Synthesis and antidiabetic activity of 5,7-dihydroxyflavonoids and analogs

Article abstract of DOI:10.1002/cbdv.201100049

In a study to evaluate the structural elements essential for the antidiabetic activity of flavonoids, we synthesized two series of flavonoids, 5,7-dihydroxyflavanones and 5,7-dihydroxyflavones. In a screening for potential antidiabetic activity, most of the flavonoids showed a remarkable in vitro activity, and compounds 1f, 2d, and 3c were significantly more effective than the positive control, metformin. The biological activity was mainly affected by structural modification at the ring B moiety of the flavonoid skeleton. The results suggest that 5,7-dihydroxyflavonoids can be considered as promising candidates in the development of new antidiabetic lead compounds. Copyright

Full text of DOI:10.1002/cbdv.201100049

162
CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
Synthesis and Antidiabetic Activity of 5,7-Dihydroxyflavonoids and Analogs
by Liu-Shuan Changa), Chun-Bao Lib), Nan Qina), Mei-Na Jina), and Hong-Quan Duan*a)
a) School of Pharmaceutical Sciences, Research Center of Basic Medical Sciences, Tianjin Medical
University, Tianjin 300070, P. R. China
(phone: þ86-22-23542018; fax: þ86-22-23542775; e-mail: duanhq@tijmu.edu.cn)
b) School of Science, Tianjin University, Tianjin 300072, P. R. China
(phone: þ86-22-27892351; fax: þ86-22-27403475; e-mail: lichunbao@tju.edu.cn)
In a study to evaluate the structural elements essential for the antidiabetic activity of flavonoids, we
synthesized two series of flavonoids, 5,7-dihydroxyflavanones and 5,7-dihydroxyflavones. In a screening
for potential antidiabetic activity, most of the flavonoids showed a remarkable in vitro activity, and
compounds 1f, 2d, and 3c were significantly more effective than the positive control, metformin. The
biological activity was mainly affected by structural modification at the ring B moiety of the flavonoid
skeleton. The results suggest that 5,7-dihydroxyflavonoids can be considered as promising candidates in
the development of new antidiabetic lead compounds.
Introduction. – Diabetes mellitus is a metabolic alteration characterized by
hyperglycemia resulting from defects in insulin secretion, action, or both, currently
affecting ca. 3% of the world population [1]. Noninsulin-dependent diabetes mellitus
(type II diabetes, T2D) is a heterogeneous disease characterized by hyperglycemia,
which is caused by a disorder of insulin secretion, insulin resistance (IR) in target
tissues, and activation of the hepatic glucose production pathway in the liver [2][3].
The key treatment strategy is keeping patient blood glucose within normal levels. So
far, several drugs have been developed to control T2D. They can be divided into the
hypoglycemic (sulfonylureas) and anti-hyperglycemic ones (biguanides, a-glucosidase
inhibitors, and thiazolidine-diones). Because the mechanism of diabetes mellitus is
quite complex, many currently available synthetic chemical antidiabetic agents have
low rates of response and remission, and even severe adverse-effects. Accordingly, it is
necessary to search for and develop more effective hypoglycemic agents with lower
adverse-effect [4].
In recent years, herbal products have started to gain importance as a source of
antidiabetic medicines. Several antidiabetic flavonoids, such as hesperidin and naringin
[5], myricetin [6], quercetin [7], and kaempferol 3,7-dirhamnoside (¼ kaempferitrin)
[8], have been reported. In this article, we describe the synthesis of 5,7-dihydroxy-
flavanone and 5,7-dihydroxyflavone derivatives, as well as their potential antidiabetic
activities.
Results and Discussion.–1. Synthesis. In an effort to define the structural elements
essential to the antidiabetic activity, we prepared two series of flavonoids, i.e., eight 5,7-
dihydroxyflavanones, 1a–1h, and nine 5,7-dihydroxyflavones, 2a–2d, 3a–3c, 4a, and
ꢀ 2012 Verlag Helvetica Chimica Acta AG, Zꢁrich

CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
163
4b. In these series, the substitution pattern at ring B of the flavonoids was modified to
investigate structureꢀbioactivity relationships.
5,7-Dihydroxyflavanones 1a–1h, including the new compound 1g, were synthesized
as racemic compounds in four steps following the procedure described in [9], starting
from 2,4,6-trihydroxyacetophenone (¼1-(2,4,6-trihydroxyphenyl)ethanone; 5), in 21–
46% yield (Scheme 1).
Scheme 1. Synthesis of 5,7-Dihydroxyflavanones 1a–1h
a) ClCH2OMe, K2CO3, acetone, reflux. b) R1ꢀCHO, MeOH, NaOH (60% aq.). c) AcONa, EtOH, H2O,
reflux. d) MeOH, 3m HCl, reflux.
5,7-Dihydroxyflavones 2a–2d, including the new compound 2d, were synthesized
according to [10] in two steps, starting from 5, in 23–52% yield (Scheme 2).
Scheme 2. Synthesis of 5,7-Dihydroxyflavones 2a–2d
a) RCOCl, K2CO3 (aq.), triethylbenzylammonium chloride (TEBA), benzene, 608. b) K2CO3 (5% aq.),
reflux.
5,7-Dihydroxyflavones 3a–3c were synthesized from 5, as outlined in Scheme 3.
After the peracylation of 5, 10a–10c were treated with KOH in pyridine at 508 to afford

164
CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
11a–11c, which then were treated with 5% aq. K2CO3 at reflux to yield 3a–3c in 12–
20% yield. In the literature, compounds 11a–11c were synthesized using K2CO3 in
pyridine [11], which failed in our cases.
Scheme 3. Synthesis of 5,7-Dihydroxyflavones 3a–3c
a) RCOCl, pyridine, r.t. b) KOH, pyridine, 508. c) K2CO3 (5% aq.), reflux.
A new 5,7-dihydroxyflavone 4a and a know compound 4b were synthesized in two
steps [12] starting from chalcone derivatives 7g and 7h in 4 and 12% yield, respectively
(Scheme 4).
Scheme 4. Synthesis of 5,7-Dihydroxyflavones 4a and 4b
a) I2, pyridine, reflux. b) MeOH, 3m HCl, reflux.
2. Biological Activities. We tested the in vitro activities of the compounds in insulin-
resistant (IR) HepG2 cells according to a well-established procedure [13][14]. Most of
the compounds showed a remarkable potential antidiabetic activity in vitro [15], and
compounds 1f, 2d, and 3c appeared significantly more effective than the positive
control, metformin (Table).

CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
165
Table. EC50 Data for the Synthesized Flavonoids Compared with the Positive Control Metformin
R (ring B)
Flavanones (C(2)ꢀC(3))
Flavones (C(2)¼C(3))
Compound
EC50 [mm]
Compound
EC50 [mm]
Ph
1a
1b
1c
1d
1e
1f
1g
1h
0.880ꢁ0.045
0.340ꢁ0.032
1.280ꢁ0.079
0.540ꢁ0.038
0.340ꢁ0.022
0.034ꢁ0.004
0.290ꢁ0.021
0.480ꢁ0.031
2a
3a
2b
3b
2c
3c
4a
4b
2d
1.566ꢁ0.102
1.250ꢁ0.062
4-MeꢀC6H4
4-CF3ꢀC6H4
3,4-Cl2ꢀC6H3
Thiophen-2-yl
Furan-2-yl
3-Cl,4-HOꢀC6H3
4-HO,3-MeOꢀC6H3
4-NCꢀC6H4
Metformina)
>10
0.320ꢁ0.023
2.310ꢁ0.175
0.083ꢁ0.007
0.430ꢁ0.037
0.590ꢁ0.052
0.170ꢁ0.011
0.270ꢁ0.018
a) Positive control.
3. Discussion. Insulin resistance in liver cells principally causes impaired glycogen
synthesis and fails to suppress glucose production, which is the major contribution to
hyperglycemia [16]. HepG2 Cells are hepatocellular carcinoma cells and have been
proven to be valuable in investigating liver-derived functions. They maintain most
functions of liver and are steady through many passages [17][18]. A number of
research groups have used HepG2 cells to investigate T2D via an insulin-resistant
model [19–21].
So far, many anti-diabetic flavonoids have been reported [5][22–24], such as
myricetin with insulinomimetic effects [6], quercetin with antidiabetic effects in
streptozotocin-induced diabetic rats [7], and kaempferol 3,7-dirhamnoside with
hypoglycemic and antioxidant effects [8][25]. However, the above-mentioned
flavonoids had weak activity, as high doses were necessary to observe the desired
effects, in comparison with market drugs. We synthesized two series of flavonoid
derivatives, which revealed for the first time significant anti-diabetic activities
compared with the market drug metformin. Furthermore, by considering the action
of flavonoid analogs in the AMPK (¼ 5’-AMP-activated protein kinase) signal
transduction pathway [26], we expect that 5,7-dihydroxyflavonoid derivatives could
activate AMPK activity, reduce acetyl-CoA carboxylase activity, and enhance glucose
consumption in insulin resistance HepG2 cells. The results suggest that flavonoid
derivatives can be considered as promising candidates in the development of a new
antidiabetic lead compound.
Conclusions. – Alteration of the 5,7-dihydroxyflavone skeleton at ring B, leads to a
smaller activity when OH substitutents are lacking, but to a rise in activity, when ring B
is replaced by a heterocycle, especially by a furan group. With the identical ring B
alteration, flavanone analogs have better antidiabetic activity than the flavone analogs,

166
CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
which could be possibly attributed to the stereochemical difference between the
saturated ring C of the flavanones and the unsaturated one of the flavones. However,
naturally occurring flavanones are enantiomerically pure compounds, racemic com-
pounds 1a–1h should be further investigated concerning the relationship of the
stereogenic center C(2) with its activity.
The results suggest that 5,7-dihydroxyflavonoids can be considered as promising
candidates in the development of new antidiabetic lead compounds.
This work was supported by the National Nature Science Foundation of China (No. 30772635).
Experimental Part
General. All reagents and solvents were obtained from commercial suppliers. The reagents were
used as received. Solvents were routinely distilled prior to use. Isolation and purification of the
compounds were performed by flash column chromatography (FC) on silica gel 60 (SiO2; 200–300
mesh). IR Spectra: Bio-Rad Excalibur FTS3000 spectrometer (4000–400 cmꢀ1) in KBr. 1H- and
13C-NMR spectra: Bruker AV-400 instrument in (D6)DMSO; chemical shifts in ppm with TMS as the
internal standard. LR-MS: Agilent 6310 Ion Trap.
General Procedure for the Preparation of 1a–1h. See [9].
(ꢁ)-2,3-Dihydro-5,7-dihydroxy-2-phenyl-4H-1-benzopyran-4-one (1a) [9]. FC (petroleum ether
(PE)/AcOEt 10 :1). Yield: 38%.
(ꢁ)-2,3-Dihydro-5,7-dihydroxy-2-(4-methylphenyl)-4H-1-benzopyran-4-one (1b) [9]. FC (PE/
AcOEt 8 :1). Yield: 36%.
(ꢁ)-2,3-Dihydro-5,7-dihydroxy-2-[4-(trifluoromethyl)phenyl]-4H-1-benzopyran-4-one (1c) [9]. FC
(PE/AcOEt 8 :1). Yield: 46%.
(ꢁ)-2-(3,4-Dichlorophenyl)-2,3-dihydro-5,7-dihydroxy-4H-1-benzopyran-4-one (1d) [9]. FC (PE/
AcOEt 8 :1). Yield: 44%. IR: 3148, 3057, 2895, 2763, 2621, 1637, 1597, 1493, 1472, 1402, 1343, 1309, 1089,
1
821, 763, 530. H-NMR (400 MHz, (D6)DMSO): 2.81 (d, J ¼ 16.5, 1 H of CH2(3)); 3.24 (dd, J ¼ 16.5,
12.0, 1 H of CH2(3)); 5.61 (d, J ¼ 12.0, HꢀC(2)); 5.90 (s, HꢀC(6)); 5.94 (s, HꢀC(8)); 7.51 (d, J ¼ 7.5,
HꢀC(6’)); 7.69 (d, J ¼ 7.5, HꢀC(5’)); 7.79 (s, HꢀC(2’)); 10.86 (s, HOꢀC(7)); 12.07 (s, HOꢀC(5)).
13C-NMR (100 MHz, (D6)DMSO): 42.3 (C(3)); 77.5 (C(2)); 95.6 (C(8)); 96.6 (C(6)); 102.2 (C(4a)); 127.4
(C(6’)); 129.2 (C(2’)); 131.3 (C(5’)); 131.6 (C(4’)); 131.8 (C(3’)); 140.2 (C(1’)); 162.8 (C(8a)); 163.9
(C(5)); 167.3 (C(7)); 195.9 (C(4)). ESI-MS: 323 ([MꢀH]ꢀ ).
(ꢁ)-2,3-Dihydro-5,7-dihydroxy-2-(thiophen-2-yl)-4H-1-benzopyran-4-one (1e) [9]. FC (PE/AcOEt
6 :1). Yield: 22%.
(ꢁ)-2-(Furan-2-yl)-2,3-dihydro-5,7-dihydroxy-4H-1-benzopyran-4-one (1f) [9]. FC (PE/AcOEt
6 :1). Yield: 25%.
(ꢁ)-2-(3-Chloro-4-hydroxyphenyl)-2,3-dihydro-5,7-dihydroxy-4H-1-benzopyran-4-one (1g) [9]. FC
(PE/AcOEt 4 :1). Yield: 24%. IR: 3440, 3144, 1647, 1516, 1461, 1428, 1400, 1347, 1291, 1227, 1163, 1089,
1
1061, 979, 824. H-NMR (400 MHz, (D6)DMSO): 2.71 (dd, J ¼ 17.2, 2.8, 1 H of CH2(3)); 3.31 (dd, J ¼
17.2, 13.2, 1 H of CH2(3)); 5.47 (dd, J ¼ 13.2, 2.8, HꢀC(2)); 5.90 (s, HꢀC(6)); 5.91 (s, HꢀC(8)); 7.01 (d,
J ¼ 8.4, HꢀC(6’)); 7.29 (d, J ¼ 8.4, HꢀC(5’)); 7.51 (s, HꢀC(2’)); 10.38 (s, HOꢀC(4’)); 10.82 (s, HOꢀC(7));
12.13 (s, HOꢀC(5)). 13C-NMR (100 MHz, (D6)DMSO): 42.3 (C(3)); 78.2 (C(2)); 95.5 (C(8)); 96.4
(C(6)); 102.2 (C(4a)); 117.0 (C(5’)); 120.0 (C(3’)); 127.2 (C(1’)); 129.0 (C(6’)); 130.8 (C(2’)); 153.8
(C(4’)); 163.2 (C(8a)); 164.0 (C(5)); 167.1 (C(7)); 196.6 (C(4)). ESI-MS: 305 ([MꢀH]ꢀ ).
(ꢁ)-2,3-Dihydro-5,7-dihydroxy-2-(4-hydroxy-3-methoxyphenyl)-4H-1-benzopyran-4-one (1h) [27].
FC (PE/AcOEt 4 :1). Yield: 21%.
General Procedure for the Preparation of 2a–2d. See [10].
Chrysin (¼ 5,7-Dihydroxy-2-phenyl-4H-1-benzopyran-4-one; 2a) [28]. FC (PE/AcOEt 4 :1). Yield:
48%.
5,7-Dihydroxy-2-[4-(trifluoromethyl)phenyl]-4H-1-benzopyran-4-one (2b). FC (PE/AcOEt 4 :1).
Yield: 52%. IR: 3393, 3087, 2953, 1746, 1653, 1615, 1581, 1500, 1428, 1326, 1270, 1168, 1023, 907, 844.

CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
167
1H-NMR (400 MHz, (D6)DMSO): 6.21 (d, J ¼ 2.0, HꢀC(6)); 6.51 (d, J ¼ 2.0, HꢀC(8)); 7.08 (s, HꢀC(3));
7.89 (d, J ¼ 9.0, HꢀC(2’), HꢀC(6’)); 8.25 (d, J ¼ 8.5, HꢀC(3’), HꢀC(5’)); 11.00 (s, HOꢀC(7)); 12.68 (s,
HOꢀC(5)). 13C-NMR (100 MHz, (D6)DMSO): 94.7 (C(8)); 99.6 (C(6)); 104.6 (C(3)); 107.2 (C(4a));
126.4 (C(3’), C(5’)); 126.6 (CF3(4’)); 127.7 (C(2’), C(6’)); 131.9 (C(4’)); 135.1 (C(1’)); 157.9 (C(8a)); 161.8
(C(5)); 161.9 (C(2)); 165.1 (C(7)); 182.2 (C(4)). ESI-MS: 321 ([MꢀH]ꢀ ).
5,7-Dihydroxy-2-(thiophen-2-yl)-4H-1-benzopyran-4-one (2c). FC (PE/AcOEt 6 :1). Yield: 41%.
IR: 3437, 3100, 1655, 1624, 1582, 1515, 1470, 1421, 1391, 1358, 1305, 1278, 1165, 1116, 1028, 956, 823.
1H-NMR (400 MHz, (D6)DMSO): 6.19 (d, J ¼ 2.0, HꢀC(6)); 6.41 (d, J ¼ 2.0, HꢀC(8)); 6.84 (s, HꢀC(3));
7.28 (m, HꢀC(4’)); 7.98 (m, HꢀC(5’)); 8.03 (m, HꢀC(3’)); 10.89 (s, HOꢀC(7)); 12.82 (s, HOꢀC(5)).
13C-NMR (100 MHz, (D6)DMSO): 94.9 (C(8)); 100.0 (C(6)); 104.4 (C(3)); 104.8 (C(4a)); 130.0 (C(3’));
130.9 (C(5’)); 133.1 (C(4’); 134.7 (C(1’)); 158.0 (C(8a)); 160.1 (C(5)); 162.5 (C(2)); 165.3 (C(7)); 182.3
(C(4)). ESI-MS: 259 ([MꢀH]ꢀ ).
4-(5,7-Dihydroxy-4-oxo-4H-1-benzopyran-2-yl)benzonitrile (2d). FC (PE/AcOEt 6 :1). Yield: 23%.
IR: 3409, 3078, 2238, 1662, 1631, 1590, 1512, 1455, 1424, 1367, 1279, 1161, 1118, 1027, 907, 844. 1H-NMR
(400 MHz, (D6)DMSO): 6.22 (d, J ¼ 1.5, HꢀC(6)); 6.54 (s, HꢀC(8)); 7.15 (s, HꢀC(3)); 8.04 (d, J ¼ 8.5,
HꢀC(2’), HꢀC(6’)); 8.24 (d, J ¼ 8.5, HꢀC(3’), HꢀC(5’)); 11.00 (s, HOꢀC(7)); 12.68 (s, HOꢀC(5)).
13C-NMR (100 MHz, (D6)DMSO): 94.7 (C(8)); 99.7 (C(6)); 104.6 (C(3)); 107.5 (C(4a)); 114.4 (C(4’));
118.7 (CN(4’)); 127.5 (C(2’), C(6’)); 133.4 (C(3’), C(5’)); 135.3 (C(1’)); 157.9 (C(8a)); 161.4 (C(5)); 161.9
(C(2)); 165.1 (C(7)); 182.1 (C(4)). ESI-MS: 278 ([MꢀH]ꢀ ).
General Procedure for the Preparation of 3a–3c. Substituted acyl chloride (9.0 mmol) was added to 5
(505.0 mg, 3.0 mmol) in anh. pyridine, and the mixture was stirred at r.t. for 75 min. After addition of ice-
water (5 ml), a precipitate was formed and filtered. Then, the filtrate was washed with H2O, and
evaporated to give 10a–10c, which was treated with KOH (1.008 g, 18.0 mmol) in anh. pyridine at 508 for
1 h. The soln. was adjusted to pH 6 with 2m HCl, then extracted with AcOEt. The org. layer was washed
with H2O, dried (MgSO4), and evaporated to give 11a–11c, which were heated in 5% aq. K2CO3 soln.
(20 ml) at reflux overnight. The soln. was adjusted to pH 6 with 2m HCl, then extracted with AcOEt. The
org. layer was washed with H2O, dried (MgSO4), and evaporated. The residue was purified by FC to give
3a–3c as yellow solids.
5,7-Dihydroxy-2-(4-methylphenyl)-4H-1-benzopyran-4-one (3a) [29]. FC (PE/AcOEt 8 :1). Yield:
12%.
2-(3,4-Dichlorophenyl)-5,7-dihydroxy-4H-1-benzopyran-4-one (3b). FC (PE/AcOEt 8 :1). Yield:
20%. IR: 3428, 3076, 1655, 1624, 1582, 1515, 1470, 1421, 1391, 1358, 1305, 1278, 1165, 1116, 1028, 956, 920,
823. 1H-NMR (400 MHz, (D6)DMSO): 6.22 (d, J ¼ 2.0, HꢀC(6)); 6.57 (d, J ¼ 2.0, HꢀC(8)); 7.12 (s,
HꢀC(3)); 7.84 (d, J ¼ 8.5, HꢀC(6’)); 8.07 (d, J ¼ 8.5, HꢀC(5’)); 8.37 (s, HꢀC(2’)); 10.98 (s, HOꢀC(7));
12.71 (s, HOꢀC(5)). 13C-NMR (100 MHz, (D6)DMSO): 94.8 (C(8)); 99.6 (C(6)); 100.0 (C(3)); 106.8
(C(4a)); 127.0 (C(6’)); 128.7 (C(2’)); 131.8 (C(1’)); 131.9 (C(4’)); 132.7 (C(2’)); 135.1 (C(1’)); 157.9
(C(8a)); 161.1 (C(5)); 161.9 (C(2)); 165.1 (C(7)); 182.3 (C(4)). ESI-MS: 321 ([MꢀH]ꢀ ).
2-(Furan-2-yl)-5,7-dihydroxy-4H-1-benzopyran-4-one (3c). FC (PE/AcOEt 6 :1). Yield: 14%. IR:
1
3423, 3127, 1653, 1626, 1598, 1513, 1470, 1430, 1360, 1278, 1251, 1166, 1110, 1016. H-NMR (400 MHz,
(D6)DMSO): 6.19 (s, HꢀC(6)); 6.41 (s, HꢀC(8)); 6.57 (s, HꢀC(4’)); 6.80 (s, HꢀC(3)); 7.44 (d, J ¼ 1.5,
HꢀC(5’)); 8.05 (s, HꢀC(3’)); 10.93 (s, HOꢀC(7)); 12.79 (s, HOꢀC(5)). 13C-NMR (100 MHz,
(D6)DMSO): 94.5 (C(8)); 99.6 (C(6)); 103.2 (C(3)); 104.4 (C(4a)); 113.6 (C(4’)); 115.1 (C(5’)); 145.5
(C(3’)); 147.9 (C(1’)); 155.5 (C(8a)); 157.4 (C(5)); 162.0 (C(2)); 164.9 (C(7)); 181.6 (C(4)). ESI-MS: 243
([MꢀH]ꢀ ).
General Procedure for the Preparation of 4a and 4b. I2 (0.69 mmol) was added to a mixture of 7g or 7h
(0.69 mmol) in anh. pyridine (6 ml) and heated at reflux for 24 h. Then, the mixture was cooled to r.t. and
partitioned between AcOEt (40 ml) and sat. brine (40 ml). The org. layer was dried (MgSO4), and then
evaporated to afford 12a or 12b, resp., which was then treaded with 3m HCl (2 ml) in MeOH (6 ml) at
reflux for 1.5 h. H2O (20 ml) was added, and the soln. was extracted with AcOEt. The org. layer was
washed with H2O and brine, dried (MgSO4), and evaporated. The residue was purified by FC to give 4a
or 4b, resp., each as a yellow solid.
2-(3-Chloro-4-hydroxyphenyl)-5,7-dihydroxy-4H-1-benzopyran-4-one (4a). FC (PE/AcOEt 4 :1).
Yield: 4%. IR: 3321, 3092, 2929, 2753, 2707, 2629, 1727, 1649, 1613, 1507, 1403, 1353, 1251, 1159, 1032, 839,

168
CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
814, 735. 1H-NMR (400 MHz, (D6)DMSO): 6.21 (d, J ¼ 2.0, HꢀC(6)); 6.53 (d, J ¼ 2.0, HꢀC(8)); 6.89 (s,
HꢀC(3)); 7.11 (d, J ¼ 8.6, HꢀC(5’)); 7.90 (dd, J ¼ 2.2, 8.6, HꢀC(6’)); 8.10 (d, J ¼ 2.2, HꢀC(2’)); 10.88 (s,
HOꢀC(7)); 11.17 (s, HOꢀC(4’)); 12.90 (s, HOꢀC(5)). 13C-NMR (100 MHz, (D6)DMSO): 94.6 (C(8));
99.4 (C(6)); 104.2 (C(3)); 117.4 (C(4a)); 121.1 (C(5’)); 122.9 (C(3’)); 127.3 (C(1’)); 128.7 (C(6’)); 129.1
(C(2’)); 157.0 (C(4’)); 157.8 (C(8a)); 161.9 (C(5)); 162.7 (C(2)); 164.7 (C(7)); 182.2 (C(4)). ESI-MS: 303
([MꢀH]ꢀ ).
5,7-Dihydroxy-2-(4-hydroxy-3-methoxyphenyl)-4H-1-benzopyran-4-one (4b) [30]. FC (PE/AcOEt
8 :1). Yield: 12%.
General Procedure for the Bioassay. HepG2 Cells were cultured in high-glucose Dulbeccoꢂs modified
eagle serum (DMEM) supplemented with 10% fetal bovine serum (FBS). After confluence, cells were
cultured in 96-well cluster plates in high-glucose DMEM supplemented with 10% FBS for 24 h, and then
the cells were treated with 10ꢀ7 m insulin for 36 h in serum-free and phenol red-free high-glucose
DMEM. After 36 h high concentration insulin stimulated, the cells were washed with pH¼4 high-glucose
DMEM for four times and phosphate buffered saline for two times, then added in serum-free and phenol
red-free high-glucose DMEM with the test compounds in different concentrations and incubated for
24 h. Then, the glucose content in the culture medium was measured by a glucose assay kit to study the
effect of insulin resistance HepG2 on glucose consumption. The enhancement ratio of glucose
consumption (GC) was calculated as follows: GC [%]¼(drug group of GCꢀmodel group of GC)/model
group of GCꢂ100. The potencies of the products, expressed as median effective concentration (EC50)
values, are collected.
REFERENCES
[1] J. P. Boyle, A. A. Honeycutt, K. M. V. Narayan, T. J. Hoerger, L. S. Geiss, H. Chen, T. J. Thompson,
Diabetes Care 2001, 24, 1936.
[2] R. A. DeFronzo, R. C. Bonadonna, E. Ferrannini, Diabetes Care 1992, 15, 318.
[3] W. T. Cefalu, Exp. Biol. Med. 2001, 226, 13.
[4] J.-E. Sun, Z.-H. Ao, Z.-M. Lu, H.-Y. Xu, X.-M. Zhang, W.-F. Dou, Z.-H Xu, J. Ethnopharmacol.
2008, 118, 7.
[5] U. J. Jung, M.-K. Lee, Y.-B. Park, M. A. Kang, M.-S. Choi, Int. J. Biochem. Cell Biol. 2006, 38, 1134.
[6] K. C. Ong, H. E. Khoo, Biochem. Pharmacol. 1996, 51, 423.
[7] M. Vessal, M. Hemmati, M. Vasei, Comp. Biochem. Physiol., C 2003, 135, 357.
[8] E. de Sousa, L. Zanatta, I. Seifriz, T. B. Creczynski-Pasa, M. G. Pizzolatti, B. Szpoganicz, F. R. M. B.
Silva, J. Nat. Prod. 2004, 67, 829.
[9] Y. Duan, Y. Qi, Z. Ji, G. Fang, Y. Cheng, S. Wu, Chin. J. Med. Chem. 2006, 16, 342.
[10] S. Saxena, J. K. Makrandi, S. K. Grover, Synthesis 1985, 697.
[11] D. C. G. A. Pinto, A. M. S. Silva, J. A. S. Cavaleiro, Synlett 2007, 1897.
[12] Y.-C. Wu, A.-S. Lin, K.-H. Lee, F.-R. Chang, U.S. Pat. US 2009/0054516 (Chem. Abstr. 2009, 150,
268028).
[13] C. G. Li, G. Ning, J. L. Chen, Chin. J. Diabetes 1999, 198.
[14] W.-D. Xie, W. Wang, H. Su, D.-M. Xing, Y. Pan, L.-J. Du, Comp. Biochem. Physiol., C 2006, 143, 429.
[15] H.-Q. Duan, L.-S. Chang, Y.-J. Zhang, N. Qin, M.-N. Jin, Chin. Pat. 201010519266.9, 2010.
[16] B. Kola, A. B. Grossman, M. Korbonits, ꢃObesity and Metabolismꢂ, Front Horm Res., Basel, Karger,
2008, Vol. 36, pp. 198–211.
[17] N. B. Javit, FASEB J. 1990, 4, 161.
[18] D. Gupta, S. Varma, R. L. Khandelwal, J. Cell. Biochem. 2007, 100, 593.
[19] K. Nakamaru, K. Matsumoto, T. Taguchi, M. Suefuji, Y. Murata, M. Igata, J. Kawashima, T. Kondo,
H. Motoshima, K. Tsuruzoe, N. Miyamura, T. Toyonaga, E. Araki, Biochem. Biophys. Res.
Commun. 2005, 328, 449.
[20] C. L. Lin, J. K. Lin, Mol. Nutr. Food Res. 2008, 52, 930.
[21] Z. Luo, Y. Zhang, F. Li, J. He, H. Ding, L. Yan, H. Cheng, Endocrine 2009, 36, 60.

CHEMISTRY & BIODIVERSITY – Vol. 9 (2012)
169
[22] M. Torres-Piedra, R. Ortiz-Andrade, R. Villalobos-Molina, N. Singh, J. L. Medina-Franco, S. P.
´
Webster, M. Binnie, G. Navarrete-Vazquez, S. Estrada-Soto, Eur. J. Med. Chem. 2010, 45, 2606.
[23] A. Kato, N. Nasu, K. Takebayashi, I. Adachi, Y. Miname, F. Sanae, N. Asano, A. A. Watson, R. J.
Nash, J. Agric. Food Chem. 2008, 56, 4469.
[24] M. Yoshikawa, H. Shimada, N. Nishida, Y. Li, I. Toguchida, J. Yamahara, H. Matsuda, Chem.
Pharm. Bull. 1998, 46, 113.
[25] J. Yang, H. Chen, L. Zhang, Q. Wang, M.-X. Lai, Drug Devel. Res. 2010, 71, 127.
[26] D. T. Ha, T. N. Trung, T. T. Phuong, N. Yim, Q. C. Chen, K. H. Bae, Bioorg. Med. Chem. Lett. 2010,
20, 6076.
[27] G. N. Zhang, C. F. Zhang, Z. T. Wang, L. S. Xu, Chin. J. Nat. Med. 2004, 2, 78.
[28] H.-Y. Wang, L.-H. Xiao, L. Liu, S.-X. Xu, J. Shenyang Pharm. Univ. 2003, 20, 339.
[29] T. T. Dao, Y. S. Chi, J. Kim, H. P. Kim, S. Kim, H. Park, Arch. Pharmacal Res. 2003, 26, 345.
[30] P.-F. Zhang, C. Li, China J. Chin. Mater. Med. 2008, 33, 2629.
Received February 11, 2011