| Research Article |
Open Access |
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| The Bioavaliability of Hepatoprotective
Flavoniods in Hypericum Japonicum Extract |
| Ning Wang1, Yonggang Wang1, Peibo Li1, Wei Peng1, Tangning Xie1, Yibin Feng2, Weiwei Su1* |
| 1Guangzhou Quality R&D Center of Traditional Chinese Medicine, School of Life Science,
Sun Yat-sen University, Guangzhou, 510275, P.R. China |
| 2School of Chinese Medicine, The University of Hong Kong, 10 Sassoon Road, Pokfulam, Hong Kong |
| *Corresponding author: |
Dr. Weiwei Su,
Guangzhou Quality R&D Center
of Traditional Chinese Medicine,
School of Life Science, Sun Yat-sen
University,
Guangzhou, 510275, P.R. China,
E-mail: nwang@hku.hk |
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| Received October 18, 2009; Accepted December 26, 2009; Published December 26, 2009 |
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| Citation: Wang N, Wang Y, Li P, Peng W, Xie T, et al. (2009) The Bioavaliability of Hepatoprotective Flavoniods in Hypericum Japonicum Extract. J Bioanal Biomed 1: 033-038. doi:10.4172/1948-593X.1000007 |
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| Copyright: © 2009 Wang N, et al. This is an open-access article distributed
under the terms of the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium,
provided the original author and source are credited. |
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| Abstract |
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| Purpose: To study the absorption of main flavonoids in
Hypericum japonicum extract (HJE) with liver protective
property; Method: HPLC-ESI-MS was introduced to identify
and evaluate the flavonoids in HJE; Caco-2 cell monolayer
model was established and validated, and the compounds
in HJE, including quercetin (Q), quercetin-3-Orhamnoside
(Q-3-R), quercetin-7-O-rhamnoside (Q-7-R)
and quercetin-3-O-glucoside (Q-3-G) were administrated
in individual, paired or mixed form of the compounds to
the monolayer to evaluate their apparent permeability coefficients
(Papp value). The transport of HJE was also investigated,
mixture of pure components and HJE Inhibitor
was added to investigate the transport mechanism of
the compound mixture. The absorption of the four main
ingredients in HJE was then investigated in vivo. Result:
transportation of Q, Q-3-R Q-3-G but not Q-7-R trhough
Caco-2 monolayer was observed when they were administrated
individually. Increase of the transport of Q-3-G
and Q-7-R and decrease in Q were observed when the four
compounds were given in paired form; when the four flavonoids
were given as a whole (either in mixture of pure
compounds or in HJE), mass permeability of Q-3-R, Q-7-
R and Q-3-G was found. In vivo study identified the in
vitro investigation that the major active components of
HJE could be absorbed after orally administrated to mice. |
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| Conclusion: The increased transport of mixed active
components in HJE gives rise to the enhanced
hepatoprotetive effect of HJE, and therefore supports the
use of botanical drugs. |
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| Keywords |
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| Flavonoids; Absorption; Interaction; Caco-2 cell
Monolayer |
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| Introduction |
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| Hypericum japonicum (HJ) is a kind of herb which has been used for hepatitis therapy for more than hundreds years in southern China. Modern investigations reveal HJ’s potent action of anti-microbial, liver protection and anti-hypertension (Ishiguro et al., 2002; Jiang et al., 1997; Liu et al., 2008). Previous study in our laboratory has established the chemical profile for the raw materials of Hypericum japonicum Thunb. (Yang et al., 2005). As well, our study showed quercetin and its aglycones, including quercetin-3-O-rhamnoside (Q-3-R), quercetin-3-Oglucoside (Q-3-G) and quercetin-7-O-rhamnoside (Q-7-R), are the main active components in Hypericum japonicum (Wang et al., 2008). Some preliminary data in our laboratory showed that the the total extract Hypericum japonicum (HJE) performs better hepatoprotective action than its component chemicals, quercetin and its analogs (Data not show). However, the underlying mechanism has not yet been documented. In this study, he intestinal absorption of components in HJE extract in different dose forms both in vitro and in vivo system were addressed. The mechanism of interaction on their transport was also investigated in this study. |
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| Materials and Experiments |
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| Chemicals and HJE preparation |
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| Q, Q-3-R and Q-3-G were purchased from the Sigma. Q-7-R
was extracted and purified from Hypericum japonicum in our
laboratory. The purity of all chemicals above was above 95%.
Verapamil, the P-glycoprotein inhibitor, was a kindly gift offered
by Dr. Ma Yan in Guangzhou University of Chinese Medicine.
HJE was prepared from Hypericum japonicum in our lab
(Batch No. 20060524, 20060605, and 20060616). Briefly, Hypericum
japonicum powder was extracted by 20-folder of boiled
water (w/v) for 1 hour and then filtered. This step was repeated
two times. The filtrate each time was then mixed and evaporated
to dryness. Residue was triturated with distilled water and then
extracted with 2-folder of ethyl acetate for two times. Ethyl acetate
was then evaporated to dryness for preparing the HJE powder.
Powders were diluted by proper solvent before use. |
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| Cell line and cell culture |
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| Caco-2 cells obtained from the Xiehe Medical School were
cultured in Eagle’s Minimum Essential Medium (Gbico) supplemented
with 1% MEM nonessential amino acids (Mediatech),
10% fetal bovine serum (PAA), 100 units/mL of penicillin, and
0.1 mg/mL of streptomycin (Sigma) and were grown in a humidified
atmosphere of 5% CO2 at 37 degree centigrade. |
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| For all transport studies, Caco-2 cells were seeded in 12 mm
i.d. Transwell inserts (polycarbonate membrane, 0.4 mm pore
size, Corning Costar Corp.) in 12-well plates at a density of
1.0×105 cells/cm2. The basolateral side (serosal, BL side) and
apical side (mucosal, AP side) compartments contained 1.5 and 0.5 mL of culture medium, respectively. Culture medium was
replaced per two days for the first ten days and daily thereafter
until the 21st day. |
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| Chemical identification and quantitative analysis on HJE by
HPLC-ESI-MS |
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| HPLC-ESI-MS (LCQ DECA XP, Thermo, USA) was introduced
to identify and quantify ingredients in HJE. Chromatographic
separation was achieved using a mobile phase consisting
of methanol (A) and water (pH 2.5, B) at the gradient as
follows: The ratio of A to B was constant at 36 to 64 during the
first 65 min, and then changed linearly to be 65 to 35 at 100 min
The flow rate was 1.0 mL/min. The column was kept at 25 degree
centigrade. The mass spectra were recorded using ESI in
both positive and negative mode with ion spray voltage at 3300
eV, source temperature at 350 degree centigrade, gas spray 1 at
60 psi, Gas spray 2 at 40 psi, current gas at 40 psi, desolvent
voltage 1 at 40 eV, desolvent voltage 2 at 15 eV, focus voltage at
200 eV and scanning from 300 to 1000 amu. 0.05 g of HJE was
dissolved by 50 mL methanol and then 10 μL of the solution was
injected and analyzed. Q, Q-3-R, Q-3-G and Q-7-R were also
analyzed as standards. Three batches of HJE were analyzed quantitatively
as above. Then the content of Q, Q-3-R, Q-3-G and Q-
7-R was calculated respectively through calibration curve
method. |
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| The establishment and evaluation of cell model |
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| Caco-2 cells in Transwells were used for transport experiments
after 21 days culturing. Transepithelial electrical resistance
(TEER) values across the cell monolayer were measured using a
Millicell-ERS voltohmmeter (Millipore Corp.). Only the inserts
whose TEER values are more than 350 V/cm2 in culture medium
were used. Alkaline phosphatase (ALP) activity by commercial
kit (Jiancheng biotechnical Co., Nanjing, P.R. China) on the 21st
day was evaluated. |
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| Propranolol was introduced as a marker to determine the
transepithelial ability of the established model (Takahashi et al.,
2002). Samples were collected from BL side of cell monolayer
at 15, 30, 45, 60, 90 and 120 min respectively and analyzed for
the propranolol content by high performance liquid chromatography
(HPLC) under literature condition (Ma, 2005). |
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| Transepithelial permeability evaluation of different doseform
agents |
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| At the 21st day of the period, inserts were washed twice before
30 minutes incubation with 37 degree centigrade PBS buffer
solution and then removed. Agents with different dose forms
were added to apical (500 ìL) or basolateral (1500 ìL) side of
the inserts, whereas the receiving chamber contained corresponding
volume of transport medium. For evaluating of transepithelial permeability of single pure compounds, chemicals (Q, Q-3-R,
Q-3-G and Q-7-R) at dose of 25, 50 or 100 μM were added to
the upper chambers. To determine the transport ability of cooccurring
form of compounds, Q, Q-3-R, Q-3-G and Q-7-R were
paired with one another with proper scales as in HJE, and added
to upper chamber at the dose of 50 and 100 μg/mL. Mixture of
Q, Q-3-R, Q-3-G and Q-7-R (with proper scale as in HJE) and
HJE at the dose of 50 and 100 μg/mL were added to upper chamber
to determine the permeability of components in mixed form.
Samples were collected from receiving chambers of cell monolayer
at 15, 30, 45, 60, 90 and 120 min respectively and analyzed
by HPLC. |
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| Influence of other flavonoids on efflux of Q-3-G and Q |
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| Experiment was carried out as described in section 2.5. Transport
mediums with chemicals (Q-3-G, Q, mixed flavonoids and
mixed flavonoids with Verapamil) at the dose of 50 μg/mL were
added to the basolateral (1500 μL) side of the inserts followed
by the addition of 500 μL to the upper chambers. |
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| In Vivo Observation on the Absorption of Main Ingredients
in HJE |
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| 42 KM mice with either sex weighing 22~25 g were divided
into seven groups. Animals were orally administrated with HJE
at the dose of 486 mg/kg after 12-h fasting but free watering.
Blood was collected at 0, 5, 15, 30, 60, 90 min after drug administration.
Animals were then sacrificed by an overdose of pentobarbitone
(Phenobarbital 200mg/kg, i.p). Plasma was then collected
by centrifuging the blood at 6000 rpm at 25 degree centigrade
for 10 min, and was extracted by 400 μL ethyl acetate for
two times. The upper layers were collected and dried in room
temperature. The residue was then dissolved by 50 μL methanol.
Blank plasma was prepared as above from mice without
HJE administration. Samples were then analyzed by HPLC. All
animal experiments were conducted with the adherence to principles of laboratory animal care and proved by the Animal Ethics
Committee of Sun Yat-sen University. |
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| Statistical Analysis |
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| Student T-test was introduced for statistical analysis. The result
was expressed by means of mean ± SD. |
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| Results |
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| HPLC-ESI-MS was introduced to analyze the chemical composition
of HJE. Our result shows that Q-3-G, Q-3-R. Q-7-R and
Q compose as the majority of HJE (Figure 1), indicating that the
hepatoprotective action of HJE is mainly contributed by the four
compounds. Peak 1, 2, 3 and 4 were identified as Q-3-G, Q-3-R,
Q-7-R and Q (Figure S1, Figure S2, chemical structure in Figure
2). The contents of Q, Q-3-R, Q-3-G and Q-7-R were measure
as Table 1 shows. The contents of four compounds in HJE were
mostly stable among different batches, and the ratio was approximately
at 5:10:20:5. |
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Figure 1: The total ion chromatogram (TICs) of HJE by HPLC-ESI-MS (A shows TIC btained in negative ionization mode; B shows TIC obtained in positive
ionization mode). |
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Figure 2: Chemical Structures of four flavonoids in HJE. |
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| Table 1: Content Measurement of four flavonoid in HJE. |
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| To well establish the Caco-2 model in our study, TEER value
between two sides of the inserts was measure and Figure 3 shows
increasedTEER value of most inserts during incubation days,
and the value reached more than 450 mΩ at the 21st day, which is
suitable for transport study. Activity of ALP in AP side (1.063 ±
0.074 U/L) of Caco-2 monolayer is approximately 3.2 fold of
that in BL side (0.333 ± 0.063 U/L), indicating the accumulation
of ALP in AP side and the biochemical differentiation of the
Caco-2 cell monolayer. Permeability of propranolol on monolayer
was 26.88 ± 1.88×10-6 cm/s, similar to literature report
(Ismael and Jibin, 1996). |
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|
Figure 3: TEER value of Caco-2 cell monolayer in different days. |
|
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| Transepithelial Permeability, expressed as apparent permeability
coefficients (Papp), was calculated by the following equation: |
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| Papp = dQ / dt A C0 |
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| where, dQ/dt is the change in drug concentration in the receiver
solution (μM/s or μg/s), A denotes the membrane surface area
(cm2), and C0 is the initial concentration in the donor compartment
(μM or μg/mL). Results in Table 2 show potent differences
of transepithelial permeability of quercetin and its analogs when
they were transported through the Caco-2 monolayer in different
dose forms, indicating a vast variety of absorption and
bioavailability in different dose forms. When better addressing
the inter-influence of quercetin analogs, Table 3 reveals that the
efflux of Q-3-G is significantly inhibited when it was co-transport with its analogs, Q-7-G, Q-7-R or Q. The Papp value of Q-3-
G fell to 0.303×10-6 cm/s from 2.126×10-6 cm/s when it was cotransported
with any of its analogs. The results also show increased
efflux of Q when it was co-transported, and this action
could not be wholly eliminated by the addition of transporter
inhibitor (10 μM Verapamil). |
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| Table 2: Papp values (×10-6) of the four compounds in different dose forms (Mean±SD, n=3). |
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| Table 3: Papp values of flavonoids from BL side to AP side in different dose form (Mean±SD, n=3). |
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| Chemical profile of plasma from mice treated with or without
HJE reveals absorption of the four main flavonoids after oral
administration to mice (Figure 4). Peak concentrations could be
found 60 minutes after HJE treatment. Plasma drug concentrations
at different time points are showed in Table 4. |
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Figure 4: Chemical profile of mice plasma after administrated with or without HJE (A for blank plasma; B for plasma from mice treated with HJE at 0 min; C for
plasma from mice treated with HJE at 5 min; D for plasma from mice treated with HJE at 15 min; E for plasma from mice treated with HJE at 30 min; F for plasma
from mice treated with HJE at 60 min; G for plasma from mice treated with HJE at 90 min. In all fig.s, peak 1 was identified as Q-3-G, peak 2 as Q-3-R, peak 3 as
Q-7-R, peak 4 as Q). |
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| Table 4: Drug concentration in mice blood at different time after administrated HJE (Mean±SD, n=6). |
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| Discussion |
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The use of herbal medicine has a long tradition in China and
other Asian countries. It is widely believed that herbal extract,
the mixture form of particular pure compounds, exhibits better
effect and less toxicity than each composing chemical therein.
However, the proposed mechanism has never been documented.
In our study, increased permeability of Q-3-G, Q-3-R and Q-7-R
through Caco-2 cell monolayer in mixture form indicates the
underlying inter-influence among different chemicals may significantly
alter their absorption. Since the potent hepatoprotective action of Q-3-R, Q-3-G and Q-7-R have been reported and defined
documented in mice (Li et al., 2007), the better
hepatoprotective effect of HJE than quercetin and its analogs
(Data not shown) may results from the increased absorption of
Q-3-R, Q-3-G and Q-7-R in HJE. |
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| In order to further study the underlying inter-influence of Q-3-
R, Q-3-G and Q-7-R in HJE, we investigated the transepithelial
permeability of each compound when they were transported
through Caco-2 monolayer in pair.. Increased Papp value of Q-3-
G and Q-7-R was observed, which gives evidence that co-transportation
of quercetin analogs may increase their absorption. Our
study also showed a collaborative inhibition of Q-3-R, Q-7-R
and Q on the efflux of Q-3-G but enhanced output of Q by Q-3-
R, Q-7-R and Q-3-G. Addition of P-gp inhibitor can not completely
suppress the interinfluence among the four flavonoids,
indicating that the interaction may not totally act via activating
the transport related protein. Further investigation is necessary
for elucidating the exact mechanism of the transport of HJE. |
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| Conclusion |
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| In conclusion, the intestinal absorption of four main compounds
in HJE was investigated and the results indicate the absorption alters in different dose forms. The increased transport of Q-7-R
and Q-3-G, which show potent liver protection when treated individually,
as well as decreased transport of quercetin can be
observed when the four compounds are co-transporting through
the Caco-2 monolayer, revealing that integrated administration
may improve the absorption of active components in HJE, which
may be the possible reason why HJE show better liver protective
action than its individual components. Utilization of herbal
drugs and its extracts are often found with lack of scientific interpretation
and experimental evidence. This present study combined
with our previous investigation provides new perspective
to validate the utilization of botanical drug. For further investigation
on exact mechanism of botanical drug, more in vivo pharmacokinetic
models and molecular approaches are expected in
addition to the above mentioned study methods. |
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| Acknowledgements |
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| The study was supported by the National Key Technology R&D
Program (No. 2006BAI06A 02-2) from Ministry of Science and
Technique of the People’s Republic of China. |
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