全 文 ：研 究 快 报
STUDY ON EXTRACTING CITRAL FROM LITSEA
CUBEBA FRUITS BY MICROWAVE RADIATION AND
DETERMINATION OF CITRAL

LIU X G
LIU Xiao-geng1 , CHEN Mei-mei1 , CHEN Xue-heng2 ,
XIE Bao-ping1＊
(1.Jiangxi Agricultural University , Nanchang 330045 , China ;2.Department of
Chemical Engineering ,Guangdong Wuyi University , Jiangmen 529020 , China)
Abstract:　Citral is extracted from Litsea cubeba with microwave radiation.Content of essential oil extracted
from L.cubeba fruit using microwave radiation is on an average 2.48% higher than that using traditional di-
rect steam distillation.Adopting gas chromatography with temperature programming , citral content in the oil
was determined to be 68.46%, at recovery 101.3%, relative standard deviation 0.28%, linear relative coef-
ficient 0.9997 , which are in good agreement with those measured by internal standard method , but the opera-
tion is simpler than both the internal standard and GB 11424-89 methods.
Key words:　Litsea cubeba;citral
CLC number:S 573.8;TQ 655　　　Document code:A　　　Article ID:0253-2417(2001)03-0087-04
Litsea cubeba is grown as deciduous shrub or small arbor.Citral and other volatile aromatic
elements exist in its leaves , flowers and fruits to exhibit pleasant fragrance.Essential oil of L .cubeba ,
in which the major component is citral , is a traditional product in forestry industry in China extracted by
steam distillation from the fruits at 4%～ 6%yield , for individuals up to 10%.High pure citral can be
obtained from essential oil of L.cubeba through chemical method.
A preliminary exploration of extracting and producing citral from L .cubeba with microwave radia-
tion were examined in this study.
Received date:2000-05-30
　Foundation item:江西省科委 1996 年重点科技计划资助项目(0514)
　Biography:刘晓庚(1962-), 男 ,江西峡江人 , 副教授 ,硕士 ,主要从事农林副产物利用化学研究等工
作。
　＊谢宝平为江西农业大学 99 届硕士毕业生。
第 21 卷第 3期
2001 年9 月
林　产　化　学　与　工　业
Chemistry and Industry of Forest Products
Vol.21 No.3
Sept.2001
1　Materials and methods
1.1　Materials
L .cubeba fruit gathered from Xiajiang County and Jinggangshan City , the essential oil of L .cube-
ba and self-produced citral;Sodium hydrogen sulphite and standard reagent of citral(AR);acetone and
acetophenone (chromatographic reagent).
GC-14A gas chromatograph(Shimadzu),ZFA rotary esteamator ,microwave oven(Xianhua E70Tf-
2/ J220 ,850 W , 2450 MHz), thermometer(no adjustment).
1.2　Methods
1.2.1　Methods of extracting and producing citral from fruits of L.cubeba 　Fresh fruits of L .cube-
ba , in a round-bottomed flask and added with 45 ℃distilled water ,was set in a microwave oven to ex-
tract citral for a certain time , taken out of microwave oven , steam-distilled to collect the distillate.Re-
peat this procedure twice to three times.Essential oil was collected from separating funnel by salting-out
of distillate with NaCl overnight ,dried.Add a certain sodium chloride to distilled substances that have
been gathered , standing overnight , and then isolate them.The content of citral was determined.
A certain amount of essential oil in a reactor was put in microwave oven , added with supersa-
turated solution of sodium hydrogen sulphite under stirring , and run in the microwave oven at tempera-
ture not over 10 ℃(controlled with ice-salt water),until citral in the material liquids have been trans-
formed completely into product.The reactor taken out from the microwave oven was kept stood to isolate
crystallized materials , rinsed with ether , and 0.1 mol/L resolved crystallized sodium hydrogen sulphite
was added , run in microwave oven until the hydrolysis is completely finished.Then citral was isolated.
1.2.2　Determination methods　Chromatographic column:SE-54 quartz capillary , 25 m , internal di-
ameter 0.2 mm;FID(hydrogen flame ionization detector);80 ～ 230 ℃,10 ℃/min programmed tem-
Fig.1　GC spectra of essential oil
from L.cubeba
1.solvent;2.impurities;3.neral;
4.geranial;5.acetophenone
perature , sample was added at 240 ℃,detected at 250 ℃;
nitrogen flow 20 mL/min;air flow 50 mL/min;sample in-
jection 0.5μL.Results are shown in Fig.1.
2　Results and discussions
2.1　The conditions where essential oil of fruits of L.
cubeba is extracted with microwave radiation and steam
distillation according to orthogonal experiment are as fol-
lows:microwave radiation time 5 ～ 20 min , temperature 60
～ 80 ℃, distillation temperature 80 ～ 100 ℃, extracted
for 3 times.Results of extracting with microwave radiation
plus steam distillation and traditional steam distillation are
showed in Table 1.
88　 林　产　化　学　与　工　业 第 21卷
Table 1　Influence of extracting essential oil of L.cubeba with microwave
radiation and traditional steam distillation %
i tems yield＊ average yield＊ extracting time(min) content of cit ral＊ average content
microwave method 5.5～ 8.6 8.38 90～ 120 68.3～ 75.9 74.78
traditional method 4.0～ 6.3 5.86 380～ 480 63.3～ 70.4 68.64
　　＊Results from eight batches , twenty-four samples.
It is obvious from Table 1 that comparing microwave radiation with traditional methods , the time of
extracting is 4 times shorter , the content of essential oil is 36.5%～ 37.5%higher , and content of cit-
ral of essential oil is more than 5%higher.These could be explained by that essential oil of L.cubeba
can infiltrate ,diffuse and exchange more effectively and quickly from the cells of fruits tissue during
microwave radiation , so that essential oil can be extracted quickly and completely.These operations are
quite complicated.
2.2　Citral can be obtained from the oil of L.cubeba by using sodium hydrogen sulphite.The reaction
between sodium hydrogen sulphite and aldehyde is very fast and can be completed in three minutes.
Temperature of reaction can be controlled easily.There are few side reactions with microwave radiation
so that the process of isolating and extracting citral can be simplified and the loss of citral could be de-
creased steeply.The loss of citral is less than 0.8%with microwave radiation , compared with 1.2%
without microwave radiation.
2.3　Contents of essential oil of L .cubeba and self-produced citral are showed in Table 2.
Table 2　Quantitative analysis result of essential oil of L.cubeba and self-produced citral %
samples analysi s methods content of citral average
standard
deviation
relative standard
deviation
essential oil of
L.cubeba
citral
reduct ion-to-one 68.7 68.8 68.4 68.5 68.8 68.64 0.19 0.28
internal standard 68.5 68.8 68.2 68.4 68.6 68.52 0.19 0.28
GB 11424-89 68.5 68.9 68.4 68.6 68.9 68.66 0.23 0.34
reduct ion-to-one 99.3 99.6 99.4 99.5 99.5 99.46 0.11 0.11
internal standard 99.2 99.6 99.3 99.5 99.4 99.40 0.18 0.18
　　From Table 2 and Fig.1 , the results determined by reduction-to-one method are basically in accor-
dance to those internal standard method.We have got the results that the relative coefficient of reduc-
tion-to-one method of capillary chromatographic column and internal standard was separately 0.9997
and 0.9998 , the content of their recoveries was 101.3% and 101.0%.Therefore reduction-to-one
method and internal standard method used to determine citral have the same accuracy.However , the
content of citral determined with reduction-to-one method is a slightly higher than that with internal
standard method.The request of quantitative analysis of citral in essential oil of L.cubeba can be com-
pletely satisfied with reduction-to-one of capillary column gas chromatography.
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微波法从山苍子中提取柠檬醛及其测定研究
刘晓庚1 , 陈梅梅1 , 陈学恒2 , 谢宝平1
(1.江西农业大学 ,江西 南昌 330045;2.广东五邑大学化学化工系 ,广东 江门 529020)
摘　要:讨论了采用微波辐照从山苍子中提取制备柠檬醛 ,精油的得率较传统的直接水蒸气蒸馏法平均提
高 2.48%以上。用程序升温毛细管柱气相色谱归一化法测定山苍子精油中的柠檬醛 , 获得了山苍子精油
中柠檬醛含量为 68.64%,回收率为 101.3%, 相对标准偏差为 0.28%,线性相关系数为 0.9997 ,准确性与内
标法相一致的实验结果 ,而且操作较内标法和 GB 11424-89法更为方便。
关键词:山苍子;柠檬醛
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90　 林　产　化　学　与　工　业 第 21卷