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Efficient synthesis of
α-aminophosphonates and evaluation of significance of P=O group towards
antioxidant activity
Kunda Uma MaheswaraRaoa, SirasanagandlaSwapnab, Darla Mark Manidhara,
KandulaMadhu Kumar Reddya, Cirandur Suresh Reddya*
a
b
Department of Chemistry, Sri Venkateswara University, Tirupati-517502, A.P, India
Department of Bio-Chemistry, Sri Venkateswara University, Tirupati-517502, A.P, India
Email : csrsvu@gmail.com
Supplemental Materials
Pharmacology:
Determination of Nitric Oxide (NO) Scavenging Activity
Sodium nitropruside (5 μg/mL) in phosphate buffer pH 7.4was incubated with 100 μg/mL
concentration of test compounds dissolved in a suitable solvent (dioxane/ methanol) and tubes
were incubated at 25 C for 120 min. Control experiment was conducted with equal amount of
solvent in an identical manner. At intervals, 0.5 ml of incubation solution was taken and diluted
with 0.5 ml of Griess reagent (1% Sulfanilamide, 0.1% Nnaphthylethylenediaminedihydrochloride and 2% o-phosphoric acid dissolved in distilled water).
The absorbance of the chromophore formed during diazotization of nitrite with sulfanilamide and
subsequent N-naphthylethylenediaminedihydrochloride was read at  546 nm. The experiment
was repeated in triplicate.
NO Scavenged (%) =
( Acont  Atest )
X 100
Acont
Where Acont is the absorbance of the control reaction and Atest is the absorbance in the presence of
the sample.
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In the case of α-aminophosphonates4a-j derivatives 4ashowed the highest NO scavenging with
IC50 of 30.12 μg/mL when compared with other compounds. The remaining compounds
exhibited reducing power activity in the following order: 4b(IC5033.4 μg/mL), 4e(IC5038.56
μg/mL), 4f(IC5039.3 μg/mL), 4c(IC5040.25 μg/mL), 4i(IC5041.2 μg/mL), 4d(IC5042.73 μg/mL),
4h(IC5042.8 μg/mL), 4g(IC5049.3 μg/mL), 4j(IC5051.3 μg/mL) and when compared with BHT
(IC5040.2 μg/mL).
In the case of imines 3a-j, NO scavenging activity exhibited in the follwing order: 3a(IC5062.3
μg/mL), 3d(IC5065.4 μg/mL), 3i(IC5066.07 μg/mL), 3f (IC5069.1 μg/mL), 3e(IC5077.03 μg/mL),
3b(IC5079.6 μg/mL), 3g(IC5082.7 μg/mL), 3h (IC5085.2 μg/mL), 3c(IC5087.4 μg/mL), 3j
(IC5091.4 μg/mL) and when compared with BHT (IC50 40.2 μg/mL).
NO Method
100
90
80
70
IC50
60
50
40
30
20
10
0
3a 4a 3b 4b
3c 4c
3d 4d
3e 4e
3f 4f
3g 4g
3h 4h
3i 4i
3j 4j
BHT
Compounds
Figure S 1: NO Radical Scavenging activity
Determination of 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) free radical Scavenging Activity
The nitrogen centered stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) has often been
used to characterize antioxidants. It is reversibly reduced and the odd electron in the DPPH free
radical gives a strong absorption maximum at  517 nm, which is purple in color. This property
makes it suitable for spectrophotometric studies. A radical scavenging antioxidant reacts with
DPPH stable free radical and converts into 1,1-diphenyl-2-picrylhydrazine. The resulting
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decolorization is stoichiometric with respect to the number of electrons captured. The change in
the absorbance produced in this reaction has been used to measure antioxidant properties.
The solutions of test compounds (100 μg/mL ) were added to DPPH (100 μg/mL ) in
dioxane/ethanol. The tubes were kept at an ambient temperature for 20 min. and the absorbance
was measured at 517 nm. The difference between the test and the control experiments was
taken and expressed as the per cent scavenging of the DPPH radical.
In the case of α-aminophosphonates4a-j derivatives 4cshowed the highest DPPH radical
scavenging activity with IC50 of 27.2 μg/mL when compared with other compounds. The
remaining compounds exhibited reducing power activity in the following order: 4b(IC5027.9
μg/mL), 4a(IC5028.7 μg/mL), 4f (IC5030.2 μg/mL), 4e (IC5030.8 μg/mL), 4h (IC5031.3 μg/mL),
4g(IC5031.9 μg/mL), 4d(IC5035.8 μg/mL), 4i(IC5034.6 μg/mL), 4j(IC5049.1 μg/mL) and when
compared with BHT (IC5030.12 μg/mL).
In the case of imines 3a-j, DPPH scavenging activity exhibited in the follwing order: 3i (IC50
57.02 μg/mL), 3a (IC50 57.06 μg/mL), 3f (IC50 59.8 μg/mL), 3e (IC50 68.1 μg/mL), 3h (IC50 76.1
μg/mL), 3d (IC50 79.5 μg/mL), 3c (IC50 81.5 μg/mL), 3b (IC50 81.8 μg/mL), 3g (IC50 88.3
μg/mL), 3j (IC50 90.5 μg/mL) and when compared with BHT (IC50 30.12 μg/mL).
DPPH Method
100
90
80
70
IC50
60
50
40
30
20
10
0
3a 4a 3b 4b
3c 4c
3d 4d
3e 4e
3f 4f
3g 4g
3h 4h
3i 4i
Compounds
Figure S 2: DPPH Radical Scavenging activity
3j 4j
BHT
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Determination of Hydrogen Peroxide (H2O2) Scavenging Activity
It was determined using a modified method of Gow Chin Yen and Hui . Yin Chen. 4mM solution
of H2O2 was prepared in phosphate - buffered saline (PBS, pH 7.4). H2O2 concentration was
determined spectrophotometrically from absorbance at 230nm using molar absorptivity 81M1
cm-1. 100 μg/mL compounds solution in 4ml distilled water were added to hydrogen peroxide-
PBS solution (0.6 mL). Absorbance of H2O2 at 230nm was determined 10 min later against a
blank solution containing parent compound with PBS without H2O2. Ascorbic acid was added in
place of compound in 4ml distilled water and the solution wad added to 0.6ml H2O2 solution in
PBS. Absorbance was determined 10 minutes later against a blank solution similar to that above.
In the case of α-aminophosphonates4a-j derivatives 4bshowed the highest H2O2 scavenging
activity with IC50 of 39.2 μg/mL when compared with other compounds. The remaining
compounds exhibited reducing power activity in the following order: 4e(IC5042.25 μg/mL),
4a(IC5043.2 μg/mL), 4f(IC5044.56 μg/mL), 4c(IC5052.7 μg/mL), 4d(IC5064.1 μg/mL),
4h(IC5064.3 μg/mL), 4i(IC5065.7 μg/mL), 4g(IC5065.8 μg/mL), 4j(IC5070.1 μg/mL), and when
compared with BHT (IC5063.5 μg/mL).
In the case of imines 3a-j, H2O2 scavenging activity exhibited in the follwing order: 3a (IC50
68.72 μg/mL), 3i (IC50 69.14 μg/mL), 3d (IC50 69.8 μg/mL), 3h (IC50 70.18 μg/mL), 3f (IC50
71.7 μg/mL), 3c (IC50 74.1 μg/mL), 3b (IC50 80.14 μg/mL), 3e (IC50 80.45 μg/mL), 3g (IC50 85.2
μg/mL), 3j (IC50 94.2 μg/mL) and when compared with BHT (IC50 63.5 μg/mL).
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H2O2 Method
100
90
80
70
IC50
60
50
40
30
20
10
0
3a 4a 3b 4b
3c 4c
3d 4d
3e 4e
3f 4f
3g 4g
3h 4h
3i 4i
Compounds
Figure S 3: H2O2 Radical Scavenging activity
Figure S 4: 1H-NMR Spectra of 4e
3j 4j
BHT
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Figure S 5: 13C NMR Spectra of 4e
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Figure S 6: 31P NMR Spectra of 4e