Rapid detection and structural characterization of methysticin metabolites generated from rat and human liver microsomes and hepatocytes using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry.

RATIONALE: Methysticin is a naturally occurring ingredient isolated from Piper methysticum Forst. The metabolic profile of methysticin is unknown. The goal of this study was to elucidate the metabolism of methysticin using rat and human liver microsomes and hepatocytes. METHODS: The incubation samples were analyzed using ultra-high-performance liquid chromatography coupled with quadrupole/orbitrap high-resolution mass spectrometry (UHPLC-HRMS). The structures of the metabolites were characterized based on the elemental composition, exact mass, and product ions. RESULTS: A total of 10 metabolites were detected and identified. Among these metabolites, M4 (ring opening of 1,3-benzodioxole) was the predominant metabolite in rat and human liver microsomes. M4 and its glucuronide conjugate (M2) were the major metabolites in rat and human hepatocytes. The metabolic pathways of methysticin are summarized as follows: (a) oxidative ring opening of 1,3-benzodioxole forms the catechol derivative (M4), which subsequently undergoes glucuronidation (M1 and M2), methylation (M8), and sulfation (M7). (b) Demethylation to yield desmethyl methysticin (M6), followed by glucuronidation (M3 and M5). (c) Hydroxylation (M9 and M10). CONCLUSIONS: For the first time, this study provides new information on the in vitro metabolic profiles of methysticin, which facilitates an understanding of the disposition of this bioactive ingredient.

Next-generation sequencing-based molecular diagnosis of 12 inherited retinal disease probands of Uyghur ethnicity.

Inherited retinal disease (IRD) is a category of genetic disorders affecting retina. Understanding the molecular basis of IRD is vital for clinical and genetic classification of patients. Uyghur people is an isolated ethnic group mainly residing in northwestern China with genetic admixture from Europeans and East Asians. The genetic etiology of IRD in this specific population still remains unknown. Here, by next-generation sequencing (NGS), we screened mutations in over 200 known retinal disease genes in a cohort of 12 unrelated Uyghur IRD probands. Out of the 12 probands, six are solved with high confidence, two with low confidence, while the remaining four are unsolved. We identified known disease-causing alleles in this cohort that suggest ancient Uyghur migration and also discovered eight novel disease-associated variants. Our results showed NGS-based mutation screening as a reliable approach for molecular diagnosis. In addition, this approach can also be applied to reveal the genetic history of a specific ethnic group.