Discovery of Novel 4-Arylisochromenes as Anticancer Agents Inhibiting Tubulin Polymerization

Article abstract of DOI:10.1021/acsmedchemlett.8b00217

XJP-L (8), a derivative of the natural product (±)-7,8-dihydroxy-3-methylisochroman-4-one isolated from the peel of Musa sapien tum L., was found to exhibit weak inhibitory activity of tubulin polymerization (IC₅₀ = 10.6 μM) in our previous studies. Thus, a series of 4-arylisochromene derivatives were prepared by incorporating the trimethoxyphenyl moiety into 8, among which compound (±)-19b was identified as the most potent compound with IC₅₀ values ranging from 10 to 25 nM against a panel of cancer cell lines. Further mechanism studies demonstrated that (±)-19b disrupted the intracellular microtubule network, caused G2/M phase arrest, induced cell apoptosis, and depolarized mitochondria of K562 cells. Moreover, (±)-19b exhibited potent in vitro antivascular and in vivo antitumor activities. Notably, the R-configured enantiomer of (±)-19b, which was prepared by chiral separation, was slightly more potent than (±)-19b and was much more potent than the S-configured enantiomer in both antiproliferative and antitubulin assays. Our findings suggest that (±)-19b deserves further research as a potential antitubulin agent for the treatment of cancers.

Full text of DOI:10.1021/acsmedchemlett.8b00217

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Letter
Discovery of Novel 4-Arylisochromenes as
Anticancer Agents Inhibiting Tubulin Polymerization
Wenlong Li, Wen Shuai, Feijie Xu, Honghao Sun, Shengtao
Xu, Hong Yao, Jie Liu, Hequan Yao, Zheying Zhu, and Jinyi Xu
ACS Med. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acsmedchemlett.8b00217 • Publication Date (Web): 25 Sep 2018
Downloaded from http://pubs.acs.org on September 26, 2018
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Discovery of Novel 4-Arylisochromenes as Anticancer Agents Inhibiting
Tubulin Polymerization
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Wenlong Lia, Wen Shuaia, Feijie Xua, Honghao Suna, Shengtao Xua, *, Hong Yaoa, Jie Liub, *, Hequan Yaoa, Zheying
Zhuc, Jinyi Xua, *
aDepartment of Medicinal Chemistry and State Key Laboratory of Natural Medicines, China Pharmaceutical Universiꢀ
ty, 24 Tong Jia Xiang, Nanjing 210009, P. R. China
bDepartment of Organic Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, P. R. China
cDivision of Molecular Therapeutics & Formulation, School of Pharmacy, The University of Nottingham, University
Park Campus, Nottingham NG7 2RD, UK
KEYWORDS: Combretastatin A-4, (±)-7,8-Dihydroxy-3-methylisochroman-4-one, Tubulin inhibitors, Enantioseparation, Anti-
tumor, Vascular disrupting
ABSTRACT: XJPꢀL (8), a derivative of the natural product (±)ꢀ7,8ꢀdihydroxyꢀ3ꢀmethylisochromanꢀ4ꢀone isolated from the peel of
Musa sapien tum L., was found to exhibit weak inhibitory activity of tubulin polymerization (IC50 = 10.6 µM) in our previous
studies. Thus, a series of 4ꢀarylisochromene derivatives were prepared by incorporating the trimethoxyphenyl moiety into 8.
Among which, compound (±)-19b was identified as the most potent compound with IC50 values ranging from 10 to 25 nM against a
panel of cancer cell lines. Further mechanism studies demonstrated that (±)-19b disrupted the intracellular microtubule network,
caused G2/M phase arrest, induced cell apoptosis and depolarized mitochondria of K562 cells. Moreover, (±)-19b exhibited potent
in vitro antiꢀvascular and in vivo antiꢀtumor activities. Notably, the Rꢀconfigured enantiomer of (±)-19b, which was prepared by
chiral separation, was slightly more potent than (±)-19b and was much more potent than the Sꢀconfigured enantiomer in both antiꢀ
proliferative and antiꢀtubulin assays. Our findings suggest that (±)-19b deserves further research as a potential antiꢀtubulin agent for
the treatment of cancers.
Combretastatin Aꢀ4 (1, CAꢀ4) (Figure 1), a natural cisꢀ stilꢀ
bene derivative isolated from the bark of the African willow
tree Combretum caffrum,1 was found to be a powerful inhibiꢀ
tor of tubulin polymerization targeting the colchicine binding
site.2 CAꢀ4 has strong cytotoxicity against a variety of tumor
cells with a broad therapeutic window. Besides, CAꢀ4 was
reported to show vascular disrupting properties at a tolerated
dose.3 The potent antimitotic and vascular disrupting profiles
of CAꢀ4 made it a promising therapy for the treatment of canꢀ
cers.4ꢀ7 However, CAꢀ4P (2, Fosbretabulin), the phosphate
prodrug of CAꢀ4, had been discontinued in clinical trials8 due
to the lack of a meaningful improvement in progressionꢀfree
survival (PFS) and unfavorable partial response data.9 In the
presence of light, heat or acid media, but also after in vivo
administration, the Zꢀisomer of CAꢀ4 easily isomerizes to the
Eꢀisomer that is significantly less potent at inhibiting tubulin
polymerization and cancer cell growth.10 Strategies to surꢀ
mount this drawback have been taken by modification on the
bridge structure of CAꢀ4, which lead to the discovery of variꢀ
ous moieties replacing the cisꢀdouble bond.11ꢀ13 Fusing cisꢀ
olefin into the ring B represents an important tactic to lock the
cis double bond, compounds 3-6 with highly potent cytotoxiciꢀ
ty were thus discovered (Figure 1).14ꢀ21
It is known to all that natural products with structurally diꢀ
verse frameworks have always been and continue to be an
important source for new drug discovery.22 (±)ꢀ7,8ꢀDihydroxyꢀ
3ꢀmethylisochromanꢀ4ꢀone [7, (±)ꢀXJP] was a structurally
unique 4ꢀisochromanone compound which was isolated from
the peel of Musa sapientum L. and total synthesized by our
group,23,24 and it exhibited a wide range of favorable pharmaꢀ
cological properties.25, 26 In our previous research for discoverꢀ
ing new antiꢀtubulin agents with novel skeletons, a series of
XJP derivatives was screened for their inhibitory activity of
tubulin polymerization. Interestingly, XJPꢀL (8) was found to
exhibit weak microtubule polymerization inhibitory activity
(IC50 = 10.6 µM).
Considering the vital roles of 3,4,5ꢀtrimethoxyphenyl on the
activity of inhibitors of tubulin polymerization targeting the
colchicine binding site,27ꢀ29 8 was further hybridized with
3,4,5ꢀtrimethoxyphenyl moiety for improving both its antiꢀ
proliferative and inhibitory activities of tubulin polymerization
using the cisꢀdouble bond locking strategy. Thus, a series of
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novel 4ꢀarylisochromenes were designed and synthesized
(Figure 1). Herein, we wish to report their synthesis and antiꢀ
tumor activities as antiꢀtubulin agents.
slightly improvement of activity [17a vs 19a, 17c vs (±)ꢀ19c
and 18b vs (±)ꢀ19b]. Especially, compound (±)ꢀ19b displayed
the most potent antiꢀproliferative activity (IC50 = 15 nM),
which exhibited nearly 1000ꢀfold improvement of activity
towards 8 (IC50 = 23.7 µM) (See Supporting Information Table
S1).
The synthetic route for the preparation of 4ꢀ
arylisochromenes is outlined in Scheme 1. Various substituted
XJP scaffolds 12a-e were synthesized according to the method
utilizing a Parhamꢀtype cyclization with the tertꢀbutyllithium
reagent reported by our group.30 Sulphurꢀcontaining XJP scafꢀ
folds 12f-g were further synthesized via a FriedelꢀCrafts cyclic
reaction.
Scheme 1. Synthetic route to 4-arylisochromenesa
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O
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R1
Br
O
R1
Br
R1
O
Br
a
b
+
OH
N
O
O
H3CO
H3CO
N
H3CO
OCH3
R2
R2
OCH3
R2
10
9a-e
9a R1, R2 = H;
11a-e
11a R1, R2 = H;
11b R1 = H, R2 = OBn;
11c R1 = H, R2 = OCH3;
11d R1 = OBn, R2 = H;
11e R1 = H, R2 = Br;
12a-e
12a R1, R2 = H;
12b R1 = H, R2 = OBn;
12c R1 = H, R2 = OCH3;
12d R1 = OBn, R2 = H;
9b R1 = H, R2 = OBn;
9c R1 = H, R2 = OCH3;
9d R1 = OBn, R2 = H;
9e R1 = H, R2 = Br;
12e R1 = H, R2 = Br;
O
O
d
c
Br
H3CO
S
S
H3CO
OH
H3CO
R
R
R 12f-g
13f-g
14f-g
13f R = H; 13g R = OCH3
14f R = H; 14g R = OCH3
12f R = H;
12g R = OCH3
O
NNHTs
R1
R1
e
f
X
X
H3CO
H3CO
R2
R2
12a-g
15a-g
OCH3
H3CO
OCH3
OCH3
H3CO
OCH3
g
h
R1
18a R1 =OH, R2 = H;
18b R1 = H, R2 = OH
O
R1
H3CO
R2
X
18a-b
OCH3
H3CO
R2
H3CO
OCH3
17a-g
17a X = O, R1, R2 = H;
17b X = O, R1 = H, R2 = OBn;
17c X = O, R1 = H, R2 = OCH3;
17d X = O, R1 = OBn, R2 = H;
17e X = O, R1 = H, R2 = Br;
17f X = S, R1 = H, R2 = H;
17g X = S, R1 = H, R2 = OCH3
Figure 1. The strategy of fusing the bridge into ring B of CAꢀ4 to surꢀ
mount its instability and the design of XJP derived tubulin inhibitor.
19a R1, R2 = H;
R1
19b R1 = H, R2 = OH;
19c R1 = H, R2 = OCH3;
19d R1 = OH, R2 = H
O
H3CO
R2
Then, 12a-g were transformed into their corresponding Nꢀ
tosylhydrazones 15a-g in refluxing EtOH with good to excelꢀ
lent yields, followed by the coupling of 15a-g with 5ꢀbromoꢀ
19a-d
aReagents and conditions: (a) NaH, DMF, 2h, 55ꢀ70%; (b) tꢀBuLi, THF,
ꢀ78 oC, 15min, 72ꢀ90%; (c) i) ethyl thioglycolate, K2CO3, CH3CN, 2h, 75ꢀ
1,2,3ꢀtrimethoxybenzene (16) via
a Pdꢀcatalyzed crossꢀ
o
88%; ii) 10% NaOH aqueous, CH3OH, 80 C, 85ꢀ90%; (d) i) oxalyl chloꢀ
ride, DMF(cat.), DCM; ii) SnCl4, chlorobenzene, 55ꢀ65% over two steps;
coupling to afford 17a-g in moderate to good yields. Utilizing
the different reducing capacity of PdꢀC/H2 in THF and CH3OH,
benzyl group of 17b and 17d were selectively deprotected
using THF as the solvent to give compound 18a and 18b, reꢀ
spectively, while double bonds were reduced to afford (±)ꢀ
19a-d with CH3OH as the solvent.
o
(e) pꢀToluenesulfonhydrazide, EtOH, 90 C, 75ꢀ90%; (f) 5ꢀbromoꢀ1,2,3ꢀ
trimethoxybenzene (16), PdCl2(CH3CN)2, Xphos, tꢀBuOLi, 90 oC, 45ꢀ70%;
(g) Pd/C, H2, THF, 65ꢀ92%; (h) Pd/C, H2, CH3OH, 72ꢀ95%.
Subsequently, compounds 18b and (±)ꢀ19b were further
evaluated for their antiꢀproliferative activity against another
five cancer cell lines including KB, HCTꢀ8, MDAꢀMBꢀ231,
K562 and H22 cells. As shown in Table 1, both 18b and (±)ꢀ
19b showed potent antiꢀproliferative activities. Especially, (±)ꢀ
19b exhibited the most active against K562 cell lines with the
IC50 value of 10 nM, which is more potent than the positive
control CAꢀ4 (IC50 = 15 nM); Human normal hepatocytes LO2
cells were also used to determine their selectivity towards
cancer cells and normal cells, which showed that 18b and (±)ꢀ
19b selectively inhibited the growth of cancer cells.
All target compounds 17a, 17c, 17e-g, 18a-b and (±)ꢀ19a-d
were initiatively evaluated for their antiꢀproliferative activities
against human hepatocellular carcinoma cells (HepG2) by the
MTT assays. Most of the synthesized compounds displayed
potent activity against HepG2 cells and the preliminary strucꢀ
ture activity relationships (SARs) were obtained. The position
of hydroxyl group on the isochroman moiety was crucial for
antiꢀproliferative activity. Compound 18b and (±)ꢀ19b, which
contain hydroxyl at the Cꢀ5 position (R2), exhibited the most
potent activity with IC50 values of 26 and 15 nM, respectively.
Moving the OH group from Cꢀ5 position to Cꢀ3 position led to
the loss of antiꢀproliferative activity (18a and 19d, IC50 > 10
µM). When R2 was substituted with other groups such as
OCH3 [17c and (±)ꢀ19c], Br (17e) or no substitution [17a and
(±)ꢀ19a], the activity significantly decreased when compared
with 18b and (±)ꢀ19b. Besides, the activity was maintained
when sulfur (X = S) was introduced into the isochroman scafꢀ
fold (17f and 17g). The reduction of double bonds led to a
The further in vitro assay for the inhibition of tubulin
polymerization demonstrated that compounds 18b and (±)ꢀ19b
were potent inhibitors of tubulin polymerization. As shown in
Table 1, compound (±)ꢀ19b (IC50 = 3.1 µM) was more potent
than 18b (IC50 = 4.2 µM) and was slightly less potent than CAꢀ
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Table 1. Cytotoxicity against five cancer cell lines, Human normal hepatocytes LO2 cells and ITP of compounds 18b, (±)-
19b, (R)-(+)-19b and (S)-(-)-19ba
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5
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8
9
IC50 values (µM)
Compd.
MDAꢀMB
ꢀ231
0.028±0.004
KB
HCTꢀ8
K562
H22
LO2
ITPb
18b
(±)ꢀ19b
(R)-(+)-19b
(S)-(-)-19b
CA-4
0.016±0.002
0.025±0.002
0.012±0.002
0.87±0.08
0.025±0.004
0.030±0.002
0.012±0.001
0.94±0.12
0.019±0.002
0.010±0.001
0.008±0.001
0.46±0.06
0.010±0.001
0.011±0.001
0.008±0.002
0.80±0.12
0.138±0.012
0.095±0.010
0.058±0.005
0.90±0.08
4.2±0.3
3.1±0.2
2.5±0.1
4.3±0.1
2.5±0.2
10.6±0.2
0.022±0.002
0.011±0.002
0.90±0.09
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0.012±0.001
25.1±0.9
0.015±0.002
35.2±1.3
0.015±0.002
30.2±2.0
0.015±0.002
20.5±1.2
0.008±0.001
18.2±2.1
0.095±0.002
22.2±1.2
8
aMTT methods; cells were incubated with indicated compounds for 72 h (means ± SD, n = 3).
b Inhibition of tubulin polymerization activity.
ꢀ4 (IC50 = 2.5 µM). Furthermore, (±)ꢀ19b exhibited nearly 3ꢀ
fold improvement of inhibitory activity of tubulin polymerizaꢀ
tion compared with 8 (IC50 = 10.6 µM), which suggested that
the trimethoxyphenyl moiety has significant roles in binding
with tubulin. In addition, in assay of the colchicine competiꢀ
tive experiment, the binding potency of (±)- 19b to the colchiꢀ
cine binding site was comparable to that of CAꢀ4 with the
inhibition rates of 76.4% and 89.6% at 1 µM and 5 µM, reꢀ
spectively (see Supporting Information Table S2), indicating
that (±)-19b binds to the colchicine binding site.
with (±)-19b at concentrations of 0, 5, 10 and 20 nM for 48 h,
the number of K562 cells with collapsed MMP increased to
0.6%, 12.7%, 26.7% and 55.1%, respectively (see Supporting
Information Figure S3), suggesting that (±)-19b caused mitoꢀ
chondrial depolarization of K562 cells in the process of apopꢀ
tosis.
Most microtubule binding agents have antiangiogenic or
vascularꢀdisrupting activities or both, which are antiꢀvascular
effects.32 Angiogenesis inhibiting agents (AIAs) interfere with
new vessel formation, require chronic administration, and are
likely to be of benefit in earlyꢀstage or asymptomatic metastatꢀ
ic disease. While vascularꢀdisrupting agents (VDAs) target the
Moreover, immunofluorescent assays were performed to inꢀ
vestigate the effect of (±)-19b on microtubule networks. As
shown in Figure 2, K562 cells exhibited normal filamentous
microtubules arrays without drug treatment. However, after
exposure to (±)-19b at three different concentrations (5 nM,
10 nM, 20 nM) for 24 h, the microtubule networks in cytosol
were disrupted, indicating that (±)-19b induced a doseꢀ
dependent collapse of the microtubule networks.
Since most microtubule polymerization inhibitors disrupt
cell mitosis and exert cell cycle arrest effects,31 the effect of
(±)-19b on cell cycle progression using propidiumiodide (PI)
staining in K562 cells was examined. When treated with (±)-
19b at 5 nM, 10 nM, 20 nM for 48 h, the percentages of cells
arrested at the G2/M phase were 17.5%, 19.5%, and 22.4%,
respectively, indicating that (±)-19b can disrupt the dynamic
balance of the tubulinꢀmicrotubule system and further induced
the cell cycle arrest at the G2/M phase (see Supporting Inforꢀ
mation Figure S1). Next, an Annexin VꢀAPC/7ꢀAAD binding
assay was carried out to assess whether (±)-19b would induce
cell apoptosis. The percentage of apoptotic cells after the 48 h
treatment was only 5.7% in the control group. The total numꢀ
bers of early (AnnexinꢀV+/PI−) and late (AnnexinꢀV+/PI+)
apoptotic cells increased to 13.7%, 29.0% and 54.1% after
treatment with (±)-19b at 5, 10, 20 nM for 48 h, respectively
(see Supporting Information Figure S2). These results conꢀ
firmed that (±)-19b effectively induced cell apoptosis in K562
cells in a doseꢀdependent manner.
Figure 2. Effects of (±)-19b on the cellular microtubule network visualꢀ
ized by immunofluorescence.
In order to determine whether (±)-19bꢀinduced apoptosis
was involved in a disruption of mitochondrial membrane inꢀ
tegrity, the fluorescent probe JCꢀ1 was employed to measure
the mitochondrial membrane potential (MMP). When treated
established tumor blood vessels, which are often given acutely
and have particular efficacy against advanced disease.33 Conꢀ
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sidering that invasion and tube formation are highly relevant
ꢀment with PTX at a dose of 8 mg/kg per 2 days led to a sigꢀ
nificant decrease of body weight (Figure 3B). Thus, (±)-19b is
worthy of further investigation for the treatment of cancers.
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properties in the process of tumor vasculature, the HUVEC
culture assay was used to assess the ability of (±)-19b to inhibꢀ
it HUVEC migration. As a result, the untreated cells migrated
to fill the area that was initially scraped after 24 h. In contrast,
(±)-19b significantly inhibited the HUVEC migration in a
doseꢀdependent manner (see Supporting Information Figure
S4A). Then we further evaluated the antiꢀvascular ability of
(±)-19b in a tube formation assay. After being seeded on matꢀ
rigel, HUVECs form the capillaryꢀlike tubules with multicenꢀ
tric junctions. After exposure to (±)-19b at doses of 0, 5, 10,
and 20 nM for 6 h, the capillaryꢀlike tubes were interrupted in
different levels (Figure S4B). These results showed that (±)-
19b effectively inhibited the tube formation of HUVECs.
Finally, in order to investigated the effects of Cꢀ4 chirality
on activity, the racemic mixture of (±)-19b were enantiosepaꢀ
rated on a chiral column (see supporting information Figure
S5) to afford (+)-19b and (-)-19b. Circular dichroism (CD)
was performed to determine the absolute configuration, and
the results indicated that the absolute configuration of (+)-19b
is Rꢀconfigured and the absolute configuration of (-)-19b is Sꢀ
configured (see supporting information Figure S6).
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Furthermore, (R)-(+)-19b and (S)-(-)-19b were evaluated
for their antiꢀproliferative and inhibitory activities of tubulin
polymerization. As shown in Table 1, the Rꢀconfigured 19b
still exhibited very potent activity against five cancer cell lines,
which were slightly potent than (±)-19b, whereas (S)-(-)-19b
displayed a significant decrease of activity. As regard to the
antiꢀtubulin assays, (R)-(+)-19b (IC50 = 2.5 µM) was about 2ꢀꢀ
fold more potent than (S)-(-)-19b (IC50 = 4.3 µM). Moreover,
in assay of the colchicine competitive experiment, the binding
ability of (R)-(+)-19b to the colchicine binding site was more
potent than (±)-19b, and was comparable to that of CAꢀ4 with
the inhibition rates of 79.4% and 92.6% at 1 µM and 5 µM
(Table S2).
Furthermore, we tested the in vivo antiꢀtumor activity of
(±)-19b based on the in vitro antiꢀproliferative activity and
mechanistic studies. Mouse liver cancer xenograft model was
established by subcutaneous inoculation of H22 cells into the
right flank of mice. The tumor size and body weights of the
mice were monitored and recorded every 2 days. Paclitaxel
(PTX) was dosed as 8 mg/kg per 2 days (i.v.) due to its severe
toxicity. To compare the antiꢀtumor efficacy of (±)-19b and
CAꢀ4, (±)-19b and CAꢀ4 were dosed at 15 and 30 mg/kg per
day (i.v.). None of the mice died in all groups after 21 days
treatments. As shown in Figure 3A, both (±)-19b at the dose
of 30 mg/kg per day and PTX at the dose of 8 mg/kg per 2
days significantly decreased the tumor volume. The reduction
in tumor weight of PTX group reached 72.1% at 21 days after
initiation of treatment as compared to vehicle, while (±)-19b
reduced tumor weight by 46.5% and 62.3% at doses of 15 and
30 mg/kg per day (i.v.), respectively, which are more potent
than CAꢀ4 treatment groups (inhibitory rates of 44.8% and
55.3% at doses of 15 and 30 mg/kg per day, respectively)
(Figure 3C). Importantly, (±)-19b did not significantly affectꢀ
ed body weight even at the dose up to 30 mg/kg, while treatꢀ
To explain the significant difference in activity for two enꢀ
antiomers of (±)-19b, molecular modeling studies were perꢀ
formed by using the DOCK program in Discovery Studio 3.0
software with the tubulin crystal structure (PDB: 5lyj). As a
result, (R)-(+)-19b adopted a very similar positioning with
that of CAꢀ4. The phenolic hydroxyl and 4ꢀmethoyl of (R)-
(+)-19b and CAꢀ4 formed hydrogen bonds with Thr179 and
Cys241 residues, respectively. The oxygen atom in isoꢀ
chromene ring interacted with residue Asn258 by a weak hyꢀ
drogen bond (see Supporting Information Figure S7A). Howꢀ
ever, the binding pose of (S)-(-)-19b was flipped over 180°
compared to that of CAꢀ4, which may explain why both the
antiꢀtubulin and antiꢀ proliferative activity of (S)-(-)-19b deꢀ
creased dramatically (Figure S7B).
In summary, a series of novel 4ꢀarylisochromenes have
been synthesized based on the structure of XJPꢀL (8). Antiꢀ
proliferative screening of these new synthesized compounds
validated the representative compound (±)-19b as a high cytoꢀ
toxic compound with IC50 ranging from 10 to 25 nM against a
panel of cancer cell lines, which displayed a 1000ꢀfold inꢀ
crease in activity compared with the lead 8. It was found that
(±)-19b also displayed potent inhibitory activity in tubulin
polymerization assay (IC50 = 3.1 µM). Further mechanism
studies demonstrated that (±)-19b caused cell cycle arrest in
the G2/M phase, induced cell apoptosis and depolarized mitoꢀ
chondria of K562 cells. And the immunofluorescent assay
indicated that (±)-19b can effectively disrupt microtubule
networks in a doseꢀdependent manner. The wound healing and
tube formation assays also identified (±)-19b as a novel inhibiꢀ
tor of tubulin polymerization with potent vascular disrupting
activity. Finally, the in vivo antiꢀtumor activity of (±)-19b was
validated in H22 liver cancer xenograft mouse model, which is
more potent than CAꢀ4. Besides, (R)-(+)-19b and (S)-(-)-19b
were obtained by chiral separation of (±)-19b and were evaluꢀ
ated for their antiꢀproliferative and antiꢀtubulin activities, reꢀ
Figure 3. A) Tumor growth curves after injection with different
formulations in H22 tumor bearing mice. B) Body weight
changes of mice during treatment. C) (±)-19b treatment resultꢀ
ed in significantly lower tumor weight compared with controls.
spectively. (R)-(+)-19b was slightly more potent than (±)-4
19b whereas (S)-(-)-19b displayed a significantly decrease
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ACS Medicinal Chemistry Letters
of activity, which was further elucidated by molecular modelꢀ
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US20040043969ꢀA1, 2004.
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ling studies. Altogether, (±)-19b may represent a novel class
of antiꢀtubulin agent with potent antiꢀvascular and antiꢀtumor
activities and deserves further investigation.
ASSOCIATED CONTENT
Supporting Information
Synthetic methods and characterization of target compounds,
procedures for pharmacological activities. This material is
available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Authors
*Eꢀmail addresses: jinyixu@china.com (J. Xu); cpuꢀ
jill@163.com (J. Liu); cpuxst@163.com (S. Xu).
ORCID
Jinyi Xu: 0000ꢀ0002ꢀ1961ꢀ0402
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
ACKNOLEDGMENTS
This study was supported from the National Natural Science
Foundation of China (No. 81673306, 81703348), The Open
Project of State Key Laboratory of Natural Medicines, China
Pharmaceutical University (No. SKLNMKF 201710), and
China Postdoctoral Science Foundation (No. 2017100424) for
financial support. The authors thank Dr. Dahong Li (Key
Laboratory of StructureꢀBased Drug Design and Discovery of
Ministry of Education and School of Traditional Chinese
Materia Medica, Shenyang Pharmaceutical University,
Shenyang, China) for the CD calculations.
Notes
The authors declare no competing financial interest.
ABBREVIATIONS
DMF,
N,
Nꢀdimethylformamide;
Xphos,
2ꢀ
Dicyclohexylphosphinoꢀ2',4',6'ꢀtriisopropylbiphenyl; DCM,
dichloromethane; THF, tetrahydrofuran; HUVECs, human
umbilical vein endothelial cell.
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