ABSTRACT
Pseudo-allergic reactions (PARs) widely occur upon application of drugs or functional foods. Anti-pseudo-allergic ingredients from natural products have attracted much attention. This study aimed to investigate anti-pseudo-allergic compounds in licorice. The anti-pseudo-allergic effect of licorice extract was evaluated in rat basophilic leukemia 2H3 (RBL-2H3) cells. Anti-pseudo-allergic compounds were screened by using RBL-2H3 cell extraction and the effects of target components were verified further in RBL-2H3 cells, mouse peritoneal mast cells (MPMCs) and mice. Molecular docking and human MRGPRX2-expressing HEK293T cells (MRGPRX2-HEK293T cells) extraction were performed to determine the potential ligands of MAS-related G protein-coupled receptor-X2 (MRGPRX2), a pivotal target for PARs. Glycyrrhizic acid (GA) and licorice chalcone A (LA) were screened and shown to inhibit Compound48/80-induced degranulation and calcium influx in RBL-2H3 cells. GA and LA also inhibited degranulation in MPMCs and increase of histamine and TNF-α in mice. LA could bind to MRGPRX2, as determined by molecular docking and MRGPRX2-HEK293T cell extraction. Our study provides a strong rationale for using GA and LA as novel treatment options for PARs. LA is a potential ligand of MRGPRX2.
Subject(s)
Anti-Allergic Agents , Glycyrrhiza , Hypersensitivity , Animals , Anti-Allergic Agents/pharmacology , Anti-Allergic Agents/therapeutic use , Calcium/metabolism , Cell Degranulation , HEK293 Cells , Humans , Hypersensitivity/drug therapy , Mast Cells/metabolism , Mice , Mice, Inbred C57BL , Molecular Docking Simulation , Nerve Tissue Proteins/metabolism , Rats , Receptors, G-Protein-Coupled/genetics , Receptors, G-Protein-Coupled/metabolism , Receptors, Neuropeptide/metabolism , Receptors, Neuropeptide/therapeutic useABSTRACT
In this study, the inhibitory effects of four anthraquinones including chrysophanol, emodin, physcione and rhein on tyrosinase were investigated by enzyme inhibition assay. The results indicated that all of anthraquinones could significantly inhibit the activity of tyrosinase in a competitive manner. To gain insight into the inhibitory mechanism of anthraquinones on tyrosinase, spectroscopic analysis combined with molecular docking studies were performed. Fluorescence results showed that anthraquinones interacted with tyrosinase by static quenching in a molecular ratio of 1:1. Circular dichroism and molecular docking suggested that anthraquinones could not chelate directly the copper ions but they could bind to amino acid residues in the active site of tyrosinase via electrostatic forces and hydrophobic interactions, as well as hydrogen bonds, and the binding processes resulted in the conformational changes of tyrosinase and prevented the substrate (L-DOPA) from entering the active site, which led to the decrease of tyrosinase activity. Our study in this paper provides a scientific basis for revealing the inhibition of tyrosinase activity by anthraquinone compounds. As a natural inhibitor of tyrosinase, anthraquinones can be used as a potential agent to reduce enzymatic browning reactions, such as food browning and melanization of skin.
Subject(s)
Anthraquinones/pharmacology , Enzyme Inhibitors/pharmacology , Monophenol Monooxygenase/antagonists & inhibitors , Catalytic Domain , Circular Dichroism , Emodin/analogs & derivatives , Emodin/pharmacology , Hydrogen Bonding , Hydrophobic and Hydrophilic Interactions , Molecular Docking Simulation/methods , Spectrometry, Fluorescence/methodsABSTRACT
In this paper, the inhibitory kinetics of aloe-emodin on the activity of tyrosinase and the inhibitory mechanism have been investigated by using spectroscopic and molecular docking techniques. The results showed that aloe-emodin inhibited tyrosinase activity in a competitive manner. The binding constants, number of binding sites and thermodynamic parameters obtained at different temperature suggested that aloe-emodin spontaneously binds to tyrosinase at one binding site, mainly via electrostatic forces. Analysis by UV-vis absorption (UV), circular dichroism (CD) and molecular docking indicated that aloe-emodin bound directly into the catalytic cavity and that binding of aloe-emodin to tyrosinase induced conformational changes of the enzyme and blocked the catalytic center of the enzyme preventing binding of the substrate, which caused the inhibition of the tyrosinase activity.
Subject(s)
Anthraquinones/metabolism , Anthraquinones/pharmacology , Monophenol Monooxygenase/chemistry , Monophenol Monooxygenase/metabolism , Anthraquinones/chemistry , Binding Sites , Catalytic Domain , Circular Dichroism , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/metabolism , Molecular Docking Simulation , Monophenol Monooxygenase/antagonists & inhibitors , Protein Conformation , Spectrometry, Fluorescence , Spectrophotometry, Ultraviolet , Static Electricity , ThermodynamicsABSTRACT
In this study, the molecular interactions between pepsin and three pyrethroid insecticides, including fenvalerate, cyhalothrin and deltamethrin, were investigated by multi-spectroscopic and molecular docking methods under mimic physiological pH conditions. The results indicated that all of these insecticides could interact with pepsin to form insecticide-pepsin complexes. The binding constants, number of binding sites and thermodynamic parameters measured at different temperatures indicated that these three pyrethroid insecticides could spontaneously bind with pepsin mainly through electrostatic forces and hydrophobic interactions with one binding site. According to the theory of Föster's non-radioactive energy transfer, the distance (r) between pepsin and three pyrethroid insecticides were all found to be less than 7 nm, which implied that the energy transfer occurred between pepsin and these insecticides, leading to the quenching of pepsin fluorescence. Synchronous and three-dimensional fluorescence, CD spectra and molecular docking results indicated that all tested pyrethroid insecticides bound directly into the enzyme cavity site and the binding of insecticides into the cavity influenced the microenvironment of the pepsin activity site which resulted in the extension of peptide strands of pepsin with loss of α-helix structures.Copyright © 2016 John Wiley & Sons, Ltd.
