Biosynthesis, characterization, and application of Cu2O nanoparticles originated from Cressa leaf extract as an efficient green catalyst in the synthesis of some chromenes

Article abstract of DOI:10.1007/s13738-021-02378-7

Cu₂O as a new heterogeneous green nanocatalyst is biosynthesized from Cressa leaf extract and characterized by some techniques including XRD, FTIR, UV–Vis, SEM, and TEM. Then, the prepared nanocatalyst was applied in the synthesis of some chrom

Full text of DOI:10.1007/s13738-021-02378-7

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-021-02378-7
ORIGINAL PAPER
Biosynthesis, characterization, and application of Cu2O nanoparticles
originated from Cressa leaf extract as an efcient green catalyst
in the synthesis of some chromenes
Hui Hui1 · Efat Esmaeili2 · Reza Tayebee3 · Qingwen He4 · Sedighe Abbaspour3 · Muhammad Akram5 · Zahra Jalili3 ·
Narges Mahdizadeh3 · Afsane Ahmadi3
Received: 4 June 2021 / Accepted: 11 August 2021
© Iranian Chemical Society 2021
Abstract
Cu2O as a new heterogeneous green nanocatalyst is biosynthesized from Cressa leaf extract and characterized by some
techniques including XRD, FTIR, UV–Vis, SEM, and TEM. Then, the prepared nanocatalyst was applied in the synthesis
of some chromeno[4,3-b]chromenes under aerobic conditions. Reusability studies warrant acceptable reproducibility of the
nanomaterial. Low reaction time, easy workup, cost-efectiveness, wide substrate scope, good to excellent yield, and com-
plete atom economy are signifcant features of this new method. At the fnal part of this study, the in vitro cellular toxicity
of Cu2O nanoparticles is examined on SKOV3 human ovarian carcinoma cell line via an MTT assay. The reduction in cell
viability proved the cytotoxicity of the nanoparticles toward the performed ovarian cancer cell line.
Keywords Heterogeneous · Nanocatalysis · Cu2O · Chromenes · SKOV3
Introduction
therapeutic outcomes, fewer side efects, and lower sys-
temic toxicity. In this regard, various environmental benign
methodologies are introduced to prepare a large number of
pharmaceutically important chromene compounds such as
preparation of pyrazolopyridines [4], 2-amino-tetrahydro-
4H-chromene-3-carbonitriles [5], 2-amino-4H-chromenes
[6, 7], and other substituted chromenes [8, 9] that have
diverse applications as important drugs.
During the past few decades, cancer has been known as the
main reason for death globally and WHO announced that
cancer is the chief cause of~26% death per year in 2030 [1].
Among all cancers, ovarian cancer is an important case with
the annual percentage increase in occurrence and remained
as the most lethal gynecological malignancy [2, 3]; there-
fore, new treatments are necessary to overcome this type of
cancer. Nanotechnology provides new treatments with better
Although some efective routes are opened to prepare
chromeno[4,3-b]chromenes [10–15], some defciencies are
combined with most of them such as using toxic solvents,
precious catalysts, long reaction time, corrosive mediators,
tedious workup, non-recyclable nature of the catalysts, high
temperature, and low yields. Thus, progress of new efec-
tive and environmental benign protocols is demanding to
synthesize these important compounds. Among all the rec-
ommended methods, plant-based routes for the biosynthesis
of nanocatalysts are important because of low cost, being
easy to handle, and eco-friendly nature of these methods.
Therefore, these environmental benign methods are favored
over most chemical and physical routes [16].
* Qingwen He
qingwenhe267@gmail.com
1
Department of Gynecologic Oncology, Shaanxi Provincial
Cancer Hospital, Xi’an 710061, China
2
Department of Chemistry, Payame Noor University (PNU),
Tehran 19395‐4697, Iran
3
Department of Chemistry, School of Sciences, Hakim
Sabzevari University, Sabzevar 96179-76487, Iran
4
Department of Gynaecology and Obstetrics, Xi’an People’s
In the extension of our previous studies on the develop-
ment of green synthetic protocols to synthesize hetero-
cyclic compounds [17–22], herein, we report a new con-
venient and simple method to synthesize chromeno[4,3-b]
Hospital (Xi’an Fourth Hospital), Xi’an 710000, China
5
Department of Eastern Medicine, Directorate of Medical
Sciences, Government College University, Faisalabad,
Punjab, Pakistan
Vol.:(0123456789)
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Journal of the Iranian Chemical Society
chromenes by means of Cu2O nanoparticles biosynthe-
sized from Cressa leaf extract as a green heterogeneous
nanocatalyst (Scheme 1). To the best of our knowledge,
there is no report on the synthesis of Cu2O nanoparticles
using Cressa leaf extract as an effective reducing agent
for Cu2+ ions.
FTIR spectroscopy
FTIR spectroscopy was used to confirm generation of
the surface-modified Cu2O nanoparticles by CLL extract
(Fig. 1). The performed FTIR showed the presence of
the polyphenols, alkaloids, and carbohydrates in the leaf
extract, allowing generation of Cu2O nanoparticles. Weak
absorption bands around 650–750 cm−1 may be due to
the Cu–O vibrations. The exact position of Cu–O vibra-
tion is impossible because of a wide range of hydrogen
bondings. Observation of a broad band at ~ 3420 cm−1
proved coordination of amine ligands to Cu2O nanoparti-
cles and confirms the existence of O–H/N–H stretchings
due to macromolecular fragments in the extract. In addi-
tion, bands at 2920 and 2860 cm−1 are attributed to the
Results and discussion
The morphology and physicochemical properties of the
as-synthesized Cu2O nanoparticles were investigated by
means of FTIR, TEM, SEM, UV–Vis, and XRD.
Scheme 1. A general scheme for the biosynthesis and application of Cu2O nanoparticles
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Journal of the Iranian Chemical Society
Fig. 1 FTIR spectra of a the
extract and b surface-modifed
Cu2O nanoparticles
asymmetric and symmetric C–H stretchings, respectively.
The band around 1740 cm−1 is due to the carbonyl group
in the extract. The weak asymmetric C–H and O–H bend-
ings are also observed at 1450 and 1320 cm−1, respec-
tively. Other bands at 1210–1164, 1073, and 903 cm−1
were, respectively, due to C-H bending, skeletal C–C,
and bending C–H.
FESEM and TEM of Cu2O nanoparticles
FE-SEM and TEM imaging are used to justify morphology
and average size of the nanoparticles, respectively. The FE-
SEM and TEM images of Cu2O nanoparticles are shown in
Fig. 2. Figure 2a shows that Cu2O nanoparticles are semi-
spherical in shape with some agglomeration and irregulari-
ties. The exact shape and size of the nanoparticles were
investigated by TEM that shows a relatively good dispersion
Fig. 2 The FE-SEM (a) and TEM (b) images of Cu2O nanoparticles after annealing at 400 °C
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Journal of the Iranian Chemical Society
of the spherical Cu2O nanoparticles and the majority of the
nanoparticles are small in size (6–15 nm), confrming the
high surface catalytic activity of Cu2O. However, a few
nanoparticles have a bigger size (~20–50 nm), which may
be due to the presence of excessive phytochemicals on the
surface of Cu2O nanoparticles, inducing aggregation and
enlargement of the nanoparticles. However, no aggregation
in most cases suggested the presence of hydrophobic coat-
ings around the nanoparticles.
36.4° and 42.4° are due to the (111) and (200) planes that
match well with the ICDD 98-018-0846. The refections at
the 2 theta of 29.8°, 36.7°, 42.3°, 61.4°, 73.3, and 77.4 can
be indexed to the (110), (111), (200), (220), (311), and (222)
lattice planes of Cu2O (JCPDS No. 05-0667). In addition,
the observed size of the nanoparticles with XRD is bigger
than in that of TEM, which may be due to the aggregation
of particles during drying before XRD analysis.
UV–Vis and XPS
XRD
Figure 4 shows the UV–Vis (Fig. 4a) and high-resolution
XPS (Fig. 4b) of Cu2O nanoparticles. Figure 4a describes
that aqueous colloidal solution of Cu2O nanoparticles con-
frms a strong fundamental absorption band at 255 nm due
to the surface plasmon resonance (SPR) of the nanoparticles.
These nanoparticles are quite stable after one month, and no
signifcant change was observed in the UV–Vis spectrum.
The high-resolution XPS Cu2p of the as-synthesized Cu2O
nanoparticles showed the photoelectron peaks at 933.2 and
953.4 eV due to Cu2p3/2 and Cu2p1/2, respectively [23].
These signals proved the presence of copper in the nano-
material that supports the FTIR observations for the Cu–O
stretching of Cu2O.
The crystalline nature of annealed Cu2O nanoparticles was
studied by XRD (Fig. 3). The intense refections around
Catalytic tests
To fnd the best reaction conditions, a model condensation
reaction was conducted by using benzaldehyde (1 mmol),
dimedone (1 mmol), and 4-hydroxycoumarin (1 mmol)
in the presence of Cu2O nanoparticles (0.005 g) in refux-
ing acetonitrile, and efects of some important reaction
Fig. 3 Wide-angle XRD pattern of (a) Cu2O nanoparticles
Fig. 4 UV–Vis spectrum (a) and high-resolution XPS Cu2p region (b) of Cu2O nanoparticles
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Journal of the Iranian Chemical Society
Table 1 Optimization of solvent on the condensation of dimedone,
parameters were evaluated in the efcacy of condensation
benzaldehyde, and 4-hydroxycoumarin
reaction.
Entry Cu2O nano- Solvent Time (min) Temp. (°C) Yield (%)b
particles
(g)
Catalyst amount
A model reaction was performed with diferent amounts of
catalyst to optimize the optimum quantity of Cu2O. As seen
in Fig. 5, 0.005 g of Cu2O has been appropriate and gave
the yield of 93% under the selected reaction conditions.
However, further increase in the catalyst amount had no a
signifcant efect on the yield% and reaction time.
1
2
3
4
5
6
0.005
0.005
0.005
0.005
0.005
0.005
–
H2O
Toluene 120
Ethanol 120
CH3CN 60
CH3CN 45
120
120
82
80
35
62
75
93
97
Refux
Refux
Refux
Refux
Refux
Reaction conditions: dimedone (1.0 mmol), benzaldehyde
(1.0 mmol), and 4-hydroxycoumarin (1.0 mmol) were mixed in ace-
tonitrile (3 mL) under refux. The prepared surface-modifed Cu2O
nanoparticles were used in all experiments, except for entry 6 with
pure nanomaterial
Efect of diferent solvents
In this experiment, efect of solvent was investigated on the
reaction progress (Table 1). Thus, condensation of dime-
done, benzaldehyde, and 4-hydroxycoumarin was performed
under the optimum conditions in some selected solvents such
as CH3CN, H2O, toluene, ethanol, and solvent-free condi-
tion. According to the obtained data in Table 2, acetonitrile
is the best choice between the examined solvents and pro-
vided the maximum yield of 93% after 60 min. To compare
the catalytic activity of the biosynthesized Cu2O nanoparti-
cles with pure Cu2O attained after annealing at 400 °C, entry
6 was run. This fnding showed that the pure nanomaterial
has a higher catalytic activity, maybe because of the more
active surface in the absence of tailed organic functional
groups.
bYield refers to the isolated product
signifcantly afects the reaction progress and the best yield
can be achieved under refux condition (82 °C). Therefore,
the temperature 82 °C was chosen as the best for all runs in
acetonitrile. Efect of reaction time was also again studied to
explore the minimum time needed to acquire the best yield.
As Fig. 6 shows, 60 min was adequate to reach the maximum
yield of 93%.
Synthesis of diferent chromeno[4, 3‑b]chromenes
Efect of reaction time and temperature
The generality of the present methodology was explored in
the synthesis of some chromeno[4,3-b]chromene derivatives
using a variety of aromatic aldehydes. Aldehydes with dif-
ferent electron withdrawing-releasing substituents provided
good to excellent yields according to the optimum reaction
conditions (Table 2). Although most aromatic aldehydes
The impact of temperature was also investigated in the
condensation of dimedone, benzaldehyde, and 4-hydroxy-
coumarin by the presence of 0.005 g Cu2O nanoparti-
cles (Fig. 6). It was found that elevation of temperature
Fig. 5 Efect of catalyst amount
0.010 mg
0.005 mg
100
90
80
70
60
50
40
30
20
10
0
on the condensation of dime-
done (1.0 mmol), benzaldehyde
(1.0 mmol), and 4-hydroxycou-
marin (1.0 mmol) in acetonitrile
under refux
0.003 mg
0.001 mg
no catalyst
0
10
20
30
40
50
60
70
Time (min.)
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Journal of the Iranian Chemical Society
Table 2 Substrate scope and generality of the condensation reaction
Aldehyde
R1 =H
R1 =4-NO2
R1 =4-Br
R1 =4-OCH3
R1 =3-NO2
R1 =3-NO2
R1 =4-OCH3
Dimedone
Yield (%)
TOFa
M.P. (°C)
Found/reported
R2 =CH3
R2 =CH3
95
186
200
220–222/221–223
[24]
100
208–210/209–212
[24]
R2 =CH3
R2 =CH3
89
78
178
156
228–230/229–231 [25]
187–189/187–188
[25]
R2 =CH3
97
94
83
194
188
166
240–245/243–244
[24]
R2 =H
R2 =H
218–220/220–221
[24]
196–197/195–198
[25]
Reaction conditions: dimedone (1.0 mmol), benzaldehyde (1.0 mmol), and 4-hydroxycoumarin (1.0 mmol) were mixed in acetonitrile (3 mL)
under refux. Reaction time was 60 min, and 0.005 g of Cu2O was used in all cases
aTOF=(yield/time (h))/catalyst amount (g)
Fig. 6 Studying efect of reac-
100
reflux
tion temperature and time
60 °C
80
60
25 °C
40
20
0
0
20
40
60
80
100
Time (min.)
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Journal of the Iranian Chemical Society
with electron-poor and electron-rich substituents aforded
the desired products in high yields, aldehydes involving elec-
tron-withdrawing groups reacted better than with electron-
donating groups.
and reusability (Fig. 7). This study showed that the activ-
ity of Cu2O has been alleviated after fve runs. The FTIR
of the nanocatalyst was checked after ffth run. This study
showed no signifcant changes have occurred after fve reus-
ing (Fig. 8). However, the decrease in the activity of catalyst
after stepwise reusing would be due to the inactivity of the
catalyst surface. It seems that these structural changes are
not so obvious that can be detected by FTIR.
Superiority of the present method
Up to now, a number of catalysts have been documented for
the preparation of chromeno[4, 3-b]chromenes under dif-
ferent reaction conditions. Herein, the present protocol is
compared to some published methods, as shown in Table 3.
In this experiment, the comparison was made in terms of
reaction time, catalyst amount, and yield%. Interestingly, the
present methodology ofers a few advantages including a
very low amount of an environmental benign catalyst under
mild reaction conditions as well as some reported method-
ologies. The distinct feature of the introduced Cu2O catalyst
is its simplicity, easy preparation, and cheap nature of the
material. Thus, this protocol is a special case, providing a
new approach in the single-step, one-pot preparation of the
desired chromenes under milder conditions.
An elementary MTT assay and in vitro cellular
cytotoxicity of Cu2O nanoparticles
One of the most challenges in achieving a standard cancer
therapy is the preparation of biocompatible and efective
carriers to prepare drugs with more infuencing therapeutic
applications to fght cancer cells. The recent cancer statis-
tics analysis by WHO (International Agency for research
on cancer) shows that ovarian cancer has been increased
in the recent decade. Since anticancer activity of various
chromenes is studied extensively, herein, we performed
a preliminary cellular cytotoxicity test on the bare Cu2O
nanoparticles against SKOV3 ovarian cancer cell line. This
study showed that the metal oxide nanoparticles afect the
mean growth of cancer cells in a dose-dependent manner
and a signifcant decrease in the MTT signal was observed in
comparison with the untreated cells. Thus, the SKOV3 cell
line was incubated with 0–50 µg/mL Cu2O nanoparticles
for 48 h. As seen in Fig. 9, cell survival was decreased with
enhancing Cu2O concentration and the results for amounts
greater than 25 µg/mL are comparable. As a result, Cu2O
Stability and reusability of Cu2O nanoparticles
To monitor stability and reusability of Cu2O nanoparticles,
Cu2O nanoparticles were removed after completion of the
frst run by centrifuge and simple fltration. Then, the recy-
cled catalyst was washed, dried at room temperature, and
prepared for the next run. Therefore, the nanocatalyst was
reused for the subsequent fve runs to prove its good stability
Table 3 The comparison
Catalyst
Catalyst amount Time (h) Temp. (°C) Solvent
Yield (%)
90 [6]
of the catalytic activity of
Cu2O nanoparticles with
some reported catalysts in the
synthesis of chromeno[4, 3-b]
chromenes
Fe3O4@SiO2@
5 mg
0.16
r.t
EtOH
propyltriethoxysilane@o‐phe-
nylenediaminea
ZnS/CuFe2O4/agarb
30 mg
20 mg
30 mg
50 mg
0.03 g
10 mol%
2 mol %
0.5
1.3
0.1
2.5
0.75
0.5
3.5
r.t
60
ultrasonic
70
25
80
EtOH
EtOH
EtOH
EtOH
–
97 [5]
93 [8]
97 [9]
90 [26]
97 [27]
91 [28]
c
Fe3O4@SiO2–NH2
pumice microparticlesd
Nano-CuFe2O4@SO3H
WO3/ZnO@NH2-EY
ZrO2 nanoparticles
Eosin Y
H2O
r.t
CH3CN 77 [29]
green LED
Cu2O nanoparticles
5 mg
1
Refux
CH3CN 97 (This work)
Reaction conditions are described in Table 1
aDue to preparation of 2‐amino‐4‐phenyl-7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromene‐3‐carboni-
trile
bDue to preparation of 2-amino-tetrahydro-4H-chromene-3-carbonitrile
cDue to preparation of methyl 2-amino-3-cyano-4-(2-methoxy-2-oxoethyl)-7,7-dimethyl-5-oxo-5,6,7,8-tet-
rahydro-4H-chromene-4-carboxylate
dDue to preparation of 7-amino-2,4-dioxo-5-phenyl-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-6-car-
bonitrile
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Journal of the Iranian Chemical Society
Fig. 7 Yield% vs cycle number
to study reusability of Cu2O
nanoparticles
93
100
80
60
40
20
0
89
84
79
73
1
2
3
4
5
Cycle number
of XRD, FTIR, UV–Vis, XPS, SEM, and TEM. Then, the
nanomaterial is used as a superior green nanocatalyst toward
the desired heterocyclic condensation reaction. The mild
reaction conditions, wide substrate tolerance, easy workup,
high atom economy, and good to excellent yields are the
major important features of this new catalytic system. The
distinct feature of the introduced Cu2O catalyst is its sim-
plicity, simple preparation, and cheap nature of the mate-
rial. The Cu2O nanoparticles could be frequently recovered
up over four runs with a little loss of the catalytic activity.
Eventually, the in vitro cellular cytotoxicity of Cu2O nano-
particles by MTT assay showed good inhibitory efect of
the performed nanoparticles against SKOV3 human ovarian
carcinoma cell line.
Experimental section
Fig. 8 FTIR spectra of fresh (a) and reused (b) Cu2O nanoparticles
after the ffth run
Materials and methods
All materials and solvents used in the present report includ-
ing copper(II) sulfate pentahydrate (CuSO4.5H2O), aromatic
aldehydes, dimedone, and 4-hydroxycoumarin were pur-
chased from commercial resources and utilized as received
without extra purifcation (analytical grade). Morphology
studies were performed on a Mira 3-XMU FE-SEM instru-
ment. Fourier transform FTIR spectra were drawn on a
Shimadzu 8700 Fourier transform spectrophotometer with
KBr pellets. UV–visible spectroscopy was run on a Photo-
nix UV–visible array spectrophotometer. X-ray difractions
(XRDs) were studied on an Xpert difractometer with Cu Kα
radiation at 40 keV, 30 mA, and a scanning rate of 2° min−1
in the 2θ domain 5°–80.
nanoparticles can be regarded as effective toxic agents
against SKOV3 cell line and the IC50 of ~ 20 µg/mL was
achieved in this experiment.
Conclusion
Herein, we opened a new green method to prepare Cu2O
nanoparticles from the leaf extract of Cressa and progressed
an ecofriendly and efcient protocol to achieve a range of
chromeno[4,3-b]chromenes under mild conditions. Thus, the
nanocatalyst Cu2O is prepared and characterized by means
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Journal of the Iranian Chemical Society
Fig. 9 The cytotoxicity assay
of Cu2O nanoparticles by the
MTT assay
Biosynthesis of copper oxide nanoparticles Cressa
leaf extract
Cancer cell culture
The cell line SKOV3 (human ovarian cancer) was pur-
chased from NCCS (National Centre for Cell Sciences),
India. This cell line was grown and maintained in a suit-
able Minimum Essential Medium (MEM) and sub-cul-
tured in the medium involving 1% glutamine, 10% fetal
bovine, and 1% penicillin solution. Then, the cells were
trypsinated by trypsin EDTA solution and seeded at the
density of 1 × 105 cells/ well in 96-well plates and cul-
tured at 37 °C for 24 h (incubation time 48 h). Finally, the
newly prepared Cu2O nanoparticles were monitored for
the in vitro cytotoxicity efects on SKOV3 by the stand-
ard MTT assay. The plates were incubated for a further
5 h at 37 °C in a humid chamber including 5% CO2. The
formazan crystals generated via reduction of the dye by
viable cells were dissolved in 200 µl dimethyl sulfoxide
(DMSO), and the absorbance was seen at 490 nm.
The extraction of phytochemicals was performed by a
standard method commonly used for extraction [30]. Thor-
oughly washed and air-dried leaves of Cressa (900 g) were
crushed into small pieces and transferred to a 150-mL
fask containing deionized water (80 mL) in a Clevenger
apparatus and heated to 65–70 °C for 45 min. Then, the
obtained extract was fltered and stored at 4°°C for further
use. For the synthesis of Cu2O nanoparticles, 5 mL of the
leaf extract was added slowly to 25 mL of CuSO4 solu-
tion, 10 mM, followed by heating at 90 °C 5 h for 5 h with
continuous stirring. The formation of Cu2O nanoparticles
was indicated by a change of the color to green.
A general instruction for the synthesis of chromenes
Acknowledgements The authors would like to acknowledge the fnan-
Benzaldehyde (100 mg, 1 mmol), dimedone (140 mg,
1 mmol), 4-hydroxycoumarin (162 mg, 1 mmol), and the
desired amount of Cu2O (5 mg) were successively added to
a round-bottomed fask equipped with a magnet containing
acetonitrile (3 mL). Then, the reaction mixture was heated
up to refux in an open-air atmosphere, and completion of
the reaction was monitored by TLC. After completion, the
mixture was quenched with H2O (10 mL) and the desired
chromene product was dissolved in EtOAc. Finally, the
attained organic layer was dried over sodium sulfate and
the crude accomplished product was purifed by column
chromatography to aford the pure chromene.
cial support of Hakim Sabzevari University.
Declarations
Conflict of interest On behalf of all authors, the corresponding author
states that there is no confict of interest.
Informed consent Informed consent was obtained from all individual
participants included in the study.
Data availability statement The original contributions presented in the
study are included in the article/supplementary material, and further
inquiries can be directed to the corresponding author.
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Journal of the Iranian Chemical Society
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