Application Of Analysis To Citrus Grandis "Tomentosa" And Citrus Grandis(L.) Osbeck By Gas Chromatography-ion Mobility Spectrometry

Citri grandis exocarpium(CGE)is the immature or nearly mature dried exocarp of Citrus grandis "Tomentosa" or Citrus grandis(L.)Osbeck and its cultivars,belong to the family Rutaceae.The former is commonly known as"Maojuhong"(MJH)which mainly produced in Huazhou district of Guangdong Province in China and the latter as "Guangjuhong"(GJH)produced in other areas.The price of MJH is higher than GJH.In recent years,the research on the flavonoids of CGE has made some progress,but there are few reports on the research and application of the volatile components(VOCs)of CGE.ObjectiveTo study the difference of VOCs in MJH and GJH by gas chromatography-ion mobility spectrometry(GC-IMS),and explore the application of GC-IMS in the VOCs of CGE.MethodsBy optimizing the parameters of GC-IMS,the VOCs of CGE were analyzed,and the characteristic spots of MJH and GJH were screened,The characteristic spots were characterized by GC-IMS database and by comparing the GC-IMS migration behavior with relative reference materials.The VOCs of commercial CGE samples were determined,and the correlation between the composition differences and the appearance characteristics(whether the surface is covered with fine hair or not)was analyzed.To compare the differences of VOCs between CGE and its relative varieties Citri fructus.The effects of different drying temperatures,different parts of fruit,different producing areas and different irradiation doses on the volatile components of MJH and GJH were investigated.Gas chromatography(GC)was used to analyze the VOCs of CGE.After establishing the GC fingerprints and analyzing of VOCs of MJH and GJH,and the differences between GC and GC-IMS were compared.ResultsA GC-IMS analysis method was established,and total of 387 spots of CGE were detected in 64 batches of definite source CGE samples.After optimizing analysis parameter,12 characteristic spots were selected for the determination of commercial CGE samples.The results of principal component analysis(PCA)showed that the VOCs of MJH from various Citrus grandis(L.)Osbeck were similar and could be divided into a group,which was different from the VOCs of MJH from Citrus grandis "Tomentosa" in Huazhou.The results of determination and analysis of VOCs in commercial CGE samples showed that the results based on the difference of VOCs were basically the same as the results based on the difference of appearance characters between MJH and GJH.Seven characteristic spots were identified by GC x IMS Library Search(v.1.0.3,G.A.S.)and standard substances,including alpha-pinene,gamma-terpinene,thymol,alpha-terpineol and trans-bata-farnesene,dimer trans-bata-farnesene,trimer trans-bata-farnesene.And traps-bata-farnesene was detected in CGE for the first time.After drying at 60℃,the composition of the fresh peel of CGE(MJH,GJH)was significantly different from that of the corresponding fresh peel,which was mainly reflected in the effect on the composition of low boiling point.The results showed that there was no significant difference in the VOCs of MJH when dried at 60℃ to 90℃.The VOCs of MJH mainly existed in the exocarp,and the experimental results suggested that the proportion of mesocarp retained should be controlled(less than 70%)during processing,so as to keep the VOCs of MJH relatively stable.The comparison of volatile constituents between Huazhou,Guangdong and Luchuan,Guangxi shows that there was no significant difference in volatile constituents between them,which may be due to their close geographical location.The VOCs of MJH treated with different doses of radiation were different.The radiation dose of MJH received can be roughly obtained by GC-IMS combined with multivariate statistical analysis.The GC fingerprints of MJH and GJH were established respectively.There were 34 and 14 common peaks in the chromatograms of MJH and GJH respectively.GC can be used to detect the differences of VOCs between MJH and GJH,but GC-IMS had fewer samples,simple pretreatment,and far higher sensitivity than GC.The information of components obtained by secondary separation(GC-IMS)was incomparable to one-dimensional(GC).ConclusionsGC-IMS can be used to investigate the differences of VOCs in CGE from different sources,and the classification results of VOCs were consistent with the classification results of appearance characters.GC-IMS can be used to compare the subtle effects of different processing and processing methods on volatile components,so as to select the appropriate technology for guiding production to obtain products with relatively stable quality.GC-IMS required less samples,simple pretreatment,high sensitivity,and large amount of information.It can present the VOCs in the samples to be tested comprehensively,which can provide a new method for the detection of the differences between traditional Chinese medicine containing VOCs and its relatives.By analyzing the differences of medicinal materials from different producing areas,the authenticity of medicinal materials was deciphered and the scientific basis was provided for the differentiation of medicinal varieties and producing areas.