Inhibitory effect of chalcones and their derivatives from Glycyrrhiza inflata on protein tyrosine phosphatase 1B

Article abstract of DOI:10.1016/j.bmcl.2009.07.054

Compounds (1-6) isolated from the CH₂Cl₂ extract of Glycyrrhiza inflata and semisynthetic licochalcone A derivatives (7-14) were evaluated for their protein tyrosine phosphatase 1B (PTP1B) inhibitory activities. Licochalcones A (4) a

Full text of DOI:10.1016/j.bmcl.2009.07.054

Bioorganic & Medicinal Chemistry Letters 19 (2009) 5155–5157
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Bioorganic & Medicinal Chemistry Letters
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Inhibitory effect of chalcones and their derivatives from Glycyrrhiza inflata
on protein tyrosine phosphatase 1B
Goo Yoon a, Woojung Lee a, Su-Nam Kim a, Seung Hoon Cheon b,
*
a KIST Gangneung Institute, Gangneung 210-340, Republic of Korea
b College of Pharmacy and Research Institute of Drug Development, Chonnam National University, 300 Yongbong-Dong, Buk-Gu, Gwangju 500-757, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Compounds (1–6) isolated from the CH2Cl2 extract of Glycyrrhiza inflata and semisynthetic licochalcone A
derivatives (7–14) were evaluated for their protein tyrosine phosphatase 1B (PTP1B) inhibitory activities.
Licochalcones A (4) and E (6), each with an allyl group at position 5 in the B ring exhibited significant
inhibitory effects. Licochalcone A derivative 7, the most potent among the series, had an IC50 value of
Received 25 April 2009
Revised 2 July 2009
Accepted 3 July 2009
Available online 24 July 2009
11.7 2.0 lM, ca. twofold better than that of licochalcone A (4).
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Glycyrrhiza inflata
Allyl retrochalcone
Licochalcone A
Semisynthetic
Protein tyrosine phosphatase 1B
Protein tyrosine phosphatase 1B (PTP1B) is an intracellular pro-
tein tyrosine phosphatase that plays a critical role in the negative
regulation of insulin and leptin signaling pathways. Transgenic
mice without PTP1B have enhanced sensitivity to insulin and are
protected against weight gain when fed a high-fat diet. In addition,
antisense-based oligonucleotides targeting PTP1B have shown effi-
cacy in type 2 diabetes and have entered phase 2 clinical trials.1
Thus inhibition of PTP1B has been proposed as a potential thera-
peutic target for drug discovery in the treatment of type 2 diabetes
to avoid the weight gain that occurs with current insulin sensitiz-
cones in particular were reported to exhibit various biological
activities, including antitumor,7,8 antiparasitic,9 antileishmanial,10
antioxidative and superoxide scavenging,11 and antibacterial ef-
fects.12 Here we report they also have PTP1B inhibitory activity
(Fig. 1).
The CH2Cl2 extract of G. inflata was repeatedly subjected to flash
silica gel chromatography and preparative TLC to obtain six known
compounds. By comparison of their spectroscopic data with previ-
ously reported values in the literature, these compounds were con-
firmed as the flavanone, liquiritigenin (1),13 the chalcone,
isoliquiritigenin (2),13 and the retrochalcones, echinatin (3),4 lic-
ochalcone A (4),5,7 licochalcone C (5),5 and licochalcone E (6).6
Compounds 7 and 8 were prepared by direct methylation of lic-
ochalcone A (4) in the presence of sodium hydride in DMSO.14,15
Compounds 9 and 10 were also obtained by direct acetylation of
licochalcone A (4) with acetic anhydride in pyridine. Compounds
11 and 12 were prepared by THP-protection of the 40-hydroxy
group in the A ring followed by methylation or acetylation of the
4-hydroxyl group in the B ring and subsequent cleavage of the
THP-ether under acidic conditions.14 Acetylation of compound 7
and compound 11 with acetic anhydride gave compounds 13 and
14, respectively (Scheme 1).
ers, for example, PPAR
c
activators.2 Although several types of
PTP1B inhibitors have been reported, because of the low selectivity
and poor pharmacokinetic properties, new types of PTP1B inhibi-
tors with improved pharmacological properties are still being
sought.3
While searching for PTP1B inhibitors from natural products, we
found that the CH2Cl2 extract of Glycyrrhiza inflata inhibited PTP1B.
Further investigation of this extract led to the isolation of six com-
pounds (1–6). G. inflata is the main species in Xinjiang licorice. The
representative compound from G. inflata is an isoprenoid-substi-
tuted retrochalcone having reversed A and B rings, licochalcone
A, which is structurally distinguished from normal chalcones by
the lack of oxygen functionalities at C-20 and C-60. Six retrochal-
cones, licochalcones A–E and echinatin, have been isolated and
characterized from the roots of G. inflata.4–7 The allyl retrochal-
The inhibitory activities of the isolated compounds and the semi-
synthetic licochalcone A derivatives against PTP1B were measured
using p-nitrophenyl phosphate (pNPP) as a substrate, and the results
are summarized in Table 1.16,17 The known PTP1B inhibitor, ursolic
acid (IC50 = 3.9 0.3
isolated compounds 4-6, allyl retrochalcones, dose-dependently
lM), was used as the positive control. The
* Corresponding author. Tel.: +82 62 530 2929; fax: +82 62 530 2911.
E-mail address: shcheon@chonnam.ac.kr (S.H. Cheon).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.07.054

5156
G. Yoon et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5155–5157
OH
OH
OH
HO
HO
HO
O
OCH3
O
OH
O
O
3
2
1
OH
OH
5
OH
4
HO
HO
HO
4'
6'
3
1
OCH3
OCH3
OCH3
O
2'
O
O
6
5
4
Figure 1. The structures of flavanone and chalcones from G. inflata.
OR2
OH
OR2
R1O
HO
R1O
e or f
a or b
OCH3
OCH3
OCH3
O
O
O
4
11 R1 = H, R2 = CH3
7
8
R1 = CH3, R2 = H
12 R1 = H, R2 = COCH3
R1 = CH3, R2 = CH3
c or d
c
c
OR2
R1O
OCOCH3
OCH3
OCH3
H3CO
H3COCO
O
OCH3
OCH3
9
10
R1 = COCH3, R2 = H
O
O
R
1 = COCH3, R2 = COCH3
13
14
Scheme 1. The semisynthesis of licochalcone A derivatives. (a) 1.2 equiv CH3I, 1.5 equiv NaOH, DMSO, rt, 40% (7); (b) 2.4 equiv CH3I, 3.0 equiv NaOH, DMSO, rt, 12% (8); (c)
1.2 equiv Ac2O, pyridine, rt, 64% (9), 53% (13), 87% (14); (d) 2.3 equiv Ac2O, pyridine, rt, 77% (10); (e) (1) 3,4-Dihydro-2H-pyran, pyridinium p-toluenesulfonate, CH2Cl2, rt, (2)
CH3I, NaOH, DMSO, rt, (3) 2 M-HCl, 30% (11); (f) (1) 3,4-Dihydro-2H-pyran, pyridinium p-toluenesulfonate, CH2Cl2, rt, (2) Ac2O, pyridine, rt, (3) 2 M-HCl, 31% (12).
Table 1
isoliquiritigenin (2), and the retrochalcone, echinatin (3), which
lacked the allyl group, had no inhibitory effects. Compounds 4 and
Inhibitory activity of compounds 1–14
Compound
PTP1B inhibitory activitya
6, each with a different allyl group at position 5 in the B ring, exhib-
ited greater PTP1B inhibitory activities than compound 5 which has
an allyl group at position 3 in the B ring. These results indicated that
the presence of the allyl group in the B ring may increase PTP1B
inhibitory activity but the degree of activation varies depending on
the configuration and substitution position of the allyl group in the
B ring.16 Thus, a study of the structure–activity relationships and
subsequent optimization of the allyl retrochalcone might enable
development of novel PTP1B inhibitors.
1
2
3
4
5
6
7
8
>50
>50
>50
19.1 0.1
30.9 0.5
20.7 1.8
11.7 2.0
19.8 1.7
19.2 0.1
> 50
9
10
In order to improve its PTP1B inhibitory activity by changing its
physicochemical properties, the 4- and/or 40-hydroxyl group on lic-
ochalcone A was methylated and/or acetylated; the resulting deriv-
atives were then evaluated for their PTP1B inhibitory effects. As
shown in Table 1, the inhibitory effects of the semisynthetic licoch-
alcone A derivatives 7–14 were improved only when the 40-hydroxy
group was methylated. Among the licochalcone A derivatives, com-
pound 7, methylated at the 40-hydroxy position, exhibited the most
11
12
13
14
18.3 1.4
17.3 1.6
19.4 3.5
29.2 2.3
3.9 0.3
Ursolic acidb
a
Results are expressed as IC50 values (
Positive control.
l
M) and as mean SD of three replicates.
b
inhibited PTP1B activity with IC50 values ranging from 19.1 0.1 to
30.9 0.5 M, but the flavanone, liquiritigenin (1), the chalcone,
potent PTP1B inhibitory activity with an IC50 of 11.7 2.0
result indicates that compound 7 is about twofold more effective
lM. This
l

G. Yoon et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5155–5157
5157
10. Nielsen, S. F.; Christensen, S. B.; Cruciani, G.; Kharazmi, A.; Liljefors, T. J. Med.
Chem. 1998, 41, 4819.
11. Haraguchi, H.; Ishikawa, H.; Mizutani, K.; Tamura, Y.; Kinoshita, T. Bioorg. Med.
Chem. 1998, 6, 339.
12. Haraguchi, H.; Tanimoto, K.; Tamura, Y.; Mizutani, K.; Kinoshita, T.
Phytochemistry 1998, 48, 125.
13. Ma, C. J.; Li, G. S.; Zhang, D. L.; Liu, K.; Fan, X. J. Chromatogr., A 2005, 1078, 188.
14. Kromann, H.; Larsen, M.; Boesen, T.; Schønning, K.; Nielsen, S. F. Eur. J. Med.
Chem. 2004, 39, 993.
than licochalcone A. Other modified compounds showed similar or
less inhibitory effect than licochalcone A. PTP1B inhibitory activities
of the isolated compounds (1–6) and the licochalcone A derivatives
(7–14) may provide valuable information regarding the structure–
activity relationships for the development of novel PTP1B inhibitors.
In conclusion, a series of retrochalcones with an allyl group at
position 5 in the B ring significantly inhibited PTP1B. Of the licoch-
alcone A derivatives, compound 7, methylated at the 40-hydroxy
position, exhibited about twofold better activity than licochalcone
A. These results provide a starting point for further optimization of
substituted allyl retrochalcone with an ether linkage at position 40
as a PTP1B inhibitor. Further SAR studies of substituted allyl retr-
ochalcones in PTP1B inhibition are currently undergoing and the
results will be published in due course.
15. 3-[5-(1,1-Dimethylallyl)-4-hydroxy-2-methoxyphenyl]-1-(4-methoxyphenyl)-pro-
penone (7): To a solution of licochalcone A (200 mg, 0.59 mmol) in DMSO
(5 ml) were added methyl iodide (44.2 lL, 0.71 mmol) and NaOH (35.6 mg,
0.89 mmol). The reaction was stirred at rt for 4 h and water was added
(20 ml). The aqueous solution was extracted with ethyl acetate (3 ꢀ 20 ml)
and the combined organic phases were dried (Na2SO4) and evaporated
under reduced pressure. The crude product was purified by flash column
chromatography (n-hexane/EtOAc = 5:1) to give 7 (83.2 mg, 40%) as a yellow
solid. 1H NMR (CDCl3, 500 MHz)
d 8.03 (d, 2H, J = 9.0 Hz), 8.01 (d, 1H,
J = 15.6 Hz), 7.59 (d, 1H, J = 15.5 Hz), 7.48 (s, 1H), 6.98 (d, 2H, J = 9.0 Hz),
6.47 (s, 1H), 6.20 (dd, 1H, J = 17.8, 10.8 Hz), 5.36 (dd, 1H, J = 17.5, 1.0 Hz),
5.34 (dd, 1H, J = 10.5, 1.0 Hz), 3.88 (s, 3H), 3.85 (s, 3H), 1.46 (s, 6H); 13C
Acknowledgment
NMR (CDCl3, 125 MHz)
d 189.9, 163.1, 159.5, 158.3, 147.8, 140.8, 131.7,
130.8, 128.8, 124.7, 120.1, 116.4, 113.73, 113.71, 101.1, 55.6, 55.5, 39.8,
27.1.
This work was supported by a grant from KIST Institutional Pro-
gram (2Z03270).
16. (a) Na, M.; Jang, J.; Njamen, D.; Mbafor, J. T.; Fomum, Z. T.; Kim, B. Y.; Oh, W. K.;
Ahn, J. S. J. Nat. Prod. 2006, 69, 1572; (b) Cui, L.; Ndinteh, D. T.; Na, M.; Thuong,
P. T.; Silike-Muruumu, J.; Njamen, D.; Mbafor, J. T.; Fomum, Z. T.; Ahn, J. S.; Oh,
W. K. J. Nat. Prod. 2007, 70, 1039; (c) Na, M.; Hoang, D. M.; Njamen, D.; Mbafor,
J. T.; Fomum, Z. T.; Thuong, P. T.; Ahn, J. S.; Oh, W. K. Bioorg. Med. Chem. Lett.
2007, 17, 3868; (d) Jang, J.; Na, M.; Thuong, P. T.; Njamen, D.; Mbafor, J. T.;
Fomum, Z. T.; Woo, E. –R.; Oh, W. K. Chem. Pharm. Bull. 2008, 56, 85; (e) Thuong,
P. T.; Lee, C. H.; Dao, T. T.; Nguyen, P. H.; Kim, W. G.; Lee, S. J.; Oh, W. K. J. Nat.
Prod. 2008, 71, 1775.
References and notes
1. (a) Zhang, S.; Zhang, Z. Y. Drug Discovery Today 2007, 12, 373; (b) Elchebly, M.
Science 1999, 283, 1544; (c) Liu, G. I. Curr. Opin. Mol. Ther. 2004, 6, 331.
2. Koren, S.; Fantus, I. G. Best Pract. Res. Clin. Endocrinol. Metab. 2007, 21, 621.
3. Montalibet, J.; Kennedy, B. P. Drug Discovery Today Ther. Strat. 2005, 2, 129.
4. Ayabe, S. I.; Kobayashi, M.; Hikichi, M.; Matsumoto, K.; Furuya, T.
Phytochemistry 1980, 19, 2179.
5. Kajiyama, K.; Demizu, S.; Hiraga, Y.; Kinoshita, K.; Koyama, K.; Takahashi, K.;
Tamura, Y.; Okada, K.; Kinoshita, T. Phytochemistry 1992, 31, 3229.
6. Yoon, G.; Jung, Y. D.; Cheon, S. H. Chem. Pharm. Bull. 2005, 53, 694.
7. Saitoh, T.; Shibata, S. Tetrahedron Lett. 1975, 50, 4461.
17. PTP1B assay: Recombinant human PTP1B was purchased from BIOMOL
International LP. For the inhibition assay,
added to a reaction mixture containing enzyme (2
50 mM citrate (pH 6.0), 0.1 M NaCl, 1 mM EDTA and 1 mM dithiothreitol],
water (35 L) and 50 L of 4 mM p-nitrophenyl phosphate (pNPP). The reaction
mixture (100 L) was incubated at 37 °C for 30 min and then quenched by
addition of 10 L of 10 N NaOH. The hydrolysis of pNPP was determined by
measuring the absorbance at 405 nm.
a
sample (3
l
L
in DMSO) was
lL), reaction buffer [10
lL,
l
l
l
8. Park, E. J.; Park, H. R.; Lee, J. S.; Kim, J. W. Planta Med. 1998, 64, 464.
9. Nielsen, S. F.; Chen, M.; Theander, T. G.; Kharazmi, A.; Christensen, S. B. Bioorg.
Med. Chem. Lett. 1995, 5, 449.
l