Synthesis and antiproliferative activities of aminoalkylated polymethoxyflavonoid derivatives

Article abstract of DOI:10.1080/14786419.2017.1413562

A series of novel aminoalkylated polymethoxyflavonoid derivatives 3–11 was synthesised from 5-hydroxy-3,7,3′,4′-tetramethoxyflavonoid (1) through extending alkoxy chain at the 5-position, and introducing amine hydrogen bond receptor at the end of the side chain. Their antiproliferative activities were evaluated in vitro on a panel of three human cancer cell lines (Hela, HCC1954 and SK-OV-3). The results showed that all the target compounds exhibited antiproliferative activities against investigated cancer cells with IC₅₀ values of 9.51–53.33?μM. Compounds 5, 7, 8, 11 on Hela cells and compounds 4–9, 11 on HCC1954 exhibited more potency as compared to positive control cis-Platin.

Full text of DOI:10.1080/14786419.2017.1413562

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
Synthesis and antiproliferative activities of
aminoalkylated polymethoxyflavonoid derivatives
Xue-Li Li, Yan-Hua Zhang, Cai-Fang Wang & Qiu-An Wang
To cite this article: Xue-Li Li, Yan-Hua Zhang, Cai-Fang Wang & Qiu-An Wang (2017): Synthesis
and antiproliferative activities of aminoalkylated polymethoxyflavonoid derivatives, Natural Product
Research, DOI: 10.1080/14786419.2017.1413562
To link to this article: https://doi.org/10.1080/14786419.2017.1413562
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Date: 27 December 2017, At: 04:43

Natural Product research, 2017
ꢁꢁpꢂ://ꢃꢄi.ꢄꢅg/10.1080/14786419.2017.1413562
ꢀ
Synthesis and antiproliferative activities of aminoalkylated
polymethoxyflavonoid derivatives
Xue-Li Li, Yan-Hua Zhang, Cai-Fang Wang and Qiu-An Wang
cꢄꢆꢆꢇgꢇ ꢄf cꢀꢇmiꢂꢁꢅy ꢈnꢃ cꢀꢇmiꢉꢈꢆ enginꢇꢇꢅing, hꢊnꢈn univꢇꢅꢂiꢁy, cꢀꢈngꢂꢀꢈ, cꢀinꢈ
ABSTRACT
ARTICLE HISTORY
A series of novel aminoalkylated polymethoxyflavonoid derivatives
rꢇꢉꢇivꢇꢃ 30 sꢇpꢁꢇmbꢇꢅ 2017
aꢉꢉꢇpꢁꢇꢃ 2 dꢇꢉꢇmbꢇꢅ 2017
3
–11 was synthesised from 5-hydroxy-3,7,3′,4′-tetramethoxyflavonoid
(
1) through extending alkoxy chain at the 5-position, and introducing
KEYWORDS
amine hydrogen bond receptor at the end of the side chain. Their
antiproliferative activities were evaluated in vitro on a panel of three
human cancer cell lines (Hela, HCC1954 and SK-OV-3). The results
showed that all the target compounds exhibited antiproliferative
activities against investigated cancer cells with IC50 values of 9.51–
Pꢄꢆymꢇꢁꢀꢄxyflꢈvꢄnꢄiꢃꢂ;
ꢈminꢄꢈꢆkyꢆꢈꢁꢇꢃ ꢃꢇꢅivꢈꢁivꢇꢂ;
ꢂynꢁꢀꢇꢂiꢂ; ꢈnꢁipꢅꢄꢆifꢇꢅꢈꢁivꢇ
ꢈꢉꢁiviꢁy
5
1
3.33 μM. Compounds 5, 7, 8, 11 on Hela cells and compounds 4–9,
1 on HCC1954 exhibited more potency as compared to positive
control cis-Platin.
1
. Introduction
Flavonoids are secondary metabolites widely distributed in higher plants that show various
biological effects including antioxidative, anti-inflammatory, antiviral, antifungal anticar-
cinogenic, cardioprotective and neurite outgrowth stimulatory activities (Singh et al. 2014;
Chang et al. 2017; Phan et al. 2017). Nevertheless, the most promising bioactive flavonoids
such as quercetin, chrisin, kaempferol and apigenin have very low bioavailability, making
them largely ineffective in vivo (Chen and Chen 2013). In fact, such compounds are
CONTACT Qiꢊ-an Wꢈng
Wꢈngqꢈ@ꢀnꢊ.ꢇꢃꢊ.ꢉn
sꢊppꢆꢇmꢇnꢁꢈꢆ ꢃꢈꢁꢈ fꢄꢅ ꢁꢀiꢂ ꢈꢅꢁiꢉꢆꢇ ꢉꢈn bꢇ ꢈꢉꢉꢇꢂꢂꢇꢃ ꢈꢁ ꢀꢁꢁpꢂ://ꢃꢄi.ꢄꢅg/10.1080/14786419.2017.1413562.
©
2017 Infꢄꢅmꢈ uK limiꢁꢇꢃ, ꢁꢅꢈꢃing ꢈꢂ tꢈyꢆꢄꢅ & Fꢅꢈnꢉiꢂ Gꢅꢄꢊp

2
X.ꢀL. LI ET AL.
polyhydroxylated flavonoids (PHFs), and the free hydroxyl groups limit the intestinal absorp-
tion and are quickly conjugated by glucuronidation and sulfation (Walle 2007).
Polymethoxylated flavonoids (PMFs) are readily absorbed in the intestine and show wide
tissue distribution and metabolic stability (Ruiu et al. 2015). PMFs may be more biologically
active flavonoids compared to their hydroxylated analogues. Some results suggest that
methylation of some natural phenolic compounds could improve P-gp modulating activity,
and polymethoxy-substituted phenyl ring may be an important pharmacophore for anti-
cancer effect (Yuan et al. 2015). 5-Hydroxy-3,7,3′,4′-tetramethoxyflavonoid (1), a polymeth-
oxyflavonoid, occurred in sweet orange (Citrus sinensis) peel, can be employed as safe and
effective modulators of BCRP-mediated drug resistance in cancer (Li et al. 2006). Our previous
studies also suggested that the polymethoxy flavonoids possess significantly enhanced
cytotoxic activity (Nguyen et al. 2017).
The introduction of the aminoalkyl group to the structure of compounds is a general
strategy for improving bioavailability and water solubility (Bonesi et al. 2008). The results
obtained in several classes of polyaromatic antitumour agent indicate that the introduction
of an aminoalkyl side chain can increase significantly the biological activity and the potency
of the parent compounds (Fu et al. 2012). These findings encourage us to investigate
whether the flavonoid skeletons which possess aminoalkyl side chain can be improved
antiproliferative activity. In the present work, we aimed to synthesise a novel series of meth-
ylated quercetin derivatives through extending alkoxy chain at the 5-position, and intro-
ducing amine hydrogen bond receptor at the end of the side chain. Furthermore, their
antiproliferative activities were evaluated in vitro on a panel of three human cancer cell lines
Hela (cervical carcinoma), HCC1954 (breast cancer) and SK-OV-3 (ovarian cancer) using CCK-8
assay.
2
. Results and discussion
The novel aminoalkylated polymethoxyflavonoid derivatives 3–11 were synthesised
according to the synthetic route shown in Scheme 1. Regiospecific methoxylation of
quercetin with dimethylsulfate and K CO provides the key intermediate 5-hydroxy-3,7,3′,4′-
2
3
tetramethoxy flavonoid (1), because of the strong intramolecular H-bond at hydroxyl of
C-5 with the adjacent carbonyl at C-4, quercetin was readily prepared from the commercial
material rutin by acid hydrolysis of rutinose unit as previously described (Nguyen et al.
2
1
015). The bromoderivative 2, which was obtained in simple one-step alkylation of 1 with
,4-dibromobutane refluxed in K CO and acetone, was further reacted with corresponding
2
3
amines in the presence of K CO in CH CN to provide the final aminoalkylated polymeth-
2
3
3
oxyflavonoid derivatives 3–11. All new compounds were purified by recrystallisation or
chromatography, and their structures were confirmed by the analytical and spectroscopic
data.
Antiproliferative activities in vitro of all synthesised compounds against three cancer cell
lines (Hela, HCC1954 and SK-OV-3) were evaluated based on a CCK-8 assay using cis-Platin
and paclitaxel as positive controls. Antiproliferative activities of the compounds indicated
by IC values were calculated by linear regression analysis of the concentration–response
5
0
curves obtained for each compound. The results were summarised in Table 1. Table 1 shows
that parent compound 5-hydroxy-3,7,3′,4′-tetramethoxyflavonoid(1) did not exhibit any
inherent cytotoxicity to investigated cancer cell lines (IC > 100 μM), while all aminoalkylated
50

NATURAL PRODUCT RESEARCH
3
OH
OH
OCH3
OCH3
OCH3
H CO
O
O
HO
O
O
H CO
O
O
3
3
OCH3
a
b
OH
OCH3
OCH3
O
OH
OH
Br
OCH3
OCH3
1
2
H CO
O
3. NR R = N(CH )
1 2
3
3 2
8. NR R =
N
OH
OCH3
1 2
4
. NR R = N(CH CH )
1 2
2
3 2
N
O
N
9
. NR R =
O
O
c
1
2
1
2
10. NR R =
N
5
. NR R = N(CH CH CH )
CH3
2
2
3 2
R2
N
1
2
1 2
1
6. NR R =
11. NR R =
N
R
N
N
N
3-11
1
2
7
. NR R =
Reagents and conditions : a. K CO , acetone, NaH, (CH ) SO , ; b. K CO , KI, Br(CH ) Br, acetone, reflux;
2
3
3 2
4
2
3
2 4
c. K CO , CH CN, amines, reflux
2
3
3
Scheme 1. synꢁꢀꢇꢂiꢂ ꢄf ꢈminꢄꢈꢆkyꢆꢈꢁꢇꢃ pꢄꢆymꢇꢁꢀꢄxyflꢈvꢄnꢄiꢃ ꢃꢇꢅivꢈꢁivꢇꢂ 3–11.
Table 1. tꢀꢇ ꢈnꢁipꢅꢄꢆifꢇꢅꢈꢁivꢇ ꢈꢉꢁiviꢁy (Ic in μM) ꢄf ꢉꢄmpꢄꢊnꢃꢂ 1, 3–11 ꢄn ꢁꢀꢇ ꢀꢊmꢈn ꢉꢈnꢉꢇꢅ ꢉꢇꢆꢆ ꢆinꢇꢂ.
50
compound
Hela
HCC1954
SK-OV-3
1
3
4
5
6
7
8
9
>100
53.33
23.05
9.51
21.74
16.56
12.02
33.33
34.43
14.66
21.30
0.0021
>100
43.82
20.75
14.63
18.73
23.27
19.84
24.75
37.99
20.61
33.57
0.0011
>100
40.90
28.29
20.93
29.43
32.02
26.71
38.37
43.42
29.01
12.07
0.0017
1
1
0
1
ꢈ
cis-Pꢆꢈꢁin
pꢈꢉꢆiꢁꢈxꢇꢆ
ꢈ
ꢈcis-Pꢆꢈꢁin ꢈnꢃ pꢈꢉꢆiꢁꢈxꢇꢆ wꢇꢅꢇ ꢇmpꢆꢄyꢇꢃ ꢈꢂ pꢄꢂiꢁivꢇ ꢉꢄnꢁꢅꢄꢆꢂ.
polymethoxyflavonoid derivatives showed moderate to potent anticancer activity against
tested cell lines with IC values ranging from 9.51 to 53.33 μM. Therefore, the presence of
5
0
an aminobutyl group in the flavonoid moiety (compounds 3–11) resulted to be a key sub-
stitution for the activity of compounds against these three cancer cells. Compounds 5, 7, 8,
1
1 towards Hela Cells and compounds 4–9, 11 on HCC1954 displayed more potency as
compared to positive control cis-Platin. Compound 4 revealed to be the most active with
IC values ranging from 9.51 to 20.93 μM against all cancer cell lines.
5
0

4
X.ꢀL. LI ET AL.
3
. Experimental
3
.1. General information
1
13
Melting points were measured on a XRC-l apparatus, uncorrected. H and C NMR spectra
were recorded on Varian INOVA-400 and Bruker AM-400 instrument, using tetramethylsilane
as internal standard, chemical shifts (δ) in ppm, coupling constants (J) in Hz. Mass spectra
were determined with ZAB-HS spectrometer. Column chromatography was carried out using
200–300 mesh silica gel (Qingdao Ocean Chemical Products of China). AR or chemical pure
reagents and solvents were purchased from commercial sources, and anhydrous solvents
were freshly distilled or purified according to standard procedures.
5-Hydroxy-3,7,3′,4′-tetramethoxyflavone (1) was prepared from quercetin according to
the previous methods (Yuan et al. 2015).
3
.2. 5-Bromobutoxy-3,7,3′,4′-tetramethoxyflavone (2)
Anhydrous potassium carbonate (250 mg, 1.81 mmol) and a catalytic amount of KI were
added in turn to a solution of 5-hydroxy-3,7,3′,4′-tetramethoxyflavone (0.25 g, 0.70 mmol)
in acetonitrile (20 mL). The reaction mixture refluxed for 1 h. Then 1,4-dibromobutane
(
0.12 mL, 1.44 mmol) was added dropwise. After addition completed, the reaction mixture
was refluxed for 22 h. The reaction was monitored by TLC. After cooling to room temperature,
the solvent was removed in vacuo. The residue was extracted with CH Cl (3 × 50 mL). The
2
2
organic phase was combined and dried over anhydrous sodium sulphate. Then, the solvent
was removed in vacuo and crude product was purified by silica gel column chromatography
(
ethyl acetate/petroleum ether, v/v, 1:3 as the eluent) to afford white solid 2 in 84% yield.
1
mp 131–133 °C; H NMR (400 MHz, CDCl ) δ 7.65 (d, J = 1.9 Hz, 1H, 6ʹ-H), 7.63 (s, 1H, 2ʹ-H),
3
6
5
.91 (d, J = 9.1 Hz, 1H, 5ʹ-H), 6.43 (s, 1H, 8-H), 6.26 (s, 1H, 6-H), 4.03 (dd, J = 11.4, 5.5 Hz, 2H,
-OCH ), 3.90 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.83 and 3.77 (2s, 6H, 3-OCH and 7-OCH ), 3.28
2
3
3
3
3
1
3
(
t, J = 6.6 Hz, 2H, CH ), 2.19–2.08 (m, 2H, CH ), 2.05–1.95 (m, 2H, CH ); C NMR (100 MHz,
2 2 2
CDCl ) δ 170.8, 160.7,157.2,155.7,149.7,147.8, 145.7, 138.1, 120.4, 118.6, 108.1, 107.8, 93.6,
3
+
8
9.5, 65.2, 65.0, 56.9,53.0, 52.9, 52.7, 26.8, 26.6, 24.4. MS(ESI): m/z 492.1 [M + H] .
3
.3. General procedure for synthesis of aminoalkylated polymethoxy flavonoid
derivatives (3–11)
Anhydrous potassium carbonate (0.28 g, 2.05 mmol) was added to a solution of 5-bromob-
utoxy-3,7,3′,4′-tetramethoxyflavone (0.20 g, 0.41 mmol) in acetonitrile (15 mL). The reaction
mixture refluxed for 1 h. Then secondary amines (0.5 mmol) were added dropwise to the
reaction mixture and refluxing was continued. Completion of the reaction was monitored
by TLC. After cooling to room temperature, the solvent was removed in vacuo. The residue
was diluted with water and extracted with CH Cl (3 × 10 mL). The organic phase was com-
2
2
bined and washed with brine (3 × 10 mL), dried over anhydrous Na SO and concentrated.
2
4
The residue was subjected to silica gel column chromatography purification (ethyl acetate/
petroleum ether, v/v, 2:3 with 3–5 drops of triethylamine as the eluent), to afford white solids
3
–11 in 71–94% yield.

NATURAL PRODUCT RESEARCH
5
3
3
.3.1. 5-(4′-Dimethylamino)butoxy-3,7,3′,4′-tetramethoxyflavone (3)
1
was afforded as a white solid in 77% yield; mp 67–69 °C; H NMR (400 MHz, CDCl ) δ 7.72
3
(
d, J = 3.1 Hz, 1H, 6ʹ-H), 7.71 (s, 1H, 2ʹ-H), 6.50 (d, J = 4.5 Hz, 1H, 5ʹ-H), 6.50 (s, 1H, 8-H), 6.34 (s,
1
H, 6-H), 4.10 (t, J = 6.5 Hz, 2H, 5-OCH ), 3.97 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.90 and 3.85 (2s,
2 3 3
6
H, 3-OCH and 7-OCH ), 2.43–2.35 (m, 2H, CH ), 2.26 (s, 6H, CH NCH ), 2.00–1.95 (m, 2H,
3
3
2
3
3
1
3
CH ), 1.75–1.78 (m, 2H, CH ); C NMR (100 MHz, CDCl ) δ 164.0, 160, 159.0, 150.9, 148.9,
2
2
3
1
41.4, 123.7, 121.8, 111.2, 96.9, 92.6, 69.5, 60.3, 59.5, 56.3, 56.2, 56.0, 45.7, 27.0, 24.3. MS(EI):
+
m/z 457.1 [M] .
3
4
.3.2. 5-(4′-Diethylamino)butoxy-3,7,3′,4′-tetramethoxyflavone (4)
1
was afforded as a white solid in 71% yield; mp 212–214 °C; H NMR (400 MHz, CDCl ) δ 7.63
3
(
s, 2H, 6ʹ-H and 2ʹ-H), 6.91 (d, J = 9.0 Hz, 1H, 5ʹ-H), 6.42 (s, 1H, 8-H), 6.26 (s, 1H, 6-H), 4.02 (t,
J = 6.5 Hz, 2H, 5-OCH ), 3.89 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.82 and 3.77 (2s, 6H, 3-OCH and
2
3
3
3
7
-OCH ), 2.52 (dd, J = 13.1, 6.1 Hz, 6H, N(CH ) ), 1.89 (dd, J = 13.6, 6.7 Hz, 2H, CH ), 1.70 (d,
3
2
3
2
1
3
J = 6.7 Hz, 2H, CH ), 0.98 (td, J = 7.0, 3.2 Hz, 6H, 2CH ); C NMR (100 MHz, CDCl ) δ 173.8,
2
3
3
1
63.7, 160.3, 158.7, 152.4, 150.7, 148.6, 141.1, 123.4, 121.5, 111.1, 110.7, 96.6, 92.3, 69.2, 59.9,
+
55.9, 55.7, 52.3, 46.7, 26.9, 23.1, 11.3. MS(ESI): m/z 485.2 [M + H] .
3
5
.3.3. 5-(4′-Dipropylamino)butoxy-3,7,3′,4′-tetramethoxyflavone (5)
1
was afforded as a white solid in 80% yield; mp 60–62 °C; H NMR (400 MHz, CDCl ) δ 7.64
3
(
dd, J = 4.2, 2.5 Hz, 2H, 6ʹ-H and 2ʹ-H), 6.92 (d, J = 4.6 Hz, 5ʹ-H), 6.42 (s, 1H, 8-H), 6.28 (s, 1H,
6
3
7
2
1
-H), 4.02 (t, J = 6.6 Hz, 2H, 5-OCH ), 3.90 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.83 and 3.79 (2s, 6H,
2 3 3
-OCH and 7-OCH ), 2.48–2.45 (m, 2H, CH ), 2.37–2.33 (m, 4H, CH NCH ), 1.89 (dd, J = 14.5,
3
3
2
2
2
.0 Hz, 2H, CH ), 1.68–1.64 (m, 2H, CH ), 1.40 (d, J = 7.0 Hz, 4H, 2CH ), 0.80 (t, J = 7.3 Hz, 6H,
2
2
2
CH3); 13C NMR (100 MHz, CDCl ) δ 174.3, 164.2, 160.9, 159.2, 151.2, 149.1, 123.9, 122.0, 111.6,
3
11.2, 110.1, 102.8, 97.1, 92.8, 69.8, 60.4, 56.5, 56.4, 56.2, 54.1, 32.1, 27.4, 23.1, 20.5, 12.4; MS
+
+
(
m/z, EI): 513.2[M] . HRMS (EI): m/z [M ] calcd for C H O N: 513.2721, found: 513.2736.
29 39 7
3
6
.3.4. 5-(4′-(Pyrrolidin-1-yl)butoxy)-3,7,3′,4′-tetramethoxyflavone (6)
1
was afforded as a white solid in 84% yield; mp 160–162 °C; H NMR (400 MHz, CDCl ) δ 7.64
3
(
dd, J = 8.5, 2.5 Hz, 2H, 6ʹ-H and 2ʹ-H), 6.92 (d, J = 8.5 Hz, 1H, 5ʹ-H), 6.46 (s, 1H, 8-H), 6.26 (s,
1
H, 6-H), 4.04 (t, J = 5.3 Hz, 2H, 5-OCH ), 3.90 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.84 and 3.73 (2s,
2 3 3
6
H, 3-OCH and 7-OCH ), 3.55–3.46 (m, 2H, CH ), 3.02–2.92 (m, 2H, CH ), 2.23–2.10 (m, 4H,
3
3
2
2
1
3
CH NCH ), 1.97 (dd, J = 11.7, 5.7 Hz, 2H, CH ), 1.79–1.76 (m, 4H, 2CH ); C NMR (100 MHz,
2
2
2
2
CDCl ) δ 173.7, 163.9, 159.7, 158.7, 152.9, 150.9, 148.7, 140.9, 123.1, 121.7, 111.1, 110.8, 109.3,
3
+
9
6.6, 92.8, 68.9, 59.8, 56.0, 55.9, 55.8, 55.2, 53.4, 25.8, 23.4. MS(ESI): m/z 488.2 [M + H] .
3
7
.3.5. 5-(4′-(Piperidin-1-yl)butoxy)-3,7,3′,4′-tetramethoxyflavone (7)
was afforded as a white solid in 91% yield (recrystallisation from ethyl acetate instead of
1
flash column chromatography purification); mp 111–113 °C; H NMR (400 MHz, CDCl ) δ
3
7
4
.66–7.60 (m, 2H, 6ʹ-H and 2ʹ-H), 6.90 (d, J = 9.0 Hz, 1H, 5ʹ-H), 6.40 (s, 1H, 8-H), 6.25 (s, 1H, 6-H),
.01 (t, J = 4.9 Hz, 2H, 5-OCH ), 3.89 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.82 and 3.78 (2s, 6H, 3-OCH
3
2
3
3
and 7-OCH ), 2.51–2.23 (m, 6H, N(CH ) ), 1.88 (dd, J = 14.4, 6.8 Hz, 2H, CH ), 1.71 (dd, J = 14.8,
3
2 3
2
13
7
.7 Hz, 2H, CH ), 1.51 (dd, J = 11.0, 5.4 Hz, 4H, 2CH ), 1.40–1.32 (m, 2H, CH ); C NMR (100 MHz,
2
2
2
CDCl ) δ 173.8, 163.7, 160.3, 158.7, 152.4, 150.7, 148.6, 141.0, 123.4, 121.5, 110.9, 109.6, 96.5,
3

6
X.ꢀL. LI ET AL.
+
9
2.3, 69.2, 59.9, 58.8, 55.9, 55.7, 54.4, 26.9, 25.7, 24.3, 23.1. MS (m/z, EI): 497.2 [M] . HRMS (EI):
+
m/z [M ] calcd for C H O N: 497.2408, found: 497.2390.
2
8
35
7
3
8
.3.6. 5-(4′-(4-Hydroxypiperidin-1-yl)butoxy)-3,7,3′,4′-tetramethoxyflavone (8)
1
was afforded as a white solid in 89% yield; mp 134–136 °C; H NMR (400 MHz, CDCl ) δ 7.65–
3
7.43 (m, 2H, 6ʹ-H and 2ʹ-H), 7.41 (d, J = 8.7 Hz, 1H, 5ʹ-H), 6.46 (s, 1H, 8-H), 6.28 (s, 1H, 6-H), 6.05
(
(
(
(
s, 1H, -CH-OH), 4.04 (t, J = 5.8 Hz, 2H, 5-OCH ), 3.90 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.84 and 3.76
2
3
3
2s, 6H, 3-OCH and 7-OCH ), 3.21 (t, J = 6.5 Hz, 2H, CH ), 2.35–2.22 (m, 4H, CH NCH ), 2.06–2.02
3
3
2
2
2
13
m, 4H, 2CH ), 1.69–1.61 (m, 1H, CH), 1.23–1.15 (m, 2H, CH ), 0.87–0.56 (m, 2H, CH ); C NMR
2
2
2
100 MHz, CDCl ) δ 178.3, 168.3, 164.5, 163.2, 155.3, 145.6, 141.8, 133.8, 126.1, 123.4, 115.6,
3
+
1
15.2, 101.1, 97.1, 73.2, 64.5, 60.5, 60.4, 60.3, 51.2, 32.5, 30.2. MS(ESI): m/z 513.2 [M + H] .
3
9
.3.7. 5-(4′-Morpholinobutoxy)-3,7,3′,4′-tetramethoxyflavone (9)
1
was afforded as a white solid in 87% yield; mp 56–58 °C; H NMR (400 MHz, CDCl ) δ 7.64–
3
7.62 (m, 2H, 6ʹ-H and 2ʹ-H), 6.91 (d, J = 9.0 Hz, 1H, 5ʹ-H), 6.42 (s, 1H, 8-H), 6.26 (s, 1H, 6-H), 4.03
(
t, J = 5.2 Hz, 2H, 5-OCH ), 3.90 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.83 and 3.78 (2s, 6H, 3-OCH
2
3
3
3
and 7-OCH ), 3.64–3.62 (m, 4H, CH NCH ), 2.41–2.38 (m, 4H, CH CH ), 1.92–1.89 (m, 4H, 2CH ),
3
2
2
2
2
2
1
3
1
1
4
.76–1.70 (m, 2H, CH ); C NMR (100 MHz, CDCl ) δ 165.1, 161.6, 151.9, 149.9, 142.4, 124.6,
2
3
22.9, 112.4, 111.9, 97.9, 93.6, 70.3, 68.2, 61.3, 59.8, 57.3, 57.0, 54.9, 28.1, 24.1. MS (m/z, EI):
+
+
99.2 [M] . HRMS (EI): m/z [M ] calcd for C H O N: 499.2201, found: 499.2188.
2
7
33
8
3
1
.3.8. 5-(4′-(4-methylpiperazin-1-yl)butoxy)-3,7,3′,4′-tetramethoxyflavone (10)
1
0 was afforded as a white solid in 84% yield; mp 157–159 °C; H NMR (400 MHz, CDCl ) δ
3
7.71–7.69 (m, 2H, 6ʹ-H and 2ʹ-H), 6.99 (d, J = 4.5 Hz, 1H, 5ʹ-H), 6.49 (s, 1H, 8-H), 6.34 (s, 1H, 6-H),
4
.09 (t, J = 6.6 Hz, 2H), 3.97 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.90 and 3.85 (2s, 6H, 3-OCH and
3
3
3
7
-OCH ), 2.72–2.36 (m, CH N(CH ) ), 2.36–2.10 (m, 6H, N(CH ) ), 2.00–1.93 (m, 2H, CH ),
3 3 2 2 2 3 2
1
3
1.79–1.72 (m, 2H, CH ); C NMR (100 MHz, CDCl ) δ 173.1, 163.0, 159.7, 158.0, 151.8, 149.9,
2
3
1
4
47.9, 140.4, 122.7, 120.9, 110.4, 109.9, 108.9, 95.9, 91.6, 68.5, 59.3, 57.4, 55.3, 55.0, 54.4, 52.5,
+
+
5.4, 26.2, 22.5. MS (m/z, EI): 512.2 [M] . HRMS (EI): m/z [M ] calcd for C H O N : 512.2517,
28 36 7 2
found: 512.2525.
3
1
.3.9. 5-(4′-(1H-imidazol-1-yl)butoxy)-3,7,3′,4′-tetramethoxyflavone (11)
1 was afforded as a white solid in 94% yield (recrystallisation from ethyl acetate instead of
1
flash column chromatography purification); mp 132–134 °C; H NMR (400 MHz, CDCl ) δ 7.64
3
(
d, J = 7.6 Hz, 2H, 6ʹ-H and 2ʹ-H), 7.54 (s, 1H, NHN), 6.95 (d, J = 9.4 Hz, 2H, NHHN), 6.91 (d,
J = 8.7 Hz, 1H, 5ʹ-H), 6.44 (s, 1H, 8-H), 6.22 (s, 1H, 6-H), 4.11 (t, J = 6.8 Hz, 2H, 5-OCH ), 3.98 (t,
2
J = 5.6 Hz, 2H, CH ), 3.89 (s, 6H, 3ʹ-OCH and 4ʹ-OCH ), 3.82 and 3.77 (2s, 6H, 3-OCH and
2
3
3
3
1
3
7
1
9
-OCH ), 2.15–2.04 (m, 2H, CH ), 1.89–1.78 (m, 2H, CH ); C NMR (100 MHz, CDCl ) δ 173.7,
3 2 2 3
63.7, 159.9, 158.7, 150.8, 148.6, 141.1, 137.2, 129.0, 123.2, 121.6, 118.8, 110.9, 109.5, 96.6,
2.6, 68.6, 59.9, 56.0, 55.9, 55.7, 46.7, 27.9, 25.7; MS (m/z, EI): 480.2 [M] . HRMS (EI): m/z [M ]
+
+
calcd for C H O N : 480.1891, found: 480.1897.
2
6
28
7
2
3
.4. Assay for antiproliferative activity
The antiproliferative activity in vitro of compounds 1, 3–11 was measured using the CCK-8
assay (Song et al. 2015). Hela, HCC1954 and SK-OV-3 cell lines were obtained from the Tumor

NATURAL PRODUCT RESEARCH
7
Cell Resoures Bank, Chinese Academy of Medical Sciences. Cell counting kit-8 was obtained
from Dojindo (Japan).
3
Hela, HCC1954 and SK-OV-3 (5 × 10 per well in a 96-well plate) were treated with different
concentrations of compounds 1, 3–11 (100, 25, 6.25, 1.56, 0.39, 0.0976, 0.0244, 0.0061 μM)
for 48 h. Then, 10% CCK-8 was added into each well and incubated with 90% humidity and
5
% CO for another 1–3 h. The supernatant was discarded, and 0.1 mL of DMSO was added
2
to dissolve precipitation. The mixture was shaken on a microvibrator for 5 min, and the
absorbance was measured at 450–490 nm by automated Fluorimeter (Novostar, BMG
LABTECH, Germany) to determine the concentration that killed 50% of cells (IC ). Data rep-
5
0
resent the means of at least three separate experiments. The IC value was defined as the
5
0
concentration that caused 50% inhibition of cell proliferation.
4
. Conclusions
In summary, a series of novel aminoalkylated polymethoxyflavonoid derivatives were syn-
thesised. The antiproliferative activity results showed that all the target compounds exhibited
antiproliferative activities against investigated cancer cells with IC values of 9.51–53.33 μM.
50
The introduction of aminoalkyl group in the flavonoid moiety (compounds 3–11) resulted
to be a key substitution for the activity of polymethoxyflavonoid 1 against these three cancer
cells. Compounds 5, 7, 8, 11 on Hela cells and compounds 4–9, 11 on HCC1954 cells displayed
more potency as compared to positive control cis-Platin. Compound 5 revealed to be the
most active with IC values ranging from 9.51 to 20.93 μM against all cancer cell lines, and
5
0
worthy of further development.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the National Natural Science Foundation of China [grant number J1210040].
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