Metabolic profiling of two medicinal Piper species

Piper sarmentosum Roxb. (PS) and Piper cathayanum M. G. Gilbert & N. H. Xia (PC) are both listed as Traditional Chinese Medicine herbs. In this study, ultra-performance liquid chromatography mass spectrometry (UPLC-MS/MS) was used to analyze secondary metabolites and metabolically profile the leaves, stems and roots in PS and PC. A total of 110 and 92 differential metabolites were shared from various organs of PS and PC, respectively. Compared to the stems and roots of PS or PC, alkaloids and phenols in leaves of PS or PC accounted for 70% and 57% of the total alkaloids and phenols, respectively. An analysis of enriched metabolic pathways demonstrated that L-tyrosine and 4-hydroxycinnamic acid in PS were directly involved in five and three metabolic pathways, which are related to the biosynthesis of isoquinoline alkaloids and phenol backbones, respectively. The L-glutamic acid and oxoglutaric acid in PC were involved in seven and two metabolic pathways, respectively. L-glutamic acid synthesizes heme, tropane, piperidine and pyridine alkaloids, and the type Ⅱ polyketide backbone. Moreover, oxoglutaric acid generated via L-glutamic acid was mainly involved in the citrate cycle and played a fundamental role in determining these important metabolic processes.