In vitro and in silico evaluations of diarylpentanoid series as α-glucosidase inhibitor

Article abstract of DOI:10.1016/j.bmcl.2017.12.048

A series of thirty-four diarylpentanoids derivatives were synthesized and evaluated for their α-glucosidase inhibitory activity. Eleven compounds (19, 20, 21, 24, 27, 28, 29, 31, 32, 33 and 34) were found to significantly inhibit α-glucosidase in which compounds 28, 31 and 32 demonstrated the highest activity with IC₅₀ values ranging from 14.1 to 15.1 μM. Structure-activity comparison shows that multiple hydroxy groups are essential for α-glucosidase inhibitory activity. Meanwhile, 3,4-dihydroxyphenyl and furanyl moieties were found to be crucial in improving α-glucosidase inhibition. Molecular docking analyses further confirmed the critical role of both 3,4-dihydroxyphenyl and furanyl moieties as they bound to α-glucosidase active site in different mode. Overall result suggests that diarylpentanoids with both five membered heterocyclic ring and polyhydroxyphenyl moiety could be a new lead design in the search of novel α-glucosidase inhibitor.

Full text of DOI:10.1016/j.bmcl.2017.12.048

Accepted Manuscript
In-vitro and In-silico evaluations of diarylpentanoid series as α-glucosidase in-
hibitor
Sze Wei Leong, Faridah Abas, Lam Kok Wai, Khatijah Yusoff
PII:
S0960-894X(17)31222-2
https://doi.org/10.1016/j.bmcl.2017.12.048
BMCL 25504
DOI:
Reference:
Bioorganic & Medicinal Chemistry Letters
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7 December 2017
21 December 2017
Please cite this article as: Wei Leong, S., Abas, F., Kok Wai, L., Yusoff, K., In-vitro and In-silico evaluations of
diarylpentanoid series as α-glucosidase inhibitor, Bioorganic & Medicinal Chemistry Letters (2017), doi: https://
doi.org/10.1016/j.bmcl.2017.12.048
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IN-VITRO AND IN-SILICO EVALUATIONS OF
DIARYLPENTANOID SERIES AS α-GLUCOSIDASE
INHIBITOR
Leave this area blank for abstract info.
Sze Wei Leonga,b, Faridah Abas,b,c*, Lam Kok Waid, Khatijah Yusoffa

Bioorganic & Medicinal Chemistry Letters
journal homepage: www.els evier.com
In-vitro and In-silico evaluations of diarylpentanoid series as α-glucosidase inhibitor
Sze Wei Leonga,b, Faridah Abasb,c*, Lam Kok Waid, Khatijah Yusoffa
aDepartment of Microbiology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
bLaboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
cDepartment of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
dDrug and Herbal Research Centre Faculty of Pharmacy, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abd. Aziz, 50300 Kuala Lumpur, Malaysia.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A series of thirty-four diarylpentanoids derivatives were synthesized and evaluated for their α-
glucosidase inhibitory activity. Eleven compounds (19, 20, 21, 24, 27, 28, 29, 31, 32, 33 and 34)
were found to significantly inhibit α-glucosidase in which compounds 28, 31 and 32
demonstrated the highest activity with IC50 values ranging from 14.1 to 15.1 µM. Structure-
activity comparison shows that multiple hydroxy groups are essential for α-glucosidase
inhibitory activity. Meanwhile, 3,4-dihydroxyphenyl and furanyl moieties were found to be
crucial in improving α-glucosidase inhibition. Molecular docking analyses further confirmed the
critical role of both 3,4-dihydroxyphenyl and furanyl moieties as they bound to α-glucosidase
active site in different mode. Overall result suggests that diarylpentanoids with both five
membered heterocyclic ring and polyhydroxypheny moiety could be a new lead design in the
search of novel α-glucosidase inhibitor.
Available online
Keywords:
Diarylpentanoids
α-Glucosidase inhibitory activity
Docking
Polyhydroxyphenyl
Furanyl
2014 Elsevier Ltd. All rights reserved.
Diabetes Mellitus (DM) is a prevalent metabolic disorder
characterized by prolonged fasting hyperglycemia resulted
from inadequate production (type 1) or inefficient utilization
(type 2) of insulin.1 The unattended chronic hyperglycemia
could narrow, block or even damage the body’s blood vessels
and eventually lead to serious complications such as heart
attack, stroke, kidney failure, leg amputation, vision loss and
nerve damage.2-7 According to Global Report on Diabetes
released by World Health Organization (WHO) in 2016, DM
has affected more than 422 million adults globally and the
number is expected to rise beyond 592 million in 2035.8 On
top of this, DM has caused 4.9 million of deaths and at least
USD 612 billion of annual global health expenditure in 2014.9
Thus, by considering global health and economics impacts,
cheaper and safer treatments for DM must be pursued urgently
and unremittingly.
and absorption. Several α-glucosidase inhibitors such as
acarbose, miglitol and voglibose have been widely used in
treating type-2 diabetes. However, various side effects
including bloating, flatulence and diarrhea were encountered
throughout the treatments.10, 13, 14 On account of this, new safer
α-glucosidase inhibitors with minimal side effects are urgently
warranted.
Diarylpentanoids is the most potent family of curcuminoid
derivatives due to its excellent stability and multiple medicinal
properties. Diarylpentanoids are well-known for their great
antioxidant and anti-inflammatory properties based upon their
ability in suppressing numerous free radicals and pro-
inflammatory cytokines such as 2,2-diphenyl-1-picrylhydrazyl
(DPPH) free radical, superoxide radical, hydroxyl radical,
tumor necrosis factor alpha (TNF-a), and interleukins.15-17 On
top of this, diarylpentanoids were also recognized as potent
anti-cancer agents by their outstanding inhibition on various
cancer cell lines as well as in-vivo tumor suppression effects on
both zebra fish and BALB/c nude mouse models.18-23
Interestingly, recent studies reported that diarylpentanoids are
non-toxic on in-vivo mice models which provide them with
extra tokens in the search of new drug with minimal side
effects.24, 25
Recently, α-glucosidase has been recognized as
a
therapeutic target for treating type-2 DM based upon its pivotal
role in carbohydrates digestion. α-Glucosidase is a membrane-
bound intestinal enzyme found in small intestine epithelium
which responsible for the hydrolysis of carbohydrates to
monosaccharides such as glucose. The converted glucose will
then absorbed into blood stream resulting in increased blood
glucose level.10-12 Thus, inhibiting α-glucosidase may reduce
postprandial hyperglycemia by delaying glucose conversion

Previously we have reported several series of
diarylpentanoids with improved stability as well as antioxidant,
anti-inflammatory and anti-Alzheimer’s properties.26-30 In
continuing our efforts in exploring the pharmacological
potential of diarylpentanoids, we further derivatize and
investigate their inhibitory effects on α-glucosidase.
All synthesized compounds were purified by flash
chromatography and characterized by 1H-NMR, 13C-NMR, and
high-resolution electron ionization-mass spectrometry. The
purified compounds used for α-glucosidase inhibitory
evaluations were of 95 to 99% purity based on their respective
HPLC profiles. All purified compounds were screened for their
α-glucosidase inhibitory activity at 50 µM test concentration
and the screening result is depicted in Figure 1.32
Scheme 1. General synthetic steps for compounds 1-21x
xReagents and conditions: (a) p-toluene-sulphonic acid, toluene, reflux
(2h); (b) benzaldehyde, 80°C (8 h); (c) H2O, reflux (0.5h); (d) NaOH,
EtOH, RT (overnight); (e) benzaldehyde, acetic acid, H2SO4, RT
(overnight).
As shown in Scheme 1, compounds 1-21 (III) were
achieved through enamine-catalyzed benzylidenation followed
by
NaOH-
or
H2SO4-catalyzed
Claisen-Schmidt
Figure 1. α-Glucosidase inhibitory effects of compounds 1–21 at a testing
concentration of 50 µM
condensations.31 Accordingly, cyclohexanone is first reacted
with pyrrolidine to form N-(1-cyclohexenyl)pyrrolidine (I) in a
Dean-Stark reflux setup. The reaction progress was determined
by measuring the amount of H2O collected in the Dean-Stark
burette collector. Upon the completion, the enamine I crude
was further reacted with benzaldehyde at 80˚C followed by
hydrolysis with water to afford the targeted intermediate II, 2-
As illustrated in Figure 1, there are three compounds
successfully suppressed α-glucosidase activity with the
percentage of inhibition greater than 50%. The three active
compounds were then subjected to IC50 determination and the
values obtained were compared to that of the positive control,
quercetin. The overall α-glucosidase inhibitory effect of
twenty-five analogs is tabulated in Table 1.
benzylidenecyclohexanone.
The purified pale yellow
intermediate II was finally reacted with appropriate aryl
aldehydes to achieve the desired compounds III (1-21). In this
step, H2SO4 was used to catalyze the reaction with
hydroxylated
benzaldehyde
while
non-hydroxylated
benzaldehydes was reacted in NaOH condition.
Table 1. α-Glucosidase suppression of compounds 1-21.
Inhibition %
at 50 µM
43.0
Inhibition %
at 50 µM
Compounds
R
IC50 (µM)
Compounds
R
IC50 (µM)
1
2
3
4
5
6
7
8
9
2-F
3-F
4-F
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
12
13
14
15
16
17
18
19
3-CH3
4-CH3
47.9
34.1
31.4
31.8
41.0
43.8
16.3
65.1
ND
ND
ND
ND
ND
ND
ND
28.4
42.3
20.3
7.8
39.8
34.0
37.8
43.0
27.6
44.0
48.4
46.8
4-OME
2,3-OME
2,4-OME
2,5-OME
3,4,5-OME
3-OH
3,4-F
2-Cl
4-Cl
2,3-Cl
3,4-Cl
2-Br
3-Br
4-Br
20
21
4-OH
3,4-OH
53.0
90.7
83.6
10
11
27.2
29.1
QUERCETIN
-
ND = Not determine
As displayed in Table 1, compound 21 was found to exhibit
strongest α-glucosidase inhibitory effect with the IC50 value of
20.3 µM. Meanwhile, compounds 19 and 20 possessed
relatively weak activities, giving IC50 values of 28.4 and 42.3
µM, respectively. This observation suggesting that hydroxyl
moiety is essential for activity as compounds 19-21 are the
only hydroxylated analogs. With respect to the substitution
pattern of hydroxyl group, meta-substitution is preferable since
compound 19 exhibited approximately 1.5-fold higher
inhibition than its respective para-hydroxylated analog 20. On
top of this, polyhydroxy moiety was found to be critical in
improving α-glucosidase inhibition of diarylpentanoids as
compound 21, a dihydroxylated analog demonstrated the
highest activity. Although none of our analogs shows
comparable activity to quercetin, however, in continuing our
efforts in identifying α-glucosidase inhibitor based on
diarylpentanoid scaffold, we further tested our previously
designed hydroxylated compounds (22-34) for their α-
glucosidase inhibitory activity. Scheme 2 and Scheme 3
represent the synthetic steps of compounds 22-24 and 25-34,
respectively.

Scheme 2. General synthetic steps for compounds 22-24y
Scheme 3. General synthetic steps for compounds 25-34z
yReagents and conditions: (a) p-toluene-sulphonic acid, toluene, reflux
(2h); (b) benzoic anhydride, RT (24h); (c) H2O, reflux (0.5h); (d)
hydoxylated benzaldehyde, acetic acid, H2SO4, RT (overnight).
zReagents and conditions: (a) POCl3 , pyridine, RT (overnight); (b) KOH,
pyridine, RT (overnight); (c) BBr3, CH2Cl2, 0 °C (8 h).
Similar to the synthesis of compounds 1-21, 22-24 were
achieved by Stork enamine acylation and Claisen-Schmidt
condensation.33 As presented in Scheme 2, enamine
intermediate was first prepared by reacting cycloxanone with
pyrrolidine in the presence of p-toluene-sulphonic acid. Then,
the acylation with benzoic anhydride was carried out to afford
2-benzoylcyclohexanone, IV. The purify IV was further
reacted with hydroxylated benzaldehydes in acid-catalyzed
Claisen-Schmidt condensation to yield compounds 22-24. In
preparing compounds 25-34 (Scheme 3), different substituted
cinnamic acids were first reacted with 2-hydroxyacetophenone
analogs to afford colourless cinnamate intermediate, VI. Then,
the purified VI analogs were introduced to Baker-
Venkataraman Rearrangement with KOH in pyridine in order
to achieve yellow methoxylated diarylpentanoids. Finally, the
methoxylated diarylpentanoids were undergone demethylation
with BBR3 in dichloromethane to give polyphenolic
diarylpentanoid analogs, compounds 25-34.34 All purified
1
compounds were characterized by H-NMR, 13C-NMR, and
high-resolution electron ionization-mass spectrometry. The
purified compounds used for α-glucosidase inhibitory
evaluations were of 95 to 99% purity based on their respective
HPLC profiles. The overall α-glucosidase inhibitory effects of
compounds 22-34 are summarized in Table 2.
Table 2. α-Glucosidase suppression of compounds 22-34.
Inhibition %
at 50 µM
IC50
(µM)
Inhibition %
at 50 µM
IC50
(µM)
Compounds
Structure
Compound
29
Structure
22
43.2
ND
62.4
45.3
85.6
98.4
36.4
ND
23
24
25
26
34.9
55.9
40.4
20.4
ND
41.0
ND
ND
30
31
32
15.1
14.1
33
34
96.9
86.6
19.6
20.0
27
28
61.2
93.6
40.7
14.3
ND = Not determine
According to Table 2, the meta-substitution of
diarylpentanoids continued demonstrates its importance in α-
glucosidase inhibition as compounds 22, 25 and 29 exhibited
better activity than compounds 23, 26 and 30, respectively. In
addition, multiple substitutions of hydroxyl groups on phenyl
ring remained to be crucial with regards to α-glucosidase
inhibition as polyhydroxylated compounds such as 28, 31, 33 and
34 exhibited highest activities. These findings further confirmed
the enhancing effect of meta-substitution and critical role of
polyhydroxyl moiety in α-glucosidase inhibitory activity. Among
polyhydroxylated compounds, 3,4-dihydroxy moiety was found
to be the most potent substitution pattern as compounds 28 and
31 are better α-glucosidase inhibitor as compared to compounds
33 and 34. Surprisingly, the replacement of 2,5-dihydroxy moiety
(33) with a furanyl ring (32) tends to enhance the inhibitory

activity which suggests that furan ring may bind α-glucosidase in
a different mode compared with hydroxylated phenyl moieties.
In order to gain functional and structural insights into the
binding mode of polyhydroxylated (31) and furanylated (32)
analogs in α-glucosidase, molecular docking was performed
using Discovery Studio 3.1.35 Compound 31 was selected over
compound 28 based on its better similarity in structural geometry
with respect to compound 32. Since the crystal structure of
Saccharomyces cerevisiae α-glucosidase is still not available, a
homology model of α-glucosidase was built according to a
previously reported method for the molecular docking analysis.
Isomaltase (PDB ID: 3A4A) from baker’s yeast was chosen as
the template for the respective homology model since it shared
71% identity and 84% similarity with Saccharomyces cerevisiae
α-glucosidase (UniProt ID: P53341). The homologous protein
was generated by MODELER protocol and the optimized
structure was further validated by Ramachandran plot (Figure 2)
obtained from RAMPAGE server.36
Figure 3. Overlay of re-docked (red) and crystallographic (blue)
conformations of alpha-D-glucose in α-glucosidase (3A4A).
As depicted in Figure 3, re-docked (red) alpha-D-glucose
was found to bind in a similar manner as its respective
crystallographic conformations (blue) with the RMSD value of
0.7147 Å, indicating that the selected docking parameters are
acceptable. The optimized parameters were then used for the
docking of compounds 31 and 32 in the active site of α-
glucosidase homology model. Figure 4 and Figure 5 illustrated
the binding interactions of compounds 31 and 32 in α-
glucosidase, respectively.
Figure 4. Binding interactions of compound 31 with the active site residues
of α-glucosidase receptor
Based on the molecular docking analysis (Figure 4), 3,4-
dihydroxyphenyl moiety of compound 31 forms two strong
hydrogen bonding (green dashed line) interactions with ASP 214
residue. Meanwhile, the phenyl ring of the respective moiety was
found to interact with GLU 276 and ARG 439 residues through
additional Pi-charge (orange dashed line) interactions. These
observations thus explained the critical role of catechol fragment
in enhancing the α-glucosidase inhibition. On top of this, both
chloro and phenyl moieties of chlrophenol fragment have
displayed hydrophobic contacts (light purple dashed line) with
PHE 331 and ARG 312 residues at the active site. This could be
used to explain the better performance of chlorinated compounds
(29 and 30) compared to their respective non-chlorinated analogs
(25 and 26). It is worth noting that the hydroxyl group of
chlorophenol fragment and the carbonyl group of pentadienone
bridge formed additional hydrogen bonding with ASP 408 and
ARG 312 residues, respectively. Ironically, the beneficial effect
of chloro moiety was not observed in the comparison of
compounds 28 and 31. This observation may be rationalized with
the much higher enhancement degree of catechol moiety which
has overshadowed the relatively weaker positive effect of chloro
group.
Figure 2. Ramachandran plot for homolog model of 3A4A
According to the Ramachandran plot, 98.1% of residues are
found in favored regions while 1.9% of residues are located in
allowed regions. Together with no detection of outlier residues,
the selected homology model is therefore acceptable. Prior to
dock the compounds 31 and 32 with the selected model, the
docking parameters were first validated by comparing the
conformation Root Mean Square Deviation (RMSD) value of
native and re-docked co-crystallized ligand. The parameters are
considered successful if the RMSD value is less than 1.5 Å.

glucosidase in
a different manner as compared to the
chlorophenol ring of compound 31. The furanyl group forms a
Pi-charge interaction with ARG 312 residue. Meanwhile, it also
shows hydrophobic contacts with ARG 439 and ARG 312
residues. On top of these, additional hydrogen bonding is also
been observed between the oxygen atom of furan ring and GLN
350 residues. The superimpose of compounds 31 and 32 in
binding pocket (Figure 6) further confirmed the unique role of
furanyl moiety as it lays in a small cavity of the active site which
failed to be fitted by a phenyl ring. The molecular docking results
of compounds 31 and 32 are summarized in Table 3.
Figure 5. Binding interactions of compound 32 with the active site residues
of α-glucosidase receptor
As depicted in Figure 5, polyhydroxylated phenyl ring of
compound 32 bind in a similar manner as catechol moiety of
compound 31. The meta-hydroxy group of compound 32 forms a
strong hydrogen bonding with ASP 214. Meanwhile, the
respective phenyl ring binds to both ASP 214 and GLU 276
residues with Pi-charge interactions. Apart from ASP 214 and
GLU 276 residues, polyhydroxylated phenyl ring of compound
32 is also interacting with TYR 71 and ASP 349 residues through
Pi-Pi stacking and hydrogen bonding, respectively. These
findings further
confirmed the binding mode of
polyhydroxyphenyl moiety in α-glucosidase. Interestingly, the
furanyl moiety of compound 32 was found to bind with α-
Figure 6. Superimpose of compounds 31 and 32 in binding pocket
Table 3. Data resulted from the molecular docking of compounds 31 and 32 in α-glucosidase.
Interacting
Amino acid residue
PHE 311
Compound Structure
Bond type
Hydrophobic
Bonding distance (Å)
5.39
4.23
ARG 312
Hydrophobic
Hydrogen bonding
Hydrogen bonding
Pi-Cation
2.03
ASP 408
ARG 439
GLU 276
ASP 214
2.00
4.67
Pi-Anion
4.10
Hydrogen bonding
1.93, 2.78
GLN 350
ARG 312
Hydrogen bonding
Pi-Cation
2.20
4.26
5.19
4.36
2.92
1.98
3.70
4.80
4.85
Hydrophobic
Hydrophobic
Hydrogen bonding
Hydrogen bonding
Pi-Anioin
ARG 439
ASP 214
THR-2151
TYR 71
Pi-Anioin
Pi-Pi stacking

Taken both in-vitro and in-silico analyses of diarylpentanoid
derivatives on α-glucosidase inhibition, 3,4-dihydroxyphenyl and
furanyl rings are the most important functionalities for α-
glucosidase inhibitory activity. Since both of them bound to α-
glucosidase in a different manner, we therefore concluded that
the combination of five membered heterocyclic ring and
polyhydroxypheny moiety could be a new lead design in the
search of novel α-glucosidase inhibitor.
15. Li Q, Chen J, Luo S, Xu J, Huang Q, Liu T. Synthesis and
assessment of the antioxidant and antitumor properties of
asymmetric curcumin analogues. Eur J Med Chem.
2015;93: 461-469.
16. Zhang Y, Zhao C, He W, et al. Discovery and evaluation of
asymmetrical monocarbonyl analogs of curcumin as anti-
inflammatory agents. Drug Des Devel Ther. 2014;8: 373-
382.
17. Feng J, Xiao B, Chen W, et al. Synthesis and Anti-
Inflammatory Evaluation of Novel C66 Analogs for the
Treatment of LPS-Induced Acute Lung Injury. Chem Biol
Drug Des. 2015;86(4): 753-763.
18. Qiu C, Hu Y, Wu K, et al. Synthesis and biological
evaluation of allylated mono-carbonyl analogues of
Acknowledgments
The authors thank the Ministry of Higher Education (MOHE) of
Malaysia for financial support under the project
FRGS/1/2014/ST01/UPM/02/1 (5538011).
curcumin
(MACs)
as
anti-cancer
agents
for
cholangiocarcinoma. Bioorg Med Chem Lett. 2016;26(24):
5971-5976.
References and notes
19. Manohar S, Khan SI, Kandi SK, et al. Synthesis,
antimalarial activity and cytotoxic potential of new
monocarbonyl analogues of curcumin. Bioorg Med Chem
Lett. 2013;23(1): 112-116.
20. Sanabria-Rios DJ, Rivera-Torres Y, Rosario J, et al.
Synthesis of novel C5-curcuminoid-fatty acid conjugates
and mechanistic investigation of their anticancer activity.
Bioorg Med Chem Lett. 2015;25(10): 2174-2180.
1. American Diabetes A. Diagnosis and classification of
diabetes mellitus. Diabetes Care. 2010;33 Suppl 1: S62-69.
2. Ceriello A. The post-prandial state and cardiovascular
disease: relevance to diabetes mellitus. Diabetes Metab Res
Rev. 2000;16(2): 125-132.
3. Idris I, Thomson GA, Sharma JC. Diabetes mellitus and
stroke. Int J Clin Pract. 2006;60(1): 48-56.
4. Aoun S, Blacher J, Safar ME, Mourad JJ. Diabetes mellitus
and renal failure: effects on large artery stiffness. J Hum
Hypertens. 2001;15(10): 693-700.
5. Mantovani AM, Fregonesi CE, Palma MR, Ribeiro FE,
Fernandes RA, Christofaro DG. Relationship between
amputation and risk factors in individuals with diabetes
mellitus: A study with Brazilian patients. Diabetes Metab
Syndr. 2017;11(1): 47-50.
21. Wang R, Chen C, Zhang X, et al. Structure-Activity
Relationship and Pharmacokinetic Studies of 1,5-
Diheteroarylpenta-1,4-dien-3-ones: A Class of Promising
Curcumin-Based Anticancer Agents.
J Med Chem.
2015;58(11): 4713-4726.
22. Velaithan V, Okuda KS, Ng MF, et al. Zebrafish
phenotypic screen identifies novel Notch antagonists. Invest
New Drugs. 2017;35(2): 166-179.
23. Liu Z, Sun Y, Ren L, et al. Evaluation of a curcumin analog
as an anti-cancer agent inducing ER stress-mediated
apoptosis in non-small cell lung cancer cells. BMC Cancer.
2013;13: 494.
6. Moss SE, Klein R, Klein BE. The incidence of vision loss
in a diabetic population. Ophthalmology. 1988;95(10):
1340-1348.
7. Takahashi H, Goto T, Shoji T, Tanito M, Park M, Chihara
E. Diabetes-associated retinal nerve fiber damage evaluated
24. Yuan X, Li H, Bai H, et al. Synthesis of novel curcumin
analogues for inhibition of 11beta-hydroxysteroid
dehydrogenase type 1 with anti-diabetic properties. Eur J
Med Chem. 2014;77: 223-230.
25. Wang Y, Yu C, Pan Y, et al. A novel synthetic mono-
carbonyl analogue of curcumin, A13, exhibits anti-
inflammatory effects in vivo by inhibition of inflammatory
mediators. Inflammation. 2012;35(2): 594-604.
26. Leong SW, Faudzi SMM, Abas F, et al. Synthesis and sar
study of diarylpentanoid analogues as new anti-
inflammatory agents. Molecules. 2014;19(10): 16058-
16081.
with scanning laser polarimetry. Am
2006;142(1): 88-94.
J Ophthalmol.
8. Roglic G, World Health Organization. Global report on
diabetes. Geneva, Switzerland: World Health Organization;
2016.
9. da Rocha Fernandes J, Ogurtsova K, Linnenkamp U, et al.
IDF Diabetes Atlas estimates of 2014 global health
expenditures on diabetes. Diabetes Res Clin Pract.
2016;117: 48-54.
10. Derosa G, Maffioli P. alpha-Glucosidase inhibitors and
their use in clinical practice. Arch Med Sci. 2012;8(5): 899-
906.
27. Faudzi SM, Leong S, Abas F, et al. Synthesis, biological
evaluation and QSAR studies of diarylpentanoid analogues
as potential nitric oxide inhibitors. MedChemComm.
2015;6(6): 1069-1080.
28. Leong SW, Mohd Faudzi SM, Abas F, et al. Nitric oxide
inhibitory activity and antioxidant evaluations of 2-benzoyl-
6-benzylidenecyclohexanone analogs, a novel series of
curcuminoid and diarylpentanoid derivatives. Bioorg Med
Chem Lett. 2015;25(16): 3330-3337.
29. Mohd Aluwi MF, Rullah K, Yamin BM, et al. Synthesis of
unsymmetrical monocarbonyl curcumin analogues with
potent inhibition on prostaglandin E2 production in LPS-
induced murine and human macrophages cell lines. Bioorg
Med Chem Lett. 2016;26(10): 2531-2538.
11. Bischoff H. The mechanism of alpha-glucosidase inhibition
in the management of diabetes. Clin Invest Med.
1995;18(4): 303-311.
12. van de Laar FA. Alpha-glucosidase inhibitors in the early
treatment of type 2 diabetes. Vasc Health Risk Manag.
2008;4(6): 1189-1195.
13. Lee MY, Choi DS, Lee MK, et al. Comparison of acarbose
and voglibose in diabetes patients who are inadequately
controlled with basal insulin treatment: randomized,
parallel, open-label, active-controlled study. J Korean Med
Sci. 2014;29(1): 90-97.
14. Shibata E, Aoki K, Tajima K, Taguri M, Terauchi Y.
Comparison of efficacy and safety of taking miglitol
dissolved in water during a meal and taking a miglitol tablet
just before a meal in patients with type 2 diabetes. Expert
Opin Pharmacother. 2016;17(7): 889-894.
30. Leong SW, Faudzi SM, Abas F, et al. Synthesis and sar
study of diarylpentanoid analogues as new anti-

inflammatory agents. Molecules. 2014;19(10): 16058-
16081.
2-Benzylidene-6-(3,4-difluorobenzylidene)cyclohexanone
(4). Yellow; m.p.: 80-81ºC; Mass calculated: 310.1169;
Mass found: 310.1178. 1H NMR (500 MHz, CDCl3) δ: 1.81
(quin, J=6.21 Hz, 2 H) 2.88 (t, J=5.49 Hz, 2 H) 2.94 (t,
J=5.49 Hz, 2 H) 7.17 - 7.21 (m, 2 H) 7.26 - 7.31 (m, 1 H)
7.32 - 7.37 (m, 1 H) 7.41 (t, J=7.51 Hz, 2 H) 7.45 - 7.48 (m,
2 H) 7.67 (s, 1 H) 7.80 (s, 1 H). 13C NMR (126 MHz,
CDCl3) δ: 22.8, 28.3, 28.3, 117.4, 118.9, 127.0, 128.4,
128.8, 130.4, 132.9, 134.5, 135.8, 135.8, 136.8, 137.4,
149.3, 151.2, 190.0
31. General procedure for synthesis of I and II. A catalytic
amount of p-toluenesulphonic acid was added into a
mixture of cyclohexanone (20 mmol) and pyrrolidine (20
mmol) in 30 mL of toluene kept in 100 mL SNRB at room
temperature. The mixture was then refluxed on a Dean &
Stark apparatus for 2 hours to prepare I. Upon completion,
20 mmol of benzaldehyde in 20 mL of toluene was added
dropwise into the reaction solution (I) and heat at 80˚C for
8 hours. Distilled water (10 ml) was then added and further
refluxed for 30 min. The resulting reaction mixture was
extracted thrice with 3M HCl and once with 20 mL water.
The toluene layer was dried over anhydrous magnesium
sulphate and concentrated in vacuo to give II, 2-
benzylidenecyclohexanone. The resulting crude product
was purified by column chromatography.
2-Benzylidene-6-(2-chlorobenzylidene)cyclohexanone (5).
Yellow; m.p.: 53-55ºC; Mass calculated: 308.0968; Mass
1
found: 308.0986. H NMR (500 MHz, CDCl3) δ: 1.78 (dt,
J=12.28, 6.29 Hz, 2 H) 2.74 - 2.79 (m, 2 H) 2.92 - 2.96 (m,
2 H) 7.25 - 7.30 (m, 2 H) 7.31 - 7.36 (m, 2 H) 7.38 - 7.49
(m, 5 H) 7.82 (s, 1 H) 7.89 (s, 1 H). 13C NMR (126 MHz,
CDCl3) δ: 23.1, 28.2, 28.6, 110.0, 126.2, 128.4, 128.7,
129.5, 129.7, 130.4, 130.5, 133.6, 134.5, 135.0, 136.0,
137.58, 137.9, 190.1
2-Benzylidene-6-(4-chlorobenzylidene)cyclohexanone (6).
Yellow; m.p.: 105-107ºC; Mass calculated: 308.0968; Mass
found: 308.0979. 1H NMR (500 MHz, CDCl3) δ: 1.79
(quin, J=6.21 Hz, 2 H) 2.86 - 2.91 (m, 2 H) 2.91 - 2.96 (m,
2 H) 7.32 - 7.43 (m, 7 H) 7.44 - 7.48 (m, 2 H) 7.73 (s, 1 H)
7.80 (s, 1 H). 13C NMR (126 MHz, CDCl3) δ: 22.9, 28.4,
28.5, 128.4, 128.65, 128.69, 130.39, 131.58, 134.37,
134.50, 135.5, 135.9, 136.0, 136.6, 137.2, 142.4, 145.0,
190.1
2-Benzylidene-6-(2,3-dichlorobenzylidene)cyclohexanone
(7). Yellow; m.p.: 94-95ºC; Mass calculated: 342.0578;
Mass found: 342.0591. 1H NMR (500 MHz, CDCl3) δ: 1.77
(dt, J=12.72, 6.36 Hz, 2 H) 2.72 (t, J=5.20 Hz, 1 H) 2.94 (t,
J=5.20 Hz, 2 H) 7.19 - 7.24 (m, 2 H) 7.32 - 7.38 (m, 1 H)
7.38 - 7.45 (m, 3 H) 7.45 - 7.49 (m, 2 H) 7.83 (d, J=2.31
Hz, 2 H). 13C NMR (126 MHz, CDCl3) δ: 23.0, 28.1, 28.6,
126.8, 128.4, 128.6, 128.8, 130.0, 130.5, 133.3, 133.5,
135.8, 135.8, 137.9, 138.5, 189.9
2-Benzylidene-6-(3,4-dichlorobenzylidene)cyclohexanone
(8). Yellow; m.p.: 85-86ºC; Mass calculated: 342.0578;
Mass found: 342.0583. 1H NMR (500 MHz, CDCl3) δ: 1.80
(dt, J=12.28, 6.29 Hz, 2 H) 2.85 - 2.90 (m, 2 H) 2.91 - 2.97
(m, 2 H) 7.25 - 7.29 (m, 1 H) 7.32 - 7.37 (m, 1 H) 7.41 (t,
J=7.51 Hz, 2 H) 7.44 - 7.49 (m, 3 H) 7.53 (s, 1 H) 7.65 (s, 1
H) 7.80 (s, 1 H). 13C NMR (126 MHz, CDCl3) δ: 22.8, 28.3,
28.4, 128.4, 128.8, 129.5, 130.4, 130.4, 130.9, 131.7, 132.5,
132.6, 134.1, 135.7, 135.9, 137.6, 189.9
General procedure for the synthesis of III (pathway d). In a
50 mL SNRB, 2-benzylidenecyclohexanone (5 mmol) and
appropriate aromatic aldehyde (5 mmol) were dissolved in
30 mL of absolute ethanol. Catalytic amount of 6M NaOH
solution was added and the reaction mixture was stirred for
overnight. The resulting mixture was then neutralized with
3M HCl followed by extraction with EA. The organic layer
was then dried over anhydrous magnesium sulphate and
evaporated using rotatory evaporator. The target compound
was purified by gravitational column chromatography.
General procedure for the synthesis of III (pathway e). In a
50 mL SNRB, 2-benzylidenecyclohexanone (5 mmol) and
appropriate aromatic aldehyde (5 mmol) were dissolved in
30 mL of acetic acid. Catalytic amount of concentrated
sulfuric acid was added and reaction mixture was stirred for
overnight. The resulting mixture was extracted with EA and
washed with 10% sodium bicarbonate solution. The organic
layer was then dried over anhydrous magnesium sulphate
and evaporated using rotatory evaporator. The target
compound was purified by gravitational column
chromatography.
2-Benzylidene-6-(2-fluorobenzylidene)cyclohexanone (1).
Yellow; m.p.: 90-92ºC; Mass calculated: 292.1263; Mass
1
found: 292.1274. H NMR (500 MHz, CDCl3) δ:1.78 (dt,
J=12.72, 6.36 Hz, 2 H) 2.78 - 2.83 (m, 2 H) 2.91 - 2.96 (m,
2 H) 7.08 - 7.14 (m, 1 H) 7.14 - 7.19 (m, 1 H) 7.29 - 7.38
(m, 3 H) 7.39 - 7.43 (m, 2 H) 7.45 - 7.49 (m, 2 H) 7.81 (s, 1
H) 7.83 (s, 1 H). 13C NMR (126 MHz, CDCl3) δ: 23.0, 28.4,
28.6, 115.8, 123.7, 128.4, 128.7, 129.4, 130.3, 130.4, 130.7,
135.9, 136.0, 137.4, 161.6, 163.6, 190.0
2-Benzylidene-6-(2-bromobenzylidene)cyclohexanone (9).
Orange gummy solid; m.p.: -; Mass calculated: 352.0463;
Mass found: 352.0468. 1H NMR (500 MHz, CDCl3) δ: 1.78
(dt, J=12.28, 6.29 Hz, 2 H) 2.72 - 2.78 (m, 2 H) 2.90 - 2.96
(m, 2 H) 7.16 - 7.21 (m, 1 H) 7.29 - 7.36 (m, 3 H) 7.39 -
7.43 (m, 2 H) 7.45 - 7.49 (m, 2 H) 7.61 - 7.66 (m, 1 H) 7.83
(s, 2 H). 13C NMR (126 MHz, CDCl3) δ: 23.11, 28.1, 28.6,
107.1, 126.9, 128.4, 128.7, 129.6, 129.8, 130.4, 130.5,
132.9, 133.7, 135.1, 135.9, 135.9, 136.0, 137.6, 190.1
2-benzylidene-6-(3-bromobenzylidene)cyclohexanone (10).
Yellow; m.p.: 108-109ºC; Mass calculated: 352.0463; Mass
found: 352.0475. 1H NMR (500 MHz, CDCl3) δ: 1.80
(quin, J=6.21 Hz, 2 H) 2.87 - 2.91 (m, 2 H) 2.92 - 2.96 (m,
2 H) 7.27 (m, J=7.51 Hz, 1 H) 7.33 - 7.38 (m, 2 H) 7.39 -
7.43 (m, 2 H) 7.44 - 7.49 (m, 3 H) 7.59 (s, 1 H) 7.70 (s, 1
H) 7.80 (s, 1 H). 13C NMR (126 MHz, CDCl3) δ: 22.9, 28.4,
28.4, 128.4, 128.7, 128.9, 129.9, 130.4, 131.4, 132.8, 135.1,
135.8, 135.9, 137.3, 137.4, 138.0, 190.1
2-Benzylidene-6-(3-fluorobenzylidene)cyclohexanone (2).
Yellow; m.p.: 92-93ºC; Mass calculated: 292.1263; Mass
found: 292.1287. 1H NMR (500 MHz, CDCl3) δ: 1.80
(quin, J=6.36 Hz, 2 H) 2.87 - 2.98 (m, 4 H) 7.01 - 7.07 (m,
1 H) 7.16 (d, J=10.40 Hz, 1 H) 7.23 (d, J=7.51 Hz, 1 H)
7.32 - 7.38 (m, 2 H) 7.41 (t, J=7.51 Hz, 2 H) 7.44 - 7.49 (m,
2 H) 7.73 (s, 1 H) 7.81 (s, 1 H). 13C NMR (126 MHz,
CDCl3) δ: 22.9, 28.4, 115.5, 116.7, 126.2, 126.2, 128.4,
128.7, 129.8, 129.9, 130.4, 135.4, 135.8, 135.9, 137.2,
137.3, 138.1, 161.6, 163.5, 190.2
2-Benzylidene-6-(4-fluorobenzylidene)cyclohexanone (3).
Yellow; m.p.: 109-110ºC; Mass calculated: 292.1263; Mass
found: 292.1281. 1H NMR (500 MHz, CDCl3) δ: 1.80
(quin, J=6.36 Hz, 2 H) 2.87 - 2.97 (m, 4 H) 7.10 (t, J=8.67
Hz, 2 H) 7.32 - 7.36 (m, 1 H) 7.41 (t, J=7.51 Hz, 2 H) 7.43
- 7.48 (m, 4 H) 7.76 (s, 1 H) 7.80 (s, 1 H). 13C NMR (126
MHz, CDCl3) δ: 23.0, 28.4, 28.4, 115.6, 128.4, 128.6,
130.4, 132.2, 132.3, 135.8, 135.9, 136.0, 137.0, 161.6,
163.61, 190.2
2-Benzylidene-6-(4-bromobenzylidene)cyclohexanone (11).
Yellow; m.p.: 123-125ºC; Mass calculated: 352.0463; Mass

1
2-Benzylidene-6-(3,4,5-
found: 352.0478. H NMR (500 MHz, CDCl3) δ: 1.79 (dt,
trimethoxybenzylidene)cyclohexanone (18). Yellow; m.p.:
105-107ºC; Mass calculated: 364.1675; Mass found:
364.1687. 1H NMR (500 MHz, CDCl3) δ: 1.80 (dt, J=12.72,
6.36 Hz, 2 H) 2.89 - 2.98 (m, 4 H) 3.86 - 3.90 (m, 9 H) 6.71
(s, 2 H) 7.31 - 7.36 (m, 1 H) 7.37 - 7.43 (m, 2 H) 7.44 - 7.48
(m, 2 H) 7.72 (s., 1 H) 7.79 (s., 1 H). 13C NMR (126 MHz,
CDCl3) δ: 23.0, 28.4, 28.5, 56.2, 61.0, 107.8, 110.0, 128.4,
128.6, 130.4, 131.4, 135.5, 135.9, 136.1, 137.0, 137.2,
152.9, 190.3
J=12.28, 6.29 Hz, 2 H) 2.85 - 2.90 (m, 2 H) 2.91 - 2.96 (m,
2 H) 7.30 - 7.37 (m, 3 H) 7.41 (t, J=7.80 Hz, 2 H) 7.44 -
7.48 (m, 2 H) 7.53 (d, J=8.67 Hz, 2 H) 7.71 (s, 1 H) 7.80 (s,
1 H). 13C NMR (126 MHz, CDCl3) δ: 22.9, 28.4, 28.5,
122.8, 128.4, 128.7, 130.4, 131.6, 131.8, 134.8, 135.6,
135.8, 135.9, 136.7, 137.3, 190.2
2-Benzylidene-6-(3-methylbenzylidene)cyclohexanone (12).
Yellow; m.p.: 92-93ºC; Mass calculated: 288.1514; Mass
found: 288.1524. 1H NMR (500 MHz, CDCl3) δ: 1.79
(quin, J=6.21 Hz, 2 H) 2.39 (s, 3 H) 2.91 - 2.97 (m, 4 H)
7.14 - 7.18 (m, 1 H) 7.25 - 7.37 (m, 4 H) 7.39 - 7.44 (m, 2
H) 7.45 - 7.49 (m, 2 H) 7.78 (s., 1 H) 7.81 (s, 1 H). 13C
NMR (126 MHz, CDCl3) δ: 21.5, 23.0, 28.5, 28.5, 127.4,
128.3, 128.4, 128.6, 129.4, 130.4, 131.1, 135.9, 136.0,
136.2, 136.9, 137.1, 137.2, 138.0, 190.4
2-Benzylidene-6-(3-hydroxybenzylidene)cyclohexanone
(19). Yellow; m.p.: 150-151ºC; Mass calculated: 290.1307;
1
Mass found: 290.1319. H NMR (500 MHz, acetone-d6) δ:
1.79 (quin, J=6.36 Hz, 2 H) 2.93 - 2.97 (m, 4 H) 6.85 - 6.89
(m, 1 H) 6.99 - 7.04 (m, 2 H) 7.25 - 7.31 (m, 1 H) 7.35 -
7.40 (m, 1 H) 7.43 - 7.49 (m, 2 H) 7.51 - 7.56 (m, 2 H) 7.63
(s, 1 H) 7.70 (s, 1 H) 8.56 (br. s., 1 H). 13C NMR (126
MHz, acetone-d6) δ: 22.8, 28.2, 28.3, 115.8, 116.8, 121.7,
128.4, 128.5, 129.5, 130.3, 135.7, 135.9, 136.0, 136.4,
136.5, 137.3, 157.4, 188.7
2-Benzylidene-6-(4-methylbenzylidene)cyclohexanone (13).
Yellow; m.p.: 93-95ºC; Mass calculated: 288.1514; Mass
1
found: 288.1527. H NMR (500 MHz, CDCl3) δ: 1.75 -
1.84 (m, 2 H) 2.39 (s, 3 H) 2.93 (td, J=6.21, 3.18 Hz, 4 H)
7.22 (d, J=8.09 Hz, 2 H) 7.31 - 7.36 (m, 1 H) 7.37 - 7.43
(m, 4 H) 7.45 - 7.49 (m, 2 H) 7.79 ( s., 1 H) 7.80 (s., 1 H).
13C NMR (126 MHz, CDCl3) δ: 21.4, 23.0, 28.4, 28.6,
128.4, 128.5, 129.2, 130.4, 130.5, 133.1, 135.4, 136.0,
136.3, 136.7, 137.1, 138.9, 190.4
2-Benzylidene-6-(4-methoxybenzylidene)cyclohexanone
(14). Yellow; m.p.: 96-97ºC; Mass calculated: 304.1463;
Mass found: 304.1477. 1H NMR (500 MHz, CDCl3) δ: 1.80
(quin, J=6.21 Hz, 2 H) 2.89 - 2.95 (m, 4 H) 3.85 (s, 3 H)
6.92 - 6.96 (m, 2 H) 7.31 - 7.36 (m, 1 H) 7.38 - 7.42 (m, 2
H) 7.44 - 7.48 (m, 4 H) 7.78 (s, 1 H) 7.80 (s, 1 H). 13C NMR
(126 MHz, CDCl3) δ: 23.0, 28.4, 28.6, 55.3, 113.9, 128.4,
128.5, 128.6, 130.3, 132.3, 134.1, 136.1, 136.3, 136.5,
137.0, 160.0, 190.3
2-Benzylidene-6-(2,3-dimethoxybenzylidene)cyclohexanone
(15). Yellow gummy solid; m.p.: -; Mass calculated:
334.1569; Mass found: 334.1577. 1H NMR (500 MHz,
CDCl3) δ: 1.76 (quin, J=6.36 Hz, 2 H) 2.77 - 2.84 (m, 2 H)
2.89 - 2.95 (m, 2 H) 3.82 (s, 3 H) 3.88 (s, 3 H) 6.93 (dd,
J=7.80, 3.18 Hz, 2 H) 7.04 - 7.09 (m, 1 H) 7.32 - 7.37 (m, 2
H) 7.40 (t, J=7.51 Hz, 2 H) 7.45 - 7.48 (m, 2 H) 7.80 (s, 1
H) 7.93 (s, 1 H). 13C NMR (126 MHz, CDCl3) δ: 23.2, 28.5,
28.7, 55.8, 61.2, 112.7, 122.1, 123.5, 128.4, 128.6, 130.4,
132.4, 136.0, 136.3, 137.1, 137.5, 148.3, 159.5, 161.1,
190.0
2-Benzylidene-6-(4-hydroxybenzylidene)cyclohexanone
(20). Yellow; m.p.: 208-210ºC; Mass calculated: 290.1307;
1
Mass found: 290.1331. H NMR (500 MHz, DMSO-d6) δ:
1.68 (dt, J=12.28, 6.29 Hz, 2 H) 2.84 (t, J=6.65 Hz, 4 H)
6.84 (d, J=8.67 Hz, 2 H) 7.33 - 7.38 (m, 1 H) 7.38 - 7.45
(m, 4 H) 7.46 - 7.52 (m, 2 H) 7.56 (s., 1 H) 7.59 (s., 1 H)
9.96 (br. s., 1 H). 13C NMR (126 MHz, DMSO-d6) δ: 22.9,
28.2, 28.5, 110.0, 116.0, 126.8, 129.0, 129.1, 130.6, 133.1,
133.5, 135.5, 135.9, 136.9, 137.0, 158.9, 189.1
2-Benzylidene-6-(3,4-dihydroxybenzylidene)cyclohexanone
(21). Yellow; m.p.: 172-174ºC; Mass calculated: 306.1256;
1
Mass found: 306.1271. H NMR (500 MHz, acetone-d6) δ:
1.79 (quin, J=6.26 Hz, 2 H) 2.90 - 2.96 (m, 4 H) 6.89 - 6.93
(m, 1 H) 6.98 (dd, J=7.93, 1.83 Hz, 1 H) 7.10 (d, J=1.83
Hz, 1 H) 7.34 - 7.39 (m, 1 H) 7.45 (t, J=7.63 Hz, 2 H) 7.49
- 7.54 (m, 2 H) 7.60 (s, 1 H) 7.68 (s, 1 H) 8.33 (br. s, 2 H).
13C NMR (126 MHz, acetone-d6) δ: 28.1, 33.3, 33.7, 120.5,
122.6, 122.7, 129.0, 133.3, 133.6, 135.4, 138.8, 140.3,
141.3, 141.9, 150.1, 151.6, 193.7
32. α-Glucosidase inhibitory assay. Briefly, 130 µL of sodium
phosphate buffer (0.03 M, pH 7.4) was first added to 96-
well microplate followed by the addition of 10 µL of α-
glucosidase solution and 10 µL of test compounds. The
mixture was incubated at 37˚C for 5 min. Then, 50 µL of
substrate (4-Nitrophenyl-α-D-glucopyranoside) was added
to initiate the enzyme reaction and the reaction mixture was
further incubated for 15 min at 37˚C. The reaction was
terminated by adding 50 µL of 2M glycine (pH 10)
solution. The absorbance of the colored end-product was
measured at 405 nm using SpectraMax Plus 384 Microplate
Reader (Molecular Devices LLC, Sunnyvale, CA, USA).
The final concentrations of α-glucosidase enzyme and
DMSO are 0.02 U/well and 0.1 %, respectively. All
reactions were carried out in triplicate. The IC50 values
were calculated in µM using Graph Pad software
2-Benzylidene-6-(2,4-dimethoxybenzylidene)cyclohexanone
(16). Yellow; m.p.: 84-86ºC; Mass calculated: 334.1569;
Mass found: 334.1579. 1H NMR (500 MHz, CDCl3) δ: 1.77
(quin, J=6.21 Hz, 2 H) 2.82 - 2.87 (m, 2 H) 2.89 - 2.94 (m,
2 H) 3.84 (s, 5 H) 6.48 (d, J=2.31 Hz, 1 H) 6.51 (dd,
J=8.38, 2.60 Hz, 1 H) 7.28 - 7.34 (m, 3 H) 7.39 (t, J=7.51
Hz, 2 H) 7.43 - 7.47 (m, 2 H) 7.79 (s, 1 H) 8.01 (s, 1 H). 13
C
NMR (126 MHz, CDCl3) δ: 23.3, 28.6, 28.8, 55.4, 55.5,
98.2, 104.1, 117.9, 128.3, 128.4, 130.3, 131.3, 132.4, 134.5,
136.2, 136.4, 136.6, 160.0, 161.7, 190.4
33. General procedure for synthesis of IV.
A
catalytic
2-Benzylidene-6-(2,5-dimethoxybenzylidene)cyclohexanone
(17). Yellow gummy solid; Mass calculated: 334.1569;
amount of p-toluenesulphonic acid was added into a
mixture of cyclohexanone (20 mmol) and pyrrolidine (20
mmol) in 30 mL of toluene kept in 100 mL SNRB at room
temperature. The mixture was then refluxed on a Dean &
Stark apparatus for 2 hours to prepare I. Upon completion,
20 mmol of benzoic anhydride in 20 mL of toluene was
added dropwise into the reaction solution (I) and stirred at
room temperature for overnight. Distilled water (10 ml) was
then added and further refluxed for 30 min. The resulting
reaction mixture was extracted thrice with 3M HCl and
1
Mass found: 334.1584. H NMR (500 MHz, CDCl3) δ:
1.77 (dt, J=12.72, 6.36 Hz, 2 H) 2.83 - 2.88 (m, 2 H) 2.90 -
2.95 (m, 2 H) 3.79 (s, 3 H) 3.82 (s, 3 H) 6.82 - 6.90 (m, 3
H) 7.31 - 7.35 (m, 1 H) 7.40 (t, J=7.51 Hz, 2 H) 7.44 - 7.48
(m, 2 H) 7.79 (s, 1 H) 7.96 (s, 1 H). 13C NMR (126 MHz,
CDCl3) δ: 23.2, 28.5, 28.6, 55.8, 56.1, 110.0, 111.5, 114.5,
116.3, 125.7, 128.3, 128.5, 130.4, 132.4, 136.1, 136.3,
136.6, 136.9, 152.8, 190.4

once with 20 mL water. The toluene layer was dried over
anhydrous magnesium sulphate and concentrated in vacuo
to give IV, 2-benzoylcyclohexanone. The resulting crude
product was purified by column chromatography.
boron tribromide (BBr3) solution in dry dichloromethane
(30 mL) at 0 °C. After 8 hours of stirring at room
temperature, the reaction mixture was poured into 150 mL
of cold water and extracted with EA. The organic layer was
collected and dried over anhydrous magnesium sulfate. The
resulting crude was finally purified through flash column
chromatography to give pure polyhydroxylated compounds
VII.
3-Hydroxy-1-(2-hydroxyphenyl)-5-(3-hydroxyphenyl)penta-
2,4-dien-1-one (25). Orange; m.p.:149-150ºC; Mass
calculated: 282.0892; Mass found: 282.0894. 1H NMR (500
MHz, acetone-d6) δ: 6.75 (s, 1 H) 6.87 (d, J=15.73 Hz, 1 H)
6.91 - 6.94 (m, 1 H) 6.95 - 7.00 (m, 2 H) 7.14 - 7.20 (m, 2
H) 7.25 - 7.31 (m, 1 H) 7.51 - 7.56 (m, 1 H) 7.63 (d,
J=16.02 Hz, 1 H) 7.94 (dd, J=8.30, 1.31 Hz, 1 H) 8.60 (s, 1
H) 12.09 (s, 1 H) 14.64 (br. s., 1 H) 13C NMR (126 MHz,
acetone-d6) δ: 97.3, 114.4, 117.4, 118.3, 119.0, 119.2,
119.7, 122.4, 129.1, 130.0, 136.1, 136.5, 139.8, 157.9,
162.5, 175.1, 196.3.
3-Hydroxy-1-(2-hydroxyphenyl)-5-(4-hydroxyphenyl)penta-
2,4-dien-1-one (26). Orange; m.p.: 149-150ºC; Mass
calculated: 282.0892; Mass found: 282.0893. 1H NMR (500
MHz, acetone-d6) δ: 6.68 (s, 1 H) 6.74 (d, J=15.73 Hz, 1 H)
6.89 - 6.99 (m, 4 H) 7.49 - 7.54 (m, 1 H) 7.59 (d, J=8.74
Hz, 2 H) 7.66 (d, J=16.02 Hz, 1 H) 7.92 (dd, J=8.30, 1.31
Hz, 1 H) 9.16 (br. s., 1 H) 12.15 (br. s., 1 H) 14.79 (br. s., 1
H). 13C NMR (126 MHz, acetone-d6) δ: 97.9, 101.6, 101.6,
121.3, 124.2, 124.3, 131.9, 134.2, 135.3, 141.0, 145.5,
165.1, 167.6, 181.4, 193.2.
General procedure for synthesis of V. In a 50 mL SNRB, 2-
benzoylcyclohexanone (5 mmol) and appropriate aromatic
aldehyde (5 mmol) were dissolved in 30 mL of acetic acid.
A catalytic amount of concentrated sulfuric acid was added
and the reaction mixture was stirred for overnight. The
resulting mixture was extracted with EA and washed with
10% sodium bicarbonate solution. The organic layer was
then dried over anhydrous magnesium sulphate and
evaporated using rotatory evaporator. The target compound
was purified by gravitational column chromatography.
2-Benzoyl-6-(3-hydroxybenzylidene)cyclohexen-1-ol (22).
Yellow; m.p.: 120-121ºC; Mass calculated: 306.1256; Mass
found: 306.1258. 1H NMR (500 MHz, CDCl3) δ: 1.66
(quin, J=6.04 Hz, 2 H) 2.53 (t, J=5.97 Hz, 2 H) 2.76 (t,
J=5.53 Hz, 2 H) 5.39 (br. s., 1 H) 6.80 (dd, J=8.01, 2.18 Hz,
1 H) 6.91 (s, 1 H) 7.02 (d, J=7.86 Hz, 1 H) 7.22 - 7.29 (m, 1
H) 7.40 - 7.50 (m, 3 H) 7.58 (d, J=7.28 Hz, 2 H) 7.70 (s, 1
H) 16.71 (s, 1 H). 13C NMR (126 MHz, CDCl3) δ: 23.5,
27.2, 27.6, 108.6, 115.4, 116.7, 122.7, 127.6, 128.2, 129.5,
130.7, 132.8, 133.1, 137.8, 138.2, 155.5, 176.2, 195.8
2-Benzoyl-6-(4-hydroxybenzylidene)cyclohexen-1-ol (23).
Yellow; m.p.: 158-160ºC; Mass calculated: 306.1256; Mass
found: 306.1268. 1H NMR (500 MHz, CDCl3) δ: 1.68
(quin, J=5.97 Hz, 2 H) 2.53 (t, J=5.82 Hz, 2 H) 2.77 (t,
J=5.53 Hz, 2 H) 6.87 (d, J=8.45 Hz, 2 H) 7.38 (d, J=8.15
Hz, 2 H) 7.41 - 7.49 (m, 3 H) 7.57 (d, J=7.28 Hz, 2 H) 7.71
(s, 1 H) 16.87 (s, 1 H). 13C NMR (126 MHz, CDCl3) δ:
23.6, 27.1, 27.7, 108.1, 115.4, 127.6, 128.1, 129.1, 130.5,
130.6, 132.1, 133.4, 138.2, 155.8, 177.5, 194.4
5-(2,4-Dihydroxyphenyl)-3-hydroxy-1-(2-
hydroxyphenyl)penta-2,4-dien-1-one (27). Brown; m.p.: 90-
92ºC; Mass calculated: 298.0841; Mass found: 298.0845.
1H NMR (500 MHz, acetone-d6) δ: 6.47 (d, J=8.45 Hz, 1 H)
6.51 (s, 1 H) 6.62 (s, 1 H) 6.83 (d, J=16.02 Hz, 1 H) 6.92 -
6.97 (m, 2 H) 7.47 - 7.53 (m, 2 H) 7.94 (d, J=8.45 Hz, 1 H)
8.00 (d, J=16.02 Hz, 1 H) 9.15 (br. s., 2 H) 12.23 (br. s., 1
H) 14.88 (br.s., 1 H). 13C NMR (126 MHz, acetone-d6) δ:
95.9, 102.8, 108.4, 114.4, 118.2, 118.3, 119.0, 119.1, 128.9,
130.4, 135.5, 136.4, 158.6, 161.1, 162.4, 177.3, 195.2.
5-(3,4-Dihydroxyphenyl)-3-hydroxy-1-(2-
2-Benzoyl-6-(3,4-dihydroxybenzylidene)cyclohexen-1-ol
(24). Yellow; m.p.: 212-213ºC; Mass calculated: 322.1205;
1
Mass found: 322.1215. H NMR (500 MHz, acetone-d6) δ:
1.67 (quin, J=5.61 Hz, 2 H) 2.54 (t, J=5.24 Hz, 2 H) 2.79 (t,
J=5.97 Hz, 2 H) 6.87 - 7.00 (m, 2 H) 7.09 (s, 1 H) 7.44 -
7.56 (m, 3 H) 7.58 - 7.68 (m, 3 H) 8.22 (br. s., 2 H) 17.12
(s, 1 H). 13C NMR (126 MHz, acetone-d6) δ: 23.4, 26.7,
27.5, 107.8, 115.4, 117.2, 123.4, 127.6, 128.1, 128.3, 129.9,
130.5, 133.7, 138.2, 144.9, 146.1, 177.8, 193.8
hydroxyphenyl)penta-2,4-dien-1-one (28). Orange; m.p.:
155-156ºC; Mass calculated: 298.0841; Mass found:
298.0843. 1H-NMR (500 MHz, acetone-d6) δ: 6.65–6.73
(m, 2 H) 6.88–7.00 (m, 3 H) 7.11 (d, J = 8.2 Hz, 1 H) 7.23
(s, 1 H) 7.52 (t, J = 7.86 Hz, 1 H) 7.61 (d, J = 15.73 Hz, 1
H) 7.92 (d, J = 8.15 Hz, 1 H) 8.28 (br. s, 1 H) 8.61 (br. s, 1
H) 12.19 (s, 1 H) 14.81 (br. s., 1 H). 13C-NMR (126 MHz,
acetone-d6) δ: 96.4, 114.3, 115.6, 118.3, 119.0, 119.1,
119.1, 121.9, 127.5, 128.9, 135.8, 140.6, 145.6, 148.0,
162.4, 176.2, 195.6.
34. General procedure for synthesis of VI.
Phosphoryl
chloride (POCl3; 20 mmol) was added slowly to a 100 mL
SNRB flask containing a mixture of appropriate cinnamic
acid (5.5 mmol) and the 2'-hydroxyacetophenone (5 mmol)
in ice cooled pyridine (30 mL) and stirred overnight. The
reaction mixture was then poured into 100 mL cold, dilute HCl
in a 250 mL EF, followed by extraction with ethyl acetate
(EA). The organic layer was dried over anhydrous magnesium
sulfate and concentrated in vacuo. The crude product obtained
was further purified by flash chromatography to give
cinnamate ester VI.
General procedure for synthesis of VII. Purified cinnamate
ester VI was dissolved with 30 mL of pyridine in 100 mL
SNRB flask. Then, ground potassium hydroxide pellets (20
mmol) were added to the solution and stirred overnight at
room temperature. Upon completion, the reaction mixture
was poured into 150 mL cold, diluted HCl in a 250 mL EF
and stirred for 10 min. The solution was extracted with EA
and dried over anhydrous magnesium sulfate, followed by
solvent removal with rotatory evaporator under vacuo. The
resulting crude product was further purified by flash
1-(5-Chloro-2-hydroxyphenyl)-3-hydroxy-5-(3-
hydroxyphenyl)penta-2,4-dien-1-one (29). Yellow; m.p.:
181-182ºC; Mass calculated: 316.0502; Mass found:
1
316.0504. H NMR (500 MHz, acetone-d6) δ: 6.82 (s, 1 H)
6.87 - 6.95 (m, 2 H) 7.00 (d, J=9.03 Hz, 1 H) 7.14 - 7.21
(m, 2 H) 7.25 - 7.32 (m, 1 H) 7.52 (dd, J=8.88, 2.48 Hz, 1
H) 7.66 (d, J=16.02 Hz, 1 H) 7.94 (d, J=2.62 Hz, 1 H) 8.62
(s, 1 H) 12.06 (s, 1 H) 14.57 (br. s., 1 H). 13C NMR (126
MHz, acetone-d6) δ: 97.4, 114.5, 117.6, 119.7, 120.0,
120.2, 122.2, 123.5, 128.2, 130.1, 135.5, 136.5, 140.5,
157.9, 161.0, 176.0, 194.7.
1-(5-Chloro-2-hydroxyphenyl)-3-hydroxy-5-(4-
hydroxyphenyl)penta-2,4-dien-1-one (30). Yellow; m.p.:
183-184ºC; Mass calculated: 316.0502; Mass found:
chromatography
to
obtained
methoxylated
diarylpentanoids.
The
purified
methoxylated
1
316.0506. H NMR (500 MHz, acetone-d6) δ: 6.74 (s, 1 H)
diarylpentanoids (0.3 mmol) were then reacted with 1.5 mL
6.77 (d, J=16.02 Hz, 1 H) 6.93 (d, J=8.74 Hz, 2 H) 6.98 (d,

J=8.74 Hz, 1 H) 7.50 (dd, J=9.03, 2.62 Hz, 1 H) 7.60 (d,
J=8.74 Hz, 2 H) 7.70 (d, J=16.02 Hz, 1 H) 7.92 (d, J=2.62
Ligands preparation. Compounds 35 and 36, as well as co-
crystallized ligands (alpha-D-glucose) were drawn with
ChemDraw Ultra 12.0. Then, the structures were imported
to the Discovery Studio 3.1 followed by ligands preparation
protocol with the default setting, as recommended by
Accelrys. The prepared ligands were then subjected to
ligands minimization with CHARMm force field before
being used for docking analyses
Flexible docking. Minimized co-crystallized ligands were
re-docked into their respective enzymes with several sets of
amino acids as flexible residues. The top-ranked
conformations resulted from the docking experiment were
compared to their original crystallographic confirmation in
terms of RMSD. The parameters with lowest RMSD values
were selected for the flexible docking of compounds 35 and
36 in the homology model. The flexible docking results
were analyzed using Discovery Studio Visualizer
v4.1.0.14169 (Accelrys, San Diego, USA).
Hz, 1 H) 9.04 (s, 1 H) 12.13 (s, 1 H) 14.73 (br. s., 1 H). 13
C
NMR (126 MHz, acetone-d6) δ: 96.5, 116.0, 118.8, 120.1,
123.4, 126.7, 128.0, 130.3, 135.2, 140.9, 157.6, 160.0,
160.9, 177.1, 194.0.
1-(5-Chloro-2-hydroxyphenyl)-5-(3,4-dihydroxyphenyl)-3-
hydroxypenta-2,4-dien-1-one (31). Orange; m.p.: 177-
178ºC; Mass calculated: 332.0452; Mass found: 332.0462.
1H NMR (500 MHz, acetone-d6) δ: 6.67 - 6.75 (m, 2 H)
6.91 (d, J=8.15 Hz, 1 H) 6.98 (d, J=9.03 Hz, 1 H) 7.11 (dd,
J=8.15, 2.04 Hz, 1 H) 7.22 (d, J=2.04 Hz, 1 H) 7.50 (dd,
J=8.88, 2.48 Hz, 1 H) 7.63 (d, J=15.73 Hz, 1 H) 7.92 (d,
J=2.33 Hz, 1 H) 8.41 (br. s., 2 H) 12.15 (br. s., 1 H) 14.72
(br. s., 1 H). 13C NMR (126 MHz, acetone-d6) δ: 96.5,
114.4, 115.7, 118.9, 120.1, 120.1, 122.1, 123.4, 127.4,
128.0, 135.2, 141.3, 145.6, 148.2, 160.9, 177.1, 194.0.
1-(2,5-Dihydroxyphenyl)-5-(furan-2-yl)-3-hydroxypenta-
2,4-dien-1-one (32). Brown; m.p.: 142-143ºC; Mass
calculated: 272.0685; Mass found: 272.0690. 1H NMR (500
MHz, acetone-d6) δ: 6.62 - 6.65 (m, 2 H) 6.67 (d, J=15.73
Hz, 1 H) 6.83 (d, J=8.74 Hz, 1 H) 6.88 (d, J=3.20 Hz, 1 H)
7.10 (dd, J=8.88, 2.77 Hz, 1 H) 7.34 (d, J=2.91 Hz, 1 H)
7.49 (d, J=15.73 Hz, 1 H) 7.76 (s, 1 H) 8.15 (s, 1 H) 11.51
(s, 1 H) 14.75 (br. s., 1 H). 3C NMR (126 MHz, acetone-d6)
δ: 97.4, 112.8, 113.5, 115.3, 118.9, 118.9, 119.8, 124.5,
126.1, 145.5, 149.6, 151.7, 155.9, 174.8, 195.7.
36. Lovell SC, Davis IW, Arendall WB, 3rd, et al. Structure
validation by Calpha geometry: phi,psi and Cbeta deviation.
Proteins. 2003;50(3): 437-450.
1,5-Bis(2,5-dihydroxyphenyl)-3-hydroxypenta-2,4-dien-1-
oneone (33). Orange; m.p.: 195-196ºC; Mass calculated:
314.0790; Mass found: 314.0800. 1H NMR (500 MHz,
acetone-d6) δ: 6.59 (s, 1 H) 6.76 - 6.86 (m, 3 H) 6.91 (d,
J=16.02 Hz, 1 H) 7.06 - 7.11 (m, 2 H) 7.33 (d, J=2.91 Hz, 1
H) 7.97 (br. s., 1 H) 8.01 (d, J=16.02 Hz, 1 H) 8.13 (br. s., 1
H) 8.58 (br. s., 1 H) 11.55 (s, 1 H) 14.85 (br. s., 1 H). 13
C
NMR (126 MHz, acetone-d6) δ: 97.0, 113.4, 113.4, 117.0,
118.9, 118.9, 119.0, 121.7, 122.4, 124.3, 135.4, 149.5,
150.0, 150.6, 155.8, 181.8, 195.6.
1-(2,4-Dihydroxyphenyl)-5-(2,5-dihydroxyphenyl)-3-
hydroxypenta-2,4-dien-1-one (34). Orange; m.p.: 190-
191ºC; Mass calculated: 314.0790; Mass found: 314.0792.
1H NMR (500 MHz, acetone-d6) δ: 6.34 - 6.38 (m, 1 H)
6.46 (dd, J=8.88, 2.18 Hz, 1 H) 6.53 (s, 1 H) 6.76 - 6.80 (m,
1 H) 6.81 - 6.88 (m, 2 H) 7.08 (d, J=2.62 Hz, 1 H) 7.83 (d,
J=8.74 Hz, 1 H) 7.93 (d, J=16.02 Hz, 1 H) 8.62 (br. s., 3 H)
12.56 (br. s., 1 H) 14.47 (br. s., 1 H). 13C NMR (126 MHz,
acetone-d6) δ: 96.5, 103.2, 108.3, 112.1, 113.4, 117.0,
118.7, 122.0, 122.6, 131.3, 134.5, 149.9, 150.6, 164.7,
165.4, 174.2, 194.8.
35. Molecular modeling. Molecular docking studies were
carried out using Discovery Studio 3.1 (Accelrys, San
Diego, USA) on an Intel® (TM)2 Quad CPU Q8200
@2.33 GHz running under a Windows XP Professional
environment.
Homology modeling. The crystal structure of isomaltase
(PDB: 3A4A) from Saccharomyces cerevisiae and α-
glucosidase sequence (P53341) of Saccharomyces
cerevisiae were obtained from the Protein Data Bank and
UniProt (www.uniprot.org), respectively. Sequence
alignment of P53341 on 3A4A was performed using the
Discover Studio 3.1. Then, homology models of α-
glucosidase was built based on the sequenced template. The
homology models built were then validated by Modeler
program in Discover Studio 3.1. The model with the lowest
modeler objective function was finally selected for
ramachandran plot validation prior to molecular docking.