Accepted Manuscript Discovery of xanthine oxidase inhibitors and/or α-glucosidase inhibitors by carboxyalkyl derivatization based on the flavonoid of apigenin Zhuo-Ran Su, Shi-Yong Fan, Wei-Guo Shi, Bo-Hua Zhong PII: DOI: Reference:
S0960-894X(15)00466-7 http://dx.doi.org/10.1016/j.bmcl.2015.05.016 BMCL 22706
To appear in:
Bioorganic & Medicinal Chemistry Letters
Received Date: Revised Date: Accepted Date:
8 March 2015 2 May 2015 7 May 2015
Please cite this article as: Su, Z-R., Fan, S-Y., Shi, W-G., Zhong, B-H., Discovery of xanthine oxidase inhibitors and/or α-glucosidase inhibitors by carboxyalkyl derivatization based on the flavonoid of apigenin, Bioorganic & Medicinal Chemistry Letters (2015), doi: http://dx.doi.org/10.1016/j.bmcl.2015.05.016
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Bioorganic & Medicinal Chemistry Letters j o ur n al h om e p a g e : w w w . e l s e v i er . c o m
Discovery of xanthine oxidase inhibitors and/or α-glucosidase inhibitors by carboxyalkyl derivatization based on the flavonoid of apigenin. Zhuo-Ran Su a, Shi-Yong Fan a, Wei-Guo Shi a, and Bo-Hua Zhong a,* a
Beijing Institute of Pharmacology & Toxicology, 27th Taiping Road, Beijing 100850, China
A R T IC LE IN F O
A B S TR A C T
Article history: Received Revised Accepted Available online
Three series of apigenin derivatives have been prepared by coupling the carboxyl alkyl group to 4'-, 5- or 7- hydroxyl groups of apigenin respectively. Preliminary biological evaluation in vitro revealed that xanthine oxidase inhibitory activity was improved by modifications at 4'-position and decreased by similar modifications at 5-, 7- positions while α-glucosidase inhibitory activity was maintained by modifications at 5-, 7- positions but lost by modifications at 4'-position. Administration (i.p.) of 7e markedly lowered serum uric acid levels in pota ssium oxonate induced hyperuricemic mouse model and administration (p.o.) of 11d or 11e effectively suppressed the elevation of serum glucose in the oral sucrose tolerance test in mice, while apigenin were not significantly effective in both tests.
Keywords: Apigenin Xanthine Oxidase α-glucosidase Gout Diabetes
2009 Elsevier Ltd. All rights reserved.
——— *
Corresponding author. Tel.: +86-10-66931639; fax: +86-10-66931639; e-mail: [email protected] (B-H Zhong)
Apigenin, 5,7-dihydroxy-2-(4-hydroxyphenyl) -4H-1-benzopyran-4-one, is one of the most investigated flavonoids. It belongs to a less-toxic and non-mutagenic flavone subclass of flavonoids and is abundantly present in human diet including in a variety of fruits and vegetables.1 Various beneficial effects of apigenin, such as antiinflammatory activity, antioxidative activity, as well as anticancer activity, have been well documented.2-4 Apigenin has been reported as a potent competitive inhibitor of xanthine oxidase (XO) and showed inhibitory activity comparable to that of allopurinol.5 Structure-based molecular modeling of six flavonoids with xanthine oxidase inhibitory activity revealed that apigenin was the most potent inhibitor which displayed the most favorable interaction in the reactive site of xanthine oxidase.6 Oral administration of apigenin or its 4'-methyl ether derivative acacetin (Figure 1) was able to elicit hypouricemic actions in hyperuricemic mice or rat induced by potassium oxonate. 7, 8 Apigenin was found to be a strong α–glucosidase (AG) inhibitor as well. 9 In streptozotocin (STZ) –induced diabetic rats, apigenin not only significantly lowered the blood glucose level and improved glucose tolerance, but also effectively protected the liver and kidney against STZ-induced damage.10 However, as is the case with most flavonoids, the clinical utility of apigenin is limited due to its low solubility in both water and lipid, which results in relatively low oral bioavailability.11-13 Various derivatives of flavonoids have been prepared to improve their biological activity or bioavailability. 14-19
Carboxyl group is one of the most common chemical groups that is presented in a variety of drugs, such as xanthine oxidase inhibitors (Febuxostat), Non-steroidal anti-inflammatory drugs (Indomethacin), cholesterol-lowering drug (Gemfibrozil). As an amphipathic group, the introduction of carboxyl group in molecules can improve the solubility in both water and lipid. In the present study, three series of apigenin derivatives have been prepared by coupling the carboxyl alkyl groups to 4’-, 5- or 7- hydroxyl groups of apigenin respectively in attempt to obtain novel derivatives of apigenin with improved phamocokinetic properties or biological activities. The purpose of introducing the sole carboxyalkyl group into apigenin is to
Figure 1. Chemical structures of apigenin and acacetin
retain the skeletal structures of flavonoids in a maximum extent to maintain the antioxidant activity, and to estimate the respective effect of each hydroxyl group over XO and AG. There are 3 hydroxyl groups with different reactivity in apigenin. As the 7-OH is the most reactive in the electrophilic substitution reaction, 7-subsituted derivatives of apigenin were conveniently prepared by reaction of bromoalkyl carboxylates with apigenin followed by hydrolysis of the carboxylates. The 4’-subsituted derivatives were prepared by 4 steps: reaction of apigenin with chloromethyl methyl ether gave the 7-OH protected derivative 4, bromoalkyl carboxylates were reacted with the 4’-OH of 4 selectively to give 5a-f, deprotection of 5af in HCl gave 6a-f, 7a-f were obtained by hydrolysis. The 5subsituted derivatives were prepared as follows: protection of both 7- and 4’-OH was realized by reaction of apigenin with 2 equivalent of bromomethyl methyl ether, the 7- and 4’-OH protected derivative 8 was then coupled with bromoalkyl carboxylates to give 5-substitued alkyl carboxylates 9a-f, deprotection of 9a-f in HCl product 10a-f, 11a-f were prepared by hydrolysis.20 Both xanthine oxidase and α-glucosidase inhibitory activity were evaluated. XO and AG inhibition assays were performed spectrophotometrically according to those described in the literature.9, 21 The results are summarized in Table 1. The activities of the apigenin derivatives are highly related to the site of the substitution. XO inhibitory activity was improved three- to thirty-fold (IC50 = 0.098-0.82µM) modifications at 4'-position but lost by similar modifications at 5-, 7- positions (IC50 > 100µM) while AG inhibitory activity was maintained (IC50 = 18.31-112.7µM) by modifications at 5-, 7- positions but lost by modifications at 4'-position (IC50 > 500µM ).
Scheme 1. Synthetic scheme for generating apigenin derivatives. Reagents and conditions: (a) Br(CH2)nCOOCH2CH3 , (n=1, 3, 4, 5, 6, 7), K2 CO3, DMF, 80 o C, 51-65%; (b) chloromethyl methyl ether, K2CO3, DMF, 0 oC, 51%; (c) bromomethyl methyl ether, N,N-Diisopropylethylamine, DMF, rt, 51%; (d) Br(CH2)nCOOCH2CH3 , (n=1, 3, 4, 5, 6, 7), DMF,120 oC, 65-78%; (e) 2N HCl, MeOH, reflux, 88-95%; (f) K2CO3 , H2 O/MeOH, reflux, 89-96%.
Table 1. Inhibitory activity of apigenin derivatives against XO and AG in vitro
a
b
Compound
R1
R2
R3
3a 3b 3c 3d 3e 3f 7a 7b 7c 7d 7e 7f 11a 11b 11c 11d 11e 11f Apigenin Allopurinol Acarbose
-CH2 COOH -(CH2 )3COOH -(CH2 )4COOH -(CH2 )5COOH -(CH2 )6COOH -(CH2 )7COOH -H -H -H -H -H -H -H -H -H -H -H -H -H — —
-H -H -H -H -H -H -CH2 COOH -(CH2 )3COOH -(CH2 )4COOH -(CH2 )5COOH -(CH2 )6COOH -(CH2 )7COOH -H -H -H -H -H -H -H — —
-H -H -H -H -H -H -H -H -H -H -H -H -CH2 COOH -(CH2 )3COOH -(CH2 )4COOH -(CH2 )5COOH -(CH2 )6COOH -(CH2 )7COOH -H — —
IC50a, b (uM) XO >100 >100 >100 >100 >100 >100 0.82 0.60 0.22 0.32 0.098 0.25 >100 >100 >100 >100 >100 >100 3.2 2.9 —
AG 61.21 44.46 33.7 101.2 90.39 18.31 >500 >500 >500 >500 >500 >500 112.7 35.86 39.04 26.15 51.43 >500 24.3 — 222.3
Concentration required to inhibit 50% of enzyme activity under the assay conditions Values represent the mean of three experiments.
Introduction of a carboxyl alkyl group into apigenin resulted in the elevated inhibitory activity against XO in vitro. Structureactivity relationship study revealed the carboxylate group in febuxostat and Y-700 is the most tightly bound part of the inhibitor molecules, suggesting that the carboxylate group is necessary for the non-purine XO inhibitors.22, 23 Thus, the introduction of a carboxyl alkyl group into 4’-OH of apigenin may also enhance its binding with XO and increase the XO inhibitory activity.
Figure 2. Effect of i.p. administration of allopurinol, apigenin and 7e on serum levels of uric acid in mice pretreated with potassium oxonate (PO) (300 mg/kg, i.p.). Control: PO; Allopurinol: PO+allopurinol (10 mg/kg, i.p.); Apigenin: PO+apigenin (10 mg/kg, i.p.); 7e: PO+7e (10 mg/kg, i.p.). Data are expressed as means±S.E. (n = 8) *p < 0.05 relative to the control group. # p < 0.05, ###p < 0.001 relative to the normal group.
7e was further evaluated for its hypouricemic effects in vivo. Intraperitoneal (i.p.) injection of potassium oxonate to mice led to a marked elevation of serum uric acid level which was maintained throughout the experiment. As shown in Figure 2, at doses of 10 mg/kg (i.p.), compound 7e and allopurinol significantly decreased the serum uric acid levels in hyperuricemic mice while the effects of apigenin was not significant.
Figure 3. Blood glucose response during OSTT in normoglycaemic mice treated with apigenin and its derivatives. Control: vehicle+sucrose; Acarbose: acarbose+sucrose; Apigenin: apigenin +sucrose; 3f: 3f+sucrose; 11c: 11c+sucrose; 11d: 11d+sucrose; 11e: 11e+ sucrose. Data are expressed as means±S.E. (n = 8) *p < 0.05, *** p < 0.001 relative to the control group.
Compounds 3f and 11c-e were tested using acute hypoglycemic as well as oral glucose and sucrose tolerance tests (OGTT and OSTT, respectively). In both tests, blood glucose levels increased after oral loading of glucose or sucrose. In the oral sucrose tolerance test, the treatments orally of 11d or 11e provoked significant decrease of the elevation of the postprandial blood glucose levels of the mice, while 3f, 11c and apigenin showed no significant effects (Figure 3). In contrast, all of the tested compounds exhibited little effect on the blood glucose levels of the mice in OGTT (data not shown). These results revealed that compounds 11d and 11e lowed the postprandial blood glucose levels by inhibition of the hydrolysis of disaccharide rather than glucose absorption in the small intestine.
10.
Though compound 7e showed much more potent XO inhibitory activity than allopurinol and compounds 11d-e displayed more potent AG inhibitory activity than acarbose in vitro, but the hypouricemic effects of 7e in vivo was lower than that of allopurinol and the hypoglycemic effects of 11d-e in vivo was weaker than that of acarbose. It might be due to the poor bioavailability or short half-life of the target compounds in vivo.
19.
In summary, three series of apigenin derivatives were prepared by coupling the carboxyl alkyl groups to 4’-, 5- or 7hydroxyl groups by a site specific strategy. Preliminary biological evaluation in vitro revealed that the XO and AG inhibitory activity of the apigenin derivatives are highly site specific. The 4'-carboxyalkyl ethers are potent xanthine oxidase inhibitors, while the 5- or 7- substituted derivatives exhibited much more potent AG inhibitory activity than that of the 4’substituted ones (IC50 > 500µM). Further in vivo evaluation revealed that administration (i.p.) of 7e markedly lowered serum uric acid levels in potassium oxonate induced hyperuricemic mouse model and administration (p.o.) of 11d and 11e effectively suppressed the elevation of serum glucose in the oral sucrose tolerance test in mice, while apigenin was not significantly effective in both tests.
Acknowledgments This work was supported by the National Key New Drug Creation Program (No 2012ZX09301003-001-004).
Supplementary Material Supplementary data associated (detailed experimental procedures for the synthesis, pharmacological investigation and the spectral datum of the target compounds) with this article can be found.
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Rauter, A. P.; Martins, A.; Borges, C.; Mota-Filipe, H.; Pinto, R.; Sepodes, B.; Justino, J. Phytother. Res. 2010, 24, S133. Block, M.J. Chemcycolpedia 2001, 19,106. Zhang, J.; Liu, D.; Huang, Y.; Gao, Y.; Qian, S. Int. J. Pharm. 2012, 436, 311. Zhang, L.; Zuo, Z.; Lin, G. Mol Pharm. 2007, 4, 833. Kim, M.K.; Park, K.S.; Lee, C.; Park, H.R.; Choo, H.; Chong, Y. J. Med. Chem. 2010, 53, 8597. Wen, X.; Walle, T. Drug Metab. Dispos. 2006, 34, 1786. Shin, J. S.; Kim, K. S.; Kim, M. B.; Jeong, J. H.; Kim, B. K. Bioorg. Med. Chem. Lett. 1999, 9, 869. Hakamata, W.; Nakanishi, I.; Masuda, Y.; Shimizu, T.; Higuchi, H.; Nakamura, Y.; Saito, S.; Urano, S.; Oku, T.; Ozawa, T.; Ikota, N.; Miyata, N.; Okuda, H.; Fukuhara, K. J. Am. Chem. Soc. 2006, 128, 6524. Wang, Q. Q.; Cheng, N.; Yi, W. B.; Peng, S. M.; Zou, X. Q. Bioorg. Med. Chem. 2014, 22, 1515. Zhang, B.; Chen, T.; Chen, Z.; Wang, M.; Zheng, D.; Wu, J.; Jiang, X.; Li, X. Bioorg. Med. Chem. Lett. 2012, 22, 7194. All the new compounds were well characterized by high resolution mass spectrum and 1H-NMR analysis. 3a: 1 H-NMR(400 MHz, DMSO-d6): δ=4.82 (2H, s), 6.37 (1H, d, J=2.24Hz), 6.77 (1H, d, J=2.24Hz), 6.87 (1H, s), 6.93 (2H, d, J=8.96Hz), 7.97 (2H, d, J=8.96Hz), 10.47(1H, s),12.97ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C17H13 O7 : 329.0583, found: 329.0659. 3b: 1H-NMR(400 MHz, DMSO-d6): δ=1.97 (3H, t), 2.41 (2H, t), 4.11(2H, t), 6.37(1H, d, J=2.24Hz), 6.79(1H, d, J=2.24Hz), 6.87(1H, s), 6.95(2H, d, J=8.96Hz), 7.97 (2H, d, J=8.96Hz), 10.44 (1H, s), 12.19(1H, s), 12.95ppm (1H, s); HRMS-ESI: m/z[M-H]calculated for C19 H15 O7 : 355.0896, found: 355.0797. 3c: 1H-NMR(400 MHz, DMSO-d6): δ=1.65-1.76(4H, m), 2.16(2H, m), 2.29 (2H, t), 4.10(2H, t), 6.37(1H, d, J=2.24Hz), 6.78(1H, d, J=2.24Hz), 6.87(1H, s), 6.94(2H, d, J=8.96Hz), 7.97 (2H, d, J=8.96Hz), 12.95ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C20H17 O7 : 369.1053, found: 369.0972. 3d: 1 H-NMR(400 MHz, DMSO-d6 ): δ=1.40-1.46 (2H, m), 1.54-1.59 (2H,m), 1.72-1.76 (2H, m), 2.25 (2H, t), 4.08 (2H, t), 6.34 (1H, d, J=2.24Hz), 6.76 (1H, s), 6.85 (1H, d, J=2.24Hz), 6.96 (2H, d, J=8.96Hz), 7.95 (2H, d, J=8.96Hz), 10.54 (1H, s), 12.06 (1H, s), 12.93ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C21H21O7 : 385.1209, found: 385.1282. 3e: 1H-NMR(400 MHz, DMSO-d6): δ=1.34-1.50 (2H, m), 1.52-1.56 (2H,m), 1.73-1.77 (2H, m), 2.22 (2H, t), 4.08 (2H, t), 6.35 (1H, d, J=2.24Hz), 6.77 (1H, s), 6.86 (1H, d, J=2.24Hz), 6.94 (2H, d, J=8.96Hz), 7.98 (2H, d, J=8.96Hz), 10.40 (1H, s), 12.01 (1H, s), 12.95ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C22 H23O7 : 399.1366, found: 399.1443. 3f: 1 H-NMR(400 MHz, DMSO-d6 ): δ=1.23-1.41 (6H, m), 1.47-1.52 (2H, m), 1.71-1.76 (2H, m), 2.22 (2H, t), 4.08(2H, t), 6.35(1H, d, J=2.24Hz), 6.77(1H, s), 6.85(1H, d, J=2.24Hz), 6.93(2H, d, J=8.96Hz), 7.96 (2H, d, J=8.96Hz), 10.40 (1H, s), 12.01 (1H, s), 12.95ppm (1H, s) HRMS-ESI: m/z[M+H]calculated for C23 H25O7 : 413.1522, found: 413.1593. 7a: 1H-NMR(400 MHz, DMSO-d6): δ=4.82(2H, s), 6.20 (1H, d, J=2.24Hz), 6.51 (1H, d, J=2.24Hz), 6.89 (1H, s), 7.10(2H, d, J=8.96Hz), 8.03(2H, d, J=8.96Hz), 10.88 (1H, s), 12.92(1H, s), 13.15ppm (1H, s); HRMS-ESI: m/z[M+H]calculated for C17 H13O7 : 329.0583, found: 329.0657. 7b: 1H-NMR(400 MHz, DMSO-d6): δ=1.95-1.99(2H, m), 2.41(2H, t), 4.10(2H,t), 6.20 (1H, d, J=2.24Hz), 6.51 (1H, d, J=2.24Hz), 6.88 (1H, s), 7.11(2H, d, J=8.96Hz), 8.03(2H, d, J=8.96Hz), 10.87 (1H, s), 12.19(1H, s), 12.93ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C19H15O7 : 355.0896, found: 355.0827. 7c: 1H-NMR(400 MHz, DMSO-d6): δ=1.64-1.68(2H, m), 1.74-1.78(2H, m), 2.30(2H, t), 4.09(2H, t), 6.20 (1H, d, J=2.24Hz), 6.51 (1H, d, J=2.24Hz), 6.88 (1H, s), 7.11(2H, d, J=8.96Hz), 8.03(2H, d, J=8.96Hz), 10.87 (1H, s), 12.00(1H, s), 12.94ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C20H17O7 : 369.1053, found: 369.0973. 7d: 1H-NMR(400 MHz, DMSO-d6): δ=1.37-1.41(2H, m), 1.51-1.55(2H, m), 1.69-1.73(2H, m), 2.20(2H, t), 4.03(2H, t), 6.16 (1H, d, J=2.24Hz), 6.47 (1H, d, J=2.24Hz), 6.84 (1H, s), 7.06(2H, d, J=8.96Hz), 7.98(2H, d, J=8.96Hz), 10.89 (1H, s), 11.97(1H, s), 12.90ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C21H19 O7 : 383.1209, found: 383.1138. 7e: 1H-NMR(400 MHz, DMSOd6): δ=1.29-1.35(2H, m), 1.36-1.40(2H, m), 1.46-1.50(2H, m), 1.681.69(2H, m), 2.18(2H, t), 4.03(2H, t), 6.16 (1H, d, J=2.24Hz), 6.47 (1H, d, J=2.24Hz), 6.83 (1H, s), 7.06(2H, d, J=8.96Hz), 7.98(2H, d, J=8.96Hz), 10.81 (1H, s), 11.99(1H, s), 12.90ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C22 H21O7 : 397.1366, found: 397.1295. 7f: 1 HNMR(400 MHz, DMSO-d6): δ=1.25-1.31(4H, m), 1.33-1.38(2H, m), 1.43-1.49(2H, m), 1.66-1.72(2H, m), 2.17(2H, t), 4.03(2H, s), 6.16(1H, d, J=2.24Hz), 6.47(1H, d, J=2.24Hz), 6.83(1H, s), 7.06(2H, d, J=8.96Hz), 7.99(2H, d, J=8.96Hz), 10.85(1H, s), 11.97(1H, s), 12.91ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C23H25O7 : 413.1522, found: 413.1598. 11a: 1 H-NMR(400 MHz, DMSO-d6): δ=4.77 (2H, s), 6.29(1H, d, J=2.24Hz), 6.60(1H, s), 6.61(1H, d,
21. 22. 23.
J=2.24Hz), 6.91(2H, d, J=8.96Hz), 7.87 (2H, d, J=8.96Hz), 10.27 (1H, s), 10.83ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C17 H11O7 : 327.0583, found: 327.0499. 11b: 1 H-NMR(400 MHz, DMSO-d6): δ=1.95-1.98(2H, m), 2.56(2H, t), 4.00 (2H, t), 6.35(1H, d, J=2.24Hz), 6.49(1H, s), 6.53(1H, d, J=2.24Hz), 6.91(2H, d, J=8.96Hz), 7.84 (2H, d, J=8.96Hz), 10.23 (1H, s), 10.70ppm (1H, s); HRMS-ESI: m/z[M+H]calculated for C19H17O7 : 357.0896, found: 357.0962. 11c: 1H-NMR(400 MHz, DMSO-d6): δ=1.74-1.77(4H, m), 2.34(2H, t), 4.00 (2H, t), 6.37(1H, d, J=2.24Hz), 6.49(1H, s), 6.53(1H, d, J=2.24Hz), 6.92(2H, d, J=8.96Hz), 7.85 (2H, d, J=8.96Hz), 10.24 (1H, s), 10.71ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C20H19O7 : 371.1053, found: 371.1128. 11d: 1 H-NMR(400 MHz, DMSO-d6): δ=1.46-1.54(2H, m), 1.56-1.64(2H, m), 1.72-1.78(2H, m), 2.33(2H, t), 3.96(2H, t), 6.35(1H, d, J=2.24Hz), 6.48(1H, s), 6.51(1H, d, J=2.24Hz), 6.90(2H, d, J=8.96Hz), 7.84 (2H, d, J=8.96Hz), 10.22 (1H, s), 10.67ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C21H21O7 : 385.1209, found: 385.1282. 11e: 1 H-NMR(400 MHz, DMSO-d6): δ=1.32-1.37(4H, m), 1.46-1.59(4H, m), 1.72-1.75(2H, m), 2.32(2H, t), 3.96(2H, t), 6.36(1H, d, J=2.24Hz), 6.49(1H, s), 6.51(1H, d, J=2.24Hz), 6.90(2H, d, J=8.96Hz), 7.83 (2H, d, J=8.96Hz), 10.27 (1H, s), 10.69ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C22H23O7 : 399.1366, found: 399.1436. 11f: 1H-NMR(400 MHz, DMSO-d6): δ=1.23-1.37(2H, m), 1.45-1.55(2H, m), 1.70-1.77(2H, m), 2.20(2H, t), 3.96(2H, t), 6.34(1H, d, J=2.24Hz), 6.48(1H, s), 6.50(1H, d, J=2.24Hz), 6.90(2H, d, J=8.96Hz), 7.83 (2H, d, J=8.96Hz), 10.20 (1H, s), 10.64(1H, s), 11.96ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C23H23 O7 : 411.1522, found: 411.1442. Noro, T.; Oda, Y.; Miyase, T.; Ueno, A.; Fukushima, S. Chem. Pharm. Bull. 1983, 31, 3984. Okamoto, K.; Eger, B.T.; Nishino, T.; Kondo, S.; Pai, E.F.; Nishino, T. J. Biol. Chem. 2003, 278, 1848. Fukunari, A.; Okamoto, K.; Nishino, T.; Eger, B.T.; Pai, E.F.; Kamezawa, M.; Yamada, I.; Kato, N. J. Pharmacol. Exp. Ther. 2004, 311, 519.
Graphical Abstract
Discovery of apigenin derivatives as inhibitors of xanthine oxidase and/or α-glucosidase
Leave this area blank for abstract info.
Zhuo-Ran Su a, Shi-Yong Fan a, Wei-Guo Shi a, and Bo-Hua Zhong a,*
S0960-894X(15)00466-7 http://dx.doi.org/10.1016/j.bmcl.2015.05.016 BMCL 22706
To appear in:
Bioorganic & Medicinal Chemistry Letters
Received Date: Revised Date: Accepted Date:
8 March 2015 2 May 2015 7 May 2015
Please cite this article as: Su, Z-R., Fan, S-Y., Shi, W-G., Zhong, B-H., Discovery of xanthine oxidase inhibitors and/or α-glucosidase inhibitors by carboxyalkyl derivatization based on the flavonoid of apigenin, Bioorganic & Medicinal Chemistry Letters (2015), doi: http://dx.doi.org/10.1016/j.bmcl.2015.05.016
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Bioorganic & Medicinal Chemistry Letters j o ur n al h om e p a g e : w w w . e l s e v i er . c o m
Discovery of xanthine oxidase inhibitors and/or α-glucosidase inhibitors by carboxyalkyl derivatization based on the flavonoid of apigenin. Zhuo-Ran Su a, Shi-Yong Fan a, Wei-Guo Shi a, and Bo-Hua Zhong a,* a
Beijing Institute of Pharmacology & Toxicology, 27th Taiping Road, Beijing 100850, China
A R T IC LE IN F O
A B S TR A C T
Article history: Received Revised Accepted Available online
Three series of apigenin derivatives have been prepared by coupling the carboxyl alkyl group to 4'-, 5- or 7- hydroxyl groups of apigenin respectively. Preliminary biological evaluation in vitro revealed that xanthine oxidase inhibitory activity was improved by modifications at 4'-position and decreased by similar modifications at 5-, 7- positions while α-glucosidase inhibitory activity was maintained by modifications at 5-, 7- positions but lost by modifications at 4'-position. Administration (i.p.) of 7e markedly lowered serum uric acid levels in pota ssium oxonate induced hyperuricemic mouse model and administration (p.o.) of 11d or 11e effectively suppressed the elevation of serum glucose in the oral sucrose tolerance test in mice, while apigenin were not significantly effective in both tests.
Keywords: Apigenin Xanthine Oxidase α-glucosidase Gout Diabetes
2009 Elsevier Ltd. All rights reserved.
——— *
Corresponding author. Tel.: +86-10-66931639; fax: +86-10-66931639; e-mail: [email protected] (B-H Zhong)
Apigenin, 5,7-dihydroxy-2-(4-hydroxyphenyl) -4H-1-benzopyran-4-one, is one of the most investigated flavonoids. It belongs to a less-toxic and non-mutagenic flavone subclass of flavonoids and is abundantly present in human diet including in a variety of fruits and vegetables.1 Various beneficial effects of apigenin, such as antiinflammatory activity, antioxidative activity, as well as anticancer activity, have been well documented.2-4 Apigenin has been reported as a potent competitive inhibitor of xanthine oxidase (XO) and showed inhibitory activity comparable to that of allopurinol.5 Structure-based molecular modeling of six flavonoids with xanthine oxidase inhibitory activity revealed that apigenin was the most potent inhibitor which displayed the most favorable interaction in the reactive site of xanthine oxidase.6 Oral administration of apigenin or its 4'-methyl ether derivative acacetin (Figure 1) was able to elicit hypouricemic actions in hyperuricemic mice or rat induced by potassium oxonate. 7, 8 Apigenin was found to be a strong α–glucosidase (AG) inhibitor as well. 9 In streptozotocin (STZ) –induced diabetic rats, apigenin not only significantly lowered the blood glucose level and improved glucose tolerance, but also effectively protected the liver and kidney against STZ-induced damage.10 However, as is the case with most flavonoids, the clinical utility of apigenin is limited due to its low solubility in both water and lipid, which results in relatively low oral bioavailability.11-13 Various derivatives of flavonoids have been prepared to improve their biological activity or bioavailability. 14-19
Carboxyl group is one of the most common chemical groups that is presented in a variety of drugs, such as xanthine oxidase inhibitors (Febuxostat), Non-steroidal anti-inflammatory drugs (Indomethacin), cholesterol-lowering drug (Gemfibrozil). As an amphipathic group, the introduction of carboxyl group in molecules can improve the solubility in both water and lipid. In the present study, three series of apigenin derivatives have been prepared by coupling the carboxyl alkyl groups to 4’-, 5- or 7- hydroxyl groups of apigenin respectively in attempt to obtain novel derivatives of apigenin with improved phamocokinetic properties or biological activities. The purpose of introducing the sole carboxyalkyl group into apigenin is to
Figure 1. Chemical structures of apigenin and acacetin
retain the skeletal structures of flavonoids in a maximum extent to maintain the antioxidant activity, and to estimate the respective effect of each hydroxyl group over XO and AG. There are 3 hydroxyl groups with different reactivity in apigenin. As the 7-OH is the most reactive in the electrophilic substitution reaction, 7-subsituted derivatives of apigenin were conveniently prepared by reaction of bromoalkyl carboxylates with apigenin followed by hydrolysis of the carboxylates. The 4’-subsituted derivatives were prepared by 4 steps: reaction of apigenin with chloromethyl methyl ether gave the 7-OH protected derivative 4, bromoalkyl carboxylates were reacted with the 4’-OH of 4 selectively to give 5a-f, deprotection of 5af in HCl gave 6a-f, 7a-f were obtained by hydrolysis. The 5subsituted derivatives were prepared as follows: protection of both 7- and 4’-OH was realized by reaction of apigenin with 2 equivalent of bromomethyl methyl ether, the 7- and 4’-OH protected derivative 8 was then coupled with bromoalkyl carboxylates to give 5-substitued alkyl carboxylates 9a-f, deprotection of 9a-f in HCl product 10a-f, 11a-f were prepared by hydrolysis.20 Both xanthine oxidase and α-glucosidase inhibitory activity were evaluated. XO and AG inhibition assays were performed spectrophotometrically according to those described in the literature.9, 21 The results are summarized in Table 1. The activities of the apigenin derivatives are highly related to the site of the substitution. XO inhibitory activity was improved three- to thirty-fold (IC50 = 0.098-0.82µM) modifications at 4'-position but lost by similar modifications at 5-, 7- positions (IC50 > 100µM) while AG inhibitory activity was maintained (IC50 = 18.31-112.7µM) by modifications at 5-, 7- positions but lost by modifications at 4'-position (IC50 > 500µM ).
Scheme 1. Synthetic scheme for generating apigenin derivatives. Reagents and conditions: (a) Br(CH2)nCOOCH2CH3 , (n=1, 3, 4, 5, 6, 7), K2 CO3, DMF, 80 o C, 51-65%; (b) chloromethyl methyl ether, K2CO3, DMF, 0 oC, 51%; (c) bromomethyl methyl ether, N,N-Diisopropylethylamine, DMF, rt, 51%; (d) Br(CH2)nCOOCH2CH3 , (n=1, 3, 4, 5, 6, 7), DMF,120 oC, 65-78%; (e) 2N HCl, MeOH, reflux, 88-95%; (f) K2CO3 , H2 O/MeOH, reflux, 89-96%.
Table 1. Inhibitory activity of apigenin derivatives against XO and AG in vitro
a
b
Compound
R1
R2
R3
3a 3b 3c 3d 3e 3f 7a 7b 7c 7d 7e 7f 11a 11b 11c 11d 11e 11f Apigenin Allopurinol Acarbose
-CH2 COOH -(CH2 )3COOH -(CH2 )4COOH -(CH2 )5COOH -(CH2 )6COOH -(CH2 )7COOH -H -H -H -H -H -H -H -H -H -H -H -H -H — —
-H -H -H -H -H -H -CH2 COOH -(CH2 )3COOH -(CH2 )4COOH -(CH2 )5COOH -(CH2 )6COOH -(CH2 )7COOH -H -H -H -H -H -H -H — —
-H -H -H -H -H -H -H -H -H -H -H -H -CH2 COOH -(CH2 )3COOH -(CH2 )4COOH -(CH2 )5COOH -(CH2 )6COOH -(CH2 )7COOH -H — —
IC50a, b (uM) XO >100 >100 >100 >100 >100 >100 0.82 0.60 0.22 0.32 0.098 0.25 >100 >100 >100 >100 >100 >100 3.2 2.9 —
AG 61.21 44.46 33.7 101.2 90.39 18.31 >500 >500 >500 >500 >500 >500 112.7 35.86 39.04 26.15 51.43 >500 24.3 — 222.3
Concentration required to inhibit 50% of enzyme activity under the assay conditions Values represent the mean of three experiments.
Introduction of a carboxyl alkyl group into apigenin resulted in the elevated inhibitory activity against XO in vitro. Structureactivity relationship study revealed the carboxylate group in febuxostat and Y-700 is the most tightly bound part of the inhibitor molecules, suggesting that the carboxylate group is necessary for the non-purine XO inhibitors.22, 23 Thus, the introduction of a carboxyl alkyl group into 4’-OH of apigenin may also enhance its binding with XO and increase the XO inhibitory activity.
Figure 2. Effect of i.p. administration of allopurinol, apigenin and 7e on serum levels of uric acid in mice pretreated with potassium oxonate (PO) (300 mg/kg, i.p.). Control: PO; Allopurinol: PO+allopurinol (10 mg/kg, i.p.); Apigenin: PO+apigenin (10 mg/kg, i.p.); 7e: PO+7e (10 mg/kg, i.p.). Data are expressed as means±S.E. (n = 8) *p < 0.05 relative to the control group. # p < 0.05, ###p < 0.001 relative to the normal group.
7e was further evaluated for its hypouricemic effects in vivo. Intraperitoneal (i.p.) injection of potassium oxonate to mice led to a marked elevation of serum uric acid level which was maintained throughout the experiment. As shown in Figure 2, at doses of 10 mg/kg (i.p.), compound 7e and allopurinol significantly decreased the serum uric acid levels in hyperuricemic mice while the effects of apigenin was not significant.
Figure 3. Blood glucose response during OSTT in normoglycaemic mice treated with apigenin and its derivatives. Control: vehicle+sucrose; Acarbose: acarbose+sucrose; Apigenin: apigenin +sucrose; 3f: 3f+sucrose; 11c: 11c+sucrose; 11d: 11d+sucrose; 11e: 11e+ sucrose. Data are expressed as means±S.E. (n = 8) *p < 0.05, *** p < 0.001 relative to the control group.
Compounds 3f and 11c-e were tested using acute hypoglycemic as well as oral glucose and sucrose tolerance tests (OGTT and OSTT, respectively). In both tests, blood glucose levels increased after oral loading of glucose or sucrose. In the oral sucrose tolerance test, the treatments orally of 11d or 11e provoked significant decrease of the elevation of the postprandial blood glucose levels of the mice, while 3f, 11c and apigenin showed no significant effects (Figure 3). In contrast, all of the tested compounds exhibited little effect on the blood glucose levels of the mice in OGTT (data not shown). These results revealed that compounds 11d and 11e lowed the postprandial blood glucose levels by inhibition of the hydrolysis of disaccharide rather than glucose absorption in the small intestine.
10.
Though compound 7e showed much more potent XO inhibitory activity than allopurinol and compounds 11d-e displayed more potent AG inhibitory activity than acarbose in vitro, but the hypouricemic effects of 7e in vivo was lower than that of allopurinol and the hypoglycemic effects of 11d-e in vivo was weaker than that of acarbose. It might be due to the poor bioavailability or short half-life of the target compounds in vivo.
19.
In summary, three series of apigenin derivatives were prepared by coupling the carboxyl alkyl groups to 4’-, 5- or 7hydroxyl groups by a site specific strategy. Preliminary biological evaluation in vitro revealed that the XO and AG inhibitory activity of the apigenin derivatives are highly site specific. The 4'-carboxyalkyl ethers are potent xanthine oxidase inhibitors, while the 5- or 7- substituted derivatives exhibited much more potent AG inhibitory activity than that of the 4’substituted ones (IC50 > 500µM). Further in vivo evaluation revealed that administration (i.p.) of 7e markedly lowered serum uric acid levels in potassium oxonate induced hyperuricemic mouse model and administration (p.o.) of 11d and 11e effectively suppressed the elevation of serum glucose in the oral sucrose tolerance test in mice, while apigenin was not significantly effective in both tests.
Acknowledgments This work was supported by the National Key New Drug Creation Program (No 2012ZX09301003-001-004).
Supplementary Material Supplementary data associated (detailed experimental procedures for the synthesis, pharmacological investigation and the spectral datum of the target compounds) with this article can be found.
References and notes 1. 2. 3. 4. 5. 6. 7. 8.
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Rauter, A. P.; Martins, A.; Borges, C.; Mota-Filipe, H.; Pinto, R.; Sepodes, B.; Justino, J. Phytother. Res. 2010, 24, S133. Block, M.J. Chemcycolpedia 2001, 19,106. Zhang, J.; Liu, D.; Huang, Y.; Gao, Y.; Qian, S. Int. J. Pharm. 2012, 436, 311. Zhang, L.; Zuo, Z.; Lin, G. Mol Pharm. 2007, 4, 833. Kim, M.K.; Park, K.S.; Lee, C.; Park, H.R.; Choo, H.; Chong, Y. J. Med. Chem. 2010, 53, 8597. Wen, X.; Walle, T. Drug Metab. Dispos. 2006, 34, 1786. Shin, J. S.; Kim, K. S.; Kim, M. B.; Jeong, J. H.; Kim, B. K. Bioorg. Med. Chem. Lett. 1999, 9, 869. Hakamata, W.; Nakanishi, I.; Masuda, Y.; Shimizu, T.; Higuchi, H.; Nakamura, Y.; Saito, S.; Urano, S.; Oku, T.; Ozawa, T.; Ikota, N.; Miyata, N.; Okuda, H.; Fukuhara, K. J. Am. Chem. Soc. 2006, 128, 6524. Wang, Q. Q.; Cheng, N.; Yi, W. B.; Peng, S. M.; Zou, X. Q. Bioorg. Med. Chem. 2014, 22, 1515. Zhang, B.; Chen, T.; Chen, Z.; Wang, M.; Zheng, D.; Wu, J.; Jiang, X.; Li, X. Bioorg. Med. Chem. Lett. 2012, 22, 7194. All the new compounds were well characterized by high resolution mass spectrum and 1H-NMR analysis. 3a: 1 H-NMR(400 MHz, DMSO-d6): δ=4.82 (2H, s), 6.37 (1H, d, J=2.24Hz), 6.77 (1H, d, J=2.24Hz), 6.87 (1H, s), 6.93 (2H, d, J=8.96Hz), 7.97 (2H, d, J=8.96Hz), 10.47(1H, s),12.97ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C17H13 O7 : 329.0583, found: 329.0659. 3b: 1H-NMR(400 MHz, DMSO-d6): δ=1.97 (3H, t), 2.41 (2H, t), 4.11(2H, t), 6.37(1H, d, J=2.24Hz), 6.79(1H, d, J=2.24Hz), 6.87(1H, s), 6.95(2H, d, J=8.96Hz), 7.97 (2H, d, J=8.96Hz), 10.44 (1H, s), 12.19(1H, s), 12.95ppm (1H, s); HRMS-ESI: m/z[M-H]calculated for C19 H15 O7 : 355.0896, found: 355.0797. 3c: 1H-NMR(400 MHz, DMSO-d6): δ=1.65-1.76(4H, m), 2.16(2H, m), 2.29 (2H, t), 4.10(2H, t), 6.37(1H, d, J=2.24Hz), 6.78(1H, d, J=2.24Hz), 6.87(1H, s), 6.94(2H, d, J=8.96Hz), 7.97 (2H, d, J=8.96Hz), 12.95ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C20H17 O7 : 369.1053, found: 369.0972. 3d: 1 H-NMR(400 MHz, DMSO-d6 ): δ=1.40-1.46 (2H, m), 1.54-1.59 (2H,m), 1.72-1.76 (2H, m), 2.25 (2H, t), 4.08 (2H, t), 6.34 (1H, d, J=2.24Hz), 6.76 (1H, s), 6.85 (1H, d, J=2.24Hz), 6.96 (2H, d, J=8.96Hz), 7.95 (2H, d, J=8.96Hz), 10.54 (1H, s), 12.06 (1H, s), 12.93ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C21H21O7 : 385.1209, found: 385.1282. 3e: 1H-NMR(400 MHz, DMSO-d6): δ=1.34-1.50 (2H, m), 1.52-1.56 (2H,m), 1.73-1.77 (2H, m), 2.22 (2H, t), 4.08 (2H, t), 6.35 (1H, d, J=2.24Hz), 6.77 (1H, s), 6.86 (1H, d, J=2.24Hz), 6.94 (2H, d, J=8.96Hz), 7.98 (2H, d, J=8.96Hz), 10.40 (1H, s), 12.01 (1H, s), 12.95ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C22 H23O7 : 399.1366, found: 399.1443. 3f: 1 H-NMR(400 MHz, DMSO-d6 ): δ=1.23-1.41 (6H, m), 1.47-1.52 (2H, m), 1.71-1.76 (2H, m), 2.22 (2H, t), 4.08(2H, t), 6.35(1H, d, J=2.24Hz), 6.77(1H, s), 6.85(1H, d, J=2.24Hz), 6.93(2H, d, J=8.96Hz), 7.96 (2H, d, J=8.96Hz), 10.40 (1H, s), 12.01 (1H, s), 12.95ppm (1H, s) HRMS-ESI: m/z[M+H]calculated for C23 H25O7 : 413.1522, found: 413.1593. 7a: 1H-NMR(400 MHz, DMSO-d6): δ=4.82(2H, s), 6.20 (1H, d, J=2.24Hz), 6.51 (1H, d, J=2.24Hz), 6.89 (1H, s), 7.10(2H, d, J=8.96Hz), 8.03(2H, d, J=8.96Hz), 10.88 (1H, s), 12.92(1H, s), 13.15ppm (1H, s); HRMS-ESI: m/z[M+H]calculated for C17 H13O7 : 329.0583, found: 329.0657. 7b: 1H-NMR(400 MHz, DMSO-d6): δ=1.95-1.99(2H, m), 2.41(2H, t), 4.10(2H,t), 6.20 (1H, d, J=2.24Hz), 6.51 (1H, d, J=2.24Hz), 6.88 (1H, s), 7.11(2H, d, J=8.96Hz), 8.03(2H, d, J=8.96Hz), 10.87 (1H, s), 12.19(1H, s), 12.93ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C19H15O7 : 355.0896, found: 355.0827. 7c: 1H-NMR(400 MHz, DMSO-d6): δ=1.64-1.68(2H, m), 1.74-1.78(2H, m), 2.30(2H, t), 4.09(2H, t), 6.20 (1H, d, J=2.24Hz), 6.51 (1H, d, J=2.24Hz), 6.88 (1H, s), 7.11(2H, d, J=8.96Hz), 8.03(2H, d, J=8.96Hz), 10.87 (1H, s), 12.00(1H, s), 12.94ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C20H17O7 : 369.1053, found: 369.0973. 7d: 1H-NMR(400 MHz, DMSO-d6): δ=1.37-1.41(2H, m), 1.51-1.55(2H, m), 1.69-1.73(2H, m), 2.20(2H, t), 4.03(2H, t), 6.16 (1H, d, J=2.24Hz), 6.47 (1H, d, J=2.24Hz), 6.84 (1H, s), 7.06(2H, d, J=8.96Hz), 7.98(2H, d, J=8.96Hz), 10.89 (1H, s), 11.97(1H, s), 12.90ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C21H19 O7 : 383.1209, found: 383.1138. 7e: 1H-NMR(400 MHz, DMSOd6): δ=1.29-1.35(2H, m), 1.36-1.40(2H, m), 1.46-1.50(2H, m), 1.681.69(2H, m), 2.18(2H, t), 4.03(2H, t), 6.16 (1H, d, J=2.24Hz), 6.47 (1H, d, J=2.24Hz), 6.83 (1H, s), 7.06(2H, d, J=8.96Hz), 7.98(2H, d, J=8.96Hz), 10.81 (1H, s), 11.99(1H, s), 12.90ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C22 H21O7 : 397.1366, found: 397.1295. 7f: 1 HNMR(400 MHz, DMSO-d6): δ=1.25-1.31(4H, m), 1.33-1.38(2H, m), 1.43-1.49(2H, m), 1.66-1.72(2H, m), 2.17(2H, t), 4.03(2H, s), 6.16(1H, d, J=2.24Hz), 6.47(1H, d, J=2.24Hz), 6.83(1H, s), 7.06(2H, d, J=8.96Hz), 7.99(2H, d, J=8.96Hz), 10.85(1H, s), 11.97(1H, s), 12.91ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C23H25O7 : 413.1522, found: 413.1598. 11a: 1 H-NMR(400 MHz, DMSO-d6): δ=4.77 (2H, s), 6.29(1H, d, J=2.24Hz), 6.60(1H, s), 6.61(1H, d,
21. 22. 23.
J=2.24Hz), 6.91(2H, d, J=8.96Hz), 7.87 (2H, d, J=8.96Hz), 10.27 (1H, s), 10.83ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C17 H11O7 : 327.0583, found: 327.0499. 11b: 1 H-NMR(400 MHz, DMSO-d6): δ=1.95-1.98(2H, m), 2.56(2H, t), 4.00 (2H, t), 6.35(1H, d, J=2.24Hz), 6.49(1H, s), 6.53(1H, d, J=2.24Hz), 6.91(2H, d, J=8.96Hz), 7.84 (2H, d, J=8.96Hz), 10.23 (1H, s), 10.70ppm (1H, s); HRMS-ESI: m/z[M+H]calculated for C19H17O7 : 357.0896, found: 357.0962. 11c: 1H-NMR(400 MHz, DMSO-d6): δ=1.74-1.77(4H, m), 2.34(2H, t), 4.00 (2H, t), 6.37(1H, d, J=2.24Hz), 6.49(1H, s), 6.53(1H, d, J=2.24Hz), 6.92(2H, d, J=8.96Hz), 7.85 (2H, d, J=8.96Hz), 10.24 (1H, s), 10.71ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C20H19O7 : 371.1053, found: 371.1128. 11d: 1 H-NMR(400 MHz, DMSO-d6): δ=1.46-1.54(2H, m), 1.56-1.64(2H, m), 1.72-1.78(2H, m), 2.33(2H, t), 3.96(2H, t), 6.35(1H, d, J=2.24Hz), 6.48(1H, s), 6.51(1H, d, J=2.24Hz), 6.90(2H, d, J=8.96Hz), 7.84 (2H, d, J=8.96Hz), 10.22 (1H, s), 10.67ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C21H21O7 : 385.1209, found: 385.1282. 11e: 1 H-NMR(400 MHz, DMSO-d6): δ=1.32-1.37(4H, m), 1.46-1.59(4H, m), 1.72-1.75(2H, m), 2.32(2H, t), 3.96(2H, t), 6.36(1H, d, J=2.24Hz), 6.49(1H, s), 6.51(1H, d, J=2.24Hz), 6.90(2H, d, J=8.96Hz), 7.83 (2H, d, J=8.96Hz), 10.27 (1H, s), 10.69ppm (1H, s); HRMS-ESI: m/z[M+H]-calculated for C22H23O7 : 399.1366, found: 399.1436. 11f: 1H-NMR(400 MHz, DMSO-d6): δ=1.23-1.37(2H, m), 1.45-1.55(2H, m), 1.70-1.77(2H, m), 2.20(2H, t), 3.96(2H, t), 6.34(1H, d, J=2.24Hz), 6.48(1H, s), 6.50(1H, d, J=2.24Hz), 6.90(2H, d, J=8.96Hz), 7.83 (2H, d, J=8.96Hz), 10.20 (1H, s), 10.64(1H, s), 11.96ppm (1H, s); HRMS-ESI: m/z[M-H]-calculated for C23H23 O7 : 411.1522, found: 411.1442. Noro, T.; Oda, Y.; Miyase, T.; Ueno, A.; Fukushima, S. Chem. Pharm. Bull. 1983, 31, 3984. Okamoto, K.; Eger, B.T.; Nishino, T.; Kondo, S.; Pai, E.F.; Nishino, T. J. Biol. Chem. 2003, 278, 1848. Fukunari, A.; Okamoto, K.; Nishino, T.; Eger, B.T.; Pai, E.F.; Kamezawa, M.; Yamada, I.; Kato, N. J. Pharmacol. Exp. Ther. 2004, 311, 519.
Graphical Abstract
Discovery of apigenin derivatives as inhibitors of xanthine oxidase and/or α-glucosidase
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Zhuo-Ran Su a, Shi-Yong Fan a, Wei-Guo Shi a, and Bo-Hua Zhong a,*
