全 文 :625 Journal of Chinese Pharmaceutical Sciences http://www.jcps.ac.cn
Rapid screening of antiHIV ingredients in Artemisia rupestris L. extracts
interacting with V3 loop region of HIV1 gp120 and reverse transcriptase
by affinity capillary electrophoresis and capillary zone electrophoresis
Yiran Zhao 1 , Zhongjie Li 1 , Yong Jiang 2 , Xiaodan Zhang 1 , Xiaomei Ling 1*
1. Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing 100191,
China
2. Department of Natural Medicines, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing 100191, China
Abstract: HIV1 gains entry into target cells by sequentially interacting with cellular receptors and coreceptors. Both the receptor
and coreceptor are recognized by HIV1 envelope protein gp120, which plays a key role in the entry process of HIV1 into cells. The
development of new inhibitors is essential since the viral enzyme reverse transcriptase (RT) is one of the first targets of antiretroviral
therapy. It has been reported that a variety of natural plants, such as Artemisia rupestris L., have antiviral pharmacological activity,
and they might be the potential inhibitors of RT or V3 loop of gp120 against HIV1. RIQRGPGRAFVTIGK (R15K), the relatively
conserved region of V3 loop, can be used for binding research. In this work, we analyzed the interactions between different extracts
from Artemisia rupestris L. and R15K by affinity capillary electrophoresis (ACE). Moreover, we analyzed the interactions between
different extracts from Artemisia rupestris L. and RT by capillary zone electrophoresis (CZE). Our data showed that the chloroform
extract of Artemisia rupestris L. was active among the different plant extracts, which was consistent with previous studies. Taken
together, our study provided a rapid screening method to seek antiHIV ingredients in natural plants’ extracts.
Keywords: HIV, V3 loop, RIQRGPGRAFVTIGK, Reverse transcriptase, Affinity capillary electrophoresis, Capillary zone electrophoresis
CLC number: R917 Document code: A Article ID: 1003–1057(2015)9–625–05
Received: 20150518, Revised: 20150620, Accepted: 20150624.
Foundation items: National Natural Science Foundation (Grant No.
81373372) and Specialized Research Fund for the Doctoral Program
of Higher Education of China (Grant No. 20110001110021 and
20130001110059).
* Corresponding author. Tel.: 861082801590,
Email: lingxm@bjmu.edu.cn
http://dx.doi.org/10.5246/jcps.2015.09.079
1. Introduction
The entry of HIV into target cells is a sophisticated,
multistep process mediated by the viral envelope proteins
gp120 and gp41, including sequential attachment, specific
bindings and membrane fusion [1,2] . Apart from the
welldefined receptors and coreceptors, a variety of
glycosphingolipids (GSL), including galactosyl ceramide
(GalCer) and a monoganglioside GM3, can also regulate
Envmediated fusion, interaction with gp120 through
a specific portion of the V3 loop region [3,4] . The V3
loop serves an important role during the entry process.
It extends and projects away from the virion spike
upon CD4 binding. Sequentially, the orientation of
gp120 is altered, and the bridging sheet and V3 loop
are positioned towards the host membrane where they
can interact with coreceptors. V3 loop also takes part
in the binding of gp120 to CCR5 and CXCR4, two
most commonly used corecptors for HIV entry in vivo.
As a synthetic V3 loop peptide corresponding to the
glycolipid binding domain of the V3 loop of HIV1 gp120,
RIQRGPGRAFVTIGK can be used to investigate
the binding studies instead of the recombinant gp120
molecules [5,6] . Although a complex process, including
multiple sequential interactions between gp120 and gp41
and host surface proteins, a large number of potential
targets to impede the entry process, now the HIV entry
can be discovered.
Successful entry of the contents of the viral core is
followed by the reverse transcription of the viral RNA
template into its complementary DNA. This process is
performed by the enzyme reverse transcriptase (RT) of
the virus. RT degrades the RNA template to subsequently
produce the doublestranded viral DNA [1] . To date,
626 Zhao, Y.R. et al. / J. Chin. Pharm. Sci. 2015, 24 (9), 625–629
the three major groups of drugs in the clinical practice
are the RT inhibitors (nucleoside/nucleotide, NRTI, and
nonnucleoside, NNRTI) and protease inhibitors (PI).
Therefore, one of the most important strategies against
HIV1 is to find out new inhibitors targeting RT.
The current therapeutic strategy, highly active anti
retroviral therapy (HAART) involves the use of agents
from at least two distinct classes of antiretroviral drugs [8] .
As the combination of HAART regiments is unable to
eradicate HIV infection, lifelong therapy is required to
avoid disease progression [9,10] . These factors necessitate
the continual development of new inhibitors that can be
used against resistant viruses. It has been reported that
a variety of natural plants, such as Artemisia rupestris L.,
have antiviral activity [11–13] . To screen the potential
HIV1 entry inhibitors in natural plants, we investi
gated the interactions between R15K and the extracts
of Artemisia rupestris L. as well as the interactions
between RT and the extracts of Artemisia rupestris L.,
respectively.
The interactions between small ligands and bio
molecules have been studied by varieties of methods.
Among these approaches, capillary electrophoresis (CE)
achieves remarkable advantages, including low sample
consumption, relatively short analysis time and high
efficiency [14,15] . In our present study, we investigated
the interactions between R15K and different extracts
from Artemisia rupestris L. by ACE and assessed the
interactions between RT and different extracts from
Artemisia rupestris L. by CZE.
2. Experimental
2.1. CE instrumentation
The experiments were performed on a Beckman
P/ACE TM MDQ system (Beckman Coulter, Fullerton,
CA, USA) equipped with a photodiode array detector as
well as the 32 Karat TM software version 5.0 (Fullerton,
CA, Beckman). The bare fused silica capillaries (365 μm,
75 μm) were purchased from Yongnian Optical Fibers
(Hebei, China). The total and effective lengths of the
capillary were 30.2 cm and 20 cm, respectively. The
detector wavelength was set at 214 nm.
2.2. Reagents
All chemicals were of analytical grade unless otherwise
indicated. Tris base (ultrapure), acetic acid and dimethyl
sulfoxide (DMSO) were purchased from Beijing Chemical
Reagent Factory (Beijing, China). The deionized water
was prepared using a Millipore Milli QPlus system
(Millipore, Bedford, MA, USA). TrisHAc (30 mM),
served as running buffer, was prepared by dissolving
0.9108 g Tris in 250 mL of deionized water, and its pH
was adjusted to 7.45 at 25 °C using diluted acetic acid. All
CE solutions were filtered through 0.45μm membranes
(Agilent, Waldbronn, Germany) before use.
The peptide, corresponding to the R15K, was obtained
from Chinese Peptide in Hangzhou (China), which was
subsequently purified (purity≥95.8%) and characterized
by RPHPLC and MS. The synthesized amino acid
sequence of R15K was ArgIleGlnArgGlyProGly
ArgAlaPheValThrIleGlyLys. RT was supplied by
Ambion Inc (TX, USA). The different extracts of
Artemisia rupestris L. were provided by Dr. Yong Jiang
(Department of Pharmacognosy, School of Pharmaceutical
Sciences, Peking University). The extracts of Artemisia
rupestris L. were petroleum ether extracts, ethyl acetate
extracts and chloroform extracts.
2.3. Sample preparation
The stock solution of R15K, prepared by dissolving
the R15K in 30 mM TrisHAc to the concentration of
2 mM, was diluted to desired concentrations by adding
appropriate amounts of buffer. The methanol was evapo
rated under nitrogen stream before it was redissolved.
DMSO was diluted to 1‰ (v/v) and then added different
extracts of Artemisia rupestris L.
The petroleum ether extracts, ethyl acetate extracts
and chloroform extracts of Artemisia rupestris L. were
dissolved in methanol as stock solutions. The methanol
was evaporated under nitrogen steam before it was
redissolved. The saturation solutions of the different
extracts were used in the present study.
To investigate the interactions between RT and different
extracts of Artemisia rupestris L., the extracts and RT
were mixed (1:1, v:v) and incubated at 37 °C for 30 min
before CE analysis.
627 Zhao, Y.R. et al. / J. Chin. Pharm. Sci. 2015, 24 (9), 625–629
2.4. ACE conditions
Before each measurement, the capillary was sequen
tially rinsed with 0.1 M sodium hydroxide, deionized
water and running buffer. Samples containing a fixed
concentration of corresponding compounds (different
extracts of Artemisia rupestris L.) were injected into
the running buffer with increasing concentration of R15K.
The electrophoretic mobility of each extract was
determined. The applied voltage was set at +15 kV
after optimization. The samples were injected using
the pressure injection mode at 0.5 p.s.i. for 5 s. The
interactions were monitored by DAD at a wavelength of
214 nm. Different volumes of the R15K stock solution
were then added into TrisHAc as the ACE running
buffer. In addition, 1‰ DMSO (v/v) in samples was
used as an internal standard.
2.5. CZE conditions
To study the interactions between RT and different
extracts of Artemisia rupestris L., the temperature of the
cartridge was set at 25 °C. Before each measurement,
the capillary was sequentially rinsed with running buffer
(30 mM TrisHAc, pH 7.45). Samples containing the
mixtures of RT and different extracts of Artemisia
rupestris L. were injected using the pressure injection
mode at 0.5 p.s.i. for 5 s. The applied voltage was set
at +15 kV. The capillary was washed between runs
using the running buffer.
3. Results and discussion
3.1. Optimization of ACE
In the present study, pH 7.45 was selected as the
buffer pH value in order to analyze the interaction
under the physiological conditions. The baseline and
peak shape were good when 30 mM TrisHAc was used
as the running buffer. Voltage of +15 kV and capillary
length of 30 cm (effective length of 20 cm) were selected
to shorten the separation time. In this investigation,
the stability of protein was investigated. R15K solutions
(1 mM) were analyzed after different incubation time
(0, 0.5, 1, 2, 4 and 8 h) at room temperature. The RSD
value of the height and the retention time of the protein
peak were 1.7 and 0.3, respectively. The result indicated
that R15K was stable within 8 h at room temperature
and could be used for the interaction study.
3.2. Interactions between Artemisia rupestrisL. extracts
and R15K
Figure 1 shows the electropherograms of the interactions
between extracts from Artemisia rupestris L. and R15K.
DMSO was used as the noninteracting marker in
the running buffer. When 3sialyllactose was used as
positive control and Dgalactose was used as negative
control, R15K remarkably changed the mobility of
3sialyllactose, and the peak of Dgalactose could not
be separated from the peak of DMSO with the increase
of R15K concentration in the running buffer [7] . In our
present study, the complexation of compounds with
R15K resulted in a decrease of the charge to mass ratio,
which lowers the mobility and extends the retention
time. The mobility of Artemisia rupestris L. shifts turned
to a gradually decreased trend as the concentrations of
R15K were increased. The results suggested that the
chloroform extract of Artemisia rupestris L. could interact
with R15K. Above all, the binding of chloroform extract
of Artemisia rupestris L./R15K should be stronger than
that of 3sialyllactose/R15K due to the less amount of
R15K that could get positive result.
3.3. Interactions between Artemisia rupestris L.
extracts and RT
Figure 2 shows the electropherograms of the interactions
between extracts from Artemisia rupestris L. and RT.
Curve 1 represents each extract only, whereas curve 2
represents the mixture of RT and different extracts at a
ratio of 1:1 (v:v). The peak of RT could not be separated
from the peaks of the extracts. As a result, the peak
height of the mixture of petroleum ether extracts and
RT was increased accordingly. The peak shape of the
mixture of ethyl acetate extracts and RT extended for
the same reason. Apparently, these two types of extracts
had no interactions with RT. The peak height of the
mixture of chloroform extracts and RT was decreased.
This finding indicated that the chloroform extracts of
Artemisia rupestris L. could interact with RT, leading
to the decrease of the peak height.
628 Zhao, Y.R. et al. / J. Chin. Pharm. Sci. 2015, 24 (9), 625–629
4. Conclusions
In the present study, we analyzed the interactions
between different extracts from Artemisia rupestris L.
and R15K by ACE. Moreover, the interactions between
different extracts from Artemisia rupestris L. and RT
were analyzed by CZE. The results suggested that
the chloroform extract of Artemisia rupestris L. could
interact with R15K and RT, suggesting the existence
of potential antagonists of R15K and inhibitors of RT.
Furthermore, the results showed that the active ingredients
in the chloroform extract of Artemisia rupestris L. might
exhibit antiHIV activity by binding to the V3 loop of
gp120 and by targeting RT. Taken together, in the
present study, an efficient, rapid and sensitive method
was developed to identify natural plants’ bioactive extracts
that can interact with specific drug targets, such as R15K
or RT, under physiological conditions.
Acknowledgements
This work was financially supported by the National
Natural Science Foundation (Grant No. 81373372) and
Specialized Research Fund for the Doctoral Program of
Higher Education of China (Grant No. 20110001110021
and 20130001110059).
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利用亲和毛细管电泳和毛细管区带电泳快速筛选新疆一支蒿提取物中
与HIV1包膜蛋白gp120上V3环以及逆转录酶相互作用的活性成分
赵怡然 1 , 李中杰 1 , 姜勇 2 , 张晓丹 1 , 凌笑梅 1*
1. 北京大学医学部 药学院 化学生物学系, 北京 100191
2. 北京大学医学部 药学院 天然药物学系, 北京 100191
摘要: HIV1侵入宿主细胞的过程中与一系列受体和协同受体结合。这些受体和协同受体都由HIV1的包膜蛋白
gp120识别, 在病毒入侵过程中是重要环节之一。逆转录酶拮抗剂是最早针对抗病毒治疗的几个靶点之一, 对其的改进对
于寻找新型拮抗剂十分关键。许多天然植物如新疆一支蒿被报道具有抗病毒的生物活性。这些天然植物也许就是潜在
的靶向针对包膜蛋白gp120上V3环或者逆转录酶的艾滋病毒抑制剂。V3环结构中的相对保守的肽段R15K可以被用来研
究蛋白的相互作用。本研究利用毛细管亲和色谱方法研究了R15K与新疆一支蒿各种粗提物之间的相互作用。利用毛细
管区带电泳法研究了逆转录酶与新疆一支蒿各种粗提物之间的相互作用。实验结果表明, 新疆一支蒿的氯仿层提取物与
R15k和逆转录酶之间均存在较明显的相互作用。本研究提供了一种可以快速高通量筛选天然植物中抗艾滋病毒的活性
成分的方法。
关键词: HIV; V3环; R15K;逆转录酶;亲和毛细管电泳;毛细管区带电泳