Tissue distribution of (Lipocurc™) liposomal curcumin and tetrahydrocurcumin following two- and eight-hour infusions in Beagle dogs

This study interrogated whether different durations of intravenous infusions of lipocurc™ would alter curcumin metabolism, tissue distribution and whether treating necropsied tissues of Beagle dogs with phosphoric acid prior to measuring curcumin and its metabolite, tetrahydrocurcumin (THC), would stabilize the compounds allowing for accurate analytic measurements. Two cohorts comprising two male and two female dogs were infused each intravenously with 10 mg/kg lipocurc™, either over two hours or over eight hours. Tissue data from each cohort was averaged from four dogs. Curcumin and THC distributed among all 13 tissues were examined at necropsy. The highest curcumin level was observed in the lungs followed by the liver. Tissue levels of curcumin in the lung, spleen and liver increased substantially following the eight-hour infusion compared to the two-hour infusion. The pancreas, kidney and urinary bladder also contained relatively high curcumin levels. Tissue partition coefficients for curcumin and THC were also higher for the eight-hour infusion than the two-hour infusion. The tissue THC/curcumin ratio varied in a tissue-specific manner and was lower for the eight-hour compared to the two-hour infusion. In conclusion, this raised the possibility that prolonged infusion of curcumin may facilitate distribution into tissues via a transporter-dependent mechanism and elevated tissue concentrations of curcumin may inhibit or saturate a putative reductase enzyme converting curcumin to THC. The addition of phosphoric acid stabilized the levels of curcumin and THC in some but not all the examined tissues, raising issues of tissue-specific curcumin and THC stability.

Infusion pharmacokinetics of Lipocurc™ (liposomal curcumin) and its metabolite tetrahydrocurcumin in Beagle dogs

Curcumin's instability and its metabolite, tetrahydrocurcumin (THC) pose a major issue for the establishment of dependable pharmacokinetics and excretion profiles. Additional pharmacokinetic variances are associated with durations of intravenous infusions. We found that stabilizing curcumin with phosphoric acid allows accurate quantitative determinations of curcuminoids in the plasma and bile, by preventing degradation during the analytical processes. Two male and two females dogs were infused with Lipocurc™ 10 mg/kg over two hours, and another four dogs (two males and two females) were infused with Lipocurc™ 10 mg/kg over eight hours. Plasma levels of curcumin and THC were determined during the infusions and at necropsy. THC levels were 6.3-9.6-fold higher than curcumin during both infusion rates, suggesting a combination of a high-rate of enzymatic curcumin metabolism and a comparatively slower rate of blood THC clearance. When levels of curcumin and THC were compared during infusion durations, the two-hour infusion levels were significantly higher than the eight-hour infusion. The plasma half-lives of both compounds following the two-hour infusion ranged from 0.4-0.7 hours, and was a consequence of both hepatic and renal clearance However, at higher plasma concentrations renal excretion predominated, particularly with THC. Enhanced clearance rates were noted during eight-hour infusions, which prevented achieving a steady state. These observations suggest that for leukemias and lymphomas, the two-hour infusion may be advantageous based upon higher concentration profiles, and unstimulated clearance rates, however data on curcumin penetration into circulating hematopoietic cancer cells and efficacy data are required in order to confirm these suggestions.