| Magnolia biondii Pamp.and Magnolia zenii Cheng belongs to the Magnoliaceae family,and M.biondii is the main specie of the traditional Chinese medicine“Xin-yi”.Volatile oil is the important medicinal substance in M.biondii.M.zenii has a morphological appearance that is similar to M.biondii,which is also rich in volatile oil,but its flowers medicinal value has not been reported.Oil cells belonging to the internal secretory structure are the main sites for the synthesis and accumulation of the volatile oil in Magnoliaceae plants.Their developmental degree of oil cells are closely related to the yield and quality of volatile oil.In addition,the climate of the environment,extraction and analysis of different methods affect the yield and composition of volatile oil.To approach the relationships between the structure and development of oil cells and the quality of volatile oils of M.biondii and M.zenii,the techniques of tissue clearing,paraffin section method,semi-thin sections,ultra-thin sections were used to study the developmental processes and changing characteristics of oil cells.In addition,we also analyzed volatile oil component in the different developmental stages and different extraction methods of M.biondii and M.zenii by GC-MS.We analyzed the dynamic accumulation of volatile oil yield and chemical composition at different growth stages and assessed the correlations between oil cell developmental characteristics and volatile oil yields in M.biondii and M.zenii.Also,we discussed the influence of the climate factors on the oil yield and composition of the volatile oils to determine the best harvest time of the medicinal plant M.biondii and evaluate the medicinal value of M.zenii.The current study provides valuable reference and scientific data for evaluating the medicinal value and improving the clinical efficacy of M.biondii and M.zenii flowers.1 Oil cells distribution,developmental characteristics and volatile oil synthesis sites.Oil cells were commonly distributed in vegetative organs(stems,leaves)and reproductive organs(flowers)in M.biondii and M.zenii.The development of oil cells may be divided into five stages according to the characteristics of volatile oil formation and accumulation:oil-less stage,volatile oil formation stage,volatile oil accumulation stage,volatile oil saturation stage and volatile oil degradation stage.According to the characteristics of oil cells at different developmental stages,the developmental processes of oil cells may be divided into four stages:initial cell stage,vacuolation stage,mature stage and degradation stage.Finally,according to the changes of the cell wall of oil cells,oil cells were divided into three stages at the ultrastructure level:primary cellulose wall stage,cork wall stage and internal cellulose wall stage.Primary cellulose wall stage,osmium-osmotic drops were observed on both the cytoplasm and the plastid,followed by decreased osmiophilic drops in the cytoplasm,and increased osmiophilic drops in the plastids.Until the inner cellulose wall stage,there is a large number of osmium-osmotic drops between the cell wall and the plasma membrane,and the plastids disintegrate to release the osmium-osmotic drops.Finally,the osmophilic drops from the two sources move into the oil sca by cupule and direct fusion.Therefore,cytoplasm and plastid are the main synthetic sites of volatile oil.2 The relationships between the structural characteristics and distribution density of oil cells and volatile oil yields.The volatile oil yields of M.biondii flowers differed significantly at different growth stages and were closely related to flower dry weight,oil cell density and degree of oil accumulation.In February of 2016,flower buds had the highest dry weight(0.53g/n),the maximum percentage of oil cells at the oil saturation stage and the highest density of oil cells(217.92n/mm~2),which coincided with the highest oil yield(3.25%).In March 2016,flower buds had a lower dry weight(0.43g/n),a higher percentage of oil cells at the oil-degrading stage and the lowest oil cell density(145.42n/mm~2),resulting in decreased oil yields(1.45%).In M.zenii,October of 2013,the flower buds had the maximum percentage of oil cells at the oil saturation stage and the highest density of oil cells(164.50g/mm~2),which coincided with the highest oil yield(11.61%).With a sharp decline in the temperature and sunshine in November of 2013,the volatile oil yield was significantly lower(5.02%).In the full flowering stage in March of 2014,flower buds had a higher percentage of oil cells at the oil degrading stage and the lowest oil cell density(23.75g/mm~2),resulting in the lowest oil yield(3.07%).3 Chemical compositions of volatile oil in M.biondii and M.zenii flower buds at different growth stages.The main pharmacological components of the volatile oils in M.biondii including bornyl acetate,camphor,1,8-cineole,linalool,limonene,?-pinene and?-pinene were detected,and the total contents of these components in the 10 samples from ten growth stages were 9.64,45.26,22.05,32.45,31.48,26.83,44.19,48.52,47.26 and 15.12%.The content of pharmacological components was thus higher in January and February of 2016.The major compounds of M.zenii included farnesol,camphor,?-cadinene,?-muurolene,caryophyllene,?-amorphene,and?-cadinol.In addition,12 species of the same compounds with M.biondii were detected,including?-pinene?camphene?limonene?1,8-cineole?linalool?camphor?terpinen-4-ol?bornyl acetate?germacrene D??-cadinol?farnesol and trans-farnesal.It contains most of the main active components in M.biondii,such as bornyl acetate,camphor,1,8-cineole,linalool,limonene and alpha-pinene,and the total content is the highest in October 2013(23.35%),followed by January 2014(22.47%).As a result,M.zenii has the same active components as M.biondii,but the total content is lower than M.biondii.4 The best extraction and analysis method of M.biondii.Three extraction methods(steam distillation-ether extraction-GC-MS,steam distillation-dichloromethaneextraction-GC-MS,headspacesolid-phase microextraction-GC-MS)were compared and analyzed.The method(team distillation-ether extraction-GC-MS)has a very good qualitative and quantitative effect for the main components,is suitable for M.biondii.5 The best harvest time of M.biondii.In January-February of the year,Magnolia biondii flower buds have higher dry weight,volatile oil content and the total content of effective medicinal compositions,which can be used as the best harvest period of herbs.6 Economic value of M.zenii.Abundant medicinal components and perfume comp.1onents in the M.zenii flower were detected by GC–MS analysis,such as farnesol??-muurolene?camphor??-cadinene?trans-farnesal??-cadinol?germacreneD?caryophyllene?carotol?1,8-Cineole?terpinen-4-ol and linalool,which had significant pharmacological effects or could serve as perfume materials. |
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