Green Synthesis Of Novel Flavonoids And Study Of Their Activity

Flavonoids are a diverse class of natural compounds found in various plant sources and have been extensively studied for their health benefits.In recent years,there has been a great deal of interest in flavonoid compounds as food additives to provide functional and sensory benefits to foods.Flavonoid compounds have been found to exhibit various functional properties such as antioxidant,antimicrobial,and anti-inflammatory,contributing to the shelf life of foods and promoting health.In addition to their functional properties,this class of compounds can also provide sensory benefits to foods such as color and flavor modulation.The increasing demand for dietary health in modern society has provided a favorable direction for the development of novel flavonoid compounds in food additives.However,flavonoid compounds extracted from natural plants suffer from low purity,low activity,or co-existence with toxicity.Biofermentation and other synthetic methods also suffer from low yields or single-product structures.Therefore,a sustainable photocatalytic chemical synthesis method was developed to prepare a series of novel flavonoid compounds with chromones and pyrrole as the central structure,and their antioxidant activities were investigated.The main contents are as follows:Chapter one:Introduction to the application of flavonoid compounds in food and their sources(including isolation from nature for extraction and purification and synthesis by chemical or biological means).The various physiologically active functions,food applications and chemical synthesis methods of flavonoid compounds are outlined to provide the basis for the selection of the topic of this thesis.Finally,the design ideas and research content of this topic are presented.Chapter two:mainly describes the chemical synthesis of the first five compounds 3-cyanocyanin and its analogues and arylglycine.By chemical means,the electron donor group or electron absorbing group modified 3-cyanocyanin and its analogues contain different substituents of arylglycine.Chapter three:The cyclization reactions of 3-cyanotryptones and their analogs and arylglycines were investigated.The reaction conditions(photosensitizer type,solvent,material concentration,different gas atmospheres,and base modulation)were optimized under blue light irradiation at 450-455 nm using 3-cyanotryptones and N-phenylglycine as template substrates.The optimal conditions obtained were:a material ratio of 1:3 for the chromone precursor and aryl glycine,addition of 2%mmol 4CzIPN as the reaction photocatalyst,a solvent of acetonitrile,a material concentration of 0.1 M(calculated for the chromone precursor),and a stirred reaction under air atmosphere with 450-455 nm blue light irradiation for 36 h at room temperature.Next,the substrates were expanded to obtain 20 novel flavonoid(chromone and pyrrolidine structure)target compounds,one decarboxylated chromone and pyrrolidine target compound,and two uncyclized chromone addition compounds.Then the mechanism of the reaction was verified by TEMPO radical trapping experiment,light switch interval experiment and Stern-Volmer fluorescence quenching experiment and a reasonable and feasible reaction mechanism was proposed.Finally,the 23 unreported novel flavonoid products were characterized with corresponding data including 1H NMR,13C NMR,19F NMR and high-resolution mass spectrometry.Chapter four:Activity testing of the obtained expected target compounds.The initial screening of the scavenging ability of DPPH radicals or ABTS+radicals revealed that the target compounds with phenolic hydroxyl groups had the strongest scavenging ability for both radicals,reaching 83%and 94%,respectively.Using Vc as the standard curve,the scavenging ability of the product with phenolic hydroxyl group for DPPH radicals and ABTS+radicals was calculated according to the regression equation as equivalent to 10.0 μg/mL and 20.8 μg/mL Vc,respectively,and the IC50 values for the two radicals in this subject were calculated using SPSS,which were 0.303 mg/mL and 0.179 mg/mL.In summary,the synthesis method used in this project is in accordance with the green and sustainable principles,and the new flavonoid compound(chromone and pyrrole structure)synthesized has high purity and certain antioxidant activity,which breaks the definition range of flavonoid compounds in the general sense.The good results obtained provide useful reference for the subsequent research of this class of compounds in food and medicine,and it is expected to be applied as an antioxidant and functional food additive of new flavonoid components.