Design, synthesis and biological evaluation of novel phthalimide-Schiff base-coumarin hybrids as potent α-glucosidase inhibitors

Article abstract of DOI:10.1007/s11696-020-01246-7

We have designed and synthesized phthalimide-Schiff base-coumarin hybrids 8a–b, 9a–d, 10a–b, and 11a–d and evaluated them for α-glucosidase inhibitory potential against yeast form of this enzyme. For the synthesis of title compounds 4-hydroxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 2-hydroxybenzaldehyde, 2-hydroxybenzaldehyde derivatives, coumarin-3-carbohydrazide, and coumarin-7-yloxy-acetohydrazide were used. In vitro α-glucosidase inhibition revealed that all the synthesized compounds exhibited outstanding α-glucosidase inhibition with IC₅₀ values ranging between 85.2 ± 1.7 and 577.7 ± 7.5?μM when compared with the standard inhibitor acarbose having IC₅₀ value 750.0 ± 12.0?μM. The most potent compounds were 4-hydroxybenzaldehyde derivative 8a with coumarin-3-carbohydrazide moiety, 2-hydroxy-5-nitrobenzaldehyde derivative 11d with coumarin-7-yloxy-acetohydrazide moiety, and 2-hydroxy-5-nitrobenzaldehyde derivative 9d with coumarin-3-carbohydrazide moiety. Molecular docking studies were carried out to understand the interaction modes and binding energies of the most active compounds and standard drug acarbose. This studies predicted that compounds 8a, 11d, and 9d (respectively with binding energies = ? 10.77, ? 8.65, and ? 8.66?kcal/mol) bind to active site α-glucosidase more easily than acarbose (binding energy = ? 4.04?kcal/mol).

Full text of DOI:10.1007/s11696-020-01246-7

Chemical Papers
https://doi.org/10.1007/s11696-020-01246-7
ORIGINAL PAPER
Design, synthesis and biological evaluation of novel
phthalimide‑Schif base‑coumarin hybrids as potent α‑glucosidase
inhibitors
Maedeh Sherafati1 · Maryam Mohammadi‑Khanaposhtani2 · Shahram Moradi1 · Mohammad Sadegh Asgari3 ·
Nadia Najafabadipour4 · Mohammad Ali Faramarzi4 · Mohammad Mahdavi5 · Mahmood Biglar5 · Bagher Larijani5 ·
Haleh Hamedifar6 · Mir Hamed Hajimiri7
Received: 1 February 2020 / Accepted: 7 June 2020
© Institute of Chemistry, Slovak Academy of Sciences 2020
Abstract
We have designed and synthesized phthalimide-Schif base-coumarin hybrids 8a–b, 9a–d, 10a–b, and 11a–d and evalu-
ated them for α-glucosidase inhibitory potential against yeast form of this enzyme. For the synthesis of title compounds
4-hydroxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 2-hydroxybenzaldehyde, 2-hydroxybenzaldehyde derivatives,
coumarin-3-carbohydrazide, and coumarin-7-yloxy-acetohydrazide were used. In vitro α-glucosidase inhibition revealed that
all the synthesized compounds exhibited outstanding α-glucosidase inhibition with IC50 values ranging between 85.2 1.7
and 577.7 7.5 µM when compared with the standard inhibitor acarbose having IC50 value 750.0 12.0 µM. The most potent
compounds were 4-hydroxybenzaldehyde derivative 8a with coumarin-3-carbohydrazide moiety, 2-hydroxy-5-nitrobenza-
ldehyde derivative 11d with coumarin-7-yloxy-acetohydrazide moiety, and 2-hydroxy-5-nitrobenzaldehyde derivative 9d
with coumarin-3-carbohydrazide moiety. Molecular docking studies were carried out to understand the interaction modes
and binding energies of the most active compounds and standard drug acarbose. This studies predicted that compounds 8a,
11d, and 9d (respectively with binding energies =−10.77, −8.65, and −8.66 kcal/mol) bind to active site α-glucosidase
more easily than acarbose (binding energy=−4.04 kcal/mol).
Keywords α-Glucosidase · Docking study · Kinetic study · Phthalimide · Schif base · Coumarin
Introduction
Diabetes mellitus (DM) is the most important disease related
to carbohydrate metabolism. In type 1 of DM, defects in
secretion of insulin as the main hormone in the regulation
of carbohydrate metabolism are observed (Atkinson and
Maedeh Sherafati and Maryam Mohammadi-Khanaposhtani have
contributed equally to this work.
4
* Mohammad Mahdavi
Department of Pharmaceutical Biotechnology, Faculty
of Pharmacy and Biotechnology Research Center, Tehran
University of Medical Sciences, Tehran, Iran
momahdavi@tums.ac.ir
* Mir Hamed Hajimiri
5
h.hajimiri@nanoalvand.com
Endocrinology and Metabolism Research Center,
Endocrinology and Metabolism Clinical Sciences Institute,
Tehran University of Medical Sciences, Tehran, Iran
1
Department of Chemistry, Tehran North Branch, Islamic
Azad University, Tehran, Iran
6
7
CinnaGen Medical Biotechnology Research Center, Alborz
2
Cellular and Molecular Biology Research Center, Health
University of Medical Sciences, Karaj, Iran
Research Institute, Babol University of Medical Sciences,
Nano Alvand Company, Avicenna Tech Park, Tehran
Babol, Iran
University of Medical Sciences, Tehran, Iran
3
School of Chemistry, College of Science, University
of Tehran, Tehran, Iran
Vol.:(0123456789)
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Chemical Papers
Eisenbarth 2001). In the more common form of this disease,
type 2, commonly, the body’s resistance to insulin is seen
which can be accompanied with inadequate insulin secre-
tion (Saltiel 2001). Type 1 DM is managed by insulin and
Type 2 DM is managed by diferent classes of drugs that are
used alone or in combination with insulin, depending on the
condition of the patient (Kahn et al. 2014). Most used drugs
to treat Type 2 DM are oral and reduce blood glucose by a
variety of mechanisms (Cheng and Fantus 2005). One of
the important mechanisms for reducing blood glucose level
is α-glucosidase inhibition; this enzyme converts carbohy-
drates to glucose. Several α-glucosidase inhibitors such as
acarbose and miglitol are available in the pharmaceutical
market for treatment of Type 2 DM (AG 1994). These drugs
can lead to intestinal disturbances such as fatulence, bloat-
ing, and cramping and abdominal pain (Hollander 1992).
Therefore, development of new potent α-glucosidase inhibi-
tors with low side efects on intestine for treatment of the
type 2 diabetes is an urgent need.
Fig. 1, 3-coumarincarbohydrazones B are Schif base deriva-
tives that can inhibit signifcantly α-glucosidase (Taha et al.
2018). On the other hand, 7-hydroxy coumarin derivative
C also exhibited significant inhibitory activity against
α-glucosidase (Fig. 1) (Singh et al. 2018). Furthermore, it
is worthy to note that coumarin ring found in several potent
α-glucosidase inhibitors (Mohammadi-Khanaposhtani et al.
2018; Xu et al. 2020).
In view of the importance of the phthalimide, Schif base,
and coumarin in the design of new and potent α-glucosidase
inhibitors, in this work, phthalimide-Schif base-coumarin
hybrids 8a–b, 9a–d, 10a–b, and 11a–d were presented as
novel α-glucosidase inhibitors (Fig. 1). These compounds
with simple and efcient chemical reactions were synthe-
sized and evaluated against yeast α-glucosidase. Kinetic and
molecular modeling studies were also performed to evaluate
the interactions of these compounds with α-glucosidase.
Phthalimide is a bicyclic compound with benzo-fused
pyrrole-2,5-dione scafold. This compound was used as an
important segment in design numerous biologically active
hybrid molecules with various properties such as anti-
noceptive, anti-infammatory, antitumor, anti-convulsant,
anti-microbial activities (Sharma et al. 2010). Furthermore,
N-(3-phenoxypropyl)phthalimide derivatives A showed high
inhibitory activity against α-glucosidase (Fig. 1) (Pascale
et al. 2010).
Experimental
Melting points of phthalimide-Schif base-coumarin hybrids
8a–b, 9a–d, 10a–b, and 11a–d were measured on a Kofer
hot stage apparatus. IR spectra and NMR (1H and 13C) were
obtained by using a Bruker FT-500 and Nicolet Magna
FTIR 550 spectrophotometer on KBr disks, respectively.
Elemental analysis was recorded by an Elementar Analysen-
system GmbH VarioEL CHN mode. Compounds 1, 6, and
7 were obtained according to previous described methods
(Nagarapu et al. 2011; Secci et al. 2011; Wang et al. 2017).
One of the pharcophores widely used for design new
α-glucosidase inhibitors is Schif base (Imran et al. 2015;
Taha et al. 2015; Zawawi et al. 2016). As can be seen in
Fig. 1 Design of phthalimide-Schif base-coumarin hybrids 8a–b, 9a–d, 10a–b, and 11a–d as potent α-glucosidase inhibitors
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Chemical Papers
3.76 (t, J = 6.6 Hz, 2H, N–CH2), 2.09 (p, J = 6.1 Hz, 2H,
CH2); 13C NMR (126 MHz, DMSO-d6) δ 168.36, 163.82,
163.00, 156.37, 154.95, 149.03, 134.87, 134.71, 132.13,
130.68, 130.02, 127.47, 125.24, 123.37, 120.32, 118.21,
118.10, 116.55, 115.17, 66.53, 35.33, 27.90; Anal Calcd
for C28H21N3O6, C, 67.87; H, 4.27; N, 8.48 found C, 67.81;
H, 4.26; N, 8.49.
General procedure for the synthesis
of 4‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)benzalde‑
hyde (4) or 2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)
benzaldehyde derivatives (5a–e)
A mixture of 2-(3-bromopropyl)isoindoline-1,3-dione 1
(2 mmol, 0.53 g), 4-hydroxybenzaldehyde derivatives 2a–b
(2 mmol, 4-hydroxybenzaldehyde 2a: 0.24 g; 4-hydroxy-
3-methoxybenzaldehyde 2b: 0.3 g) or 2-hydroxybenzalde-
hyde derivatives 3a–d (2 mmol, 2-hydroxybenzaldehyde
3a: 0.24 g; 2-hydroxy-3-methoxybenzaldehyde 3b: 0.3 g;
2-hydroxy-5-bromobenzaldehyde 3c: 0.4 g; 2-hydroxy-5-ni-
trobenzaldehyde 3d: 0.33 g), and K2CO3 (2.4 mmol, 0.33 g)
in DMF (50 mL) was stirred for 6–11 h at 80 °C. After
completion of reaction (checked by TLC), water (100 mL)
was added to reaction mixture and the obtained participates
fltered of to give pure title compounds 4a–b or 5a–d.
(E)‑N’‑(4‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)‑3‑me
thoxybenzylidene)‑2‑oxo‑2H‑chromene‑3‑carbohy‑
drazide (8b)
White solid; yield 69%; m.p. 180–182 °C; IR (KBr, υ): 3283,
3076, 2922, 1661, 1645, 1087 cm−1; 1H NMR (500 MHz,
DMSO-d6) δ 9.01 (s, 1H, NH), 8.72 (s, 1H, coumarin), 8.49
(s, 1H, N=CH), 7.91–7.88 (m, 2H, Ar), 7.74–7.70 (m, 2H,
Ar), 7.48 (dd, J=8.2, 1.7 Hz, 1H, Ar), 7.42–7.37 (m, 4H,
Ar), 7.27 (s, 1H, Ar), 7.07 (d, J =8.3 Hz, 1H, Ar), 4.13 (t,
J=5.7 Hz, 2H, O–CH2), 3.77 (t, J=6.4 Hz, 2H, N–CH2),
3.53 (s, 3H, OCH3), 2.11 (p, J=6.0 Hz, 2H, CH2); 13C NMR
(126 MHz, DMSO-d6) δ 168.41, 163.01, 156.39, 154.96,
153.83, 149.54, 149.06, 134.90, 134.58, 132.28, 130.70,
129.98, 126.40, 125.26, 123.29, 120.75, 118.23, 118.11,
116.57, 112.23, 109.75, 67.38, 55.70, 35.85, 27.92; Anal
Calcd for C29H23N3O7, C, 66.28; H, 4.41; N, 8.00 found C,
66.22; H, 4.36; N, 8.11.
General procedure for the synthesis of phthalim‑
ide‑Schif base‑coumarin derivatives 8a–b, 9a–d,
10a–b, and 11a–d
A mixture of 4-(3-(1,3-dioxoisoindolin-2-yl)propoxy)ben-
zaldehyde 4a–b (1 mmol, 4-(3-(1,3-dioxoisoindolin-2-yl)
propoxy)benzaldehyde 4a: 0.31 g; 4-(3-(1,3-dioxoisoin-
dolin-2-yl)propoxy)-3-methoxybenzaldehyde 4b: 0.34 g)
or 2-(3-(1,3-dioxoisoindolin-2-yl)propoxy)benzaldehyde
derivatives 5a–d (1 mmol, 2-(3-(1,3-dioxoisoindolin-2-yl)
propoxy)benzaldehyde 5a: 0.31 g; 2-(3-(1,3-dioxoisoin-
dolin-2-yl)propoxy)-3-methoxybenzaldehyde 5b: 0.34 g;
2-(3-(1,3-dioxoisoindolin-2-yl)propoxy)-5-bromoben-
zaldehyde 5c: 0.39 g; 2-(3-(1,3-dioxoisoindolin-2-yl)
propoxy)-5-nitrobenzaldehyde 5d: 0.35 g) and 2-oxo-
2H-chromene-3-carbohydrazide 6 (1 mmol, 0.2 g) or
2-((2-oxo-2H-chromen-7-yl)oxy)acetohydrazide 7 (1 mmol,
0.23 g) in the presence of PTSA (20 mol%) in ethanol
(15 mL) was refuxed for 1–3. After completion of reac-
tion (checked by TLC, eluent: petroleum ether/ethyl ace-
tate=1:1, retention factor (Rf) value=0.3), reaction mixture
was added to 25 mL of cold water, this new mixture was
fltered of, and resulting residue was purifed with recrys-
tallization in ethanol for produce compounds 8a–b, 9a–d,
10a–b, and 11a–d.
(E)‑N’‑(2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)benzy
lidene)‑2‑oxo‑2H‑chromene‑3‑carbohydrazide (9a)
White solid; yield 74%; m.p. 166–168 °C; IR (KBr, υ): 3281,
3075, 2922, 1666, 1641, 1089 cm−1; 1H NMR (500 MHz,
DMSO-d6) δ 9.01 (s, 1H, NH), 8.72 (s, 1H, coumarin), 8.41
(s, 1H, N=CH), 7.91–7.87 (m, 2H, Ar), 7.74–7.69 (m, 3H,
Ar), 7.64–7.57 (m, 2H, Ar), 7.42–7.37 (m, 3H, Ar), 7.13
(d, J=8.4 Hz, 1H, Ar), 7.02 (t, J=7.5 Hz, 1H, Ar), 4.15 (d,
J=5.7 Hz, 2H, O–CH2), 3.80 (t, J=6.6 Hz, 2H, N–CH2),
2.13 (p, J=6.2 Hz, 2H, CH2); 13C NMR (126 MHz, DMSO-
d6) δ 168.37, 163.12, 163.01, 161.30, 156.38, 139.66,
136.76, 134.89, 134.73, 132.07, 130.69, 127.81, 125.25,
124.58, 123.36, 121.03, 118.22, 118.11, 116.56, 113.82,
112.19, 66.51, 35.23, 27.98; Anal Calcd for C28H21N3O6,
C, 67.87; H, 4.27; N, 8.48 found C, 67.82; H, 4.29; N, 8.49.
(E)‑N’‑(2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)‑3‑me
thoxybenzylidene)‑2‑oxo‑2H‑chromene‑3‑carbohy‑
drazide (9b)
(E)‑N’‑(4‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)benzy
lidene)‑2‑oxo‑2H‑chromene‑3‑carbohydrazide (8a)
White solid; yield 71%; m.p. 173–175 °C; IR (KBr, υ): 3284,
3075, 2924, 1667, 1641, 1084 cm−1; 1H NMR (500 MHz,
DMSO-d6) δ 9.05 (s, 1H, NH), 8.70 (s, 1H, coumarin), 8.49
(s, 1H, N=CH), 7.88 (d, J=7.7 Hz, 1H, Ar), 7.83–7.76 (m,
6H, Ar), 7.71 (t, J=9.0 Hz, 1H, Ar), 7.42–7.35 (m, 2H, Ar),
6.95 (d, J=8.3 Hz, 2H, Ar), 4.12 (t, J=5.8 Hz, 2H, O–CH2),
White solid; yield 68%; m.p. 154–156 °C; IR (KBr, υ): 3280,
3077, 2922, 1667, 1646, 1085 cm−1; 1H NMR (500 MHz,
DMSO-d6) δ 9.04 (s, 1H, NH), 8.74 (s, 1H, coumarin), 8.34
(s, 1H, N=CH), 7.91 (d, J=7.5 Hz, 2H, Ar), 7.86–7.81 (m,
4H, Ar), 7.73 (t, J=8.3 Hz, 2H, Ar), 7.34 (d, J=8.1 Hz, 1H,
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Ar), 7.26 (d, J=9.9 Hz, 1H, Ar), 7.17 (t, J=8.3 Hz, 1H, Ar),
4.31 (t, J=7.7, 1.6 Hz, 2H, O–CH2), 4.14 (t, J=6.1 Hz, 2H,
N–CH2), 3.81 (s, 3H, OCH3), 2.08 (p, J=6.5 Hz, 2H, CH2);
13C NMR (126 MHz, DMSO-d6) δ 168.39, 163.03, 156.41,
154.97, 153.19, 151.35, 134.91, 134.75, 132.15, 130.71,
129.75, 127.20, 125.28, 124.66, 123.41, 119.25, 118.72,
118.25, 118.14, 116.59, 72.29, 61.69, 35.20, 29.10; Anal
Calcd for C29H23N3O7, C, 66.28; H, 4.41; N, 8.00 found C,
66.25; H, 4.46; N, 7.94.
7.85–7.78 (m, 6H), 7.60 (d, J=8.6 Hz, 1H), 6.98–6.89 (m,
5H), 6.27 (d, J=9.5 Hz, 1H), 4.73 (s, 2H, O=C–CH2), 4.13
(t, J=5.9 Hz, 2H, O–CH2), 3.77 (t, J=6.7 Hz, 2H, N–CH2),
2.09 (p, J=5.9 Hz, 2H, CH2); 13C NMR (126 MHz, DMSO-
d6) δ 170.31, 168.41, 165.79, 163.84, 161.64, 160.68, 157.89,
155.63, 144.67, 140.34, 134.74, 132.17, 130.04, 129.83,
123.40, 118.56, 115.20, 113.02, 112.97, 106.93, 101.87, 66.55,
65.98, 35.35, 27.89; Anal Calcd for C29H23N3O7, C, 66.28; H,
4.41; N, 8.00 found C, 66.22; H, 4.45; N, 8.02.
(E)‑N’‑(5‑bromo‑2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)
propoxy)benzylidene)‑2‑oxo‑2H‑chromene‑3‑carbo‑
hydrazide (9c)
(E)‑N’‑(4‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)‑3‑me
thoxybenzylidene)‑2‑((2‑oxo‑2H‑chromen‑7‑yl)oxy)
acetohydrazide (10b)
White solid; yield 63%; m.p. 160–162 °C; IR (KBr, υ): 3285,
3072, 2928, 1668, 1642, 1088 cm−1; 1H NMR (500 MHz,
DMSO-d6) δ 9.07 (s, 1H, NH), 8.71 (s, 1H, coumarin), 8.41
(s, 1H, N=CH), 7.89 (dd, J=7.7, 1.4 Hz, 1H, Ar), 7.84–7.79
(m, 4H, Ar), 7.74–7.69 (m, 1H, Ar), 7.48–7.43 (m, 2H, Ar),
7.42–7.36 (m, 2H, Ar), 7.27–7.26 (m, 1H, Ar), 4.08 (t,
J=5.8 Hz, 2H, O–CH2), 3.77 (t, J=6.7 Hz, 2H, N–CH2),
2.08 (p, J=6.2 Hz, 2H, CH2); 13C NMR (126 MHz, DMSO-
d6) δ 168.39, 163.01, 159.34, 156.38, 149.04, 137.98,
134.88, 134.71, 132.16, 130.69, 128.87, 126.68, 125.25,
123.38, 122.85, 121.55, 118.22, 118.11, 116.56, 113.96,
66.29, 35.41, 27.95; Anal Calcd for C28H20BrN3O6, C,
58.55; H, 3.51; N, 7.32 found C, 58.48; H, 3.57; N, 7.36.
White solid; yield 69%; m.p. 190–192 °C; IR (KBr,
1
υ): 3284, 3073, 2927, 1661, 1645, 1088 cm−1; H NMR
(500 MHz, DMSO-d6) δ δ 9.03 (s, 1H, NH), 7.84–7.78
(m, 3H), 7.62–7.59 (m, 4H), 7.50 (d, J = 9.6 Hz, 1H),
7.28 (s, 1H), 7.08 (d, J=8.3 Hz, 1H), 6.94–6.93 (m, 2H),
6.27 (d, J =9.5 Hz, 1H), 4.73 (s, 2H, O=C–CH2), 4.14 (t,
J=5.7 Hz, 2H, O–CH2), 3.77 (t, J=6.4 Hz, 2H, N–CH2),
3.53 (s, 3H, O–CH3), 2.14–2.08 (m, 2H, CH2); 13C NMR
(126 MHz, DMSO-d6) δ 170.29, 168.45, 164.78, 161.63,
160.69, 155.63, 153.84, 149.55, 144.69, 134.61, 132.30,
129.99, 129.84, 126.44, 123.31, 118.04, 113.03, 112.99,
112.26, 109.77, 101.88, 67.40, 65.95, 55.71, 35.88, 30.77,
27.91; Anal Calcd for C30H25N3O8, C, 64.86; H, 4.54; N,
7.56 found C, 64.83; H, 4.51; N, 7.59.
(E)‑N’‑(2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)‑5‑n
itrobenzylidene)‑2‑oxo‑2H‑chromene‑3‑carbohy‑
drazide (9d)
(E)‑N’‑(2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)ben
zylidene)‑2‑((2‑oxo‑2H‑chromen‑7‑yl)oxy)acetohy‑
drazide 11a
Yellow solid; yield 61%; m.p. 188–190 °C; IR (KBr,
1
υ): 3281, 3077, 2929, 1662, 1648, 1089 cm−1; H NMR
White solid; yield 66%; m.p. 159–161 °C; IR (KBr, υ): 3287,
3068, 2922, 1661, 1647, 1079 cm−1; 1H NMR (500 MHz,
DMSO-d6) δ 9.06 (s, 1H, NH), 7.95 (d, J = 9.5 Hz, 1H),
7.82–7.75 (m, 4H), 7.64–7.56 (m, 4H), 7.13 (d, J=8.4 Hz,
1H), 7.02 (t, J = 7.5 Hz, 1H), 6.93 (d, J = 10.1 Hz, 2H),
6.27 (d, J =9.5 Hz, 1H), 4.79 (s, 2H, O=C–CH2), 4.15 (t,
J=5.7 Hz, 2H, O–CH2), 3.80 (t, J=6.6 Hz, 2H, N–CH2),
2.13 (p, J=6.0 Hz, 2H, CH2); 13C NMR (126 MHz, DMSO-
d6) δ 170.17, 168.38, 161.43, 161.29, 160.64, 155.62,
155.45, 144.61, 136.76, 134.71, 132.06, 129.87, 127.83,
124.58, 123.36, 121.03, 113.80, 113.14, 112.99, 101.89,
66.51, 65.55, 35.23, 27.98; Anal Calcd for C29H23N3O7, C,
66.28; H, 4.41; N, 8.00 found C, 66.22; H, 4.35; N, 8.08.
(500 MHz, DMSO-d6) δ 9.01 (s, 1H, NH), 8.89 (s, 1H, cou-
marin), 8.72 (s, 1H, N=CH), 8.46–8.38 (m, 1H, Ar), 8.33 (s,
1H, Ar), 7.89 (d, J=7.7 Hz, 2H, Ar), 7.72 (t, J=7.8 Hz, 2H,
Ar), 7.42–7.36 (m, 5H, Ar), 4.33 (t, J=5.6 Hz, 2H, O–CH2),
3.82 (t, J = 6.4 Hz, 2H, N–CH2), 2.18 (p, J = 5.9 Hz, 2H,
CH2); 13C NMR (126 MHz, DMSO-d6) δ 168.41, 163.01,
154.95, 149.05, 145.03, 141.15, 134.90, 134.76, 132.07,
131.33, 130.70, 125.26, 124.25, 123.63, 123.39, 118.22,
118.11, 116.57, 115.05, 61.68, 35.00, 27.76; Anal Calcd for
C28H20N4O8, C, 62.22; H, 3.73; N, 10.37 found C, 62.17; H,
3.66; N, 10.34.
(E)‑N’‑(4‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)ben
zylidene)‑2‑((2‑oxo‑2H‑chromen‑7‑yl)oxy)acetohy‑
drazide (10a)
(E)‑N’‑(2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)‑3‑me
thoxybenzylidene)‑2‑((2‑oxo‑2H‑chromen‑7‑yl)oxy)
acetohydrazide (11b)
White solid; yield 71%; m.p. 178–180 °C; IR (KBr, υ): 3277,
1
3071, 2925, 1669, 1641, 1085 cm−1; H NMR (500 MHz,
White solid; yield 64%; m.p. 170–172 °C; IR (KBr, υ):
1
DMSO-d6) δ 9.04 (s, 1H, NH), 7.96 (d, J=9.5 Hz, 1H),
3283, 3071, 2928, 1669, 1643, 1086 cm−1; H NMR
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Chemical Papers
(500 MHz, DMSO-d6) δ 9.07 (s, 1H, NH), 7.99–7.98 (m,
2H), 7.97–7.95 (m, 1H), 7.88–7.85 (m, 2H), 7.83–7.80
(m, 2H), 7.62–7.60 (m, 2H), 7.35 (d, J = 9.4 Hz,
1H), 7.27 (d, J = 9.2 Hz, 1H), 7.18 (t, J = 7.9 Hz, 1H),
6.29 (d, J = 9.5 Hz, 1H), 4.81 (s, 2H, O=C–CH2),
4.14 (t, J = 6.1 Hz, 2H, O–CH2), 3.92–3.74 (m, 5H,
OCH3&N–CH2), 2.10–2.06 (m, 2H, CH2); 13C NMR
(126 MHz, DMSO-d6) δ 170.09, 168.42, 164.86, 161.35,
160.65, 155.63, 153.17, 151.36, 144.66, 137.27, 134.75,
132.16, 129.92, 129.76, 124.68, 123.42, 119.26, 118.75,
113.22, 113.02, 101.92, 72.30, 65.38, 56.50, 35.21, 29.10;
Anal Calcd for C30H25N3O8, C, 64.86; H, 4.54; N, 7.56
found C, 64.78; H, 4.56; N, 7.58.
Biological evaluations
In vitro α-glucosidase inhibition of phthalimide-Schif base-
coumarin hybrids 8a–b, 9a–d, 10a–b, and 11a–d, kinetic
analysis of the most potent compound 8a, and docking study
of the standard drug and the most potent compounds 8a,
11d, and 9d in the active site of α-glucosidase were per-
formed exactly according to our previous work (Adib et al.
2018).
Results and discussion
Chemistry
(E)‑N’‑(5‑bromo‑2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)pro‑
poxy)benzylidene)‑2‑((2‑oxo‑2H‑chromen‑7‑yl)oxy)
acetohydrazide (11c)
Chemical reactions for preparation of phthalimide-Schif
base-coumarin hybrids 8a–b, 9a–d, 10a–b, and 11a–d are
depicted in Scheme 1. These reaction were started with reac-
tion between 2-(3-bromopropyl)isoindoline-1,3-dione 1 and
4-hydroxybenzaldehyde derivatives 2a–b or 2-hydroxyben-
zaldehyde derivatives 3a–d in presence of K2CO3 in DMF
to give aldehyde derivatives 4a–b or 5a–d. The next step,
depending on the type of used coumarin, target compounds
were obtained. For preparation of 3-coumarincarbohy-
drazone-phthalimides 8a–b or 9a–d, we used of reaction
between aldehyde derivatives 4a–b or 5a–d and 2-oxo-
2H-chromene-3-carbohydrazide 6 in the presence of PTSA
in ethanol and for synthesis of coumarin-7-yloxy-carbohy-
drazone-phthalimides 10a–b or 11a–d, aldehyde derivatives
4a–b or 5a–d reacted with 2-((2-oxo-2H-chromen-7-yl)oxy)
acetohydrazide 7 in the latter condition.
White solid; yield 63%; m.p. 166–168 °C; IR (KBr, υ):
1
3279, 3074, 2929, 1661, 1645, 1081 cm−1; H NMR
(500 MHz, DMSO-d6) δ 9.06 (s, 1H, NH), 7.96 (d,
J = 9.5 Hz, 2H), 7.61 (m, 3H), 7.46 (d, J = 6.3 Hz, 2H),
7.14–7.09 (m, 1H), 6.95–6.91 (m, 4H), 6.28 (d, J =9.5 Hz,
1H), 4.76 (s, 2H, O=C–CH2), 4.09 (t, J = 5.9 Hz, 2H,
O–CH2), 3.78 (t, J = 6.7 Hz, 2H, N–CH2), 2.08 (d,
J = 6.1 Hz, 2H, CH2); 13C NMR (126 MHz, DMSO-d6) δ
170.24, 168.43, 161.53, 160.67, 159.35, 155.63, 144.66,
137.99, 134.73, 132.18, 130.72, 129.86, 123.40, 122.87,
121.58, 117.61, 113.98, 113.10, 113.02, 106.54, 101.89,
66.31, 65.74, 35.42, 27.93; Anal Calcd for C29H22BrN3O7,
C, 57.63; H, 3.67; N, 6.95 found C, 57.69; H, 3.66; N,
6.91.
In vitro α‑glucosidase inhibition activity
The α-glucosidase inhibitory activity of the synthesized
phthalimide-Schiff base-coumarin hybrids was evalu-
ated against yeast α-glucosidase and the obtained results
were compared with acarbose as a standard inhibitor
(IC50 =750.0 12.0 µM). The IC50 values of the synthesized
compounds 8a–b, 9a–d, 10a–b, and 11a–d demonstrated
that all these compounds were more potent than acarbose
(IC50s≤577.7 7.5 µM) (Table 1). The most potent com-
pound was compound 8a with inhibitory activity around
ninefold more than acarbose.
(E)‑N’‑(2‑(3‑(1,3‑dioxoisoindolin‑2‑yl)propoxy)‑5‑n
itrobenzylidene)‑2‑((2‑oxo‑2H‑chromen‑7‑yl)oxy)
acetohydrazide (11d)
Yellow solid; yield 63%; m.p. 195–197 °C; IR (KBr,
1
υ): 3281, 3073, 2927, 1661, 1642, 1087 cm−1; H NMR
(500 MHz, DMSO-d6) δ δ 9.02 (s, 1H, NH), 8.45 (dd,
J=9.2, 3.0 Hz, 1H), 8.35 (d, J=3.0 Hz, 1H), 7.97 (m, 4H),
7.82–7.79 (m, 4H), 7.60 (s, 1H), 7.38 (d, J =9.3 Hz, 1H),
6.27 (d, J =9.5 Hz, 1H), 4.80 (s, 2H, O=C–CH2), 4.33 (t,
J=5.7 Hz, 2H, O–CH2), 3.82 (t, J=6.5 Hz, 2H, N–CH2),
2.18 (p, J = 6.1 Hz, 2H, CH2); 13C NMR (126 MHz,
DMSO-d6) δ 170.11, 168.44, 165.29, 161.38, 160.64,
155.62, 144.65, 141.18, 134.77, 132.09, 131.36, 129.90,
124.28, 123.68, 123.41, 115.06, 113.19, 113.14, 113.01,
107.03, 101.90, 67.94, 65.43, 35.01, 27.75; Anal Calcd for
C29H22N4O9, C, 61.05; H, 3.89; N, 9.82 found C, 61.00; H,
3.88; N, 9.86.
In order to evaluate the structure–activity relationships
and to optimize of anti-α-glucosidase activity, 4-hydroxy-
benzaldehydes 2a–b, 2-hydroxybenzaldehyde derivatives
3a–d, coumarin-3-carbohydrazide 6, and coumarin-7-yloxy-
acetohydrazide 7 were used in the synthesis of the title
compounds.
As can be seen in Table 1, 4-hydroxybenzaldehyde deriv-
ative 8a with coumarin-3-carbohydrazide moiety showed
the highest inhibitory activity among the synthesized
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Chemical Papers
Scheme 1 Reaction scheme for synthesis of phthalimide-hydrazone-coumarin hybrids 8a–b, 9a–d, 10a–b, and 11a–d. Reagents and condition:
a K2CO3, DMF, 80 °C, 6–11 h; b PTSA, ethanol, refux, 1–3 h
compounds. 4-Hydroxy-3-methoxybenzaldehyde derivative
8b containing coumarin-3-carbohydrazide and 4-hydroxy-
benzaldehyde derivatives 10a–b containing coumarin-
7-yloxy-acetohydrazide were significantly weaker than
4-hydroxybenzaldehyde derivative 8a against α-glucosidase.
Among the 2-hydroxybenzaldehyde derivatives 9a–d
containing coumarin-3-carbohydrazide moiety, 2-hydroxy-
5-nitrobenzaldehyde derivative 9d with electron-with-
drawing substituent nitro was the most potent compound.
Replacement of nitro group with other electron-withdraw-
ing substituent bromo, as in compound 9c, led to a slight
decrease in the inhibitory activity. Moreover, 2-hydroxy-
benzaldehyde and 2-hydroxy-3-methoxybenzaldehyde
derivatives 9a–b cannot inhibit α-glucosidase well bromo
and nitro derivatives 9c–d. In summary, in this series the
trend of the inhibitory activity based on the substituent on
phenoxy group produced from benzaldehyde derivatives
was 5-nitro > 5-bromo > H > 3-methoxy. Interestingly, the
trend of the inhibitory activity in the 2-hydroxybenzal-
dehyde derivatives 11a–d containing coumarin-7-yloxy-
acetohydrazide is similar to their corresponding analogs
with coumarin-3-carbohydrazide moiety.
The comparison of IC50 values of 2-hydroxybenzaldehy
derivatives containing coumarin-7-yloxy-acetohydrazide
with their corresponding coumarin-3-carbohydrazide
analogs against α-glucosidase revealed that coumarin-
7-yloxy-acetohydrazide derivatives were more active than
their coumarin-3-carbohydrazide analogs.
As can be seen in Table 1, parent compounds 4a–b
and 5a–d did not show inhibitory activity against
α-glucosidase. Moreover, we have not been able to deter-
mine the inhibitory activity of parent compounds 6 and 7
due to non-solubility in standard solvent used in biological
evaluation.
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Chemical Papers
Table 1 In vitro α-glucosidase inhibitory activities of compounds
8a–b, 9a–d, 10a–b, and 11a–d and parent compounds 4a–b, 5a–d,
6, and 7
and 9d against α-glucosidase (Fig. 2). On the other hand,
observed IC50 value of coumarin derivative C (3.6-fold
more potent than acarbose) demonstrated that replacement
of benzyl group in 7-position with phthalimide-Schif base
led to a signifcant increase in anti-α-glucosidase activity
as observed in compound 11d (7.9-fold more potent than
acarbose) (Fig. 2).
Compound
IC50 (μM)a
Compound
IC50 (μM)a
8a
85.2 1.7
423.3 5.0
248.3 3.5
360.6 4.4
124.0 2.6
104.5 2.2
447.2 5.5
577.7 7.5
219.1 3.0
347.3 4.0
750.0 12.0
11c
112.0 2.5
94.2 2.0
>750
>750
>750
>750
>750
8b
11d
9a
4a
9b
4b
Kinetic study
9c
5a
9d
5b
The kinetic study of the most potent compound 8a was car-
ried out in order to determination of the type of inhibition
and Ki value of this compound against α-glucosidase. As
can be depicted in Fig. 3a, with increasing the concentra-
tion of compound 8a (inhibitor), the value of Vmax remained
constant and the value of Km increased. Therefore compound
8a is a competitive inhibitor for α-glucosidase. Moreover,
the secondary plot between Km and various concentrations
of compound 8a gave an estimate of Ki (Inhibition constant)
value of 80 μM for compound 8a (Fig. 3b).
10a
10b
11a
11b
Acarbose
5c
5d
>750
6
7
NDb
NDb
Acarbose
750.0 12.0
aValues are mean SD. All experiments were performed in triplet
bNot determined
Structures and inhibitory activities of the most potent
compounds A and B and compound C that were used as
lead compounds for designing of phthalimide-Schif base-
coumarin hybrids are shown in Fig. 2 (Pascale et al. 2010;
Taha et al. 2018; Singh et al. 2018). As can be seen in Fig. 2,
the most potent compound among the N-(3-phenoxypropyl)
phthalimide derivatives A was compound A4 with an inhibi-
tory activity around 4.5-fold more than standard inhibitor
acarbose. The comparison of IC50 values of N-(3-phenoxy-
propyl)phthalimide derivative A4 with the most potent new
compounds 8a, 11d, and 9d revealed that the latter our new
hybrid compounds in comparison to simple N-(3-phenoxy-
propyl)phthalimide derivatives were more active against
α-glucosidase. In contrast, lead compounds B with cou-
marin-3-carbohydrazone scafold can be acted better than
phthalimide-coumarin-3-carbohydrazone derivatives 8a
Docking study
In order to clarify interactions of the synthesized compounds
in the active site of α-glucosidase, docking study of the
standard inhibitor acarbose and the most potent compounds
8, 11d, and 9d was performed on the modeled α-glucosidase
by AutodockTools (version 1.5.6) (Adib et al. 2018). As can
be seen in Fig. 4, the standard drug interacted with the resi-
dues Asn241, Glu304, Thr307, Pro309, Ser308, Arg312,
His279, Thr301, and Gln322.
The most potent compound 8a established a hydrogen
bond and two hydrophobic interactions with active site resi-
due Arg312 through phthalimide moiety (Fig. 4). Phenoxy
group of this compound formed a π-anion and a hydropho-
bic interaction with Glu304 and Pro309, respectively. In
Fig. 2 Structures and inhibitory activities of the most potent derivatives of lead compounds A and B and lead compound C
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Chemical Papers
(a)
(b)
7
6
5
4
3
2
1
0
30
20
10
0
Concentration of Inhibitor
0 µM
35 µM
60 µM
85 µM
-1.5
-1.0
-0.5
0.0
0.5
1.0
1/[S](PNPG, mM-1)
-10
-100
-80
-60
-40
-20
0
20
40
60
80
100
Compound (8a)
Fig. 3 a Lineweaver–Burk plots for the inhibition of α-glucosidase by compound 8a and b the secondary plot between Km and various concen-
trations of compound 8a
Fig. 4 Acarbose and compound 8a in the active site of α-glucosidase
addition, two hydrophobic interactions were also observed
between coumarin moiety of compound 8a and active site
residue Val305.
Further studies on binding energies of the compound 8a
and acarbose showed that compound 8a has a lower free
binding energy (−10.77 kcal/mol) in comparison to acar-
bose (−4.04 kcal/mol) and therefore binds to α-glucosidase
more easily than acarbose. On the other hand, values of
binding energies of the second and third most potent com-
pounds 11d (−8.65 kcal/mol) and 9d (−8.66 kcal/mol) are
approximately same together and more than the most potent
compound 8a. The mentioned results are in accordance with
in vitro evaluation results (Table 1).
In the case of the second active compound 11d, 5-nitro
substituent and oxygen atom of phenoxy moiety formed
hydrogen bonds with Asn241 and His279, respectively
(Fig. 5). Furthermore, phenyl group of phenoxy moiety
established two π-π interactions with His239 and His279.
Several hydrophobic interactions were also observed
between phthalimide and coumarin moiety of the compound
11d and the active site residues Arg312, Tyr313, Val305,
and Pro309.
The third most potent compound 9d formed hydrogen
bonds with Arg312 and Pro309 through carbonyl unit of cou-
marin moiety and carbonyl and NH units of carbohydrazide
moiety (Fig. 5). This compound also created hydrophobic
interactions with Val305, Pro309, and Arg312 through
phthalimide, phenoxy, and coumarin moieties, respectively.
Conclusion
The synthesized phthalimide-Schiff base-coumarin
hybrids 8a–b, 9a–d, 10a–b, and 11a–d exhibited in vitro
α-glucosidase inhibition activity better than the reference
inhibitor acarbose. Among the synthesized compounds,
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Chemical Papers
Fig. 5 Compounds 11d and 9d in the active site of α-glucosidase
future. Lancet 383:1068–1083. https://doi.org/10.1016/S0140
-6736(13)62154-6
compounds 8a, 11d, and 9d showed the highest inhibitory
activity. The comparison of IC50 values of the synthesized
compounds 8a–b, 9a–d, 10a–b, and 11a–d with their par-
ent molecules 4a–b and 5a–d with N-(3-phenoxypropyl)
phthalimide scafold against α-glucosidase revealed that all
the new compounds were more active than their parent com-
pounds. Kinetic study of compound 8a demonstrated that
this compound is a competitive inhibitor for α-glucosidase.
Docking study of the synthesized most potent compounds
confrmed that they with low binding energy in comparison
with standard inhibitor acarbose attached to α-glucosidase
active site. These results are in agreement with the results
obtained from biological evaluation.
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