In order to find better LODs LOQs and peak

In order to find better LODs, LOQs and peak shape researchers used different derivatization agents along with dansyl chloride. However, these procedures required longtime for sample preparation, low recovery, the chance of contamination; products instability and some reagents were unable to derivatize the secondary amines [29]. Dansyl chloride (1-dimethylaminonaphthalene-5-sulphonyl chloride) is the most popular reagent since its reaction with HA, and other BAs is simple, fast, and can simultaneously analyze HA along with others BAs. However, on the other hand, the use of ammonia and the reaction above 65 °C can distort peaks, as well as ammonia, is a hazardous chemical for health [30]. Dabsyl chloride (4-dimethylaminoazobenzene-4-sulphonyl chloride) derivatization is superior to dansyl chloride as ammonia is not required [31]. Benzyl chloride also reacts with the phenolic compounds present in the sample and form derivatives. O-phthaldialdehyde, N-acetyl-l-cysteine [32] and naphthalene 2,3-dicarboxaldehyde/cyanide ions [33] need long time for the analysis, and both are specific to the primary amines while 2,6-dimethyl-4-quinolinecarboxylic HG-9-91-01 N-hydroxysuccinimide ester [34] used for the analysis of primary and secondary amines. The reaction of 4-chloro-3,5-dinitrobenzotrifluoride with histamine was pH dependent which also does not have good solubility without the addition of organic solvent methanol, and undergoes hydrolysis which may cause precipitation of reagent and derivatives [35]. So far, in best of our knowledge histamine was not indirectly detected by HPLC-UV without derivatization. There are few papers in the literature which reported HA along with others BAs without derivatization by using HPLC-MS technique, which is very expensive and also operational principle is different from HPLC-UV [36]. Thus, efficient and improved methods are always pre-requisite that validates the acceptance or rejection of food products within a short time. Herein, we proposed a novel method for the detection of histamine indirectly without sample derivatization by HPLC-UV. In order to find the appropriate probe, we applied different UV absorbing probes for determination of histamine. In this method, we used 2,5-DHBA UV probe in the mobile phase which works as a co-ion in the mobile phase and reacts with HA online on the column when the sample is passing through the column. The absorptivity of the HA was lower than the UV probe, so it appeared as a negative peak in the chromatogram. LOD and LOQs were enhanced by applying different pH and the concentration of the UV probe in the mobile phase. Thus, we were able to determine the histamine within 5 min.
Materials and methods
Results and discussion
Conclusion
Acknowledgment The research project was financed by the Shanghai Municipal Natural Science Foundation (16ZR1401400).
Introduction Astrocytes are the most abundant cell type in the central nervous system. They are involved in a wide range of physiological processes, including blood flow regulation, energy metabolism, ionic homoeostasis, and synaptic function.4, 5 The ability of astrocytes to modulate synaptic function is, in part, mediated by their ability to bind locally released neurotransmitters, and respond with the release of gliotransmitters, such as adenosine triphosphate (ATP), glutamate, and d-serine.6, 7 Gliotransmitter release appears to be disturbed under pathological conditions, and is associated with neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease.8, 9 Released neurotransmitters bind to various subclasses of G protein-coupled receptors (GPCRs) on astrocytes to activate intracellular signalling and regulate intracellular second messengers. Signalling through Gq-coupled GPCRs can increase intracellular Ca2+ ([Ca2+]i) concentration through the activation of phospholipase C (PLC); PLC cleaves the membrane phospholipid phosphatidylinositol 4,5-bis-phos-phate to yield 1,2-diacylglycerol (DAG) and inositol 1,4,5-triphosphate (InsP3), the latter of which can bind to InsP3 receptors leading to Ca2+ release from intracellular stores. In contrast, signalling through Gs-coupled GPCRs activates adenylyl cyclase, which increases the formation of cyclic AMP (cAMP). The importance of Gq-linked intracellular Ca2+ signalling for gliotransmitter release has been highlighted in several studies.8, 9, 12 Furthermore, a connection between cAMP treatment and enhanced glutamate release from astrocytes was reported.