GC-MS Analysis of Chemical Components of Volatile Oil in Different Parts of Fennel (Foenicuzu vulgare Mill.)

Wei CHEN Kaibin LI Lina LONG Wen YANG Jianghai WANG Qiuyue KONG Fujun SUN

Abstract [Objectives] This study was conducted to analyze the composition of volatile oil in different parts of fennel （Foenicuzu vulgare Mill.） and to compare the differences in the composition of volatile oil in different parts of fennel.

[Methods] The steam distillation method was applied to extract volatile oil from different parts of fennel， and the components of volatile oil from different parts of fennel were separated and identified by GC-MS. The relative content of each component was determined by the peak area normalization method.

[Results] 37， 33， 18， and 44 chemical components were separated from the volatile oil of fennel roots， stems， young leaves and fruit， respectively， accounting for 98.64%， 99.34%， 99.59% and 95.99% of the total volatile oil of corresponding parts. A total of 77 chemical components were identified in the four parts， of which 5 were common components. The main component of the volatile oil in the stems and young leaves was trans-anethole. The main components of the volatile oil in fruit were estragole and trans-anethole. And the main component of the volatile oil in the roots was  dill apiol. The components in the volatile oil of fennel roots， stems， young leaves and fruit were different in type and content.

[Conclusions] This study provides a theoretical reference for the further effective development and utilization of fennel resources.

Key words Foenicuzu vulgare Mill.; Different parts; Volatile oil; GC-MS

Fennel （Foenicuzu vulgare Mill.） is a plant with a long history and a wide range of uses. It is recorded in the history of China as a seasoning， Chinese medicine and spices[1]. Many regions of China use different parts of fennel and whole plants as a medicine. Fennel was first published in Theory of Medicinal Properties （Yaoxinglun）. It is recorded in Eastern Medicine Book （Dongyi Baojian） as one of the "Seven Elixirs"， which is used to treat symptoms such as premature graying of hair because of its effects of nourishing yin for invigorating the kidney and replenishing qi to invigorate the spleen. The use of fennel roots as a medicine was first published in the Bencao Tujing. According to the Tianbao Bencao， fennel roots are mild in nature， and are widely used to treat bladder hernia， flatulence and  stagnation of the circulation of vital energy. The tender leaves of fennel are often used as a condiment or eaten directly. The whole fennel plants contain volatile oil， which is abundant in fruits[2-6].  Modern research has shown that fennel essential oil has antioxidant， liver-protective， gastrointestinal function regulating， and immune enhancing effects[7-11]. Because the composition of fennel volatile oil is more complicated， there are obvious differences in results due to different producing areas[4，6，12]. At present， reports on fennel volatile oil are mainly concentrated on fruits[3-5]， and there are also a few reports on roots， stems and leaves. In this study， volatile oil was extracted from different parts of fennel by steam distillation and analyzed by GC-MS method， and the differences of the volatile oil components in different parts were compared， aiming to provide a scientific basis for the application of fennel and the further development of its resources.

Materials and Methods

Instrument and Materials

Agilent 7890B-7000C gas chromatograph mass spectrometer （Agilent， USA）; AY-120 electronic balance （Shimadzu， Japan）; anhydrous sodium sulfate （analytically pure， Tianjin Damao Chemical Reagent Factory）; fennel fruits， fennel stems， fennel tender leaves and fennel roots， all collected in Xixiu District， Anshun City， Guizhou Province.

Methods

Extraction of volatile oil

Fennel roots， stems， young leaves and fruit were dried and pulverized and sieved through a 30-mesh sieve， respectively. A certain amount of each powder （50 g） was weighed for the extraction of the volatile oil according to the method （volatile oil determination method） in the fourth part of Chinese Pharmacopoeia （2015 edition）. The extracted volatile oil was dried with anhydrous sodium sulfate for later use. The yield of volatile oil was 0.9 ml/100 g from the roots，  1.5 ml/100 g from the stems and 2.1 ml/100 g from the fruit.

GC-MS conditions

Chromatographic conditions： HP-5MS quartz capillary column （30 m×250 μm×0.25 μm）; carrier gas： high-purity nitrogen; injection temperature： 250 ℃; injection mode： split injection; split ratio： 20∶1; injection volume： 1 μl; flow rate of carrier gas： 0.8 ml/min; temperature programming： starting with an initial temperature at 60 ℃， which is held for 3 min and then increased at 2 ℃/min to 70 ℃， at 8 ℃/min to 140 ℃ and at 5 ℃/min to 170 ℃， which is held for 1 min and then increased at 15 ℃/min to 230 ℃， which is held for 4 min and then increased at 20 ℃/min to 260 ℃， which is held for 1 min.

Mass spectrometry conditions： ion source： EI; ion source temperature： 230 ℃; mass spectrometry interface temperature： 280 ℃; electron bombardment energy： 70eV; full ion scanning within a scanning range m∶z： 35-500; acquisition delay： 3.5 min.

Results and Analysis

According to the above conditions and methods， the volatile oil in samples was analyzed by GC/MS， and the total ion current diagrams of volatile oil components were obtained， as shown in Fig.1-Fig. 4.  Computerized mass spectrometry database NIST14.L and NIST MS Search 2.2 were used to perform a comparative search. The chemical components in the volatile oil were finally determined in combination with the retention time， and the relative content of each chemical component was obtained by peak normalization. The results are shown in Table 1.

Conclusions and Discussion

The steam distillation method was applied to extract the volatile oil components from the roots， stems， young leaves and fruit of fennel. The yield of volatile oil from the fruit was the highest， followed by the yield from tender leaves， and the yield of volatile oil from the roots was the lowest. It could be seen from the results of GC-MS analysis that the volatile oil components of roots， stems and fruit were not significantly different， and the volatile oil components of young leaves were much different from those of roots， stems and fruit.

As can be seen from Table 1， 77 compounds were identified from fennel roots， stems， fruit and young leaves， of which 5 were common components. A total of 37 compounds were identified in the fennel root volatile oil， accounting for 98.64% of the total chromatographic peak area， and the main component was dill apiol， which accounted for 92.63% of the total chromatographic peak area. A total of 33 compounds were identified in the fennel stem volatile oil， accounting for 99.34% of the total chromatographic peak area， and the main components were trans-anethole， D-limonene and fenchyl acetate， which accounted for 43.64%， 21.53% and 7.14% of the total chromatographic peak area， respectively. A total of 44 compounds were identified in fennel fruit， accounting for 99.59% of the total chromatographic peak area， and the main components were trans-anethole， estragole and D-limonene， which accounted for 20.30%， 51.59%， and 11.49% of the total chromatographic peak area， respectively. A total of 18 compounds were identified in the young leaves of fennel， accounting for 95.99% of the total chromatographic peak area， and the main components were trans-anethole， 1-methyl-4-（1-methylvinyl）cyclohexyl acetate and dodecamethylcyclohexasiloxane， which accounted for 49.06%， 10.58%， and 7.81% of the total chromatographic peak area， respectively.

The identified chemical structure types are simple monoterpenes， oxidized monoterpenes， aromatic compounds， etc. The simple monoterpenes are rich but not high in content， mainly including limonene， α-pinene， β-phellandrene， etc.[4]. Estragole and trans-anethole were the main components of stems， young leaves and fruit， which is consistent with the reports by Guo et al.[5]. Dill apiol was the main component of fennel roots， which is consistent with that reported by Song et al.[6].

Through comparative research， the composition of volatile oil in different parts of fennel was made clear. The composition and distribution of volatile oil in different parts of the fennel differed greatly. The correlation between the efficacy and edible value of each part needs further study. This study provides a theoretical reference for the further effective development and utilization of fennel resources.

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