Synthesis, anti-bacterial and anti-oxidant properties of thiadiazaphosphol-2-ones

Article abstract of DOI:10.1248/cpb.56.1486

4-Amino-5-phenyl-4H-1,2,4-triazole-3-thiol (1) underwent facile condensation with various phosphorus dichlorides (2a-j) in the presence of triethylamine in dry tetrahydrofuran at 60-65° C and afforded corresponding thiadiazaphosphol-2-ones (3a-j). Their c

Full text of DOI:10.1248/cpb.56.1486

1486
Notes
Chem. Pharm. Bull. 56(10) 1486—1489 (2008)
Vol. 56, No. 10
Synthesis, Anti-bacterial and Anti-oxidant Properties of
Thiadiazaphosphol-2-ones
Avula BALAKRISHNA,a Mudamala VEERA NARAYANA REDDY,a Sandip KUMAR NAYAK,b
Manubolu MANJUNATH, Chichili DEVENDRANATH REDDY, and Cirandur SURESH REDDY
a
a
,a
*
a Department of Chemistry, Biochemistry, S.V. University; Tirupati 517 502, India: and b Bio-Organic Division, BARC;
Mumbai 400 085, India. Received May 31, 2008; accepted July 26, 2008; published online July 30, 2008
4-Amino-5-phenyl-4H-1,2,4-triazole-3-thiol (1) underwent facile condensation with various phosphorus
dichlorides (2a—j) in the presence of triethylamine in dry tetrahydrofuran at 60—65 °C and afforded correspon-
1
ding thiadiazaphosphol-2-ones (3a—j). Their chemical structures were characterized using IR, H-, 13C-, 31P-
NMR and Mass spectral studies. All the title compounds were screened for antioxidant properties by radical
scavenging methods such as 1,1-diphenyl-2-picryl hydrazyl (DPPH), hydroxyl and lipid peroxidation. They exhib-
ited potent in vitro antioxidant activity dose dependently. Their bioassay showed them to possess significant anti-
bacterial activity.
Key words thiadiazaphosphol-2-one; spectral analysis; in vitro antioxidant activity; antibacterial activity
Syntheses of 1,2-dihydro-2l5-[1,2,4]triazolo[4,3-d][1,3,4,2]- a singlet at d 5.44—5.82.14) The 13C-NMR chemical shifts
thiadiaza-phosphol-2-one derivatives are presently reported. for them appeared in the expected region.13) 31P-chemical
1,2,4 Triazole derivatives are reported to possess a broad shifts occurred at d 16.34—ꢂ14.31.15)
spectrum of biological activities such as systemic pesticides,
The radical scavenging capacity of 3a—j was evaluated by
antifungal/microbial/lukemic/parasitic/viral/inflammatory/ methods such as 1,1-diphenyl-2-picryl hydrazyl (DPPH)
tumor/hypertensive/oxidant and anti-human immunodefi- (Fig. 1), lipid peroxidation (Fig. 2) and hydroxyl radical
ciency virus properties.1—8) They also have hypoglycemic, scavenging techniques (Fig. 3). 3g, 3h and 3i displayed ap-
hypocholesteremic activity. This background prompted syn- preciable antioxidant activity. This points to the fact that any
thesis of new thiadiazaphosphol-2-ones as continuation of electron withdrawing substituent moiety at the phosphorus in
our work in phosphorus heterocycles.9)
3a—j appears to prevent to some extent oxidative metabolic
Antioxidants are widely studied for their capacity to pro-
tect organisms and cells from damage induced by oxidative
stress during metabolism. Search for active components that
prevent or reduce the impact of oxidative stress on cells10) is
a contemporary field. Exogenous chemicals in food system
and endogenous metabolic processes in human body produce
highly reactive free radicals, especially oxygen derived ones.
They are capable of oxidizing biomolecules and cause cell
death and consequently cause tissue damage. Free radical ox-
idative processess also play a significant pathological role in
causing human diseases. Many disease manifestations such
as cancer, emphysema, cirrhosis, atherosclerosis and arthritis
have been correlated with oxidative tissue damage. Also, ex-
cessive generation of reactive oxygen species (ROS) induced
by various stimuli leads to variety of pathophysiological ab-
normalities such as inflammation, diabetes, genotoxicity and
cancer.11) In the present investigation, radical scavenging and
antioxidative activity for the newly synthesized compounds
are evaluated using three antioxidant methodologies.
Chart 1
Results and Discussion
Compounds 3a—j were synthesized by condensation of
phosphonic dichlorides 2a—d substituted phosphorodichlo-
ridates 2e—i and bis(2-chloroethyl)amine dichloride 2j with
4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol 1 in the presence
of a base in dry tetrahydrofuran (THF)12) (Chart 1).
Characteristic IR absorptions were observed in the regions
1219—1254 cmꢀ1 for PꢁO and 3170—3260 cmꢀ1 for P–
N–H stretching frequencies for 3a—j.13) The aromatic pro-
1
tons resonated as multiplets at d 6.91—8.11 in their H-
Fig. 1. DPPH Radical Scavenging Activity of Compounds
© 2008 Pharmaceutical Society of Japan
NMR spectra. The P–N–H proton chemical shift appeared as
∗ To whom correspondence should be addressed. e-mail: csrsvu@gmail.com

October 2008
1487
from 2-propanol.
6-Phenyl-2-propyl-1,2-dihydro-2l5-[1,2,4]triazolo[4,3-d][1,3,4,2]thiadi-
azaphosphol-2-one (3a): Yield was found to be 72%, mp 128—130 °C. IR
(KBr) cmꢀ1: 1247, 3173. 1H-NMR (DMSO-d6): d 4.2 (2H, m), 2.3 (2H, m),
1.3 (3H, t), 7.97—8.00 (t, 2H), 7.57—7.59 (t, 3H), 5.61 (1H, s). 31P-NMR
data: d ꢀ13.41. Anal. Calcd for C11H13N4OPS: C, 47.14; H, 4.68; N, 19.99.
Found C, 47.05; H, 4.61; N, 19.92.
2,6-Diphenyl-1,2-dihydro-2l5-[1,2,4]triazolo[4,3-d][1,3,4,2]thiadiaza-
phosphol-2-one (3b): Yield was found to be 75%, mp 166—168 °C. IR
(KBr) cmꢀ1: 1236, 3200. 1H-NMR (DMSO-d6): d 7.28—8.77 (10H, m),
5.78 (1H, s). 13C-NMR data: 131.01 (C-1ꢃ), 130.47 (C-2ꢃ), 129.82 (C-3ꢃ),
128.47 (C-4ꢃ), 129.82 (C-5ꢃ), 130.47 (C-6ꢃ), 131.01 (C-1ꢄ), 128.0 (C-2ꢄ),
127.68 (C-3ꢄ), 126.95 (C-4ꢄ), 127.68 (C-5ꢄ), 128.0 (C-6ꢄ), 161.12 (C-3),
148.24 (C-5). 31P-NMR data: d 13.76. Anal. Calcd for C14H11N4OPS: C,
53.50; H, 3.53; N, 17.83. Found C, 53.40; H, 3.52; N, 17.72.
2,6-Diphenyl-1,2-dihydro-2l5-[1,2,4]triazolo[4,3-d][1,3,4,2]thiadiaza-
phosphol-2-thione (3c): Yield was found to be 63%, mp semi-solid. IR
Fig. 2. Effect of Compounds on Ferric Ion and Ascorbic Acid Induced
Lipid Peroxidation
1
(KBr) cmꢀ1: 806 (PꢁS), 3179. H-NMR (DMSO-d6): d 7.42—8.03 (10H,
m), 5.73 (1H , s). 31P-NMR data: d ꢀ15.34. Anal. Calcd for C14H11N4PS2:
C, 50.90; H, 3.36; N, 16.96. Found C, 50.81; H, 3.29; N, 16.89.
2,6-Diphenyl-1,2-dihydro-2l5-[1,2,4]triazolo[4,3-d][1,3,4,2]thiadiaza-
phosphol-2-selone (3d): Yield was found to be 65%, mp semi-solid. IR
1
(KBr) cmꢀ1: 685 (PꢁSe); 3209. H-NMR (DMSO-d6): d 7.51—8.01 (10H,
m), 5.82 (1H, s). 13C-NMR data: 131.11 (C-1ꢃ), 130.58 (C-2ꢃ), 129.64 (C-
3ꢃ), 128.12 (C-4ꢃ), 129.72 (C-5ꢃ), 130.34 (C-6ꢃ), 130.87 (C-1ꢄ), 129.01 (C-
2ꢄ), 126.92 (C-3ꢄ), 126.01 (C-4ꢄ), 126.92 (C-5ꢄ), 129.01 (C-6ꢄ), 161.02 (C-
3), 148.72 (C-5). 31P-NMR data: d ꢀ14.41. Anal. Calcd for C14H11N4PSSe:
C, 44.57; H, 2.94; N, 14.84. Found C, 44.46; H, 2.89; N, 14.78.
2-Methoxy-6-phenyl-1,2-dihydro-2l5-[1,2,4]triazolo[4,3-d][1,3,4,2]thia-
diazaphosphol-2-one (3e): Yield was found to be 68%, mp semi-solid. IR
(KBr) cmꢀ1: 1254, 3170. 1H-NMR (DMSO-d6): d 7.95—8.03 (t, 2H),
7.54—7.56 (3H, t), 3.12 (3H, s), 5.52 (1H, s). 13C-NMR data: 149.21 (C-1ꢃ),
134.12 (C-2ꢃ), 128.12 (C-3ꢃ), 130.34 (C-4ꢃ), 127.21 (C-5ꢃ), 134.12 (C-6ꢃ),
61.24 (O–CH3), 160.12 (C-3), 149.21 (C-5). 31P-NMR data: d ꢀ13.27.
Anal. Calcd for C9H9N4O2PS: C, 40.30; H, 3.38; N, 20.89. Found C, 40.21;
H, 3.32; N, 20.81.
Fig. 3. Hydroxyl Radical Scavenging Activity
2-Ethoxy-6-phenyl-1,2-dihydro-2l5-[1,2,4]triazolo[4,3-d][1,3,4,2]thiadi-
azaphosphol-2-one (3f): Yield was found to be 80%, mp 148—150 °C. IR
(KBr) cmꢀ1: 1219, 3210. 1H-NMR (DMSO-d6): d 7.98—8.00 (t, 2H),
7.51—7.52 (3H, t), 3.84 (q, 2H), 3.06—3.07 (t, 3H), 5.76 (1H, s). 31P-NMR
data: d 14.31. FAB-MS m/z: 283 (Mꢂ1), Anal. Calcd for C10H11N4O2PS: C,
42.55; H, 3.93; N, 19.85. Found C, 42.46; H, 3.93; N, 19.77.
pathways in the living systems. In conclusion, synthesis of a
series novel thiadiazaphosphol-2-ones in high yields was ac-
complished. Some of them were found to possess good an-
tioxidant and significant antimicrobial activity. These results
encourage further in vivo studies and explore their possible
therapeutic applications.
2-(2-Chlorophenoxy)-6-phenyl-1,2-dihydro-2l5-[1,2,4]-triazolo-[4,3-
d][1,3,4,2]thiadiazaphosphol-2-one (3g): Yield was found to be 72%, mp
1
240—242 °C. IR (KBr) cmꢀ1: 1234, 3205. H-NMR (DMSO-d6): d 6.91—
8.02 (9H, m), 5.74 (1H, s). 13C-NMR data: 149.09 (C-1ꢃ), 128.48 (C-2ꢃ),
128.01 (C-3ꢃ), 130.43 (C-4ꢃ), 128.01 (C-5ꢃ), 128.48 (C-6ꢃ), 149.41 (C-1ꢄ),
125.76 (C-2ꢄ), 123.89 (C-3ꢄ), 121.2 (C-4ꢄ), 123.35 (C-5ꢄ), 122.50 (C-6ꢄ),
166.81 (C-3), 128.48 (C-5). 31P-NMR data: d ꢀ16.43. FAB-MS m/z: 365
(Mꢂ1). Anal. Calcd for C14H10ClN4O2PS: C, 46.10; H, 2.76; N,15.36.
Found C, 46.01; H, 2.69; N, 15.31.
Experimental
General The melting points were determined in open capillary tubes on
a Mel-Temp apparatus and were uncorrected. Elemental analyses were per-
formed by Central Drug Research Institute, Lucknow, India. The IR spectra
1
were recorded as KBr pellets on PERKIN-ELMER 1000 unit. All H- and
13C-NMR spectra were recorded on a VARIAN XL-300 spectrometer oper-
ating at 300 MHz for 1H and 75.46 MHz for 13C. 31P-NMR spectra were
recorded on a VARIAN XL-spectrometer operating at 161.89 MHz. The
compounds were dissolved in DMSO-d6 and chemical shifts were referenced
to TMS (1H and 13C) and 85% H3PO4 (31P). Mass spectral data was recorded
on FAB-MS instrument at 70 eV with a direct inlet system.
2-(4-Chlorophenoxy)-6-phenyl-1,2-dihydro-2l5-[1,2,4]triazolo[4,3-
d][1,3,4,2]thiadiazaphosphol-2-one (3h): Yield was found to be 73%, mp
semi-solid. IR (KBr) cmꢀ1: 1229, 3217. 1H-NMR (DMSO-d6): d 6.94—8.01
(9H, m), 5.72 (1H, s). 13C-NMR data: 147.91 (C-1ꢃ), 128.44 (C-2ꢃ), 126.41
(C-3ꢃ), 129.32 (C-4ꢃ), 126.13 (C-5ꢃ), 128.44 (C-6ꢃ), 148.18 (C-1ꢄ), 120.12
(C-2ꢄ), 119.18 (C-3ꢄ), 115.12 (C-4ꢄ), 119.18 (C-5ꢄ), 120.12 (C-6ꢄ), 165.71
(C-3), 127.45 (C-5). 31P-NMR data:
C14H10ClN4O2PS: C, 46.10; H, 2.76; N, 15.36. Found C, 46.02; H, 2.71; N,
15.30.
d
16.39. Anal. Calcd for
4-Amino-5-phenyl-4H-1,2,4-triazole-3-thiol (1) and various phosphoro-
dichloridates/phosphorus dichlorides 2a—j were procured from Sigma-
Aldrich Chemical Company, Milwaukee, U.S.A. and were used without fur-
ther purification.
6-Phenyl-2-(4-nitrophenoxy)-1,2-dihydro-2l5-[1,2,4]triazolo[4,3-
d][1,3,4,2]thiadiazaphosphol-2-one (3i): Yield was found to be 70%, mp
164—166 °C. IR (KBr) cmꢀ1: 1248, 3260. 1H-NMR (DMSO-d6): d 7.192—
8.11 (m, 9H), 5.70 (1H, s). 31P-NMR data: d 13.82. Anal. Calcd for
C14H10N5O4PS: C, 44.81; H, 2.69; N, 18.61. Found C, 44.72; H, 2.61; N,
18.53.
General Procedure for Preparation of 2-(Substituted)-6-phenyl-1,2-
dihydro-2l5-[1,2,4]-triazolo-[4,3-d][1,3,4,2]thiadiazaphosphol-2-one
(3a—j) A solution of respective phosphorodichloridate 2a—j (0.003 mol,
0.48 ml) in dry THF was added drop wise over a period of 20 min to a
stirred solution of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol 1 (0.003 mol,
570 mg) in the presence of triethylamine (0.003 mol, 0.42 ml) in 60 ml of dry
THF. After completion of addition, the temperature was increased to 60—
65 °C and stirring was continued for an additional 4—6 h. Progress of the re-
action was monitored by thin layer chromatography analysis using silica gel
as adsorbent and ethyl acetate–hexane (1 : 2) mixture as eluent. Product was
isolated from the reaction mixture by separating triethylamine hydrochloride
by filtration and evaporation of the filtrate under reduced pressure. The
residue was purified by washing with water followed by recrystallization
2-[Bis(2-chloroethyl)amino]-6-phenyl-1,2-dihydro-2l5-[1,2,4]tria-
zolo[4,3-d][1,3,4,2]thiadiazaphosphol-2-one (3j): Yield was found to be
1
70%, mp semi-solid. IR (KBr) cmꢀ1: 1252, 3181. H-NMR (DMSO-d6): d
7.97—8.01 (t, 2H), 7.53—7.55 (t, 3H), 5.44 (1H, s). 31P-NMR data: d
ꢀ12.28. Anal. Calcd for C12H14Cl2N5OPS: C, 38.11; H, 3.73; N, 18.52.
Found C, 38.02; H, 3.73; N, 18.47.
Antioxidant Activity. 1,1-Diphenyl-2-picryl Hydrazyl (DPPH) Radical
Scavenging Activity The free radical scavenging activity of 3a—j and

1488
Vol. 56, No. 10
Table 1. Antibacterial Activity (Diameter of Zone of Inhibition in mm) of Compounds 3a—j (mg/ml)
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
Chloramphenicol
50 100
Bacteria
50 100
50 100
50 100
50 100
50 100
50 100
50 100
50 100
50 100
50 100
E. coli
S. typhimurium 15 18
S. aureus
B. faecalis
16 23
10 13
8 12
10 12
10 13
8
7
8
7
11
10
11
10
7
8
5
5
10
11
8
8
9
7
8
11
12
10
10
13 17
12 15
14 16
13 17
7
8
8
8
10
11
12
12
6
8
7
8
8
11
10
10
7
6
6
6
10
8
8
12 16
13 15
14 17
13 16
—
—
—
—
22
22
25
26
15 20
17 22
8
8
a) Each well contains 50 and 100 mg of compound.
Table 2. MIC of Compounds 3a—j (mg/ml)
Bacteria
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
E. coli
S.typhimurium
S. aureus
80
90
70
70
350
290
410
370
410
460
360
440
600
570
510
530
380
410
330
460
140
130
170
120
560
440
520
400
640
520
610
560
570
540
490
470
120
130
110
130
B. faecalis
ascorbic acid were measured by the method of Blois (1958),16) and the data
are presented in Fig. 1. The antioxidant activity of these compounds was ex-
pressed as IC50 (inhibitory concentration, 50%). DPPH forms a stable mole-
cule on accepting an electron or a hydrogen and thus found application in
the determination of radical scavenging and antioxidant activity.17,18) In the
case of triazole thiadiazaphosphol-2-ones derivatives 3h showed highest
DPPH scavenging activity with IC50 of 1.51 mg/ml when compared with
other compounds. The remaining compounds exhibited DPPH radical scav-
enging activity in the following order: 3i (IC50 2.07 mg/ml)ꢅ3b (IC50 2.42
mg/ml)ꢅ3a (IC50 2.58 mg/ml)ꢅ3g (IC50 2.81 mg/ml)ꢅ3f (IC50 3.09 mg/
ml)ꢅ3e (IC50 3.14 mg/ml)ꢅ3j (IC50 4.0 mg/ml)ꢅ3c (IC50 4.41 mg/ml)ꢅ
3d (IC50 4.34 mg/ml) and was significant (pꢆ0.001) when compared with
that of ascorbic acid (IC50 1.36 mg/ml).
(pꢆ0.001) when compared to ascorbic acid (IC50 0.99 mg/ml).
(AcontꢀAtest
)
OH scavenged (%)ꢁ
ꢇ100
Acont
Where Acont is the absorbance of the control reaction and Atest is the ab-
sorbance in the presence of the sample.
Antibacterial Activity Agar well bioassay was employed for testing an-
tibacterial activity of 3a—j (Table 1). Diluted inoculum (105 CFU/ml) of
bacteria was spread on nutrient agar plates. Wells in the agar medium were
punched and filled with the title compounds at concentration of 50 and
100 mg in each well. The plates were incubated for 24 h at 37 °C for test bac-
teria. The antimicrobial activity was evaluated by measuring the zone of in-
hibition against test organisms. Chloramphenicol was used as standard. Con-
trols were maintained with dimethylsulphoxide (DMSO).24)
Minimum inhibitory concentration (MIC) was determined for the com-
pounds 3a—j (Table 2) that showed total growth inhibition using the proto-
col described below. The compound concentration of 50 mg to 700 mg/ml in
steps of 25 mg/ml was evaluated. Specifically 0.1 ml of standardized inocu-
lum (1—2ꢇ107 CFU/ml) was added to each test tube. Two controls (DMSO
with bacteria and antibiotics with bacteria) were maintained for each test
sample. The tubes were incubated aerobically at 37 °C for 24 h.25)
(AcontꢀAtest
)
DPPH scavenged (%)ꢁ
ꢇ100
Acont
where Acont is the absorbance of the control reaction and Atest is the ab-
sorbance in the presence of the sample.
Lipid Peroxidation Assay Lipid peroxidation was induced by
Fe2ꢂ–ascorbate complex system in rat red blood cells and estimated as thio-
barbituric acid reacting substances (TBARS) by the method of Buege and
Aust (1978).19) Experiments in vitro lipid peroxidation were carried out to
clarify the mode of the protective effect of the triazole compounds against
oxidative stress-induced cell damage. The inhibition of lipid peroxidation
has been used as a model to elucidate antioxidant activity. According to the
results obtained, 3h significantly (pꢆ0.001) inhibited the ferric ion plus
ascorbic acid in rat red blood cells (Fig. 2). The remaining compounds
exhibited hydroxyl radical scavenging activity in the following order: 3g
(IC50 2.72 mg/ml)ꢅ3b (IC50 3.14 mg/ml)ꢅ3i (IC50 3.51 mg/ml)ꢅ3e (IC50
3.79 mg/ml)ꢅ3a (IC50 4.37 mg/ml)ꢅ3f (IC50 4.92 mg/ml)ꢅ3j (IC50 5.16
mg/ml)ꢅ3c (IC50 4.73 mg/ml)ꢅ3d (IC50 4.66 mg/ml) and the results are sig-
nificant (pꢆ0.001) when compared with that of ascorbic acid (IC50 0.98
mg/ml).
Hydroxyl Radical Scavenging Activity It was carried out by measur-
ing the competition between deoxyribose and the compounds that generate
hydroxyl radicals from the Fe3ꢂ/ascorbate/EDTA/H2O2 system. Attack of the
hydroxyl radicals on deoxyribose led to thiobarbituric acid-reactive sub-
stances (TBARS) formation. The formed TBARS were measured by the
method of Ohkawa et al. (1979).20) The hydroxyl radical is the most reactive
oxygen species (ROS) that attacks almost every molecule in the body. It ini-
tiates the peroxidation of cell membrane lipids21,22) yielding malondialde-
hyde, which is mutagenic and carcinogenic.23) Even though the triazoles are
known to scavenge the hydroxyl radical, the compound 3h showed signifi-
cant hydroxyl radical scavenging activity with IC50 of 1.03 mg/ml when
compared with other compounds. The remaining compounds exhibited hy-
droxyl radical scavenging activity in the following order respectively: 3f
(IC50 1.93 mg/ml)ꢅ3b (IC50 2.05 mg/ml)ꢅ3a (IC50 2.57 mg/ml)ꢅ3e (IC50
2.79 mg/ml)ꢅ3i (IC50 2.99 mg/ml)ꢅ3g (IC50 3.17 mg/ml)ꢅ3j (IC50 3.89
mg/ml)ꢅ3c (IC50 3.61 mg/ml)ꢅ3d (IC50 3.69 mg/ml) and was significant
Acknowledgements The authors thank BRNS, Department of Atomic
Energy (DAE), Govt. of India, Mumbai for providing financial assistance
(2006/37/39/BRNS/2292).
References
1) Eto M., “Organophosphorus Pesticides, Organic and Biological Chem-
istry,” CRC Press, Ohio, 1974, p. 152.
2) Yuksek H., Demibas A., Ikizler A., Johansson C. B., Celik C., Ikizler
A. A., Arzneim. Forsch./Drug Res., 47, 405—409 (1997).
3) Ikizler A. A., Demirbas A., Johansson C. B., Celik C., Serdar M., Yuk-
sek H., Acta Pol. Pharm. Drug Res., 55, 117—123 (1998).
4) Alkan M., Yuksek H., Islamoglu F., Bahceci S., Calapoglu M., Elmas-
tas M., Aksit H., Ozdemir M., Molecules, 12, 1805—1816 (2007).
5) Bhat A. R., Bhat G. V., Shenoy G. G., J. Pharm. Pharmacol., 53,
267—272 (2001).
6) Yuksek H., Alkan M., Akmak I., Ocak Z., Bahceci S., Calapoglu M.,
Elmastas M., Kolomuc A., Aksu H., Int. J. Mol. Sci., 9, 12—32
(2008).
7) Yuksek H., Kucuk M., Alkan M., Bahceci S., Kolayli S., Ocak Z.,
Ocak U., Sahinbas E., Ocak M., Asian J. Chem., 18, 539—550 (2006).
8) Yuksek H., Kolayli S., Kucuk M., Yuksek M. O., Ocak U., Sahinbas E.,
Sivrikaya E., Ocak M., Indian J. Chem., 45B, 715—718 (2006).
9) Siva Kumar B., Ravi Sankar A. U., Chandra Sekhar Reddy G.,
Narayana Reddy M. V., Devendranath Reddy C., Suresh Reddy C.,
ARKIVOC, Xii, 109—116 (2008)
10) Hussain H. H., Babic G., Durst T., Wright J., Flueraru M., Chichirau
A., Chepelev L. L., J. Org. Chem., 68, 7023—7032 (2003).

October 2008
1489
11) Mc Clements J., Decker, J. Food Sci., 65, 1270—1282 (2000).
12) Gogoi P. C., Kataky C. S., Heterocycles, 32, 269—272 (1991).
13) Naidu M. S. R., Raju C. N., Indian J. Chem., 27B, 88 (1988).
14) Silverstein R. M., Bassler G. C., Morrill T. C., “Spectrometric Identifi-
cation of Organic Compounds,” Vol. 4, John Wiley & Sons, New York,
1981.
19) Buege J., Aust D. S., “Methods in Enzymology,” Vol. 52, ed. by Fleiss-
cher S., Packer L., Academic Press, New York, 1978, pp. 302—310.
20) Okhawa H., Ohishi N., Yagi K., Anal. Biochem., 95, 351—358 (1979).
21) Halliwell B., Gutteridge J. M. C., “Free Radicals Ageing and Disease,
Free Radicals in Biology and Medicine,” 2nd ed., Clarendron Press,
Oxford, 1985, pp. 279—315.
15) Quin L. D., Verkade J. G., “Phosphorus-31 NMR Spectral Properties
22) Halliwell B., Am. J. Med., 91, 14S—22S (1991).
Compound Characterization and Structural Analysis,” VCH Publish- 23) Miyake T., Shibamoto T., J. Agric. Food Chem., 45, 1819—1822
ers, Inc., New York, 1994.
(1997).
16) Blois M. S., Nature (London), 181, 1199—1200 (1958).
17) Duh P. D., Tu Y. Y., Yen G. C., Leben. Wissen. Technol., 32, 269
(1999).
24) Mangte D. V., Deshmukh S. P., Bhokare D. D., Deshponde Arti R., In-
dian J. Pharm., 69, 295 (2007).
25) Omer E., Biologia, 61, 275 (2006).
18) Yen G. C., Chen H. Y., J. Agric. Food Chem., 46, 849—854 (1995).