001). IL-1beta secretion was also inhibited from 12.5 microM onwards (P < 0.01). This inhibition was demonstrated to be caused by down-regulation of inducible enzymes, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2), without direct effect upon iNOS or COX-2 enzyme activity. HMP only inhibited iNOS (P < 0.001) and IL-1beta (P < 0.05) gene expression at the highest tested concentration. HMP did not affect the secretion of chemokines IL-8 and monocyte chemotactic protein-1 (MCP-1) and the anti-inflammatory cytokine IL-10. The most striking effect of HMP was its NO inhibitory activity and therefore we conclude that HMP is a selective inhibitor of iNOS.

In this study, thirty-eight chalcone analogs were synthesized and evaluated for nitric oxide (NO) inhibition activity on RAW 264.7 cells. Among these compounds, chalcones bearing furanyl group showed remarkable anti-inflammatory activity. Both compounds 2d and 2j were identified as the most potent NO inhibitor on IFN-c/LPS-activated RAW 264.7 cells. In order to examine the structure-activity relationship, a 3D QSAR analysis was carried out by comparative molecular field analysis (CoMFA) method on the selected chalcones. Partial least square analysis produced a statistically coherent model with good predictive value, r 2 = 0.989 and a good cross validated value, q 2 = 0.583.