Abstract
Sixteen flavonoid triazolyl glycosides 4–19 were synthesized in good yields via Cu(I)-catalyzed azide-alkyne cycloadditions of terminal alkynes of flavonoids 1–3 with acetylated sugar azides followed by deacetylation with sodium methoxide in anhydrous methanol. The antiproliferative activity of the synthesized compounds against three human cancer cell lines (Hela, HCC1954 and SK-OV-3) in vitro was evaluated. Flavonoids 1, 2 and flavonoid triazolyl glycosides 7, 12, 17 exhibit potent antiproliferative activity against these cancer cell lines.
Introduction
Flavonoid glycosides exhibit a wide range of biological activities, such as anti-inflammatory, cardioprotective, antitumor, antiviral and enzymatic inhibition properties [1], [2], [3], [4], [5], [6], [7], [8]. In order to study the function of glycosylated flavonoids at the molecular level, numerous glycosylation methods have been developed for the assembly of complex flavonoid glycosides [9], [10], [11], [12]. However, these traditional approaches often involve laborious synthetic transformations and tremendous protecting group manipulations, which complicate the overall synthesis and decrease the synthetic efficiency. Hence, development of new strategies and tactics in glycosylation reactions is of growing importance.
Towards our goal of designing new flavonoid compounds, we attempted to develop a practical general strategy for the synthesis of triazole-linked flavonoid glycoconjugates by a ‘click chemistry’ approach. The Cu(I) catalyzed azide-alkyne cycloaddition (CuAAc) can be considered as a typical ‘click chemistry’, in which a 1,2,3-triazole is formed in high yield and good regioselectivity [13], [14], [15]. On the basis of our previous experience in flavonol glycoconjugates as antitumor agents [16], [17], [18], [19], in this work we synthesized two series of glucose and maltose glycosyl derivatives. Overall, 16 new flavonoid triazole glycosides were synthesized and tested in vitro for their antiproliferative activity against three human cancer cell lines Hela (cervical cancer), HCC1954 (breast cancer) and SK-OV-3 (ovarian cancer).
Results and discussion
The flavonoid triazolyl glycosides were synthesized as shown in Scheme 1. According to previous procedures reported by us, the flavonoids apigenin (1), acacetin (2), 5,7,3′,4′-tetramethoxyflavonol (3) and O-benzyl or O-methylflavonoids 20, 23, 24, 25 were prepared starting with naringin or hesperidin [20]. The synthesis of the target triazolyl glycosides involved the initial preparation of acetylenic flavonoids and acetylated sugar azides. Sugar azides were synthesized from D-glycose by adopting the literature procedure [21], [22]. In the next step, an O-alkylation reaction was used to obtain the acetylenic flavonoids 21, 22, 26 and 27. Then, the copper-catalyzed CuAAc reaction of sugar azides and flavonoids followed by deacetylation furnished the desired products. The azide-alkyne cycloaddition reactions are regioselective and produce triazolyl glycosides in the β-configuration exclusively. Existence of the β-anomeric form in these sugar derivatives was confirmed by the large axial-axial coupling constant of 8.0–9.2 Hz between the anomeric atoms H(1) and H(2) in the proton nuclear magnetic resonance (1H NMR) spectra of glycosyl derivatives.
Synthetic routes to flavonoids 1–3 and their triazolyl glycosides 4–19.
Reagents and conditions: (a) 3-bromo-1-propyne, K2CO3, acetone, reflux; (b) acetyl glycosyl azide, CuSO4, ascorbic acid, CH2Cl2, NaHCO3, room temperature, then H2, Pd/C for 4, 6, 12 and 14; (c) CH3ONa, CH3OH; (d) oxone, acetone, CH2Cl2, Na2CO3, NaHCO3.
Flavonoids 1–3 and 16 novel synthesized flavonoid triazolyl glycosides 4–19 were investigated for their antiproliferative activity employing the Cell Counting Kit-8 (CCK-8) assay using cis-platin as a positive control against three human cancer cell lines (Hela, HCC1954 and SK-OV-3). Antiproliferative activities of the compounds indicated by half maximal inhibitory concentration (IC50)values were calculated by linear regression analysis of the concentration-response curves obtained for each compound. The results are summarized in Table 1. As can be seen, parent flavonoid 1 is active against all three cancer cells, and flavonoid 2 exhibits antiproliferative activity against Hela and HCC1954 cells. The flavonoid triazolyl glycosides 7, 12 and 17 exhibit moderate to potent antiproliferative activities. In particular, compound 7 is active against Hela cells and the activity of compound 12 against HCC1954 cells is greater than that of cis-platin.
The antiproliferative activity [IC50 (μm)]a of flavonoids and their triazolyl glycosides on human cancer cell lines.
| Compounds | Hela | HCC1954 | SK-OV-3 |
|---|---|---|---|
| 1 | 8.40±0.04 | 13.40±0.30 | 42.54±0.92 |
| 2 | 44.51±0.79 | 39.37±0.46 | >100 |
| 3–6 | >100 | >100 | >100 |
| 7 | 14.67±0.67 | >100 | >100 |
| 8–11 | >100 | >100 | >100 |
| 12 | 36.67±0.48 | 30.56±0.46 | 43.42±1.02 |
| 13–16 | >100 | >100 | >100 |
| 17 | 53.33±1.99 | 39.79±1.21 | >100 |
| 18, 19 | >100 | >100 | >100 |
| cis-Platinb | 21.30±0.21 | 33.57±0.20 | 12.07±0.77 |
aData are mean results±S.D. of three independent experiments.
bcis-Platin was employed as a positive control.
Conclusion
A synthetic route to flavonoid triazolyl glycosides using a ‘click chemistry’ approach was developed. The flavonoids and flavonoid triazolyl glycosides were evaluated in vitro for antiproliferative activity against three human cancer cells (Hela, HCC1954 and SK-OV-3). Most of the compounds have low activity or are inactive compared with the positive control cis-platin. However, the flavonoid 1 against Hela (IC50 8.40 μm) and HCC1954 (IC50 13.40 μm) cells, new flavonoid triazolyl glycosides 7 against Hela cells (IC50 14.67 μm) and 12 against HCC1954 cells (IC50 30.56 μm) possess higher activity than cis-platin.
Experimental
1H NMR spectra were recorded at 400 MHz on a Bruker AM-400 instrument, using tetramethylsilane as an internal standard. Mass spectra were determined with a ZAB-HS spectrometer operating in the electrospray ionization (ESI) mode. Infrared (IR) spectra were measured on a Bruker Tensor-27 spectrometer. Melting points were measured on a XRC-l apparatus and are uncorrected. Column chromatography was carried out using 200–300 mesh silica gel (Qingdao Ocean Chemical Products of China). Apigenin (1), acacetin (2), 5,7,3′,4′-tetramethoxyflavonol (3), 4′-O-benzylapigenin (20), 5,7,3′,4′-tetramethoxyluteolin (23), 5,7,4′-tribenzyloxydiosmetin (24) and 3-hydroxy-4′-methoxy-5,7,3′-tribenzyloxyflavonol (25) were prepared from naringin and hesperidin as reported previously [17], [18]. β-D-acetyl glucosyl azide and β-O-acetyl maltosyl azide were prepared by a minor modification of the procedure published previously [21].
General procedure for the synthesis of flavonoids substituted with a terminal alkyne 21, 22, 26 and 27
A mixture of flavonoid compounds 2, 3, 20 or 25 (1.8 mmol) and anhydrous K2CO3 (1 g, 7.2 mmol) in acetone (50 mL) was treated dropwise with propargyl bromide (1.5 mL, 2 mmol) and then heated under reflux for 2 h. The progress of the reaction was monitored by thin-layer chromatography (TLC). After cooling to room temperature, the resultant precipitate was filtered, washed with acetone and crystallized from ethyl acetate.
7-O-Propargylacacetin (21)
Yellow solid; yield 85%; mp 184–186°C; 1H NMR (CDCl3): δ 12.84 (s, 1H, 5-OH), 7.84 (d, 2H, J=9 Hz, 2′-H, 6′-H), 7.03 (d, 2H, J=9 Hz, 3′-H, 5′-H), 6.59 (s, 1H, 3-H), 6.57 (d, 1H, J=2 Hz, 8-H), 6.44 (d, 1H, J=2 Hz, 6-H), 4.78 (d, 2H, J=2 Hz, OCH2), 3.9 (s, 3H, 4′-OCH3), 2.59 (t, 1H, J=2 Hz, CH); ESI-MS: m/z 323 [M+Na]+. Anal. Calcd for C19H14O5: C, 70.80; H, 4.38. Found: C, 70.68; H, 4.22.
4′-O-Benzyl-7-O-propargylapigenin (22)
Yellow solid; yield 83%, mp 192–194°C; 1H NMR (CDCl3): δ 12.83 (s, 1H, 5-OH), 7.83 (d, 2H, J=8 Hz, 2′-H, 6′-H), 7.62–7.25 (m, 5H, C6H5), 7.07 (d, 2H, J=12 Hz, 3′-H, 5′-H), 6.58 (s, 1H, 3-H), 6.56 (d, 1H, J=2 Hz, 8-H), 6.43 (d, 1H, J=2 Hz, 6-H), 5.15 (s, 2H, CH2), 4.76 (d, 2H, J=2 Hz, OCH2Ph), 2.59 (t, 1H, J=2 Hz, CH); ESI-MS: m/z 399 [M+Na]+. Anal. Calcd for C25H18O5: C, 75.37; H, 4.55. Found: C, 75.25; H, 4.49.
3-O-Propargyl-5,7,3′,4′-tetramethoxyflavonoid (26)
White solid; yield 80%; mp 148–150°C; 1H NMR (CDCl3): δ 7.83 (d, 1H, J=2 Hz, 2′-H), 7.73 (m, 1H, 6′-H), 2.35 (t, 1H, J=2 Hz, CH), 3.91, 3.97, 3.96, 3.99 (4s, 12H, 4OCH3), 6.98 (d, 1H, J=9 Hz, 5′-H), 6.52 (d, 1H, J=2 Hz, 8-H), 6.36 (d, 1H, J=2 Hz, 6-H), 4.98 (d, 2H, J=2 Hz, CH2); ESI-MS: m/z 397 [M+Na]+. Anal. Calcd for C22H20O7: C, 66.66; H, 5.09. Found: C, 66.59; H, 4.98.
3-Hydroxy-4′-methoxy-5,7,3′-tribenzyloxyflavonoid (27)
White solid; yield 85%; mp 148–150°C; 1H NMR (CDCl3): δ 7.82 (d, 1H, J=2 Hz, 2′-H), 7.73 (dd, 1H, J=2 Hz and 8 Hz, 6′-H), 7.30–7.64 (m, 15H, Ar-H), 7.00 (d, 1H, J=8 Hz, 5′-H), 6.55 (d, 1H, J=2 Hz, 8-H), 6.47 (d, 1H, J=2 Hz, 6-H), 5.27 (s, 2H, 3′-OCH2Ph), 5.24 (s, 2H, 7-OCH2Ph), 5.11 (s, 2H, 5-OCH2Ph), 4.86 (s, 2H, CH2), 3.97 (s, 3H, OCH3), 2.37 (t, 1H, J=2 Hz, CH); ESI-MS: m/z 625 [M+Na]+. Anal. Calcd for C40H32O7: C, 76.91; H, 5.16. Found: C, 76.82; H, 5.23.
General procedure for the synthesis of compounds 4–7 and 12–15
A mixture of acetylated sugar azide (1.05 mmol), alkyne (1 mmol), CuSO4·5H2O (1 N, 0.05 mmol), sodium ascorbate (0.1 mmol), tetrabutylammonium bromide (TBAB, 0.1 mmol), dichloromethane (15 mL) and aqueous NaHCO3 (1 m, 15 mL) was stirred at room temperature until TLC showed no trace of the alkyne. The aqueous layer was washed with dichloromethane, and the combined extract was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The residue was subjected to silica gel chromatography eluting with EtOAc/petroleum ether, 1:2, to afford the benzyl-protected products 4, 6, 12, 14. Removal of the benzyl groups by hydrogenation over 10% Pd/C at room temperature for 16 h afforded compounds 5, 7, 13, 15.
1-[N-(2,3,4,6-Tetra-O-acetyl-β-D-glucosyl)]-4-(7-O-methyleneapigenin)-[1,2,3]-triazole (4)
Yellow solid; yield 86%; mp 201–202°C; 1H NMR (CDCl3): δ 12.98 (s, 1H, 5-OH), 10.40 (s, 1H, 4′-OH), 7.49 (s, 1H, triazole-H), 7.9 (d, 2H, J=9 Hz, 2′-H, 6′-H), 7.15 (d, 2H, J=9 Hz, 3′-H, 5′-H), 6.54 (s, 2H, 6-H, 8-H), 6.42 (s, 1H, 3-H), 5.76 (d, 1H, J=9 Hz, 1″-H), 5.6 (s, 2H, 6″-CH2OAc), 5.36 (s, 2H, OCH2), 5.18 (d, 1H, J=3 Hz, 5″-H), 4.20–4.11 (m, 3H, 2″, 3″, 4″-H), 2.32–1.75 (4s, 12H, 4COCH3); ESI-MS: m/z 704 [M+Na]+. Anal. Calcd for C32H31N3O14: C, 56.39; H, 4.58; N, 6.16. Found: C, 56.43; H, 4.46; N, 6.11.
1-[N-(2,3,4,6-Tetra-O-acetyl-β-D-glucosyl)]-4-(7-O-methyleneacacetin)-1,2,3]-triazole (5)
Yellow solid; yield 76%; mp 198–200°C; 1H NMR (CDCl3): δ 12.82 (s, 1H, 5-OH), 7.8 (d, 2H, J=8.8 Hz, 2′-H, 6′-H), 7.59 (s, 1H, triazole-H), 7.03 (d, 2H, J=9.2 Hz, 3′-H, 5′-H), 6.58 (s, 2H, 6-H, 8-H), 6.40 (s, 1H, 3-H), 5.80 (d, 1H, J=9 Hz, 1″-H), 5.5 (s, 2H, 6″-CH2OAc), 5.29 (s, 2H, OCH2), 5.20 (d, 1H, J=3 Hz, 5′-H), 4.20–4.10 (m, 3H, 2″, 3″, 4″-H), 3.89 (s, 3H, 4′-OCH3), 2.20–1.80 (4s, 12H, 4CH3CO); ESI-MS: m/z 718 [M+Na]+. Anal. Calcd for C33H33N3O14: C, 56.98; H, 4.78; N, 6.04. Found: C, 56.83; H, 4.65; N, 6.19.
1-[N-(2,3,6,2′,3′,4′,6′-Hepta-O-acetyl-β-D-maltosyl)]-4-(7-O-methyleneapigenin)-[1,2,3]-triazole (6)
Yellow solid; yield 81%; mp 226–228°C; 1H NMR (CDCl3): δ 12.78 (s, 1H, 5-OH), 7.85 (s, 1H, triazole-H), 7.75 (d, 2H, J=8 Hz, 2′-H, 6′-H), 6.95 (d, 2H, J=8.0 Hz, 3′-H, 5′-H), 6.76 (s, 1H, 4′-OH), 6.54–6.52 (m, 2H, 2-H, 6-H), 6.39 (d, 1H, J=2 Hz, 3-H), 5.92 (d, 1H, J=8 Hz, 1′″-H), 5.50–5.45 (m, 2H, 6′″-CH2OAc), 5.41–5.30 (m, 2H, 6″-CH2OAc), 5.26 (s, 2H, OCH2-triazole), 5.08 (t, 1H, J=8 Hz, 1″-H), 4.88 (dd, 1H, J=4 Hz and 10 Hz, 4′″-H), 4.52 (dd, 1H, J=2 Hz and 12 Hz, 4″-H), 4.30–3.97 (m, 6H, sugar-H), 2.13, 2.11, 2.07, 2.04, 2.03, 2.02, 1.85 (s, 3H/each, COCH3); ESI-MS: m/z 992 [M+Na]+. Anal. Calcd for C44H47N3O22: C, 54.49; H, 4.88; N, 4.33. Found: C, 54.36; H, 4.78; N, 4.25.
1-[N-(2,3,6,2′,3′,4′,6′-Hepta-O-acetyl-β-D-maltosyl)]-4-(7-O-methyleneacacetin)-[1,2,3]-triazole (7)
Yellow solids, yield 68%, mp 215–217°C. 1H NMR (CDCl3) δ 12.83 (s, 1H, 5-OH), 7.90 (s, 1H, triazole-H), 7.84 (2H, d, J=8 Hz, 2′-H, 6′-H), 7.02 (d, 2H, J=8 Hz, 3′-H, 5′-H), 6.95–6.58 (m, 2H, 6-H, 8-H), 6.41 (d, 1H, J=2 Hz, 3-H), 5.92 (d, 1H, J=8 Hz, 1′″-H), 5.48–5.45 (m, 2H, 6′″-CH2OAc), 5.41–5.35 (m, 2H, 6″-CH2OAc), 5.28 (s, 2H, OCH2-triazole), 5.08 (t, 1H, J=8 Hz, 1″-H), 4.90–4.87 (dd, 1H, J=4 Hz and 10 Hz, 4′″-H), 4.52–4.49 (dd, 1H, J=2 Hz and 12 Hz, 4″-H), 4.29–3.98 (m, 8H, sugar-H), 3.90 (s, 3H, 4′-OCH3), 2.13, 2.11, 2.07, 2.04, 2.03, 2.02, 1.84 (s, 3H/each, COCH3); ESI-MS: m/z 1006 [M+Na]+. Anal. Calcd for C45H49N3O22: C, 54.93; H, 5.02; N, 4.27. Found: C, 54.82; H, 5.24; N, 4.25.
1-[N-(2,3,4,6-Tetra-O-acetyl-β-D-glucosyl)]-4-[3-O-methylene-(5,7,3′-trihydroxy-4′-methoxyflavonol)]-[1,2,3]-triazole (12)
Yellow solid; yield 77%; mp 185–187°C; 1H NMR (CDCl3): δ 12.52 (s, 1H, OH), 8.67 (s, 1H, OH), 7.88 (s, 1H, triazole-H), 7.63 (dd, 2H, J=2 x 2 Hz, 6′-H, 2′-H), 7.61–7.57 (m, 1H, 5′-H), 7.54 (s, 1H, 8-H), 6.86 (s, 1H, 6-H), 5.82 (d, 1H, J=9 Hz, 1″-H), 5.44–5.34 (m, 2H, 6″-CH2OAc), 5.32–5.29 (m, 2H, OCH2), 5.27–5.24 (m, 1H, 2″-H), 4.33 (dd, 1H, J=2 x 5 Hz, 3″-H), 4.23–4.20 (m, 1H, 4″-H), 4.12–4.09 (m, 1H, 5″-H), 3.95 (s, 3H, 4′-OCH3), 2.11, 2.08, 2.03, 1.87 (4s, 12H, 4COCH3); ESI-MS: m/z 750 [M+Na]+. Anal. Calcd for C33H33N3O16: C, 54.47; H, 4.57; N, 5.77. Found: C, 54.56; H, 4.59; N, 5.88.
1-[N-(2,3,4,6-Tetra-O-acetyl-β-D-glucosyl)]-4-[3-O-methylene-(5,7,3′,4′-tetramethoxyflavonol)]-[1,2,3]-triazole (13)
Yellow solid; yield 82%; mp 118–120°C; 1H NMR (CDCl3): δ 8.12 (s, 1H, triazole-H) 7.74 (d, 1H, J=2 Hz, 6′-H), 7.72 (d, 1H, J=2 Hz, 2′-H), 6.98 (d, 1H, J=9 Hz, 5′-H), 6.53 (d, 1H, J=2 Hz, 8-H), 6.38 (d, 1H, J=2 Hz, 6-H), 5.83 (d, 1H, J=9 Hz, 1″-H), 5.48–5.38 (m, 2H, 3″-H, 4″-H), 5.28–5.20 (m, 3H, 2″-H, CH2), 4.31–4.27 (m, 2H, 6″-CH2OAc), 4.16–4.12 (m, 1H, 5″-H), 4.00, 3.95, 3.93, 3.92 (4s, 12H, 4OCH3), 2.10, 2.07, 2.03, 1.83, (4s, 12H, 4COCH3); ESI-MS: m/z 770 [M+Na]+. Anal. Calcd for C36H39N3O16: C, 56.18; H, 5.11; N, 5.46. Found: C, 56.29; H, 5.24; N, 5.56.
1-[N-(2,3,6,2′,3′,4′,6′-Hepta-O-acetyl-β-D-maltosyl)]-4-[3-O-methylene-(5,7,3′-trihydroxy-4′-methoxyflavonol)]-[1,2,3]-triazole (14)
Yellow solid; yield 74%; mp 143–144°C; 1H NMR (CDCl3): δ 12.50, 8.90 (s, 2H, 2OH), 7.78 (d, 2H, J=10 Hz, 2′, 6′-H), 7.75 (s, 1H, triazole-H), 6.82 (d, 1H, J=9 Hz, 5′-H), 6.20 (s, 1H, 8-H), 6.18 (s, 1H, 6-H), 5.74 (d, 1H, J=9 Hz, 1″-H), 5.40–5.28 (m, 3H, 2′″-H, 3′″-H, 1′″-H), 5.20 (s, 2H, OCH2), 5.15–5.12 (m, 1H, 3″-H), 5.03–5.02 (m, 1H, 2″-H), 4.59–4.57 (m, 2H, 4′″-H, 4″-H), 4.20–4.03 (m, 4H, 6′″-CH2OAc, 6″-CH2OAc), 4.93–3.94 (m, 2H, 5″-H, 5′″-H), 3.95 (s, 3H, OCH3),2.18, 2.17, 2.08, 2.07, 1.99, 1.84, 1.73 (s, 3H/each, COCH3); ESI-MS: m/z 1038 [M+Na]+. Anal. Calcd for C45H49N3O24: C, 53.20; H, 4.86; N, 4.14. Found: C, 53.35; H, 4.98; N, 4.23.
1-[N-(2,3,6,2′,3′,4′,6′-Hepta-O-acetyl-β-D-maltosyl)]-4-[3-O-methylene-(5,7,3′,4′-tetramethoxy flavonol)]-[1,2,3]-triazole (15)
Yellow solid; yield 87%; mp 129–132°C; 1H NMR (CDCl3): δ 8.17 (s, 1H, triazole-H), 7.76 (d, 2H, J=9 Hz, 2′, 6′-H), 6.99 (d, 1H, J=9 Hz, 5′-H), 6.55 (d, 1H, J=2.4 Hz, 8-H), 6.40 (d, 1H, J=2 Hz, 6-H), 5.89 (d, 1H, J=9 Hz, 1″-H), 5.51–5.38 (m, 3H, 2′″-H, 3′″-H, 1′″-H), 5.19 (s, 2H, OCH2), 5.13–5.08 (m, 1H, 3″-H), 4.94–4.90 (dd, 1H, J=3 Hz and 9 Hz, 2″-H), 4.51–4.47 (m, 1H, 4′′′-H), 4.25–4.32 (m, 4H, 6′″-CH2OAc, 6″-CH2OAc), 4.19–4.07 (m, 3H, 4″-H, 5″-H, 5′″-H), 4.02, 3.98, 3.96, 3.95 (4s, 12H, 4OCH3), 2.17, 2.06, 2.04, 1.84 (s, 3H/each, CH3CO); ESI-MS: m/z 1058 [M+Na]+. Anal. Calcd for C48H55N3O24: C, 54.49; H, 5.24; N, 3.97. Found: C, 54.53; H, 5.36; N, 5.37.
General procedure for the synthesis of compounds 8–11 and 16–19
A solution of compounds 4–7 or 12–15 in NaOCH3 in anhydrous CH3OH (0.3 m, 3 mL) was stirred for 4–6 h at room temperature, during which time the color of the solution changed to light yellow from dark orange. Then the solution was concentrated in vacuo and the residue was purified by silica gel chromatography eluting with EtOAc MeOH, 3:1.
1-(N-β-D-Glucosyl)-4-(7-O-methylene apigenin)-[1,2,3]-triazole (8)
Yellow solid; yield 76%; mp 230–232°C; 1H NMR (DMSO-d6): δ 12.98 (s, 1H, 5-OH), 10.40 (s, 1H, 4′-OH), 8.51 (s, 1H, triazole-H), 7.9 (d, 2H, J=9 Hz, 2′-H, 6′-H), 6.95 (s, 1H, 6-H), 6.93 (d, 2H, J=2 Hz, 3′-H, 5′-H), 6.86 (s, 1H, 3-H), 6.50 (d, 1H, J=2 Hz, 8-H), 5.58 (d, 1H, J=5 Hz, 2″-OH), 5.44 (d, 1H, J=3 Hz, 3″-OH), 5.30 (d, 1H, J=6 Hz, 4″-OH), 5.29 (s, 2H, OCH2), 5.17 (d, 1H, J=6 Hz, 6″-OH), 4.63 (t, 1H, J=6 Hz, 1″-H), 3.7–3.1 (m, 5H, sugar-H); ESI-MS: m/z 536 [M+Na]+. Anal. Calcd for C24H23N3O10: C, 56.14; H, 4.52; N, 8.18. Found: C, 56.36; H, 4.68; N, 8.06.
1-(N-β-D-Glucosyl)-4-(7-O-methylene acacetin)-[1,2,3]-triazole (9)
Yellow solid; yield 82%; mp 229–230°C, 1H NMR (DMSO-d6): δ 12.95 (s, 1H, 5-OH), 8.53 (s, 1H, triazole-H), 8.07 (d, 2H, J=9 Hz, 2′-H, 6′-H), 7.13 (d, 2H, J=9 Hz, 3′-H, 5′-H), 6.98 (s, 1H, 3-H), 5.57 (d, 1H, J=9 Hz, 2″-OH), 5.45 (d, 1H, J=6 Hz, 3″-OH), 5.33 (d, 1H, J=5 Hz, 4″-OH), 5.19 (d, 1H, J=5 Hz, 6″-OH), 5.29 (s, 2H, OCH2), 3.87 (s, 3H, 4′-OCH3), 3.22–3.21 (m, 6H, sugar-H); IR: 3413, 2042, 1637, 1617, 1503, 1400, 1301, 1114, 828, 626 cm−1; ESI-MS: m/z) 550 [M+Na]+. Anal. Calcd for C25H25N3O10: C, 56.92; H, 4.78; N, 7.97. Found: C, 56.79; H, 4.83; N, 8.06.
1-(N-β-D-Maltosyl)-4-(7-O-methyleneapigenin)-[1,2,3]-triazole (10)
Yellow solid; yield 73%; mp 194–196°C; 1H NMR (DMSO-d6): δ 12.99 (s, 1H, 5-OH), 10.41 (s, 1H, 4′-OH), 8.53 (s, 1H, triazole-H), 7.96 (d, 2H, J=8 Hz, 2′-H, 6′-H), 6.95–6.93 (m, 3H, 3′-H, 5′-H and 8-H), 6.87 (s, 1H, 6-H), 6.51 (d, 1H, J=2 Hz, 3-H), 5.77 (d, 1H, J=4 Hz, 6′″-OH), 5.66 (d, 2H, J=8 Hz, 6″-OH, 6′″-OH), 5.60 (d, 1H, J=4 Hz), 5.55 (d, 1H, J=4 Hz, 3″-OH), 5.30 (s, 2H, OCH2-triazole), 5.08 (d, 1H, J=4 Hz, 4′′′-OH), 4.93 (d, 2H, J=4 Hz, 2″-OH, 2′″-OH), 4.62 (t, 1H, J=6 Hz, 1′″-H), 4.54 (t, 1H, J=4 Hz, 1″-H), 3.87 (dd, 1H, J=8 Hz and 15 Hz, 4′′′-H), 3.75–3.39 (m, 11H, sugar-H), 3.30–3.25 (dd, 1H, J=6 Hz and 10 Hz, 3′″-OH), 3.12–3.06 (dd, 1H, J=9 Hz and 14 Hz, 3″-OH); IR: 486, 592, 615, 704, 773, 883, 907, 1038, 1056, 1099, 1127, 1175, 1209, 1254, 1275, 1304, 1400, 1447, 1505, 1603, 1637, 1662, 2039, 3231, 3412 cm−1; ESI-MS: m/z 698 [M+Na]+. Anal. Calcd for C30H33N3O15: C, 53.33; H, 4.92; N, 6.22. Found: C, 53.47; H, 5.11; N, 6.03.
1-(N-β-D-Maltosyl)-4-(7-O-methyleneacacetin)-[1,2,3]-triazole (11)
Yellow solid; yield 77%; mp 198–200°C; 1H NMR (DMSO-d6): δ 12.93 (s, 1H, 5-OH), 8.53 (s, 1H, triazole-H), 8.07 (d, 2H, J=8 Hz, 2′-H, 6′-H), 7.13 (d, 2H, J=8 Hz, 3′-H, 5′-H), 6.96 (s, 2H, 6-H, 8-H), 6.51 (s, 1H, 3-H), 5.78 (d, 1H, J=4 Hz, 6′″-OH), 5.67–5.61 (m, 3H, 3″-OH, 3′″-OH and 6″-OH), 5.30 (s, 2H, OCH2-triazole), 5.08 (d, 1H, J=6 Hz, 4′″-OH), 4.95 (m, 2H, 2″-OH, 2′″-OH), 4.63–4.55 (m, 2H, 4″-H, 4′″-H), 3.86 (s, 3H, 4′-OCH3), 3.61–3.09 (m, 12H, sugar-H); IR: 481, 616, 768, 830, 907, 1035, 1073, 1119, 1178, 1251, 267, 1301, 1400, 1505, 1617, 1637, 2054, 3412; ESI-MS: m/z 712 cm−1; [M+Na]+. Anal. Calcd for C31H35N3O15: C, 53.99; H, 5.12; N, 6.09. Found: C, 54.09; H, 5.23; N, 6.20.
1-(N-β-D-Glucosyl)-4-[3-O-methylene-(5,7,3′-trihydroxy-4′-methoxyflavonol)]-[1,2,3]-triazole (16)
Yellow solid; yield 92%; mp 210–212°C; 1H NMR (DMSO-d6): δ 12.68 (s, 1H, OH), 8.30 (s, 1H, triazole-H), 7.59 (d, 2H, J=9 Hz, 2′ -H, 6′-H), 7.04 (d, 1H, J=9 Hz, 5′-H), 6.39 (s, 1H, 8-H), 6.18 (s, 1H, 6-H), 5.48 (d, 1H, J=9 Hz, 1″-H), 5.46 (s, 1H, 6″-OH), 5.36 (s, 1H, 4″-OH), 5.25 (s, 1H, 3″-OH), 5.12 (s, 2H, OCH2), 4.67 (s, 1H, 2″-OH), 4.02 (t, 1H, J=6 Hz, 2″-H), 3.84 (s, 3H, OCH3), 3.72 (d, 1H, J=6 Hz, 5″-H), 3.51–3.47 (m, 3H, 6″-H, 3″-H), 3.46–3.45 (1H, m, 4″-H); ESI-MS: m/z 582 [M+Na]+. Anal. Calcd for C25H25N3O12: C, 53.67; H, 4.50; N, 7.51. Found: C, 53.84; H, 4.63; N, 7.42.
1-(N-β-D-Glucosyl)-4-[3-O-methylene-(5,7,3′,4′-tetramethoxyflavonol)]-[1,2,3]-triazole (17)
Yellow solid; yield 91%; mp 154–156°C; 1H NMR (DMSO-d6): δ 8.46 (s, 1H, triazole-H), 7.80 (d, 2H, J=9 Hz, 2′-H, 6′-H), 7.20 (d, 1H, J=9 Hz, 5′-H), 6.94 (d, 1H, J=2 Hz, 8-H), 6.61 (d, 1H, J=2 Hz, 6-H), 5.64 (d, 1H, J=9 Hz, 1″-H), 5.47 (d, 1H, J=6 Hz, 6″-OH), 5.38 (d, 1H, J=4 Hz, 4″-OH), 5.23 (s, 2H, OCH2), 5.26 (d, 1H, J=5 Hz, 3″-OH), 4.73 (t, 1H, J=5 Hz, 2″-OH), 4.00 (s, 3H, OCH3), 3.96 (s, 3H, OCH3), 3.94 (s, 3H, OCH3), 3.84 (s, 3H, OCH3), 3.80–3.78 (m, 2H, 6″-H), 3.56–3.51 (m, 3H, 2″-H, 3″-H, 5″-H), 3.36–3.32 (m, 1H, 4″-H); ESI-MS (m/z): 624 [M+Na]+. Anal. Calcd for C28H31N3O12: C, 55.90; H, 5.19; N, 6.99. Found: C, 55.83; H, 5.05; N, 7.11.
1-(N-β-D-Maltosyl)-4-[3-O-methylene-(5,7,3′-trihydroxy-4′-methoxyflavonol)]-[1,2,3]-triazole (18)
Yellow solid; yield 87%; mp 202–205°C; 1H NMR (DMSO-d6): δ 12.47 (s, 1H, OH), 9.49 (s, 1H, OH), 8.32 (s, 1H, triazole-H), 7.62 (m, 1H, 6′-H), 7.47 (d, 1H, J=2 Hz, 2′-H), 7.05 (d, 1H, J=9 Hz, 5′-H), 6.42 (s, 1H, 8-H), 6.21 (s, 1H, 6-H), 5.71 (d, 1H, J=9 Hz, 1″-H), 5.61 (d, 1H, J=6 Hz, 1′″-H), 5.23 (s, 1H, OH), 5.12 (s, 2H, OCH2), 4.91 (s, 1H, OH), 4.83 (d, 1H, J=4 Hz, OH), 4.71 (s, 2H, 2OH), 4.52 (d, 1H, J=7 Hz, OH), 4.22 (d, 1H, J=7 Hz, OH), 3.87–3.64 (m, 4H, 3″-H, OCH3), 3.61–3.53 (m, 2H, 6′″-H), 3.51–3.29 (m, 9H, sugar-H); ESI-MS: m/z 744 [M+Na]+. Anal. Calcd for C31H35N3O17: C, 51.60; H, 4.89; N, 5.82. Found: C, 51.52; H, 4.78; N, 5.96.
1-(N-β-D-Maltosyl)-4-[3-O-methylene-(5,7,3′,4′-tetramethoxyflavonol)]-[1,2,3]-triazole (19)
Yellow solid; yield 84%; mp 186–189°C; 1H NMR (DMSO-d6): δ 8.39 (s, 1H, triazole-H), 7.71 (m, 2H, 2′-H, 6′-H), 7.10 (d, 1H, J=8 Hz, 5′-H), 6.84 (s, 1H, 8-H), 6.51 (s, 1H, 6-H), 5.78 (s, 1H, OH), 5.55 (d, 2H, J=4 Hz, sugar-H), 5.51 (s, 1H, OH), 5.17–5.08 (m, 3H, 3OH), 4.95 (s, 2H, OCH2), 4.63 (d, 1H, J=6 Hz, OH), 4.56 (d, 1H, J=2 Hz, OH), 3.90, 3.87, 3.84, 3.75 (4s, 12H, 4OCH3), 3.73–3.41 (m, 10H, sugar-H), 3.29–3.06 (m, 3H, sugar-H); ESI-MS: m/z 786 [M+Na]+. Anal. Calcd for C34H41N3O17: C, 53.47; H, 5.41; N, 5.50. Found: C, 53.33; H, 5.50; N, 5.67.
Assay for antiproliferative activity
Proliferation of Hela, HCC1954 and SK-OV-3 cells was evaluated by the CCK-8 (Dojingdo, Kumamoto, Japan) assay according to the manufacturer′s instructions [22]. This assay is based on the cleavage of the tetrazolium salt WST-8 by mitochondrial dehydrogenase in viable cells. Briefly, 1×103 cells/well were incubated with 45 μL culture medium in 384-well plates. After being adhered to the well, the cells were treated with 5 μL of tested compounds at different concentrations, and then cultured for 72 h before addition of 5 μL CCK-8 to the culture medium in each well. After a 2 h incubation at 37°C, absorbance at 450 nm of each well was measured (Novostar, BMG LABTECH, Germany). Each experiment was repeated 3 times, and the data represent the mean values of all measurements. The IC50 values were calculated using the Graphpad prism 5 software.
Statistical analysis
Data represent the means of at least three separate experiments. Statistical analysis was performed using the SAS statistical software. A value of p<0.05 was considered significant.
Acknowledgments
We thank the Hubei Provincial Natural Science Foundation of China (grant 2017CFC859) and the Education Department of Hubei Province Science and Technology Research Project of China (grant Q20162803) for the financial support.
References
[1] Daskiewicz, J. B.; Depeint, F.; Viornery. L.; Bayet, C.; Comte-Sarrazin, G.; Comte, G.; Gee, J. M.; Johnson, I. T.; Ndjoko, K.; Hostettmann, K.; et al. Effects of flavonoids on cell proliferation and caspase activation in a human colonic cell line HT29: an SAR study. J. Med. Chem.2005, 48, 2790–2804.10.1021/jm040770bSearch in Google Scholar PubMed
[2] Dofe, V. S.; Sarkate, A. P.; Kathwate, S. H.; Gill, C. H. Synthesis, antimicrobial activity and anti-biofilm activity of novel tetrazole derivatives. Heterocycl. Commun.2017, 23, 325–330.10.1515/hc-2017-0016Search in Google Scholar
[3] Evseeva, O. S.; Andreeva, O. A.; Oganesyan, É. T. Studies of the hydrolysis of hesperidin. Pharm. Chem. J.2014, 47, 606–609.10.1007/s11094-014-1018-6Search in Google Scholar
[4] Singh, M.; Kaur, M.; Silakari, O. Flavones: an important scaffold for medicinal chemistry. Eur. J. Med. Chem.2014, 84, 206–239.10.1016/j.ejmech.2014.07.013Search in Google Scholar PubMed
[5] Pavlova, S. I.; Albegova, D. Z.; Vorob′Eva, Y. S.; Laptev, O. S.; Kozlov, I. G. Flavonoids as potential immunosuppressants affecting intracellular signaling pathways. Pharm. Chem. J.2016, 49, 3–10.10.1007/s11094-016-1345-xSearch in Google Scholar
[6] Huang, W.; Chen, Q.; Yang, W. C.; Yang, G. F. Efficient synthesis and antiproliferative activity of novel thioether-substituted flavonoids. Eur. J. Med. Chem.2013, 66, 161–170.10.1016/j.ejmech.2013.05.037Search in Google Scholar PubMed
[7] Pandey, R. P.; Gurung, R. B.; Parajuli, P.; Koirala, N.; Tuoi, I. T.; Sohng, J. K. Assessing acceptor substrate promiscuity of YjiC-mediated glycosylation toward flavonoids. Carbohyd. Res.2014, 393, 26–31.10.1016/j.carres.2014.03.011Search in Google Scholar PubMed
[8] Marchiori, M. F.; Souto, D. E. P.; Bortot. L. O.; Pereira, J. F.; Kubota, L. T.; Cummings, R. D.; Dias-Baruffi, M.; Carvalho, I.; Campo, V. L. Synthetic 1,2,3-triazole-linked glycoconjugates bind with high affinity to human galectin-3. Bioorg. Med. Chem.2015, 23, 3414–3425.10.1016/j.bmc.2015.04.044Search in Google Scholar PubMed
[9] Zhang, Z. J.; Yu, B. Total synthesis of the antiallergic naphtho-α-pyrone tetraglucoside, cassiaside C2, isolated from cassia seeds. J. Org. Chem.2003, 68, 6309–6313.10.1021/jo034223uSearch in Google Scholar PubMed
[10] Urgaonkar. S.; Shaw, J. T. Synthesis of kaempferitrin. J. Org. Chem.2007, 72, 4582–4585.10.1021/jo070502wSearch in Google Scholar PubMed
[11] Yang. M.; Davies, G. J.; Davis, B. G. A glycosynthase catalyst for the synthesis of flavonoid glycosides. Angew. Chem. Int. Ed.2007, 46, 3885–3888.10.1002/anie.200604177Search in Google Scholar PubMed
[12] Li, Z.; Ngojeh, G.; Dewitt, P.; Zheng, Z.; Chen, M.; Lainhart, B.; Li, V.; Felpo, P. Synthesis of a library of glycosylated flavonols. Tetrahedron Lett.2008, 49, 7243–7245.10.1016/j.tetlet.2008.10.032Search in Google Scholar PubMed PubMed Central
[13] Thirumurugan, D. P.; Matosiuk, D.; Jozwiak, K. Click chemistry for drug development and diverse chemical–biology applications. Chem. Rev.2013, 113, 4905–4979.10.1021/cr200409fSearch in Google Scholar PubMed
[14] Akolkara, H. N.; Karalea, B. K.; Randhavanea, P. V.; Dalavi, N. R. Synthesis and characterization of novel fluorinated thiazolyl 1,3,4-thiadiazoles, 1,2,4-triazoles and 1,3-thiazoles by conventional and non-conventional methods. Indian. J. Chem. B.2017, 56B, 348–355.Search in Google Scholar
[15] Totobenazara, J.; Burke, A. J. New click-chemistry methods for 1,2,3-triazoles synthesis: recent advances and applications. Tetrahedron Lett.2015, 56, 2853–2859.10.1016/j.tetlet.2015.03.136Search in Google Scholar
[16] Wang, L. F.; Jin, J. Z.; Zhao, L. W.; Shen, H. Y.; Shen, C.; Zhang, P. F. Synthesis of C-glycosyl triazolyl quinoline-based fluorescent sensors for the detection of mercury ions. Carbohyd. Res.2016, 433, 41–46.10.1016/j.carres.2016.07.006Search in Google Scholar PubMed
[17] Cai, S. L.; Wu, Z.; Wu, J.; Shan, Y.; Wang, Q. A. Synthesis and biological activities of natural flavonoid diosmetin and its derivatives. Chin. J. Org. Chem.2012, 32, 560–566.10.6023/cjoc1109081Search in Google Scholar
[18] Liu, J. D.; Chen, L.; Cai, S. L.; Wang, Q. A. Semi synthesis of apigenin and acacetin-7-O-β-D-glycosides from naringin and their cytotoxic activities. Carbohyd. Res.2012, 357, 41–46.10.1016/j.carres.2012.05.013Search in Google Scholar PubMed
[19] Nguyen, V, S.; Shi, L.; Luan, F. Q.; Wang, Q. A. Synthesis of kaempferide Mannich base derivatives and their antiproliferative activity on three human cancer cell lines. Acta. Biochim. Pol.2015, 62, 547–552.10.18388/abp.2015_992Search in Google Scholar PubMed
[20] Adams, T. E.; Sous, M. E.; Hawkins, B. C.; Hirner, S.; Holloway, G.; Khoo, M. L.; Owen, D. J.; Savage, G. P.; Scammells, P. J.; Rizzacasa, M. A. Total synthesis of the potent anticancer Aglaia metabolites (-)-silvestrol and (-)-episilvestrol and the active analogue (-)-4′-desmethoxyepisilvestrol. J. Am. Chem. Soc.2003, 131, 1607–16016.10.1021/ja808402eSearch in Google Scholar PubMed
[21] Maier, M. A.; Yannopoulos, C. G.; Mohamed, N.; Roland, A.; Fritz, H.; Mohan, V.; Just, G.; Manoharan, M. Synthesis of antisense oligonucleotides conjugated to a multivalent carbohydrate cluster for cellular targeting. Bioconjugate. Chem.2003, 14, 18–29.10.1021/bc020028vSearch in Google Scholar PubMed
[22] Song, Y.; Xin, Z.; Wan, Y.; Li, J.; Ye, B.; Xue, X. Synthesis and anticancer activity of some novel indolo[3,2-b]andrographolide derivatives as apoptosis-inducing agents. Eur. J. Med. Chem.2015, 90, 695–706.10.1016/j.ejmech.2014.12.017Search in Google Scholar PubMed
©2018 Walter de Gruyter GmbH, Berlin/Boston
This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
