Background/Aim: The aim of this study was to investigate the distribution of curcumin (in the form of Lipocurc™) and its major metabolite tetrahydrocurcumin (THC) in Beagle dog and human red blood cells, peripheral blood mononuclear cells (PBMC) and hepatocytes. Materials and Methods: Lipocurc™ was used as the source of curcumin for the cell distribution assays. In vitro findings with red blood cells were also compared to in vivo pharmacokinetic data available from preclinical studies in dogs and phase I clinical studies in humans. Results: High levels of curcumin were measured in PBMCs (625.5 ng/g w.w. cell pellet or 7,297 pg/10⁶ cells in dog and 353.7 ng/g w.w. cell pellet or 6,809 pg/10⁶ cells in human) and in hepatocytes (414.5 ng/g w.w. cell pellet or 14,005 pg/10⁶ cells in dog and 813.5 ng/g w.w. cell pellet or 13,780 pg/10⁶ cells in human). Lower curcumin levels were measured in red blood cells (dog: 78.4 ng/g w.w. cell pellet or 7.2 pg/10⁶ cells, human: 201.5 ng/g w.w. cell pellet or 18.6 pg/10⁶ cells). A decrease in the medium concentration of curcumin was observed in red blood cells and hepatocytes, but not in PBMCs. Red blood cell levels of THC were ~5-fold higher in dog compared to human and similar between dog and human for hepatocytes and PBMCs. The ratio of THC to curcumin found in the red blood cell medium following incubation was 6.3 for dog compared to 0.006 for human, while for PBMCs and hepatocytes the ratio of THC to curcumin in the medium did not display such marked species differences. Conclusion: There was an excellent correlation between the in vitro disposition of curcumin and THC following incubation with red blood cells and in vivo plasma levels of curcumin and THC in dog and human following intravenous infusion. The disposition of curcumin in blood cells is, therefore, species-dependent and of pharmacokinetic relevance.

Muhammad Majeed

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