Spectroscopic Studies Of The Interaction Between Flavonoids From Citri Reticulatae Pericarpium And Immunoglobulin E

Type I allergic reaction is a kind of immune response mediated byimmunoglobulin E, it can cause bronchial asthma, urticaria, eczema, allergic rhinitisand many other disease symptoms. Most of the clinical allergy drugs are chemicalsynthetic which are mainly used to inhibit cytokine, such as astemizole,diphenhydramine etc.. As is known to all, these synthetic drugs have certain sideeffects. So, it has become a hot spot of research to search active components fromnatural products with the stronger anti-allergic and lower toxic side effects. Accordingto the allergic reaction mechanism, The reaction of IgE and its high affinity receptorsFcεRI has applied as a new drug target to screen the active anti-allergic drugs, such asH1receptor antagonists. So, this is a new research direction that search smallmolecule active compounds from the natural product which can inhibit combinationIgE and FcεRI.Citri Reticulatae Pericarpium as the dried fruit peel is a medicinal herbcommonly used in clinical practice. The modern pharmacological study have provedthat Citri Reticulatae Pericarpium has the functions of anti-allergic effect.5,6,7,8,4′-pentamethoxyflavone (Hesperetin) and3,5,6,7,8,3′,4′-heptamethoxyflavone extractedfrom Citri Reticulatae Pericarpi were used as the research objects in this work. Theinteraction between flavonoids and immunoglobulin E were studied by spectroscopyand molecular docking technology, the research results will play an important role inthe application of natural small molecules in the allergic disease. The experimentwas divided into two parts:In the first part, cadmium telluride (CdTe) quantum dots (QDs) was synthesizedcapped with glutathione (GSH) in aqueous solution. The transmission electronmicroscopy and fluorescence emission were applied to characterize the GSH-CdTeQDs. And then, GSH-CdTe QDs was used as a fluorescence probe to discuss thepossible reaction mechanisms about Hesperetin and3,5,6,7,8,3′,4′-heptamethoxyflavone by fluorescence quenching. According to the results, thefluorescence intensity of QDs was quenched significantly with the adding offlavonoids. Then, At the optimum experiment condition, IgE was added into thesystem, the fluorescence of QDs restored. Based on those results suggest that there are some interactions between flavonoids and IgE, the flavonoids from off the surface ofQDs, The mechanism was possible happened electron transfer from QDs toflavonoids respectively, So, the fluorescence of QDs restored.In the second part, the spectroscopy were applied to investigate the interactionsbetween Hesperetin,3,5,6,7,8,3′,4′-pentamethoxyflavone and Immunoglobulin IgErespectively basis on the above. Molecular docking is also applied to study interactionbetween flavonoids and IgE on the base of theory. Firstly, The binding constants,binding sites and the thermodynamic parameters were obtained by the fluorescencespectrometry. The effects of flavonoids on IgE secondary structure were studied usingthree-dimensional fluorescence, circular dichroism and synchronous fluorescence.The data from fluorescence spectrometry indicated that those interactions result in theendogenous fluorescence quenching of flavonoids, which mainly belongs to staticquenching mechanism, and the results revealed that hydrophobic forcesplayed a major role in the binding of flavonoids and IgE. Secondly, The data ofcircular dichroism range from195to250nm were applied computer fitting byprogram SELCON3, its fitting results show that compared with single IgE proteinsystem, The content of α-helix and β-turn structure of IgE are reduced, and thecontent of β-sheet and random coil structure are increased when the system containsHesperetin and3,5,6,7,8,3′,4′-pentamethoxyflavone, respectively.The research meaning of this paper is established the interaction between IgEand flavonoids extracted from Citri Reticulatae Pericarpium based on CdTe quantumdots by spectroscopy and molecular docking technology.In a word, it provides new research method for the study of natural products inanti-allergy activities and its mechanism.