Curcumin and four synthetic analogs were examined for anti-inflammatory potential in carrageenin-induced foot paw edema and cotton pellet granuloma models of inflammation in rats^8,9. The antiinflammatory potency of tested curcumin, curcumin analogs and phenylbutazone were established in the following order:

• sodium curcumin
• tetrahydrocurcumin
• curcumin
• phenylbutazone
• triethylcurcumin.

The sodium salt of curcumin was effective at half the dose of the parent compound, curcumin. Comparison of curcumin and its analogs in acute and subacute models of inflammation revealed that curcumin analogs are more active in alleviating acute inflammation. (Fig 3)

Fig 3: Effect of curcumin and its analogs on carrageenin-induced paw edema in rats⁸
C : Curcumin, NaC : Sodium curcuminate
THC : Tetrahydrocurcumin, PB : Phenylbutazone

In a series of studies conducted by Sabinsa Corporation¹⁰, the free radical scavenging ability of various curcuminoids were evaluated by using the DPPH (1.1 diphenyl-2-picrylhydrazyl) -radical scavenging method. The results are shown in Figure 4:

Concentration (µg/ml)

Fig 4: Free radical scavenging ability of curcuminoids
BDMC : Bisdemethoxycurcumin; C: Curcumin
THC: Tetrahydrocurcumin

These results indicate that the addition of curcuminoids resulted in the significant neutralization of free radicals in a dose-dependent manner, Tetrahydrocurcumin being the most effective, followed by curcumin and Bisdemethoxycurcumin.

One study evaluated the comparative antioxidant activity of curcuminoids and tetrahydrocurcumin in vitro using linoleic acid as the substrate in an ethanol/ water system as well as using rabbit erythrocyte membrane and rat liver. It was found that Tetrahydrocurcumin had the strongest antioxidant activity among all curcuminoids in each assay system (Figures 5-8)⁴. The authors concluded that these results suggest that Tetrahydrocurcumin must play an important role in the antioxidant mechanism of Curcumin in vivo⁴

Fig 5: Comparative Antioxidant Activity of the Curcuminoids and Tetrahydrocurcuminoids in rabbit erythrocyte membrane system model (determined by TBA method)

Fig 6: Comparative Antioxidant Activity of the Curcuminoids and Tetrahydrocurcuminoids in rat liver microsomes model (determined by TBA method)

Fig 7: Comparative Antioxidant Activity of the Curcuminoids and Tetrahydrocurcuminoids in linoleic acid autoxidation model (determined by TBA method )

Fig 8: Comparative Antioxidant Activity of the Curcuminoids and Tetrahydrocurcuminoids in linoleic acid autoxidation model (determined by Thiocyanate method )