OBJECTIVETo investigate the antipyretic mechanism of Herba Ephedrae (Eph)-Ramulus Cinnamomi (RC) herb pair on yeast-induced pyrexia in rats.

METHODSTotally 30 qualified male SD rats were randomly assigned to the normal control (NC) group, the pyrexia model (model) group, the Eph, RC and Eph-RC treatment groups by a random digital table, 6 rats in each group. Each rat received a 20% aqueous suspension of yeast (10 mL/kg) except the NC group. The 3 treatment groups were administered 8.1, 5.4 and 13.5 g/kg Eph, RC and Eph-RC respectively at 5 and 12 h after yeast injection, the NC group and the model groups were administered equal volume of distilled water. Rectal temperatures were measured at 0, 6, 8, 10, 12, 15, 18, 24 and 30 h and urine was collected prior to yeast injection and at 6, 10, 18, 24, 30, and 36 h after yeast injection. Then urine metabolomic profiling by gas chromatography tandem mass spectrometry, coupled with multivariate statistical analysis and pattern recognition techniques were used to explore the antipyretic effects of Eph-RC. Partial least squares discriminate analysis was used to analyze the metabolomics dataset including classification and regression in metabolomics plot profiling.

RESULTSCompared with the NC group, rectal temperatures were significantly higher in the model group (P<0.01), while 3 treatment groups decreased significantly compared with the model group (P<0.05 or P<0.01). Rectal temperatures of Eph-RC-treated rats started to go down at 6 h, and markedly decreased at 8, 12, 15, 18 and 24 h (P<0.05 or P<0.01), while those of the Eph and RC groups had decreased firstly at 8 h and were markedly lower at 12 h (P<0.05 or P<0.01). Seventeen potential biomarkers related to pyrexia were confirmed and identified, including pyruvic acid, L-phenylalanine, L-tyrosine, phenylacetic acid, hippuric acid, succinic acid, citrate and so on. Eight potential alterations of metabolic pathways including phenylalanine metabolism, citrate cycle, tryptophan metabolism, biosynthesis of valine, leucine and isoleucine, were identified in relation to the antipyretic effects of Eph-RC using MetPA software.

CONCLUSIONThe antipyretic effect of Eph-RC herb pair on yeast-induced pyrexia in rats involved correction of perturbed amino acid, fatty acid, and carbohydrate metabolism according to the metabolic pathway analysis with MetPA.