See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/244323647
Microwave-assisted extraction of tea
polyphenols and tea caffeine from green tea
leaves. Chem Eng Process Process Intensif
ARTICLE in CHEMICAL ENGINEERING AND PROCESSING FEBRUARY 2003
Impact Factor: 1.96 DOI: 10.1016/S0255-2701(02)00037-5
CITATIONS
201
3 AUTHORS, INCLUDING:
Guoguang Niu
International Union of Science and Education
21 PUBLICATIONS 535 CITATIONS
SEE PROFILE
Available from: Guoguang Niu
Retrieved on: 23 August 2015
Chemical Engineering and Processing 42 (2003) 129 /133
www.elsevier.com/locate/cep
Microwave-assisted extraction of tea polyphenols and tea caffeine
from green tea leaves
Xuejun Pan, Guoguang Niu, Huizhou Liu *
Young Scientist Laboratory of Separation Science and Engineering, State Key Laboratory of Biochemical Engineering, Institute of Process Engineering,
Chinese Academy of Sciences, Beijing, 100080, People s Republic of China
Received 17 October 2001; received in revised form 20 March 2002; accepted 20 March 2002
Abstract
A microwave-assisted extraction (MAE) method is presented for the extraction of tea polyphenols (TP) and tea caffeine from
green tea leaves. Various experimental conditions, such as ethanol concentration (0 /100%, v/v), MAE time (0.5 /8 min), liquid/solid
1
ratio (10:1 /25:1 ml g ), pre-leaching time (0 /90 min) before MAE and different solvents for the MAE procedure were investigated
to optimize the extraction. The extraction of tea polyphenols and tea caffeine with MAE for 4 min (30 and 4%) were higher than
those of extraction at room temperature for 20 h, ultrasonic extraction for 90 min and heat reflux extraction for 45 min (28 and
3.6%), respectively. From the points of extraction time, the extraction efficiency and the percentages of tea polyphenols or tea
caffeine in extracts, MAE was more effective than the conventional extraction methods studied.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Polyphenols; Caffeine; Green tea leaves; Extraction; Microwave-assisted
1. Introduction hydroxyanisole, butylated hydroxytoluene and DL-a-
tocopherol [3].
Green tea leaves contain tea polyphenols, tea caffeine, Microwave digestion of matrices for their eventual
amino acids, saponins, tannins, etc., with about 10 /30% elemental analysis has been routinely used for several
(w/w) polyphenols and 2 /4% (w/w) caffeine. Tea poly- years [4]. Recently, microwave-assisted extraction
phenols include catechines, flavanols, flavanones, phe- (MAE) has been used for the extraction of biologically
active compounds, such as extraction of essential oils
nolic acids, glycosides and the aglycons of plant
from the leaves of rosemary and peppermint [5],
pigments. They are soluble in water, ethanol, methanol,
extraction of taxanes from Taxus biomass [6], extraction
acetone etc. Tea polyphenols isolated from green tea
of ergosterol and total fatty acids from fungal hyphae
leaves, are natural antioxidant [1], and have a scaven-
and spores, mushrooms, filtered air, artificially con-
ging effect on active oxygen radical [2]. Tea polyphenols
taminated corn, naturally contaminated grain dust, and
have important applications in food industry and
soil [7] and the extraction of azadirachtin-related
medicine for daily use. Tea polyphenols have a stronger
limonoids from neem seed kernel [8].
anti-oxidative activity than butylated hydroxyanisole,
Extraction of tea polyphenols and tea caffeine from
butylated hydroxytoluene and DL-a-tocopherol; and the
green tea leaves has been reported [9 /11]. However, no
toxicity of tea polyphenols is lower than butylated
report has been done on the use of MAE for the
extraction of tea polyphenols and tea caffeine from
green tea leaves. The purpose of this work was to
develop a MAE method and evaluate MAE and
conventional extraction methods for the extraction
* Corresponding author. Tel.: /86-10-6255-5005; fax: /86-10-
of tea polyphenols and tea caffeine from green tea
6255-4264.
E-mail address: hzliu@home.ipe.ac.cn (H. Liu). leaves.
0255-2701/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 2 5 5 - 2 7 0 1 ( 0 2 ) 0 0 0 3 7 - 5
130 X. Pan et al. / Chemical Engineering and Processing 42 (2003) 129 /133
2. Materials and methods
2.1. Plant materials and chemicals
Whole green tea leaves (Thea sinensis L.) (producing
area: Hangzhou, China) were purchased from a local
market.
Ethanol, methanol and acetone used in the experi-
mental work were all of analytical reagent grade
chemicals. Caffeine and all other chemicals for analysis
of tea polyphenols and tea caffeine used were all of
analytical reagent grade chemicals.
2.2. Microwave-assisted extraction
Fig. 2. Effect of MAE time on the extraction of polyphenols and
A household microwave oven (full power 700 W,
caffeine Solvent: ethanol/water (1:1 v/v) 100 ml; whole green tea leaves:
1
National, Japan) was modified in our laboratory [12]. 5 g; liquid/solid ratio: 20:1 ml g (j) the extraction of tea
polyphenols; (k) the extraction of tea caffeine.
Green tea leaves were mixed with an appropriate
solvent. The suspensions were irradiated with micro-
waves as follows: 45 s power on (heating to the desired
temperature about 85 /90 8C) and 10 s power off and
water and 5 ml ferrous tartrate tetrahydrate solution (1
then 3 s power on (for heating) and 10 s power off (for
g ferrous sulfate and 5 g potassium sodium tartrate
cooling) and so on to the pre-set extraction time. Super-
tetrahydrate were dissolved in 1000 ml water in 1000-ml
boiling of the solution did not occur.
volumetric flask) were mixed with 15 ml buffer solution
Except MAE, other extraction methods are tradi- 1
(0.067 mol l pH 7.5 potassium phosphate) in 25-ml
tional in the references, such as heat reflux extraction
capacity bottle. It takes several minutes for color to
and Soxhlet extraction [13], and ultrasonic extraction
develop.
[14]. There is no microwave energy radiation by
With blank solution (prepared with solvent before
magnetic stirring for 0 /90 min pre-leaching at room
used in extraction according to the procedure as
temperature and then MAE for 4 min.
mentioned above for analysis of tea polyphenols) as
reference solution, absorbance (A) at Vis 540 nm with a
2.3. Colorimetric analysis of tea polyphenols [15]
10 mm quartz cell was used to calculate the extraction of
tea polyphenols according to Eq. (1) [15]. The errors
One milliliter extraction solution (obtained with
were controlled to less than 0.5% through duplicated
different volume of extraction solvent and appropriate
experiments and analysis.
mass of leaves described in different experiments), 4 ml
Fig. 1. Effect of ethanol concentration in water on the extraction of
polyphenols and caffeine Solvent: 100 ml; whole green tea leaves: 5 g; Fig. 3. Effect of liquid/solid ratio on the extraction of polyphenols and
1
caffeine Solvent: ethanol/water (1:1 v/v) 100 ml; MAE for 4 min (j)
MAE for 5 min; liquid/solid ratio: 20:1 ml g (j) the extraction of
tea polyphenols; (k) the extraction of tea caffeine. the extraction of tea polyphenols; (k) the extraction of tea caffeine.
X. Pan et al. / Chemical Engineering and Processing 42 (2003) 129 /133 131
The extraction of tea polyphenols (%; w=w) The percentage of tea polyphenols or tea caffeine
in extracts (%; w=w)
L1
2A 1:957 100% (1)
Mass of tea polphenols or tea caffeine in extracts
L2M
Mass of extracts
100%
where, L1, total volume of extraction solution, ml; L2,
(3)
volume of extraction solution used for colorimetric
analysis, ml; M, mass of tea leaves, mg; A, absorbance
at Vis 540 nm; 1.957, when absorbance was 0.5 at Vis
540 nm with a 10 mm quartz cell, the concentration of
1
tea polyphenols was 1.957 mg ml .
3. Results and discussion
3.1. The effect of ethanol concentration on the extraction
2.4. Colorimetric analysis of tea caffeine [16]
of polyphenols and caffeine
Twenty milliliters of extraction solution (obtained
Fig. 1 shows that the extraction of polyphenols and
with different volume of extraction solvent and appro-
caffeine in green tea leaves was greatly influenced by the
priate mass of leaves described in different experiments),
ethanol concentration in water. When the ethanol
1
10 ml hydrochloric acid (0.01 mol l ) and 2 ml lead
volume percentage in the solvent was lower than 50%
acetate basic solution (50 g Pb(CH3COO)2 Pb(OH)2 (v/v), the extraction was increased with the increase of
were mixed in 100 ml water and then were collected to
ethanol concentration. When the ethanol volume per-
stand at least for 12 h) were mixed with 218 ml water in
centage in the solvent was higher than 50% (v/v), the
a 250-ml volumetric flask. The mixed solution was stand
extraction was decreased with the further increase of
for 1 h and then was filtered. After that, 50 ml filtered
ethanol concentration. So 50% (v/v) ethanol concentra-
solution and 0.2 ml sulfuric acid (H2SO4) solution (4.5
tion in water was used in the following experiments.
1
mol l ) were mixed with 49.8 ml water in a 100-ml
volumetric flask. The mixed solution was stand for 30
3.2. The effect of MAE time on the extraction of
min and then was filtered. With blank solution (pre-
polyphenols and caffeine
pared with solvent before used in extraction according
to the procedure for analysis of tea caffeine) as reference
Fig. 2 shows the effect of MAE time on the extraction
solution, the filtered solution was measured at UV 274
of polyphenols and caffeine. The results indicate that the
nm with a 10 mm quartz cell.
extraction of polyphenols and caffeine was increased
1
A good linear ranging from 0 to 0.02 mg ml
with the increase of MAE time. MAE reached a high
caffeine (analytical reagent grade chemicals caffeine as
point in 4 min. If MAE time was longer than 4 min, the
standard) was found. Regression equation (at UV 274
extraction of caffeine was decreased with the increase of
nm) and correlation coefficient were Abs /50.13C /
time. So MAE time for 4 min was used in the following
0.0002 and R /0.9996 (n /9) respectively. Calculation
experiments.
of the concentration of caffeine from the calibrated
regression equation according to absorbance at UV 274
3.3. The effect of liquid/solid ratio on the extraction of
nm and it was used to calculate the extraction efficiency
polyphenols and caffeine
of tea caffeine according to the following Eq. (2) [16].
The errors were controlled to less than 0.2% by
Fig. 3 shows that the extraction of polyphenols and
duplicated experiments and analysis.
caffeine was increased with the increase of liquid/solid
The extraction of tea caffeine (%; w=w)
ratio. If the extraction was carried out under high liquid/
solid ratio, the concentration of tea polyphenols and tea
C L1 250=20 100=50
100% (2)
caffeine in extraction solution was low. The liquid/solid
M
1
ratio of 20:1 (ml g ) was sufficient to reach the high
extraction, and it was used afterwards.
where C, the concentration of caffeine calculated from
the calibrated regression equation based on the absor- 3.4. The effect of different solvents on the extraction of
1
bance at UV 274 nm, mg ml ; L1, total volume of polyphenols and caffeine
extraction solution, ml; M, mass of green tea leaves, mg.
In the present work, the percentage of tea polyphenols Fig. 4(a) shows that acetone can be used to obtain
or tea caffeine in extracts was defined as following Eq. higher extraction of polyphenols than using methanol,
(3): water and ethanol respectively. The methanol can give
132 X. Pan et al. / Chemical Engineering and Processing 42 (2003) 129 /133
Fig. 5. Effect of pre-leaching time at room temperature on the
extraction of polyphenols and caffeine Solvent: ethanol/water (1:1 v/
1
v) 100 ml; whole green tea leaves: 5 g; liquid/solid ratio: 20:1 ml g ;
MAE for 4 min; room temperature: about 20 8C(j) the extraction of
tea polyphenols; (k) the extraction of tea caffeine.
time was 90 min, the extraction of polyphenols was
increased from 28.06 to 29.59%, while the extraction of
caffeine was increased from 3.55 to 4.04%. It is obvious
that pre-leaching before the MAE is useful for improv-
ing the extraction of both polyphenols and caffeine.
3.6. Comparison of MAE and conventional extraction
methods
Table 1 shows that the MAE for 4 min after pre-
leaching for 90 min gave higher extraction of polyphe-
nols and caffeine than the extraction at room tempera-
ture for 20 h, ultrasonic extraction for 90 min and heat
reflux extraction of 45 min respectively. The results
show that the time of heat reflux extraction, ultrasonic
extraction and extraction at room temperature was
respectively about 10, 20, 300-folds of time of extraction
with MAE. MAE can greatly reduce the extraction time
Fig. 4. The effect of solvents used on the extraction of polyphenols
for the same extraction.
and caffeine Solvent: 100 ml; whole green tea leaves: 5 g; MAE for 4
Table 2 shows that MAE also gives higher percen-
1
min; liquid/solid ratio: 20:1 ml g .
tages of polyphenols and caffeine in extracts in compar-
ison with those of ultrasonic extraction and heat reflux
higher extraction of caffeine than using water, ethanol
extraction respectively. The MAE can give the highest
and acetone respectively (Fig. 4(b)). If water was added
extraction selectivity.
to ethanol, the ethanol/water (1:1 v/v) solution gave
higher extraction of polyphenols and caffeine than the
other solvents tested. As the ethanol is non-toxic and
can be mixed with water in different ratio, so it is chosen
4. Conclusion
to extract polyphenols and caffeine from green tea
leaves.
Conditions for MAE of polyphenols and caffeine
from green tea leaves have been studied. MAE has been
3.5. The effect of pre-leaching time before MAE on the shown to be an efficient method for extraction of
extraction of polyphenols and caffeine polyphenols and caffeine from green tea leaves. Com-
pared with the conventional extraction methods, the
Fig. 5 shows that the extraction of polyphenols and MAE procedure provided high extraction, high extrac-
caffeine were influenced by pre-leaching time at room tion selectivity, requiring short time, and less labor
temperature before MAE for 4 min. If the pre-leaching intensive.
X. Pan et al. / Chemical Engineering and Processing 42 (2003) 129 /133 133
Table 1
Comparison of the results of the extraction with MAE and conventional extraction methods
Extraction method Extraction time The extraction, w/w
Polyphenols Caffeine
Extraction at room temperature 20 h 28 3.6
Ultrasonic extraction 90 min 28 3.6
Heat reflux extraction 45 min 28 3.6
MAE (after pre-leaching for 90 min at room temperature) 4 min 30 4
1
Solvent: ethanol/water (1:1 v/v) 100 ml; whole green tea leaves: 5 g; liquid/solid ratio: 20:1 ml g ; room temperature: 20 8C; Ultrasonic
extraction: 20 /40 8C; Heat reflux extraction at boiling point about 85 8C.
Table 2
Comparison of the percentage of polyphenols and caffeine in extracts obtained with different extraction methods
Extraction meth- The extraction of polyphe- The extraction of caffeine The percentage of polyphenols in The percentage of caffeine in
ods nols (%) (w/w) (%) (w/w) extracts (%) (w/w) extracts (%) (w/w)
MAE 30 4 77 10
Ultrasonic ex- 28 3.6 75 10
traction
Heat reflux ex- 28 3.6 72 9
traction
1
Solvent: ethanol/water (1:1 v/v) 100 ml; whole green tea leaves: 5 g; liquid/solid ratio: 20:1 ml g ; MAE for 4 min after pre-leaching for 90 min at
room temperature about 20 8C; ultrasonic extraction at 20 /40 8C for 90 min; heat reflux extraction at boiling pointing point about 85 8C for 45
min.
[6] M.J.I. Mattina, W.A.I. Berger, C.L. Denson, Microwave assisted
MAE was suitable for fast extraction of polyphenols
extraction of taxanes from Taxus biomass, J. Agric. Food Chem.
and caffeine from green tea leaves. Food and medicinal
45 (1997) 4691 /4696.
industries would be benefited from this emerging
[7] J.C. Young, Microwave-assisted extraction of the fungal meta-
technology of MAE, which was rapid, safe and more
bolite ergosterol and total fatty acids, J. Agric. Food Chem. 43
eco-friendly than conventional extraction methods.
(1995) 2904 /2910.
[8] J. Dai, V.A. Yaylayan, G.S.V. Raghavan, J.R. ParŁ, Extraction
and colorimetric determination of azadirachtin-related limonoids
in neem seed kernel, J. Agric. Food Chem. 47 (1999) 3738 /3742.
Acknowledgements
[9] Y.Z. Ge, H. Jin, New methods for extraction of tea polyphenols,
Chin. Herbal Med. 25 (3) (1994) 124 /125.
This work was supported by National Natural
[10] J. Li, Y.S. Feng, A study on extraction of tea polyphenols with
Science Foundation of China (No. 29836130).
supercritical carbon dioxide, Nat. Prod. Res. Dev. 8 (3) (1996)
42 /47.
[11] Q.H. Hu, M. Jiang, J.C. Zhu, Research on technology of
extraction of tea caffeine and polyphenols, Nat. Prod. Res. Dev.
References
9 (2) (1997) 63 /66.
[12] X.J. Pan, H.Z. Liu, G.H. Jia, Y.Y. Shu, Microwave-assisted
[1] H. Tanizawa, S. Toda, Y. Sazuka, T. Taniyama, T. Hayashi, S.
extraction of glycyrrhizic acid from licorice root, Biochem. Eng. J.
Arichi, Y. Takino, Natural antioxidants. I. Antioxidative compo-
5 (2000) 173 /177.
nents of tea leaf (Thea sinensis L .), Chem. Pharm. Bull. 32 (1984)
[13] Y.R. Lu, Chinese Medicine Chemistry, Xueyuan Publishing
2011 /2014.
House, Beijing, 1995, pp. 10 /11.
[2] B.L. Zhao, X.J. Li, R.G. He, S.J. Cheng, W.J. Xin, Scavenging
[14] G.B. L, J. Liu, Determination of Glycyrrhizin in Radix
effect of extracts of green tea and natural antioxidants on active
Glycyrrhizae and its preparation by HPLC, Chin. J. Pharm.
oxygen radicals, Cell Biophys. 14 (1989) 175 /185.
Anal. 8 (3) (1988) 137 /139.
[3] W.J. Chen, S.Q. Wan, Research progress on polyphenols of tea,
[15] M.G. Song, F.K. Yang, N.Y. He, R.Y. Fei, J.X. Wang, L.M.
Nat. Prod. Res. Dev. 6 (2) (1994) 74 /80.
Wang, Determination of tea polyphenols content, China National
[4] H.M. Kingston, L.B. Jassie, Introduction to Microwave Sample
Standard GB8313-87 , 1987.
Preparation: Theory and Practice, American Chemical Society,
[16] M.J. Li, L. Zhong, J.H. Yan, K. Cheng, W.J. Guo, J.A. Wang,
Washington DC, 1988.
Determination of tea caffeine content, China National Standard
[5] S.S. Chen, M. Spiro, Study of microwave extraction of essential
oil constituents from plant materials, J. Microwave Power GB8312-87 , 1987.
Electromagn. Energy 29 (1994) 231 /241.
Wyszukiwarka
Podobne podstrony:
Przepis na herbatę leczącą ponad 60 chorób i zabijającą pasożytyJak zrobic przekładane herbatniki28 29 Luty 2000 Mamy herbatęJak Rośnie HerbataEkstraparty lanaliza przedzabiegowa czyli konieczne czynnosci przed ekstrakcja Kawa czy herbata ( Chemia w Szkole 4 2006 r )więcej podobnych podstron