Metabolites and Metabolic Pathway of Quinocetone in Apostichopus japonicus
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Abstract:
A high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method was established to conduct qualitative analysis and structural elucidation of the unknown quinocetone metabolites in the body wall of Apostichopus japonicus. Apostichopus japonicus were exposed to the one-time feed containing 20 mg/kg of quinocetone for 24 h, and then were transferred to clean seawater for 72 h. Sea cucumber samples were collected regularly during the experiment for analysis after removal of the viscera. In this study, acetonitrile was used for direct extraction, the extract was dried, and the dried sample was reconstituted in a volumetric flask. After hydrochloric acid hydrolysis, sample enrichment and purification were performed on a solid-phase extraction (SPE) cartridge to detect the quinocetone in the Apostichopus japonicus body wall due to the two pre-treatments as well as to extract and purify the possible metabolites. The metabolites were separated on an ACQUITYTM ? BEH C18（2.1 mm?50 mm, 1.7 μm）column by gradient elution with acetonitrile-water (containing 0.1% formic acid) as the mobile phase, and were detected using full-scan-data-dependent scan (Fullscan-DDA) by positive ion electrospray ionization (ESI+). By comparing the MS1 and MS2 ions of the test sample with those of quinocetone and other metabolite standards, the metabolite MQCA (3-methyl-quinoxaline-2-carboxylic acid) was identified in Apostichopus japonicus body wall, along with other four possible, metabolites for the first time.
