Mechanism Of Garlic Thioethers Regulating Monoamine Oxidase A And Antidepressant Effect

As a medicinal and edible resource,garlic contains a variety of pharmacological activities of sulfides.In addition,garlic is activated by thiols to release hydrogen sulfide in vivo,and the target protein cysteine is modified by thiols similar to post-translational modification.Monoamine oxidase A（MAOA）is a key enzyme reflecting depression,and its inhibitor is one of the earliest antidepressants.Compared with other mental diseases,depression has higher treatment costs and serious side effects of synthetic drugs.Therefore,it is the main goal of this paper to study the mechanism of garlic sulfide and MAOA to explore the effect of this mechanism on antidepressant,and provide ideas for finding natural enzyme inhibitors in onion sulfides.The research content is mainly divided into three parts.In the first part,the in vitro reaction was used to explore the interaction mechanism.The inhibitory effect of allicin,diallyl trisulfide（DATS）,diallyl disulfide（DADS）on the activity of monoamine oxidase A was monitored by UV.The interaction mechanism between garlic sulfide and MAOA through the release of H₂S pathway was also investigated.The second part verifies the mechanism by molecular docking simulation.The third part of animal experiments verifies the effect of this mechanism in vivo.The experimental results are as follows:（1）Garlic sulfide and MAOA alone:UV-Vis absorption spectrum analysis showed that allicin/DATS inhibited the time of substrate decomposition,and DADS did not significantly inhibit the enzyme;enzyme kinetics revealed that the inhibitory effect of allicin on MAOA was a common inhibition.DATS has competitive inhibition on MAOA;fluorescence spectroscopy showed that allicin/DATS/DADS could combine with fluorescent amino acids in MAOA to produce endogenous static quenching,suggesting that the binding ability was allicin>DATS>DADS;circular dichroism showed that the secondary structure of enzyme protein changed after binding to sulfide;thermodynamic analysis revealed that allicin combined with MAOA mainly through hydrogen bond and van der Waals force,and DATS/DADS mainly through hydrophobic interaction.Molecular docking further verifies the thermodynamic results.（2）The effect of garlic sulfide as hydrogen sulfide donor on MAOA:UV showed that after MAOA was treated with inorganic hydrogen sulfide donor reagents Na₂S/Na HS/K₂S_nand allicin/DATS/DADS（reacting with GSH）,the enzyme activity was inhibited and the production was reduced.The enzyme activity was also inhibited after the thiol oxidant（H₂O₂）and thiol derivative（NEM）acted on the enzyme.The recovery of enzyme activity after adding thiol protector（DTT）showed that the action site was thiol.The changes in the mass spectra after DATS,K₂S_nand ASH treatment were analyzed by time-of-flight mass spectrometry,and it was found that sulfides could also modify the enzyme by sulfur alkylation.（3）Animal experiments to verify the antidepressant effect of sulfideThe forced swimming test,open field test and water maze test were used to preliminarily determine that the intragastric administration of allicin,DATS,DADS and Na HS could prevent LPS-induced depression.The activity of monoamine oxidase was inhibited,the level of nitric oxide was decreased,the activity of antioxidant enzymes was increased,and the content of malondialdehyde was decreased.It was proved that the sulfur compounds in garlic were similar to inorganic sulfides,which could inhibit the activity of monoamine oxidase A and prevent depression.