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Abstract

Pharmacokinetic studies of plant extract have been carried out worldwide. Our previous pharmacokinetic study of andrographolide, a major diterpenoid of Andrographis paniculata leaves given orally in inflammation-induced New Zealand rabbits, demonstrated that this compound was excreted in the form of free andrographolide and an unknown metabolite. This work aimed to study the RP-HPLC profile of andrographolide-glucuronic acid and andrographolide-glycine in rabbit feces by reacting equimols of the reactants (5 mg of andrographolide with 2.77 mg of glucuronic acid and 1.07 mg of glycine, in separate reaction, spiked into 10 g of rabbit feces), liquid-liquid extracted using water-ethylacetate (1:1) at 45-50 ^oC for 2 h, and subsequently, the extract was injected in a C18 column (particle size 5 µm, pore size 120 Å) with methanol-water (55:45) as the mobile phase. Moreover, ligand-ligand docking simulation also studied the binding mode of andrographolide with glucuronic acid and andrographolide with glycine. Results revealed that the maximum absorbance of standard andrographolide was detected at 227 nm and this compound was eluted at 6.120 min, glucuronic acid was eluted at 1.840 min, and glycine was at 2.207 min. The HPLC chromatogram of andrographolide-glucuronic acid extract demonstrated almost negligible peaks at 6.113 min and 6.107 min, which probably belong to each of the complexes, respectively. Moreover, andrographolide interacts with glucuronic acid via 1 hydrogen bond, although not favorable, and interacts with glycine via 2 hydrogen bonds. Taken together, andrographolide might undergo phase 2 biotransformation by glucuronidation and/or glycine conjugation in rabbits.

Keywords: Andrographolide, Anti-inflammatory, Biotransformation, In vitro study, Molecular docking simulation

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