Botanical Traceability And Chemical Composition Of Honey Based On Extractive Electrospray Ionization Mass Spectrometry

Honey is widely favored and concerned because of its high edible,medicinal,health and economic value.Honeys vary greatly in the chemical composition,quality and price.However,shoddy and adulterated honeys often exist in the market,which seriously damages the interests of consumers and is not conducive to the healthy development of the bee industry.At present,the methods of honey traceability mainly include chromatography,mass spectrometry and spectroscopy.However,most of these methods require complex sample pretreatments such as extraction,separation,and derivatization,which lead to the prolongation of analytical time,the consumption of the sample,and the loss of information,and are also not conducive to the rapid identification of honey varieties.Besides,honeys are diverse in metabolic chemicals collected by bees from nectariferous plants,therefore,investigating the chemical composition and typical metabolites of nectar and analyzing their distribution in honey are the keys to honey traceability research.For this purpose,a method based on extractive electrospray ionization mass spectrometry(EESI-MS)combined with chemometrics was used for the quick identification of rape honey,jujube honey,linden honey,acacia honey and Sapium discolor honey.What’s more,a facile and effective method was established by EESI-high resolution mass spectrometry(EESI-HRMS)for simultaneous and rapid detection of polyphenols and amino acids in nectar and honey.Combined with principal component analysis(PCA),the influence of nectar compounds on honey was explored in Citrus nectar and honey.And high-performance liquid chromatography with ultraviolet detector(HPLC-UV)was used to validate the results and explore the phenolic composition more comprehensively.The main research are as follows:1.EESI-MS combined with chemometric analysis was used for the identification of rape honey,jujube honey,linden honey,acacia honey and Sapium discolor honey.And 21 compounds were detected including 7 amino acids,7 organic acids,and 7 polyphenols.The detection time of a single sample is less than 1 min,and the composition of amino acids,organic acids and phenolic acids can be detected simultaneously.PCA showed that the 5 kinds of honeys were clearly distinguishable,and the cumulative contribution rate of PC1,PC2,and PC3 reached 87.1%.The mass spectral signals with the significant contribution were glyceric acid(m/z 105),succinic acid(m/z 117),and phenylacetic acid(m/z 13 5),citric acid(m/z 191),gluconic acid(m/z 195),and chlorinated peaks of monosaccharides(m/z 215)among the qualitative compounds.Cluster analysis(CA)showed that 5 honeys could be effectively distinguished when the critical value was 6.Partial least square discriminant analysis(PLS-DA)showed that 5 kinds of honey could effectively distinguished and R2 and Q2 were 0.881 and 0.876,respectively.Discriminant analysis(DA)showed that the discriminant accuracy of honey from these 5 types of different floral origin was 100%.2.The chemical composition of navel orange,mandarin,and tangerine nectars and their corresponding honeys of three Citrus plants were detected by EESI-HRMS,which was combined with PCA to clarify the similarities and differences of floral plants and their influence on honey composition.A total of 20 compounds were detected,including 12 phenolic compounds such as benzoic acid,hesperetin and 8 amino acids such as proline and serine.Results of the PCA indicated that there was no significant difference in chemical composition among three Citrus nectars and among three Citrus honeys,but significant chemical variation was found in nectars and their corresponding honeys.And caffeic acid(m/z 179),genistein(m/z 269),and hesperetin(m/z 301)may be the major differentiating substance for Citrus nectars and honeys among the qualitative compounds.The reason may be that the coffee acid is mainly derived from propolis rather than nectar,and hesperetin is derived from the hydrolysis of hesperidin in nectar.And hesperetin could be a typical metabolite of Citrus nectar.3.HPLC-UV combined with standards was used to identify and quantify 9 phenolic compounds in the nectar and honey samples of navel orang.e,mandarin,and tangerine.Four phenolic acid such as gallic acid and protocatechuic acid were detected in all samples.Chlorogenic acid was higher concentration in nectar than in honey as for mandarin(0.722μg/g in nectar and 0.158 μg/g in honey)and tangerine(1.008 μg/g in nectar and 0.158 μg/g in honey).Hesperidin was detected in all samples and showed higher concentrations in nectars(14.999-96.822 μg/g)than in honeys(0.784-2.751μg/g),and it represented the most abundant flavonoid compound in nectar.PCA using HPLC-UV data showed that chemical compositions were similar among three Citrus nectars,as well as among three Citrus honeys,but significant chemical variation was found in nectars and their corresponding honeys,which was consistent with EESI-HRMS and can prove the stability and reliability of EESI-HRMS.This paper established an identification model of honeys from different floral origins and the method for detecting compounds in nectar and honey based on EESI-MS.It is a fast and green method with low reagent consumption and simple sample pretreatment,which can be used for rapid analysis of samples with complex matrix such as honey and nectar.Especially for the chemical analysis of nectar which is very difficult to obtain,EESI-HRMS has a good application prospect and positive significance.The work could provide reference for identification of potential marker of Citrus honey,as well as theoretical basis and feasible method for the traceability,authenticity,and quality control of honey.