Metabolite identification of the antimalarial naphthoquine using liquid chromatography–tandem high‐resolution mass spectrometry in combination with multiple data‐mining tools

Abstract

Naphthoquine (NQ) is one of important partner drugs of artemisinin-based combination therapy (ACT), which is recommended for the treatment of uncomplicated Plasmodium falciparum. NQ shows a high cure rate after a single oral administration. It is absorbed quickly (time to peak concentration 2-4 h) and has a long elimination half-life (255 h). However, the metabolism of NQ has not been clarified. In this work, the metabolite profiling of NQ was studied in six liver microsomal incubates (human, cynomolgus monkey, beagle dog, mini pig, rat and CD1 mouse), seven recombinant CYP enzymes (1A2, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4) and rat (plasma, urine, bile and feces) using liquid chromatography tandem high-resolution LTQ-Orbitrap mass spectrometry (HRMS ) in conjunction with online hydrogen/deuterium exchange. The biological samples were pretreated by protein precipitation and solid-phase extraction. For data processing, multiple data-mining tools were applied in tandem, i.e. background subtraction and followed by mass defect filter. NQ metabolites were characterized by accurate MS/MS fragmentation characteristics, the hydrogen/deuterium exchange data and cLogP simulation. As a result, five phase I metabolites (M1-M5) of NQ were characterized for the first time. Two metabolic pathways were involved: hydroxylation and N-oxidation. This study demonstrates that LC-HRMS in combination with multiple data-mining tools in tandem can be a valuable analytical strategy for rapid metabolite profiling of drugs.

The gender-related variability in the pharmacokinetics and antiplasmodial activity of naphthoquine in rodents

“…Furthermore, gender-specific pre-clinical pharmacological testing will enable comprehensive assessment of pharmacokinetic and pharmacodynamic actions of drugs. In a previous study, species similarity has been observed in NQ metabolism between human and rodents [17]. The major metabolic pathways included hydroxylation and N-oxidation, which were mainly mediated by CYP2D6.…”

“…To achieve sustainable use of NQ, collective efforts should be concerned to understand the inter-individual differences in response toward NQ therapy. In a previous study, the metabolism of NQ was mainly mediated by CYP2D6, which is known for its polymorphism and a gender-specific difference in its expression [17]. Women have been found to have a higher CYP2D6 activity [22].…”

“…The time to peak plasma concentration (t max ) of NQ was around 2-4 h with an extremely long elimination half-life (t 1/2 , 250-300 h) [16]. The major metabolic pathways of NQ were hydroxylation and N-oxidation, which were mainly mediated by CYP2D6, an enzyme well-known for its polymorphism and gender-specific differences in expression [17]. NQ was widely distributed in the tissue (liver, kidney and lung) and predominantly excreted from urine [9].…”