| Polymethoxyflavones(PMFs)are a unique class of flavonoids in citrus plants with a series of significant bioactivities.Surface-enhanced Raman spectroscopy(SERS),with outstanding characteristics of high sensitivity and efficiency,especially the "fingerprints" mapping features,can be used for the detection of PMFs.The optimization study of surface-enhanced Raman spectroscopy(SERS)detection for polymethoxyflavones(PMFs)was carried out for high performance of SERS in the detection of citrus bioactive components.The disciplinarian of TLC-SERS technique in separation and detection of PMFs,improvement of the detection rate through TLC-SERS was systematically studied,with the purpose to establish efficient SERS methods for the detection of PMFs from complex samples.SERS barcodes were also established based on the relasionship between SERS results and PMFs chemical structures,combined with structure-activity relationship study to reveale the relevant laws between SERS barcodes and biological activity.Simultaneous identification of chemical structures and biological activities of bioactive components was achieved with SERS barcodes,which further enhances the detection function of SERS in the practical application,and provides important scientific guidance for the efficient and rapid detection of specific chemical components in food and other complex matrices.The main results are as follows:(1)In the case of nobiletin,the optimization of the detection conditions was carried out and the optimal condition was finally obtained as follows,laser wavelength 514 nm,exposure time 20 s,power 3.0 mW and the reaction time of Ag dendrites 20 s,which was applicable to both PMFs and hydroxylated PMFs.These results not only improved the SERS detection efficiency of PMFs,but also laid a firm foundation for the further use and development of SERS technology in efficient and rapid detection of food bioactive ingredients.(2)Efficient separation and detection of 12 PMFs with TLC-SERS technology: TLC analogues and their separation effect in UV fluorescence(254 nm and 365 nm)and dyeing(hydrochloride vanillin-sulfuric acid and hydrochloric acid-ferric chloride)were detailed analysis,the optimal 2D-TLC elution conditions(DCM/MeOH=20:1 and Pet/Ace=6:4)were obtained and under this condition,the separation effect is better than that of HPLC.All of 12 PMFs were well separated.Further combined detection for PMFs was SERS,which achieved simultaneous separation and detection of a variety of PMFs and laied the foundation for the efficient extraction and detection of bioactive components in complex matrix.(3)The simultaneous characterization of chemical structures and bioactivities of different kinds of citrus components: all of nine citrus bioactive components were characterized and discriminated by surface-enhanced Raman spectroscopy(SERS)and constructed SERS barcodes based on data processing to recognize chemical structures of citrus ingredients.The relationships between antioxidant activities and the characteristic peaks of SERS barcodes were also established,which increased the function of SERS barcodes in recognition of bioactivities.Thus,SERS barcodes,which can be used for simultaneous characterization of chemical structures and bioactivities of different kinds of citrus components,were established for the first time.What's more,SERS barcodes also exhibited the potential in quantitative analysis of citrus bioactive components with high sensitivity low to 40 ng for analogues of nobiletin and 60 ng for analogues of tangeretin,hesperidin,synephrine and ?-carotene.The innovative use of SERS to achieve the simultaneous determination of chemical structures and biological activities of components in food,which can greatly enhance the detection function of SERS with high efficiency.At the same time,if combined with appropriate separation technology,SERS technology will greatly promote the rapid,convenient and efficient detection of functional components in food complex matrix. |
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