Development of an online UPLC-PDA-ESI-Q-TOF-MS-LOX-FLD system for rapid screening of anti-inflammatory compounds in Polygala tenuifolia Willd.

In this study, the first ultra-high performance liquid chromatography-photo-diode array-electrospray ionization-quadrupole-time-of-flight-mass spectrometry-lipoxygenase-fluorescence detector (UPLC-PDA-ESI-Q-TOF-MS-LOX-FLD) online system was developed for the identification and evaluation of anti-inflammatory active ingredients in Polygala tenuifolia Willd. Using this system, the UPLC fingerprints, mass fragments and LOX-binding peak profiles in the samples were rapidly and simultaneously obtained. A total of 101 compounds were isolated and identified and 38 compounds (11 oligosaccharide esters, nine xanthones, 17 saponins, and one glycosyloxyflavone) showed strong LOX-binding activity. Six compounds were selected to study their LOX-binding ability, and the results indicated that the content of the six compounds had a good linear relationship with the LOX-binding ability, and it was found that the substitution position, the type of substituent and the number of glycosyl groups all had a certain influence on the LOX-binding ability of the compounds. The LOX-binding activities of 10 compounds were verified by the surface plasmon resonance (SPR) technique and the activity results were consistent with the online system. After validation, we identified 7 active compounds that combined with LOX to exert anti-inflammatory effects for the first time. All the results fully demonstrate the efficiency, stability and reliability of the online system and this work provides an exemplary and useful method for the rapid screening of potential anti-inflammatory active compounds in P. tenuifolia and other traditional Chinese medicines. At the same time, it provides a new direction for screening small molecule inhibitors of enzymes like LOX.

The Ubiquitin E3 Ligase PRU2 Modulates Phosphate Uptake in Arabidopsis.

Phosphorus is an essential macronutrient for plants. The phosphate (Pi) concentration in soil solutions is typically low, and plants always suffer from low-Pi stress. During Pi starvation, a number of adaptive mechanisms in plants have evolved to increase Pi uptake, whereas the mechanisms are not very clear. Here, we report that an ubiquitin E3 ligase, PRU2, modulates Pi acquisition in Arabidopsis response to the low-Pi stress. The mutant pru2 showed arsenate-resistant phenotypes and reduced Pi content and Pi uptake rate. The complementation with PRU2 restored these to wild-type plants. PRU2 functioned as an ubiquitin E3 ligase, and the protein accumulation of PRU2 was elevated during Pi starvation. PRU2 interacted with a kinase CK2α1 and a ribosomal protein RPL10 and degraded CK2α1 and RPL10 under low-Pi stress. The in vitro phosphorylation assay showed that CK2α1 phosphorylated PHT1;1 at Ser-514, and prior reports demonstrated that the phosphorylation of PHT1;1 Ser-514 resulted in PHT1;1 retention in the endoplasmic reticulum. Then, the degradation of CK2α1 by PRU2 under low-Pi stress facilitated PHT1;1 to move to the plasma membrane to increase Arabidopsis Pi uptake. Taken together, this study demonstrated that the ubiquitin E3 ligase-PRU2-was an important positive regulator in modulating Pi acquisition in Arabidopsis response to low-Pi stress.