6种丁香花挥发性成分的动态顶空吸附ATD-GC/MS分析

秦 颖，杨晓霞，冷平生，胡增辉

（北京农学院园林学院，北京102206）

6种丁香花挥发性成分的动态顶空吸附ATD-GC/MS分析

秦 颖，杨晓霞，冷平生，胡增辉*

（北京农学院园林学院，北京102206）

丁香是一种重要的芳香木本观赏植物，花开繁茂，芳香浓郁。该研究采用活体植物动态顶空套袋-吸附法收集了香雪丁香、花叶丁香、关东丁香、蓝丁香、小叶丁香、四季蓝丁香6种不同丁香花的挥发物，通过自动热脱附-气质联用分析技术分析丁香花的挥发物成分，为研究其花香释放机理、进一步开发利用丁香资源及新品种选育提供依据。结果表明：（1）在6种丁香花挥发物中共检测到80种成分，分别属于苯形烃、萜类、醇、醛、酮、脂肪烃、酯、酸及其它类。（2）花叶丁香花的挥发物释放量最高，且为释放量最低的四季蓝丁香的1.8倍。（3）除香雪丁香外其他5种丁香花的挥发物中苯形烃在9类挥发物成分中含量最多，而萜类是香雪丁香花挥发物的主要成分。（4）乙苯、间二甲苯、对二甲苯、二丁基羟基甲苯、2-乙基-1-己醇、5-乙基-2，2，3-三甲基庚烷这6种成分在不同丁香花挥发物成分中含量均较高，是6种丁香花挥发物的主要成分。

丁香；挥发物；释放量

Floral scent is an important characteristic of flowers，and acts as key factors influencing flower' s ornamental value and economic value.The floral scent plays a significant role in many ecophysiological processes［1］.Floral scent is one of crucial strategies that plants employ to attract pollinators to assure reproduction，and it also plays a significant role in plant defense，plant-plant interactions［2-3］. Moreover，floral scent is used in aromatherapy to treat some psychological and physiological illnesses of human［4-5］.In recent years，the floral volatiles of many plants have been investigated，including peony，camellia，lavender，rose，lily and so on，but previous studies focus on the herbaceous plants，so little attention was paid to the floral scent of woody plants.

Syringa is an important aromatic woody plant including 32 species，and is widely planted in gardens and urban forests worldwide，which plays an important role in urban greening and beautification.The breeding of new varieties is the active research field of Syringa.Though strong floral scent is a key characteristic of Syringa，few breeding research focuses on the modification of floral volatiles，which is an important breeding direction in future.Some previous studies have investigated floral scent of Syringa by using the methods of steam distillation，solid phase micro-extraction（SPME），surface acoustic wave sensor（SAW），silica gel column chromatography and supercritical CO2extraction［6-10］，but in these experiments，the flowers used are all in vitro or damaged，which are unnatural condition and lead to changes in emission profiles. So the floral scent of Syringa in the state of nature is little known.

In the study，the floral volatiles of 6 Syringa species and varieties were collected in vivo by dynamic headspace sampling，and then were analyzed using automated thermal desorption-gas chromatography/mass spectrometry（ATD-GC/MS），which ensured that the results truly reflected the natural state of Syringa，contributing to comparing components and release amounts.Thus the results would provide theoretical basis for the research on the mechanism of floral scent formation，and furthermore for modification of floral scent in the breeding of Syringa.

1 Materials and methods

1.1 Plant materials

6 Syringa species and varieties including S. oblata×S.vulgaris‘Xiangxue'，S.persica，S.velutina，S.meyeri，S.pubescens subsp.microphylla and S.meyeri‘Si Ji Lan'grown under a natural photoperiod in the lilac garden of Beijing Botanical Garden were chosen.The floral volatiles emitted from healthy Syringa plants at the full flowering stage were collected.The collection of floral volatile was carried out at 9：00 AM on with the temperature（22±2）℃.Three repetitions were set up.

1.2 Floral volatiles collection

The volatile compounds were collected using dynamic headspace sampling method［11-12］.Sampling bag（355 mm×508 mm，Reynolds，USA）wrap the chosen individual inflorescence.A portable air sampler（QC-1，Beijing Municipal Institute of Labour Protection，China）was used as the pump to draw out air removing the impurities and then filled with filtered air through activated carbon. Repeat twice and let stand for 10 min to stabilize gas inside the bag.A stainless steel tube containing Tenax-GR（60—80 mesh，Chrompack）was used as the volatile trap，unscented silicone tube connections of the entire pneumatic system.The volatiles were collected for 20 min at a flow rate of 300 m L·min—1.In the experiment，ambient air collect-ed at the same time as a control.

1.3 Floral volatiles analysis

The ATD-GC/MS technique was used to analyze the floral volatiles.The floral volatiles collected in the stainless steel tube was desorbed by heating in an ATD（Auto Thermal Desorber，Turbo M-atrix 650，PerkinElmer）at 260℃for 10 min，and then cryofocused in a cold trap whose temperature was maintained at—25℃for 3 min.The cold trap was then quickly heated to 300℃maintained for 5 min to transport the volatiles to GC（Clarus 600，Perkin EImer）.

The GC was equipped with a capillary DB-5MS column（30 m×0.25 mm i.d.，with a 0.25μm film thickness）.Helium was used as the carrier gas.The GC was programmed at 40℃for 2 min，4℃·min—1up to 160℃，then 20℃·min—1up to 270℃，and held at 270℃for 3 min.

The MS（Clarus 600T，Perkin EImer）was operated in EI ionization mode at 70 e V，and a mass scan range of 29—600 amu was monitored.Interface and ion source temperatures were 250℃and 220℃，respectively.

1.4 Floral volatiles identification and quantification

Preliminary identification of the compounds was made by searching the NIST08 and WIELY library in the Turbo Mass Ver5.4.2 software and checked according to its retention index.In order to enable the release amounts of volatile components to be compared，α-pinene（Fluka，USA）was used as an external standard.As described previously with some modification，theα-pinene was dissolved in ethyl acetate with different solution concentrations.（μg·h—1）was used as unit to describe the release amount.

2 Results and analysis

2.1 The difference in categories and release amounts of foral volatiles among 6 different Syringa plants

Fig.1 showed the chromatographic profiles of floral volatiles emitted from 6 different Syringa species and varieties，and visible difference was found from different peak sites and relative abundance.Totally 80 volatile compounds were identified in the floral volatiles of these plants through the analysis of Fig.1，which belonged to 9 categories including benzenoid and derivative，alcohol，aldehyde，terpenoid，ketone，fatty hydrocarbon，ester，acid and others（Table 1），and most of them were first found in Syringa plants.Among these compounds，23 compounds of fatty hydrocarbon were found，which were more than other categories.Only 1 acid and 4 ester compounds were found.

Among 6 Syringa plants，the most number of volatile compounds were emitted from the flowers of S.velutina with 65 kinds.The number of floral components in S.persica，S.meyeri，S.pubescens subsp.microphylla was also exceeded 60.The total release amounts of floral volatiles emitted from S. persica and S.velutina both exceeded 1 000μg· h—1，which were much higher than other Syringa plants，expecially S.persica whose total release amount was 2.8 times as much as S.meyeri‘Si Ji Lan'.

2.2 The difference in relative contents of 9 volatile categories among 6 different Syringa plants

It was obvious expressed that benzenoid and derivative showed the highest release amount in 6 Syringa plants except S.oblata×S.vulgaris‘Xiangxue'（Fig.2）.The relative release amounts of benzenoid and derivative in floral volatiles emitted from S.velutina and S.meyeri‘Si Ji Lan'were all exceeded 50%of the total release amount，while S.oblata×S.vulgaris‘Xiangxue'showed the lowest release amount of these 6 Syringa plants，and in S.velutina which was about 3 times as much as S.oblata×S.vulgaris‘Xiangxue'.However，in S.oblata×S.vulgaris‘Xiangxue'and S.persica，the amounts of terpenoid were（306.69±1.89）μg· h—1and（380.45±11.52）μg·h—1respectively，in comparison，which were only around 6.00—32.00 μg·h—1in other 4 Syringa plants.It was found that the release amount of 3，7-dimethyl-1，3，6-octatriene accounted for 80.00%of terpenoid.Acid compounds displayed lowest release amounts，whichwere all below 5.00μg·h—1.The other categories did not presented remarkable difference in release amount among these 6 Syringa plants.

Table 2 showed the relative amounts of 9 volatile categories.It was found that among the volatile components of all Syringa plants studied except S. oblata×S.vulgaris‘Xiangxue'，the relative amount of benzenoid and derivative was the most in floral volatiles，which accounted for more than 35.00% of total release amount，even（57.54±3.39）%in S. velutina.In addition terpenoid compounds were main components，which occupied comparatively big percentage in S.oblata×S.vulgaris‘Xiangxue'（42.30±0.59）%and S.persica（27.46±1.99）%.

Fig.1 The chromatographic profiles of floral volatiles emitted from 6 different Syringa plantsXX.S.oblata×S.vulgaris‘Xiangxue'；HY.S.persica；GD.S.velutina；L.S.meyeri；XY.S.pubescens subsp. microphylla；SJL.S.meyeri‘Si Ji Lan'.The same as below

Table 2 The relative amount of 9 categories of floral volatile components in 6 Syringa plants

Fig.2 The release amounts of different aroma categories in 6 Syringa plantsThe released amount of every volatile category（Benzenoid and derivative；Alcohol；Aldehyde；Ketone；Terpenoid；Fatty hydrocarbon；Acid；Ester；Others）was significantly different among different species. Each point was average of three independent replications at least. Statistical significance of difference among different species was indicated by different normal letters（P＜0.05）.

Alcohol and fatty hydrocarbon compounds were also important components in Syringa floral volatiles，whose relative amounts varied from 8. 00%to 17.00%.Aldehyde，ketone，ester，acid and others compounds were also found in the floral volatiles of 6 Syringa plants，but the release amounts were all below 12.00%.

2.3 The difference in the main volatile components among 6 different Syringa plants

Not all 80 components detected were emitted from the every Syringa plant.Camphene and 6-amino-2-methyl-2-heptanol were only found in the floral volatiles of S.oblata×S.vulgaris‘Xiangxue'.2-mehyl-3-phenyl propanal，lilac alcohol C，and（E，E）-2，6-dimethyl-1，3，5，7-octatetraene were only emitted from S.persica.The release amount of benzaldehyde from S.persica and S.velutina was far higher than other 4 plants.

Fig.3 showed the diversity of release amounts of the major volatile substances.Among the 6 main volatile components，the release amount of 1，3-dimethyl benzene was comparatively highest in 6 Syringa species except S.velutina.For S.velutina，butylated hydroxyl toluene was most abundant component among the floral components，the release amount of which was significantly above other species.In addition，2-ethyl-1-hexanol was the second abundant component whose release amount accounted for about 50.00—130.00μg·h—1of floral volatiles emitted from those 6 Syringa plants. The highest release amount of 2-ethyl-1-hexanol was detected from S.velutina which almost 1.2times more than the lowest that from S.oblata× S.vulgaris‘Xiangxue'.

Fig.3 exhibited that the release amounts of 6 main volatile components from S.meyeri‘Si Ji Lan'and S.oblata×S.vulgaris‘Xiangxue'were almost all below other 4 species.On the whole，the 6 main volatile components accounted for over 50.00%of total released amount of floral volatiles emitted from those 6 Syringa plants except S.oblata×S.vulgaris‘Xiangxue'and S.persica，in which（E）-3，7-dimethyl-1，3，6-octatriene and（2）-3，7-dimethyl-1，3，6-octatriene were analyzed as another essential compound，whose released amount reached（246.13±0.86）μg·h—1and（296.98± 13.04）μg·h—1respectively.

Fig.3 The release amounts of main components of floral volatiles in 6 Syringa speciesEach point is the average of three independent replications. Statistical significance［least significant difference（LSD）test］of difference among different species was indicated by different small letters（P＜0.05）.Bars represented standard errors.

3 Discussions

3.1 Categories and contents of floral volatiles emitted from 6 Syringa plants

The chemical constituents of floral volatiles have been extensively investigated for hundreds of years.Comprehensive results of previous studies，floral scent is mixtures of volatile compounds including terpenoid，aromatics，fatty acid and derivative，as well as some sulfur or nitrogen-containing compounds［13-16］，and which are biosynthesized via various pathways.It has been found that there is significant difference in the floral scent components among different plants.The main aromatic compounds of camellia flowers are alcohol，aldehyde，ester，alkyl，alkene and linaloloxide［17］.Chrysanthenome，isocyclocitral，caryophyllene，β-farnesene，eucalyptol are the main components identified in Chrysanthemum morifolium（Ramat.）Kitam.［18］. Rose contains a variety of biological active ingredients，which are more essential terpenoid components，such asα-pinene，myrcene，α-phellandrene，（Z）-β-ocimene，（E）-β-ocimene，linalool，geraniol and so on［19］.

In this study，80 kinds of volatile substances were identified in the floral volatiles of 6 Syringa plants.These compounds belonged to 9 categories including benzenoid and derivative，alcohol，aldehyde，terpenoid，ketone，fatty hydrocarbon，ester，acid and others.The quantity of volatile compounds was more than the results of Li's［20］and Cao's［21］studies，in which 48 and 25 components were identified respectively using solid-phase micro-extraction（SPME）collection method.In these 6 Syringa plants，1，3-dimethyl benzene，2-ethyl-1-hexanol，ethylbenzene were found to be the main flroal volatile components.In addition，the release amount of terpenoid of S.oblata×S.vulgaris‘Xiangxue'and S.persica was also in a high level. In previous study，germacrene-D（22.37%），βbourbonene（15.97%），benzaldehyde（11.03%），βcaryophyllene（7.56%），β-gurjunene（3.43%），linalool（3.18%）were found to be the most abundant volatile compounds released from S.oblate flowers［20］.Another study reported that（Z）-3，7-dimethyl-1，3，6-octatriene（59.90%），β-linalool（9.78%），α-pinene（3.19%），benzyl methyl ether（3.05%），lilac alcohol D（2.85%）were the main components of S.oblata flowers［21］.Significantdifference in result was found among different studies，which may resulted from the difference in growth environment of plants and collection method of volatiles.Compared to the distillation extraction and solid-phase micro-extraction technology，dynamic headspace the was the optimal method to detect the plant volatiles under natural condition［22］.Despite this，the same components were found compared with previous studies，such as pinene，3，7-dimethyl-1，3，6-octatriene，some isomers of lilac aldehyde and lilac alcohol witch were considered as the characteristic components of floral scent of Syringa plants［20］.

3.2 The Main Components of Floral Scent Emitted from 6 Syringa Plants

Benzaldehyde is thought to be an important component of aldehyde perfume，which is similar to the fragrance of almond，cherries and nuts，and benzaldehyde is also used as material of medication with anti-inflammatory，analgesic，and anticancer efficacy.Benzaldehyde was found to be emitted from S.persica and S.velutina flowers in a high level.In addition，S.oblata×S.vulgaris‘Xiangxue'and S.persica emitted an important monoterpene（E）-3，7-dimethyl-1，3，6-octatriene［（33.95± 0.03）%］and（2）-3，7-dimethyl-1，3，6-octatriene［（21.43±0.23）%］in a high relative release amount.Therefore，3，7-dimethyl-1，3，6-octatriene was the characteristic floral volatile component of S.oblata×S.vulgaris‘Xiangxue'and S.persica.

Among the components，ethylbenzene，1，3-dimethyl benzene，p-xylene，butylated hydroxyl toluene，2-ethyl-1-hexanol，and 5-ethyl-2，2，3-trimethyl heptane were all detected in the floral volatiles of 6 Syringa plants，and their release amounts were significantly higher than other components，so these compounds were thought to be the main floral volatile components.However，not sure whether the higher content components more contributed to the aromatic character of these Syringa plants，which determined by volatile content and volatile matter of distinctive floral aroma attribute of vilatile substances［23-24］.It has been also found that floral volatiles components were vary widely among species in terms of the constituents and the release amounts，which is due to different genotypes and individual difference and leads to forming various aromatic characteristics in different species and varieties.

A total of 80 volatile components were identified in the floral volatiles of 6 Syringa plants，and difference in components and release amounts were found.Among the components，1，3-dimethyl benzene，2-ethyl-1-hexanol，ethylbenzene，p-xylene，butylated hydroxyl toluene，5-ethyl-2，2，3-trimethyl heptane were mian volatile components.The unique fragrance constitutes an important part of ornamental value of Syringa plants，and breed new ornamental varieties with pleasant floral scent has been an important development trend［25］.But the release pattern and biosynthesis mechanism of floral volatile components in Syringa plants are still unclear，which need to be investigated in future study.

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（编辑：潘新社）

Analysis of Floral Volatile Components from 6 Syringa Plants Collected by Dynamic Headspace Sampling by ATD-GC/MS

QIN Ying，YANG Xiaoxia，LENG Pingsheng，HU Zenghui*
（College of Landscape Architecture，Beijing University of Agriculture，Beijing 102206，China）

Syringa is an important woody ornamental plant with lush flowers and aromatic scent.The research on volatile compositions is necessary for floral scent release mechanism，and provides scientific basis for botanical garden application and new varieties breeding.In this study，the floral volatiles emitted from 6 different Syringa species and varieties including S.oblata×S.vulgaris‘Xiangxue'，S.persica，S.velutina，S.meyeri，S.pubescens subsp.microphylla and S.meyeri‘Si Ji Lan'were collected with dynamic headspace method，and then were identified by automated thermal desorption-gas chromatography/mass spectrometry（ATD-GC/MS）technique.The results showed that：（1）the floral volatile components of the 6 different Syringa species and varieties were distinct qualitatively and quantitatively.A total of 80 volatile components were identified，and these compounds belonged to 9 volatile categories including benzenoid and derivative，terpenoid，alcohol，aldehyde，ketone，fatty hydrocarbon，ester，acid，and others.（2）Among the 6 different species，the highest release amount of volatile components was emitted from S.persica，which was almost 1.8 times more than the lowest that from S.meyeri‘Si Ji Lan'.（3）Except S.oblata×S.vulgaris‘Xiangxue'，benzenoid and derivative showed the highest release amount among the 9 categories，so benze-noid and derivative was the main volatile category of the floral fragrances.In S.oblata×S.vulgaris‘Xiangxue'，the release amount of terpenoid was the highest among 9 categories.（4）Among the components，1，3-dimethyl benzene，2-ethyl-1-hexanol，ethylbenzene，p-xylene，butylated hydroxyl toluene，5-ethyl-2，2，3-trimethyl heptane were exhibited higher release amount in these Syringa plants，which suggested that these compounds were main volatile components of lilac flowers.

Syringa；floral volatiles；release amount

Q946.8

A

1000-4025（2015）10-2078-11

10.7606/j.issn.1000-4025.2015.10.2078

2015-04-13；修改稿收到日期：2015-08-12

北京市属高等学校创新团队建设与教师职业发展计划（IDHT20150503）；国家自然科学基金（31071817）；北京市教委科技提升计划（PM2014014207）

秦 颖（1991—），女，在读硕士研究生，主要从事园林植物生理与生态的研究。E-mail：jyqinying@163.com

*通信作者：胡增辉，副教授，硕士生导师，主要从事园林植物生理与生态的研究工作。E-mail：buahuzenghui@163.com