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Phospholipid fatty acids play the crucial role in biophysical properties and the function of cellular membranes. In the present study, an accurate and sensitive method was developed to quantify phospholipid fatty acids in biological samples by using chemical isotope labeling coupled with atmospheric pressure gas chromatography quadrupole-time-of-flight mass spectrometry (APGC/Q-TOF MS). APGC, a soft ionization source, was operated under proton-transfer condition by introducing methanol into the ionization source as a modifier, which provided high quantifiable molecular ion peaks to substantially enhance the sensitivity. Fatty acid standards were methylated with methanol-d4 to yield FAMEs-d3 that were used as one-to-one internal standards to ensure accurate quantification. Thirty fatty acids in phospholipids were accurately quantified in wide linear range with limit of quantification ranging from 84.6 to 113.2 pg/mL. The newly developed method was successfully applied to quantify phospholipid fatty acids in brain and liver tissues from both fat-1 and WT mice. This method might be expanded to quantify free fatty acids or other conjugated fatty acids in biological samples or other matrices.

Phyllanthus Urinaria L. (PUL) is a traditional Chinese medicine used to treat hepatic and renal disorders. However, the mechanism of its hepatoprotective action is not fully understood. In the present study, blood biochemical indexes and liver histopathological changes were used to estimate the extent of hepatic injury. GC/MS and LC/MS-based untargeted metabolomics were used in combination to characterize the potential biomarkers associated with the protective activity of PUL against CCl4-induced liver injury in rats. PUL treatment could reverse the increase in ALT, AST and ALP induced by CCl4 and attenuate the pathological changes in rat liver. Significant changes in liver metabolic profiling were observed in PUL-treated group compared with liver injury model group. Seventeen biomarkers related to the hepatoprotective effects of PUL against CCl4-induced liver injury were screened out using nonparametric test and Pearson's correlation analysis (OPLS-DA). The results suggested that the potential hepatoprotective effects of PUL in attenuating CCl4-induced hepatotoxicity could be partially attributed to regulating L-carnitine, taurocholic acid, and amino acids metabolism, which may become promising targets for treatment of liver toxicity. In conclusion, this study provides new insights into the mechanism of the hepatoprotection of Phyllanthus Urinaria.

Citri Reticulatae Pericarpium, mainly including the pericarp of Citrus reticulata Blanco and the pericarp of Citrus reticulata 'Chachi', has been consumed daily as food and dietary supplement for centuries. In this study, GC-MS based metabolomics was employed to compare comprehensively the volatile constituents in Citrus reticulata Blanco and Citrus reticulata 'Chachi'. Principal component analysis and orthogonal partial least squares discrimination analysis indicated that samples could be distinguished effectively from one another. Fifteen metabolites were finally identified for use as chemical markers in discrimination of Citri Reticulatae Pericarpium samples. The antimicrobial activity against Gram-negative and Gram-positive bacteria of the volatile oil from Citrus reticulata Blanco and Citrus reticulata 'Chachi' was investigated preliminarily.