Curcumin is a widely studied natural compound which has shown tremendous in vitro therapeutic potential. Despite that, the clinical efficacy of the native curcumin is weak due to its low bioavailability and high metabolism in the gastrointestinal tract. During the last decade, researchers have come up with different formulations with a focus on improving the bioavailability of curcumin. As a result, a significant number of bioavailable curcumin-based formulations were introduced with the varying range of enhanced bioavailability. The purpose of this review is to collate the published clinical studies of curcumin products with improved bioavailability over conventional (unformulated) curcumin. Based on the literature search, 11 curcumin formulations with available human bioavailability and pharmacokinetics data were included in this review. Further, the data on clinical study design, analytical method, pharmacokinetic parameters and other relevant details of each formulation were extracted. Based on a review of these studies, it is evident that better bioavailability of formulated curcumin products is mostly attributed to improved solubility, stability, and possibly low first-pass metabolism. The review hopes to provide a quick reference guide for anyone looking information on these bioavailable curcumin formulations. Based on the published reports, NovaSol^?(185), CurcuWin^? (136) and LongVida^? (100) exhibited over 100-fold higher bioavailability relative to reference unformulated curcumin. Suggested mechanisms accounting for improved bioavailability of the formulations and details on the bioanalysis methods are also discussed.

Key words: Curcuma longa, Plant extracts, Curcumin, Human pharmacokinetics, Bioavailability, Liquid chromatography–mass spectrometer/mass spectrometer