Purpose: To develop a bioanalytical assay using RP-HPLC to quantify the curcuminoid calebin A, to characterize its pharmacokinetics in rats after intravenous (IV) and oral (PO) administration, to identify its pharmacological activities and to evaluate its content in natural health products.
Methods: An RP-HPLC method was developed for the detection of calebin A. Separation was carried out using a Phenomenex® Kinetex® C18 column with UV detection at 339 nm. An isocratic mobile phase consisting of acetonitrile and water with 10 mM ammonium formate (pH 7.0) (40:60, v/v) at a flow rate of 0.8 mL/min was employed. Linear standard curves were established and applied in the pharmacokinetic study. Calebin A was administered to male Sprague-Dawley (CD) rats IV (20 mg/kg) or PO (500 mg/kg) (n=4/route of administration). Serum and urine samples were collected for 72 h post dose. In vitro antioxidant activity, anti-inflammatory activity (cyclooxygenase and lipoxygenase inhibition), dipeptidyl peptidase-4 (DPP-4) inhibition and cytochrome P450 inhibitory activties of calebin A were examined using commercial assay kits. Content analysis of calebin A in 14 natural health products advertised to contain turmeric were carried out using methanolic extraction.
Results: The HPLC method was successfully applied to a pharmacokinetic study of calebin A in rats. After IV and PO administration of calebin A, the compound was detected as the aglycone and a glucuronidated metabolite. Oral bioavailabitily was found to be ~0.5%, serum half-life was ~1-3 h. Calebin A appears to be primarily excreted via non-renal routes. Calebin A possessed concentration-dependent antioxidant activity and DPP-4 inhibition. Calebin A appears to be a non-selective cyclooxygenase inhibitor and also a poor lipoxygenase inhibitor. The curcuminoid displayed in vitro interactions with CYP2D6 and CYP1A2. Content analysis of 14 natural health products that claimed to contain turmeric showed that concentration of calebin A was inconsistent among the products.
Conclusion: A successful assay was developed for the detection of calebin A using RP-HPLC. Preliminary pharmacokinetic studies indicate that an unoptimised formulation of calebin A has poor oral bioavailability. Calebin A exhibits various pharmacological activities. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.