Concise synthesis and antiangiogenic activity of artemisinin-glycolipid hybrids on chorioallantoic membranes

Article abstract of DOI:10.1016/j.bmcl.2010.08.013

Novel hybrids of non acetal and acetal-type derivatives at C-12 of artemisinin and glycolipids were synthesized via efficient coupling reactions. Some of these hybrids showed potent in vivo antiangiogenic activity on the chorioallantoic membrane (CAM) that was higher than or comparable to those of fumagillin and thalidomide at a concentration of 2.5 nmol.

Full text of DOI:10.1016/j.bmcl.2010.08.013

Bioorganic & Medicinal Chemistry Letters 20 (2010) 6858–6860
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Concise synthesis and antiangiogenic activity of artemisinin–glycolipid
hybrids on chorioallantoic membranes
Jérémy Ricci a, Jeehyun Park a, Won-Yoon Chung b, Kwang-Kyun Park b, Mankil Jung a,
*
a Department of Chemistry, Yonsei University, Seoul 120-749, Republic of Korea
b Department of Oral Biology, College of Dentistry, Yonsei University, Seoul 120-752, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel hybrids of non acetal and acetal-type derivatives at C-12 of artemisinin and glycolipids were syn-
thesized via efficient coupling reactions. Some of these hybrids showed potent in vivo antiangiogenic
activity on the chorioallantoic membrane (CAM) that was higher than or comparable to those of fumagil-
lin and thalidomide at a concentration of 2.5 nmol.
Received 25 June 2010
Revised 1 August 2010
Accepted 3 August 2010
Available online 8 August 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Anticancer activity
Artemisinin
Glycolipid
Non-acetal type
Antiangiogenesis
Angiogenesis is a physical process in which new blood vessels
are formed from pre-existing vessels. The blockade of vascular
endothelial growth factor results in regression of the disease and
prolongation of survival when used for anticancer therapy.1 Dis-
covery of new antiangiogenic agents based on small molecules is
an attractive approach for the treatment of cancer.
amide side chains were the most potent anticancer compounds
that we surveyed, with effective concentrations in the nanomolar
range, which is comparable to that of doxorubicin.8 Although de-
tails of the mechanism of apoptosis remain unclear, lipophilicity
may play an important role in glycolipid anticancer activity.8
Although various antiangiogenic agents have been developed,
adverse side effects and limitations associated with antitumor
therapies have recently become apparent. Cancer is a complex dis-
ease. In order to improve the activity of anticancer agents, treat-
ment using hybrid drugs, an approach that incorporates two
drugs in a single molecule, has been developed.9 The use of hybrid
drugs can impact multiple targets simultaneously.
In the present article, we report the synthesis and the antiangio-
genic activity of artemisinin–glycolipid hybrid agents.
Carboxymethyldeoxoartemisinin (1a) and various derivatives
as outlined in Figure 2 were prepared according to previously-de-
scribed procedures.10 Glycolipid (2a) and its derivatives (Fig. 2)
were synthesized according to the previously-reported
Artemisinin (1), a sesquiterpene endoperoxide isolated from
Artemisia annua L.,2 (Fig. 1) and its derivatives have been reported
as potential antitumor3 and virtually nontoxic3a agents. Artemisi-
nin has also been reported to have antiangiogenic activity.4 In a
previous report, we described the potent antiangiogenic effects of
artemisinin derivatives.5 Non acetal-type derivates at C-12 of arte-
misinin and their dimers including a fullerene conjugate were syn-
thesized and some of them showed potent in vivo antiangiogenic
activity on the chorioallantoic membrane that was higher than or
comparable to those of fumagillin and thalidomide.5 Furthermore,
novel amide derivatives of a C-12 non acetal deoxoartemisinin tri-
mer were synthesized and showed potent in vivo antiangiogenic
activity according to the results of mouse matrigel plug assays.3d
Recently, some studies have reported the antiangiogenic activity
of glycolipids.6 Daumone (2), originally isolated from Caenorhabdi-
tis elegans, was identified by our laboratory (Fig. 1) and its total
synthesis was presented.7 In a continuation of the investigation,
we studied the anticancer activity of daumone against human cell
lines.8 Daumone and tri-deoxyrhamnose derivatives containing
H
O
OH
O
O
O
HO
O
O
H
O
OH
O
1
2
* Corresponding author. Tel.: +82 2 2123 2648; fax: +82 2 364 7050.
E-mail address: mjung@yonsei.ac.kr (M. Jung).
Figure 1. Structures of artemisinin (1) and daumone (2).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.08.013

J. Ricci et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6858–6860
6859
O
O
O
O
O
O
O
O
HO
O
O
O
O
HO
O
O
O
O
O
H
O
H
HO
BzO
O
O
OH
3b
H
H
OH
H
O
O
O
O
OH
OBz
O
H
O
O
O
3a
3c
3d
O
O
O
O
O
H
O
H
H
O
H
O
O
O
O
O
O
O
BzO
O
H
BzO
O
OH
O
O
O
O
H
O
O
O
O
OBz
O
O
OBz
O
O
H
H
O
O
O
O
O
O
3e
3f
3g
3h
O
O
OH
H
H
H
H
H
OBz
OH
O
O
O
O
O
O
O
O
O
H
O
O
H
O
O
H
O
OH
OBz
O
O
OH
O
O
O
O
O
O
O
3i
3j
3k
O
OH
Figure 2. Structures of artemisinin–glycolipid hybrids.
procedures.7,8 Then, a short series of artemisinin–glycolipid hy-
brids (Fig. 2) covalently linked were prepared by efficient coupling
reactions (EDC/DMAP, rt, DMF, 12 h), as shown in Scheme 1, and
their structures were confirmed by spectral analysis (see Supple-
mentary data). The hybrid regioisomers (3g, 3h, 3j) were formed
with glycolipids containing protected terminal olefin or primary
alcohol instead of free carboxylic acid.
The in vivo antiangiogenic activity of the various hybrid com-
pounds was evaluated using the CAM vessel development assay
as previously described.5,11
At day 5 of incubation, test sample loaded on a quarter size
Thermanox coverslip (Nunc, Roskilde, Denmark) was applied to
the CAM of each individual embryo at
a concentration of
2.5 nmol/egg. After 2 incubation days, a 20% fat emulsion was in-
jected into the CAM for observation of the inhibition avascular
zone. If an avascular zone of about 3–6 mm diameter, as indicated
with an arrow in Figure 3, was observed, then it was considered to
represent effective inhibition on neovascularization. The results of
these experiments are listed in Table 1. The standard drugs used
for comparison were (À)-fumagillin and (À)-thalidomide.
As shown in Table 1, it is interesting to note that most hybrids
exhibited twice the antiangiogenic activity at a concentration of
2.5 nmol/egg than that of fumagillin or thalidomide as the standard
drug.
Briefly, fertilized eggs (Pulmuone Co., Kyungki-do, Korea) were
incubated at 37 °C with 80–90% relative humidity. At day 3, a win-
dow was opened after the removal of 2 ml albumin in the eggs.
Artemisinin (1) showed a weak inhibitory effect at the given
concentration, while glycolipid (2) remained stronger than stan-
dard drugs. Generally hybrids showed higher antiangiogenic activ-
ity than artemisinin (1) and comparable to that of glycolipid (2).
H
OH
O
O
O
O
HO
+
O
H
O
OH
COOH
2a
1a
H
OH
O
O
O
EDC/DMAP,
DMF, r.t. 12h.
H
O
O
O
OH
O
O
Figure 3. Antiangiogenic effect of artemisinin–glycolipid hybrids on the chick CAM.
Membranes were treated with (a) control, (b) artemisinin–glycolipid hybrids in a
concentration of 2.5 nmol/egg.
3i
Scheme 1. Coupling reaction of artemisinin and glycolipid.

6860
J. Ricci et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6858–6860
Table 1
potency as fumagillin and thalidomide, known as antiangiogenic
agents. In particular, hybrid 3i showed complete inhibition at
2.5 nmol/egg with no toxicity. Compounds 3a and 3h showed sim-
ilar activity to that of fumagillin. Evidence that acetal-type analogs
at C-12 of artemisinin are more neurotoxic in animal studies than
non acetal-type analogs is also emerging,12 and may thus lead to
the future abandonment of the currently clinically used acetal-type
potential anticancer drug candidates. Therefore, nonacetal 12b
(C–C)-type derivatives of artemisinin–glycolipid hybrids deserve
further evaluation as possible anticancer drug candidates because
of their high acid stability,3b low toxicity and high in vivo antian-
giogenesis. The synthesis and antiangiogenic activity of hybrids
between glycolipids and other anticancer drugs are under investi-
gation and will be reported in due course.
Inhibitory effect of artemisinin–glycolipid hybrids on CAM antiangiogenesis in a
concentration of 2.5 nmol/egg
Compounds
Positive eggs/eggs
tested
Inhibition
effecta
Inhibition
(%)
1
2
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3/10
7/10
30
70
50
60
60
10
60
80
70
50
100
50
50
40
40
0
++
+
+
5/10 (1)b
6/10 (2)
6/10 (2)
1/10 (2)
6/10 (2)
8/10
+
+
+++
++
Low toxic
+++
+
7/10 (2)
5/10 (5)
10/10
5/10
3k
5/10 (2)
4/10 (1)
4/10 (4)
0/10
+
Acknowledgments
(À)-Fumagillin
(À)-Thalidomide
Controlc
Low toxic
This study was supported by a grant of the Korea Healthcare
technology R&D Project (A084166), the Ministry of Health & Wel-
fare, Republic of Korea. J.R. and J.P. received fellowships from the
BK 21program of the Ministry of Education and Human Resources
Development, the Republic of Korea.
a
Inhibition effect; antiangiogenic effect of plus (+) is similar to thalidomide or
fumagillin, double plus (++) is stronger and triple plus (+++) is the strongest.
b
Number in parentheses describes eggs in which the embryo died.
Control; solvent only (chloroform) to embryo.
c
Supplementary data
However, C-12 acetal-type artemisinin–glycolipid hybrids (3a
and 3d) exhibited weaker activity than non-acetal type hybrids.
A benzoyl protected hybrid (3d) with acetal function at C-12 of
artemisinin displayed the weakest inhibitory activity, while a hy-
brid (3i) with free hydroxyl groups of glycolipid with non-acetal
function of artemisinin showed complete (100%) inhibition of
angiogenesis.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2010.08.013.
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Among the 11 synthetic compounds tested, hybrids 3f, 3g and
3i showed the most potent antiangiogenic activity, twice as much