Curcumin Pharmacokinetics and Plasma Determination

Abstract

Although curcumin has been shown to exert a plethora of desirable biochemical, physiological and pharmacological activities, poor solubility and poor absorption in the free form in the gastrointestinal tract as well as rapid biotransformation to inactive forms greatly limit its utility. As a consequence, various formulations have been developed to enhance curcumin bioavailability, including those with liposomes, micelles, gelatin and polysaccharide complexes, and nano-particulate preparations including nano-crystals, nano-gels, nano-emulsions, nano-micelles, polymers, dendrimers, solid dispersions and conjugates. For various reasons, including differences in curcumin dose and material (administered) dose, inappropriate use of hydrolysis, differences in subjects and variations in plasma sample handling and analytical methods, meaningful comparisons of efficacy and bioavailability have been difficult to achieve. Due to the low detectability of curcumin and its metabolites in early studies with unformulated curcumin, hydrolysis of curcumin conjugates in plasma samples has been employed to enhance detectable levels of curcumin. Unfortunately, this practice has continued, with most pharmacokinetic studies of curcumin in humans still employing hydrolysis of plasma samples. As a consequence, plasma levels of free, bioactive curcumin are not being determined. This chapter reviews human pharmacokinetic studies involving curcumin formulations that have been conducted and published to date.