Fluorescent and antioxidant studies of effectively synthesized isochromenopyrrolone analogues

Article abstract of DOI:10.1039/c4ra02792b

An efficient strategy for the synthesis of 3-acetyl-2-methyl-1- phenylisochromeno [4,3-b] pyrrol-5(1H)-ones 4a-f have been developed using montmorillonite K10 as a catalyst. The reaction proceeded from acetyl acetone, substituted primary amines and ninhydrin via acidic media under solvent-free conditions. Compounds 4a-c exhibit green fluorescence under UV light, and their fluorescent properties in the liquid state were investigated. All the synthesized compounds were subjected for the evaluation of their free radical scavenging activity. Among all the tested compounds 4a and 4c exhibited good percentage inhibition in comparison with the standard, i.e. ascorbic acid. the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra02792b

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Fluorescent and antioxidant studies of effectively
synthesized isochromenopyrrolone analogues
Cite this: RSC Adv., 2014, 4, 29999
Hariyapureddy Raveendranatha Reddy, Chitreddy V. Subba Reddy,
*
*
Radhakrishnan Subashini and Selvaraj Mohana Roopan
An efficient strategy for the synthesis of 3-acetyl-2-methyl-1-phenylisochromeno [4,3-b] pyrrol-5(1H)-
ones 4a–f have been developed using montmorillonite K10 as a catalyst. The reaction proceeded from
acetyl acetone, substituted primary amines and ninhydrin via acidic media under solvent-free conditions.
Compounds 4a–c exhibit green fluorescence under UV light, and their fluorescent properties in the
liquid state were investigated. All the synthesized compounds were subjected for the evaluation of their
free radical scavenging activity. Among all the tested compounds 4a and 4c exhibited good percentage
inhibition in comparison with the standard, i.e. ascorbic acid.
Received 29th March 2014
Accepted 17th June 2014
DOI: 10.1039/c4ra02792b
www.rsc.org/advances
These natural antioxidants avoid the toxicity problems, which
may arise from the use of synthetic antioxidants such as
1. Introduction
butylated hydroxy anisole (BHA), butylated hydroxy toluene
(BHT) and propyl gallate (PG). Due to the complexity of anti-
oxidant activity in foods, the evaluation of synthetic heterocyclic
compounds has been widely focused on recently.28
In this paper, synthesis of isochromenopyrrolone analogues
using MK-10 under solvent-free conditions as an approach for
organic synthesis is described, which involves microwave
exposure of the neat reactants. The synthesis of 3-acetyl-2-
methyl-1-phenylisochromeno [4,3-b] pyrrol-5(1H)-ones 4a–f
were carried out using MK-10 as a catalyst was found to be more
efficient with high yields compared to conventional synthesis
methods.29
Aromatic heterocyclic compounds are known to show a wide
range of ecotoxic effects, e.g. acute toxicity, cytotoxicity,1 photo-
induced toxicity,2 mutagenicity3 and carcinogenicity.4 New effi-
cient methods for the synthesis of heterocycles are a topic of
major interest in modern synthetic organic chemistry.5 Among
the heterocycles isocoumarin represents the foremost class of
naturally occurring lactones that display a wide range of bio-
logical activities such as protease inhibitor properties, anti-
fungal, cytotoxic, anti-allergic, antimicrobial and antimalarial
effects.6–10 Isocoumarins are a class of natural products with a
broad spectrum of biological activity,11,12 including anti-
oxidative,13 antiangiogenic,14 antifungal,15,16 anti-allergic and
antimicrobial8–10 activities. They are also important in medic-
inal chemistry as building blocks for bioactive compounds.17,18
In addition to its natural occurrence,19,20 various synthetic
methodologies for construction of isocoumarins have been
demonstrated.11 Note that isocoumarins are useful synthetic
precursors to other heterocyclic and carbocyclic compounds.21,22
Free radicals oxidatively damage lipids, proteins and
genomic DNA integrity, and they are widely recognized as the
root cause of numerous degenerative diseases including
cancer.23 Antioxidants are potent scavengers of free radicals and
serve as inhibitors of neoplastic processes.24 Vegetables, fruits
and their seeds are rich sources of vitamins C, E, b-carotene and
other compounds that might protect the organism against free
radical induced injury and diseases.25,26 There has been an
increasing interest in the use of natural antioxidants, such as
tocopherols, avonoids for the preservation of food materials.27
2. Results and discussion
2.1 Chemistry
In this work, we have reported the synthesis of a novel series of
3-acetyl-2-methyl-1-phenylisochromeno [4,3-b] pyrrol-5(1H)-
ones 4a–f using MK-10 as a catalyst. The antioxidant activity and
uorescence properties of these 3-acetyl-2-methyl-1-phenyl-
isochromeno [4,3-b] pyrrol-5(1H)-ones 4a–f have also been
reported.
The formation of 4a–f was conrmed by FTIR, 1H NMR, 13
C
NMR and mass spectral analysis. FT-IR data of compound 4a
shows an absorption peak at 1462 cmꢀ1, indicating benzene
C]C stretching, a peak at 1668 cmꢀ1, indicating alkene C]C
stretching, a peak at 1732 cmꢀ1, indicating C]O stretching,
and peaks at 3199–3057 cmꢀ1, indicating sp3 C–H stretching.
1H-NMR data of compound 4a conrms the existence of one
methyl of pyrrole ring, one methyl group of the acetyl group and
two methyl groups of substituted amine groups at d 1.04, 1.04,
2.32, 2.79 ppm respectively, as well as two methylene protons of
Organic Chemistry Division, School of Advanced Sciences, VIT University, Vellore
632014, Tamilnadu, India. E-mail: mohanaroopan.s@gmail.com; dr.subashini.r@
gmail.com; Fax: +91-416-224-3092; Tel: +0416-220-2352
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Scheme
1 Synthesis of 3-acetyl-2-methyl-1-phenylisochromeno
[4,3-b] pyrrol-5(1H)-ones 4a–f.
the ethyl groups at d 2.26 and the seven aromatic protons that
exist between d 6.2 to 8.36 ppm. 13C-NMR data of compound 4a
conrms the existence of six aliphatic carbons at d 12.26–31.30
ppm, sixteen aromatic carbons between d 110.4–142.1 ppm and
two carbonyl groups at d 161.99 (–C]O of isocoumarin ring)
and 193.66 (–C]O of the acetyl group) (Scheme 1).
Fig. 1 Comparison of the percentage inhibition of H2O2 assay of 3-
acetyl-2-methyl-1-phenylisochromeno [4,3-b] pyrrol-5(1H)-ones
4a–f.
Table 2 Percentage inhibition of DPPH assay of 3-acetyl-2-methyl-1-
phenylisochromeno [4,3-b] pyrrol-5(1H)-ones 4a–f
2.2 Fluorescence studies
For the uorescence studies, we found that the compound 4c
exhibits a strong emission at 464 nm, the compound 4b shows
emission at 462 nm, which is similar to that of 4c, and the
compound 4a shows weak emission at 456 nm.
% Inhibition
Conc. mL
4a
4b
4c
4d
4e
4f
4a
10
50
100
IC50
24.96
55.73
92.77
1.76
21.62
51.89
88.15
1.88
22.13
50.20
85.73
1.91
18.70
54.00
86.92
1.90
17.28
48.55
67.35
2.22
19.15
52.26
85.09
1.93
16.78
41.51
64.42
2.38
2.3 Hydrogen peroxide scavenging assay
In the present study, hydrogen peroxide scavenging assay was
performed for isochromenopyrrolones 4a–f. The absorbance of
the standard (ascorbic acid) and the compounds 4a–f was
measured at 230 nm, and the results were tabulated in Table 1.
The percentage inhibition of the target molecules 4a–f has been
plotted against the various concentrations of the standard
(ascorbic acid) and the test solutions (Fig. 1). All readings were
obtained in triplicate to check their accuracy.
2.4 DPPH assay
In the present study, the DPPH assay was performed for the
isochromenopyrrolones 4a–f. The absorbance of the standard
(ascorbic acid), and compounds 4a–f were measured at 520 nm,
and the results are listed in Table 2. The percentage inhibition
of the target molecules have been plotted against the various
concentrations of the standard (ascorbic acid) and the test
Fig. 2 Comparison of the percentage inhibition of DPPH assay of 3-
acetyl-2-methyl-1-phenylisochromeno [4,3-b] pyrrol-5(1H)-ones
4a–f.
Table 1 Percentage inhibition of H2O2 assay of 3-acetyl-2-methyl-1-
phenylisochromeno [4,3-b] pyrrol-5(1H)-ones 4a–f
% Inhibition
solutions 4a–f (Fig. 2). All readings were obtained in triplicate to
Conc. mL
4a
4b
4c
4d
4e
4f
check their accuracy.
10
20
30
50
100
IC50
41.63
50.85
58.38
84.46
88.70
1.84
40.62
45.68
53.64
83.82
87.64
2.07
40.81
48.14
54.76
74.05
83.64
2.07
11.07
20.84
32.42
52.68
76.21
2.46
22.61
31.74
48.89
72.14
82.38
2.90
10.54
18.19
32.16
52.05
74.89
2.38
3. Experimental
Solvents and reagents were commercially sourced and used
without further purication. Thin-layered chromatography
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(TLC) was performed on preparative plates of silica gel. Visu- microwave irradiation methods. The results of the comparison
alization was made using a UV chamber. Column chromatog- are listed in Table 3.
raphy was performed by using silica gel (60–120 mesh). Melting
points were measured on a Elchem Microprocessor-based DT pyrrol-5(1H)-one (4a). Pale brown solid, mol. formula:
apparatus using an open capillary tube, and they are corrected 24H23NO3, exact mass: 373.1678, mol. wt.: 373.4443, yield 82%,
3-Acetyl-1-(2,6-diethylphenyl)-2-methylisochromeno [4,3-b]
C
with the standard, i.e. benzoic acid. IR spectra were obtained on m. pt. 209–211 C. FT-IR (KBr pellets, cmꢀ1): 3388.93, 3199.91,
a Nucon infrared spectrophotometer (KBr disc). UV-vis spec- 3057.17, 2966.52, 1732.08, 1668.43, 1462.04. 1H NMR (500 MHz,
trum was obtained on UV-2550, Shimadzu Corporation, Kyoto, CDCl3): d ¼ 8.35–8.36 (1H, dd, J1 ¼ 1.5 Hz J2 ¼ 1 Hz, –CH), 7.55–
Japan. The NMR spectrum was recorded on a Bruker Avance III- 7.57 (1H, t, –CH), 7.34 (2H, m, –CH), 7.30 (1H, d, -CH), 7.28 (1H,
400 & 500 MHz spectrometer with tetramethylsilane (TMS) as an d, -CH), 6.27–6.28 (1H, d, J ¼ 5 Hz, –CH), 2.79 (3H, s, –CH3), 2.32
internal standard. Chemical shis were reported in d units (3H, s, –CH3), 2.23 (2 ꢂ 2H, m, 2-CH2) of Et, 1.01–1.05 (2 ꢂ 3H, t,
(ppm). GC-MS spectra were recorded on a Perkin Elmer spec- 2-CH3) of Et. 13C NMR (125 MHz, CDCl3): d ¼ 193.6, 161.9, 142.1,
trophotometer, GC model: clarus 680, mass spectrometer 141.0, 138.8, 134.9, 133.8, 131.7, 130.6, 130.5, 2 ꢂ 127.1, 2 ꢂ
model: clarus 600 (EI). The uorescence spectra were obtained 125.6, 117.8, 117.7, 111.5, 110.4, 31.3, 2 ꢂ 23.7, 2 ꢂ 13.7, 12.2.
ꢁ
on Hitachi F-7000 FL spectrophotometer.
Mass: m/z 373.21.
3-Acetyl-1-(2,3-dimethylphenyl)-2-methylisochromeno[4,3-b]
pyrrol-5(1H)-one (4b). Pale brown solid, mol. formula:
3.1 General procedure for the synthesis of 3-acetyl-2-methyl-
1-phenylisochromeno [4,3-b] pyrrol-5(1H)-one (4f)
C
22H19NO3, exact mass: 345.1365, mol. wt.: 345.3912, yield 84%,
m. pt. 202–204 C. FT-IR (KBr pellets, cmꢀ1): 3201.83, 1761.65,
ꢁ
Method A: (E)-2-hydroxy-2-(2-oxo-4-(phenylimino)pentan-3-yl)- 1664.57. 1H NMR (500 MHz, CDCl3): d ¼ 1.85 (3H, s, –CH3), 2.36
1H-indene-1,3(2H)-dione (3f). A mixture of acetyl acetone 1 (1.1 (3H, s, –CH3), 2.43 (3H, s, –CH3), 2.77 (3H, s, –CH3), 6.28–6.30
mmol) and aniline 2f (1.1 mmol) were heated at 85 ꢁC for 15–30 (1H, d, J ¼ 10 Hz, –CH), 7.14–7.16 (1H, d, J ¼ 10 Hz, –CH), 7.33
min. Then, the reaction mixture was added to a solution of (3H, m, –CH), 7.44–7.46 (1H, d, J ¼ 10 Hz, –CH), 8.36–8.35 (1H,
ninhydrin (1.1 mmol) in acetic acid (10 mL), and stirred at room d, J ¼ 5 Hz –CH). 13C NMR (100 MHz, CDCl3): d ¼ 12.3, 13.8,
temperature until the reactants disappeared. The progress of the 20.5, 31.4, 110.25, 117.8, 118.0, 125.7, 126.1, 2 ꢂ 127.2, 130.8,
reaction was monitored by TLC. Aer the completion, the reac- 131.8, 131.9, 2 ꢂ 135.0, 135.5, 136.0, 139.2, 139.5, 162.1, 193.9.
tion mixture was cooled to room temperature, and then this GC-MS (EI): 345.26.
mixture was quenched using crushed ice. The solid formed was
3-Acetyl-1-benzyl-2-methylisochromeno[4,3-b]pyrrol-5(1H)-
allowed to stand for 30 min and then ltered. Compound 3f was one (4c). Pale brown solid, mol. formula: C21H17NO3, exact
recrystallized by mixture of acetone and hexane (2 : 8) to afford mass: 331.1208, mol. wt.: 331.3646, yield 95%, m. pt. 182 C29
the crystals of intermediate compound 3f.
(lit. 182). FT-IR (KBr pellets, cmꢀ1): 3194.12, 3126.61, 2968.45,
ꢁ
3-Acetyl-2-methyl-1-phenylisochromeno [4,3-b]pyrrol-5(1H)- 2877.79, 1722.43, 1666.50, 1612.49. 1H NMR (500 MHz, CDCl3):
one (4f). About 0.5 mL of conc. H2SO4 was added to a solution of d ¼ 2.67 (3H, s, –CH3), 2.74 (3H, s,–CH3), 5.57 (2H, s, –CH2), 7.07
200 mg of compound 3 in 10 mL of aceticꢁacid. The reaction (2H, d, J ¼ 10 Hz, –CH), 7.34 (4H, m, –CH), 7.44–7.46 (1H, d, J ¼
mixture was heated on a water bath at 85 C for about 30–45 10 Hz, –CH), 7.54 (1H, m, –CH), 8.39 (1H, m, –CH). 13C NMR
min. The initial pale green color of the solution was intensied (125 MHz, CDCl3): d ¼ 11.4, 31.6, 48.6, 110.4, 111.6, 117.9, 118.8,
to brown, which indicated the conversion of product 4a. The 125.5, 126.7, 2 ꢂ 128.2, 129.3, 129.5, 130.4, 132.3, 135.1, 135.2,
progress of the reaction was monitored by TLC. Then, the 139.1, 141.1, 161.9, 193.8. Mass: m/z 331.17.
reaction mixture was cooled to room temperature and poured
3-Acetyl-2-methyl-1-m-tolylisochromeno[4,3-b]pyrrol-5(1H)-
into crush ice with continuous stirring. The precipitated solid one (4d). Pale brown solid, mol. formula: C21H17NO3, exact
was allowed to stand for 30 min and then ltered. Then, the mass: 331.1208, mol. wt.: 331.3646, yield 88%, m. pt. 185–
solid obtained was puried by column chromatography using 187 ꢁC. FT-IR (KBr pellets, cmꢀ1): 2918.30, 2848.86, 1772.58,
petroleum ether: ethyl acetate (8 : 2) as the eluent to afford the
reddish brown crystals of isochromenopyrrolone 4a.
Method-B:
3-acetyl-2-methyl-1-phenylisochromeno[4,3-b]-
Table
3 Reaction parameters of 3-acetyl-2-methyl-1-phenyl-
isochromeno [4,3-b] pyrrol-5(1H)-ones 4a–f
pyrrol-5(1H)-one (4f). Acetyl acetone 1 (1.1 mmol), aniline 2f (1.1
mmol), ninhydrin (1.1 mmol), followed by addition of MK-10
(10 mg) were introduced in an Erlenmeyer ask. This mixture
was subjected to microwave irradiation for sufficient intervals of
time using resting intervals of 1 min aer every 30 s of irradi-
ation. The progress of the reaction was monitored by TLC. Aer
cooling, the reaction mixture became sticky, and the sticky solid
was then triturated to afford the product. The product was
recrystallized by mixture of acetone and hexane (2 : 8) to afford
the crystals of compound 4f. Optimization of 3-acetyl-2-methyl-
1-phenylisochromeno [4,3-b]pyrrol-5(1H)-one 4a–f was per-
formed by comparing the yield of the conventional and
Time
Yield (%)
Entry
Product
CHa (h)
MWb (min)
CHa
MWb
M.P. (ꢁC)
1
2
3
4
5
6
4a
4b
4c
4d
4e
4f
2.45
2.40
2.50
2.45
2.45
3.05
1.20
1.10
1.40
1.20
1
79
78
86
83
85
82
82
84
95
88
89
85
209
202
18029
187
194
1.10
24529
a
Conventional heating–stirring, 85 ꢁC, gla. AcOH, conc. H2SO4.
Microwave irradiated, MK-10.
b
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1
1699.29, 1633.71. H NMR (400 MHz, CDCl3): d ¼ 2.48 (3H, s,
Ab ¼ absorbance of blank
DPPH radical scavenging assay. Radical scavenging activity
–CH3), 2.56 (3H, s, –CH3), 2.82 (3H, s, –CH3), 6.50–6.48 (1H, d, J
¼ 8 Hz, –CH), 7.25 (1H, s, –CH), 7.35 (1H, s, –CH), 7.43–7.41 (1H, of the compounds against stable DPPH (2,2-diphenyl-2-pic-
d, J ¼ 8 Hz, –CH), 7.54 (1H, s, –CH), 7.59–7.58 (2H, d, J ¼ 4 Hz, rylhydrayl hydrate) was determined spectrophotometrically.
–CH), 8.43–8.41 (1H, d, J ¼ 8 Hz, 1H). 13C NMR (100 MHz, When DPPH reacts with an antioxidant compound, which can
CDCl3): d ¼ 12.6, 13.7, 20.5, 96.11, 112.5, 117.4, 117.5, 124.5, donate hydrogen, DPPH is reduced. The changes in colour
126.5, 126.8, 131.2, 131.6, 131.8, 133.3, 134.5, 136.0, 137.4, (from deep-violet to light yellow) were measured at 520 nm on a
139.0, 142.5, 163.2, 190.4. Mass: m/z 331.18.
UV-vis spectrophotometer. A solution of DPPH was mixed with
3-Acetyl-2-methyl-1-p-tolylisochromeno[4,3-b]pyrrol-5(1H)- the synthesized compounds 4a–f gives rise to the reduced form
one (4e). Pale brown solid, mol. formula: C21H17NO3, exact with the loss of violet color.
mass: 331.1208, mol. wt.: 331.3646, yield 89%, m. pt. 192–
194 ꢁC. FT-IR (KBr pellets, cmꢀ1): 3199.91, 2966.52, 1786.08,
1670.35, 1606.70. H NMR (500 MHz, CDCl3): d ¼ 2.40 (3H, s,
DPPHc + RH ¼ DPPH + Rc
1
where RH is the reduced form and Rc is free radical.
The DPPH radical scavenging activities of all the synthe-
sized compounds 4a–f and ascorbic acid were determined
according to the reported method.31 Initially, 1 mg mLꢀ1 of
the test material solutions and the standard (ascorbic acid) at
a concentration of 10, 50 and 100 mg mLꢀ1, respectively, were
added to 1 mL of 0.2 mM freshly prepared solution of DPPH
in ethanol. The reaction mixture was stirred vigorously and
allowed to stand for 30 min at room temperature under
dark conditions. The absorbance of each reaction mixture
was measured at 520 nm. The percentage of DPPH radical
scavenging activity (%) of the sample was calculated as
follows:
–CH3), 2.55 (3H, s, –CH3), 2.74 (3H, s, –CH3), 6.47–6.45 (1H, dd,
J1 ¼ 4.4 Hz, J2 ¼ 1.4 Hz,–CH), 7.29 (3H, m, –CH), 7.38 (1H, m,
–CH), 7.44–7.42 (2H, d, J ¼ 8 Hz, –CH), 8.35–8.33 (1H, d, J ¼ 8
Hz, –CH). 13C NMR (100 MHz, CDCl3): d ¼ 12.6, 13.7, 20.5,
96.11, 112.5, 117.4, 117.5, 124.5, 126.5, 126.8, 131.2, 131.6,
131.8, 133.3, 134.5, 136.0, 137.4, 139.0, 142.5, 163.2, 190.4.
Mass: m/z 331.18.
3-Acetyl-2-methyl-1-phenylisochromeno[4,3-b]pyrrol-5(1H)-
one (4f). Pale brown solid, mol. formula: C20H15NO3, exact
mass: 317.1052, mol. wt.: 317.3380, yield 85%, m. pt. 245–
247 C29 (lit. 248). FT-IR (KBr pellets, cmꢀ1): 3057.17, 2918.30,
ꢁ
1
1712.79, 1612.49, 1494.33. H NMR (400 MHz, CDCl3): d¼ 2.38
(3H, s, –CH3), 2.73 (3H, s, –CH3), 6.36 (1H, s, –CH), 7.26 (1H, s,
–CH), 7.31–7.29 (2H, t, d, J ¼ 8 Hz, –CH), 7.44–7.42 (3H, d, J ¼ 8
% (Inhibition) ¼ [(Ab ꢀ As)/Ab] ꢂ 100
Hz, –CH), 7.64 (1H, s, –CH), 8.35–8.33 (1H, d, J ¼ 8 Hz, –CH). 13
C
NMR (100 MHz, CDCl3): d ¼ 11.4, 31.6, 118.2, 124.0, 124.4,
125.0, 125.9, 126.9, 127.3, 130.4, 130.7, 131.9, 132.0, 134.9,
135.7, 136.8, 139.0, 139.3, 190.4, 201.3. Mass: m/z 317.26.
where
Ab ¼ absorption of blank sample
As ¼ absorption of sample
3.2 Antioxidant assay
Preparation of stock solution. A solution of hydrogen
peroxide (40 mM) was prepared in phosphate buffer saline (PBS)
at pH 7.4. A stock solution (1 mg mLꢀ1) was prepared for the
synthesized compounds 4a–f in methanol and subsequently
diluted as 10, 20, 30, 50 and 100 mL.
3.3 Fluorescence studies
UV-vis spectra. The UV absorption spectrum of compound 4a
in various solvents, such as DMF, ethanol and DMSO solution,
were recorded in the range of 200–800 nm. The excitation peaks
appears at 314 nm and 365 nm (Fig. 3a).
Fluorescence spectra. The uorescence emission spectra of
the synthesized compounds 4a–c were recorded in DMSO with
excitation wavelength at 365 nm. The uorescence emission
spectra of the compounds 4a–c are shown in Fig. 3b.
Hydrogen peroxide scavenging anti-oxidant activity. Antiox-
idant activity was measured by a previously reported method-
ology.30 For the present study, the samples were prepared by
taking 1 mg of the compounds 4a–f dissolved in 1 mL of AR
grade methanol. The samples 10, 20, 30, 50 and 100 mL were
taken in different test tubes, to which 20 mL of hydrogen
peroxide was added and made up to 2 mL using phosphate
buffer and incubated at room temperature for 10 min. The
absorbance of the incubated solutions and the blank solution
(phosphate buffer without hydrogen peroxide) were recorded
against ascorbic acid. The absorbance was measured at 230 nm
using a UV-vis spectrophotometer. Radical scavenging capacity
(RSC) in percent was calculated by the following equation:
% of RSC (%) ¼ [(Ab ꢀ As)/Ab] ꢂ 100
where
RSC ¼ radical scavenging capacity
Fig. 3 3[a] Comparison of the UV-vis spectrum (DMF, ethanol and
DMSO) of 4a. [b] Fluorescence emission spectra of compounds 4a–c.
As ¼ absorbance of sample
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Conclusions
In the present study, we report an efficient one-pot MK-10-cat-
alysed synthesis of fused isochromenopyrrole-5(1H)-ones,
which gave an enhanced yield with reduced time compared to
conventional heating methods. Among the synthesized
compounds, 4c and 4b exhibits strong uorescence emission.
The synthesized compounds were successfully screened for the
free radical scavenging activity by H2O2 and DPPH assay
method. Compounds 4a, 4b and 4c showed a high percentage of
inhibition similar to that of the standard, i.e. ascorbic acid.
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