Synthesis, labeling, and biological evaluation of 2-{[benzyl(cyanomethyl) amino]methyl}-3-(ethoxycarbonyl)- quinoxaline 1,4-dioxide in ascites bearing mice1

Article abstract of DOI:10.1134/S1066362212040157

Quinoxaline 1,4-dioxide derivative, 2-{[benzyl(cyanomethyl)amino]methyl}-3- (ethoxycarbonyl) quinoxaline 1,4-dioxide (Q₃D), was synthesized and labeled with radioiodine via direct electrophilic substitution giving labeling yield above 90%. The product was examined by paper electrophoresis. ¹²⁵I-Q₃D was prepared using Chloramine T as oxidizing agent. ¹²⁵I-Q₃D was stable for up to 72 h post labeling, in contrast to 99mTc-AQCD which is stable only for a short time. Biodistribution study of ¹²⁵I-Q₃D in ascites tumor bearing mice revealed large uptake of the labeled compound in tumor sites. In addition, in vitro incubation of the labeled compound with Ehrlich cells indicated incorporation of these compounds in DNA of tumor cells. This uptake of ¹²⁵I-Q ₃D in DNA of tumor cells may be helpful in tumor diagnosis and therapy. Pleiades Publishing, Inc., 2012.

Full text of DOI:10.1134/S1066362212040157

ISSN 1066-3622, Radiochemistry, 2012, Vol. 54, No. 4, pp. 395–400. © Pleiades Publishing, Inc., 2012.
Published in Russian in Radiokhimiya, 2012, Vol. 54, No. 4, pp. 364–368.
Synthesis, Labeling, and Biological Evaluation
of 2-{[Benzyl(cyanomethyl)amino]methyl}-3-(ethoxycarbonyl)-
quinoxaline 1,4-Dioxide in Ascites Bearing Mice1
I. T. Ibrahim*a, M. A. Walyb, and M. El-Tawoosya
a Labelled Compounds Department, Radioisotopes Production and Radioactive Sources Division,
Hot Laboratories Center, Atomic Energy Authority, P.O. Box 13759, Cairo, Egypt;
* e-mail: ismailtaha_73@yahoo.com
b Chemistry Department, Faculty of Science (Damiatta), Mansoura University, Mansoura, Egypt
Received September 5, 2011
Abstract—Quinoxaline 1,4-dioxide derivative, 2-{[benzyl(cyanomethyl)amino]methyl}-3-(ethoxycarbonyl)
quinoxaline 1,4-dioxide (Q3D), was synthesized and labeled with radioiodine via direct electrophilic substitu-
tion giving labeling yield above 90%. The product was examined by paper electrophoresis. 125I-Q3D was pre-
pared using Chloramine T as oxidizing agent. 125I-Q3D was stable for up to 72 h post labeling, in contrast to
99mTc-AQCD which is stable only for a short time. Biodistribution study of 125I-Q3D in ascites tumor bearing
mice revealed large uptake of the labeled compound in tumor sites. In addition, in vitro incubation of the la-
beled compound with Ehrlich cells indicated incorporation of these compounds in DNA of tumor cells. This
uptake of 125I-Q3D in DNA of tumor cells may be helpful in tumor diagnosis and therapy.
Keywords: quinoxaline, iodine, labeling, biodistribution, ascites, DNA
DOI: 10.1134/S1066362212040157
Quinoxaline (benzopyrazine) is a heterocyclic com-
pound containing fused benzene and pyrazine rings. It
is an isomer of quinazoline. The synthesis and chemis-
try of quinoxalines have attracted considerable atten-
tion in the last years [1]. Quinoxaline 1,4-di-N-oxide
derivatives seem to have very interesting anticancer
activity [2]. Also, some of them exhibit biological ac-
tivity, in particular, antiviral, antibacterial, antiinflam-
matory, and antiprotozoal activity [2]. The antitumor
activity of these compounds was observed mainly on
solid tumors containing hypoxic cells, as quinoxalines
act by bioreductive alkylation of DNA of cancer cells
[3]. In addition, some of them exhibit activity against
Ehrlich ascites carcinoma. Labeling of some of these
derivatives was attempted to study the biodistribution
of these compounds and also to know the possible
mechanism of action [4]. Biodistribution study of
99mTc-3-amino-2-quinoxalinecarbonitrile 1,4-dioxide
against ascites tumor showed concentration of the la-
beled compound in tumor sites [5]. 99mTc-labeled qui-
noxaline derivatives may be suitable for imaging pur-
poses, despite their low stability. Iodine labeling may
overcome this drawback, and also the Auger effect of
iodine may contribute to the cytotoxic effect of qui-
noxaline, especially when it become near the DNA [6].
In this study, we synthesized 2-{[benzyl(cyano-
methyl)amino]methyl}-3-(ethoxycarbonyl)quinoxaline
1,4-dioxide (Q3D), performed its iodine labeling using
Chloramine T as an oxidizing agent, and examined the
factors affecting the labeling yield. Biodistribution of
the labeled compound in normal and ascites bearing
mice was also studied. In addition, 125I-Q3D was incu-
bated with Ehrlich cells in vitro. DNA of Ehrlich cells
was separated by centrifugation at high speed and
counted for activity in a γ-ray counter.
EXPERIMENTAL
Drugs and chemicals. Iodine-125 was purchased
from the Institute of Isotope Production, Belguim. Ben-
zofurazan oxide, malononitrile, dimethyl formal (DMF),
triethylamine, and diethyl ether were supplied from ICN
(USA). Chloramine T was purchased from Sigma (USA).
3-Benzylaminopropionitrile was purchased from Alfa
Aesar (CAS 706-03-6). All the other chemicals were of
analytical grade (AR), obtained from reputed manufac-
turers. Ehrlich ascites carcinoma (EAC) was kindly sup-
plied from the National Cancer Institute, Cairo, Egypt.
1 The text was submitted by the authors in English.
395

396
IBRAHIM et al.
Animals. Female Swiss Albino mice weighing 20–
methylquinoxaline 1,4-dioxide 1 (2.48 g, 0.01 mol) in
CCl4 (50 ml) and CHCl3 (50 ml) in the presence of
benzoyl peroxide (0.20 g) as initiator. The solution was
stirred and heated under reflux for 24 h. The organic
layer was washed with cold water (3 × 30 ml), dried
over anhydrous Na2SO4, and evaporated in a vacuum
to give an oily material. The resulting oil was triturated
with diethyl ether and recrystallized from 90% ethanol
to give pure product 2 (2.41 g, 73.7% yield), mp 112–
114°C. IR (KBr, ν, cm–1): 1739 (CO), 1346 (N–O).
1H NMR (CDCl3), δ, ppm: 1.52 t (3H, J = 7.2 Hz, CH3,
ester), 4.63 q (2H, J = 7.2 Hz, CH2, ester), 4.75 s (2H,
CH2Br), 7.84–7.90 m (4H, Qu). Calculated for
C12H11BrN2O4 (M = 327.13): C 44.06; H 3.39; N 8.56.
Found: C 44.36; H 3.65; N 8.30.
25 g were purchased from the Institute of Eye Re-
search, Cairo, Egypt. The environmental and nutri-
tional conditions were kept constant throughout the
experimental period. The mice were kept at room tem-
perature (22 ± 2°C) with a 12 h on/off light schedule.
Female mice were used in this study because their sus-
ceptibility to Ehrlich ascites carcinoma was higher
than that of the male mice [7]. Animals were kept with
free access to food and water throughout the experi-
ment.
Synthesis of Q3D. The scheme of the synthesis of
the target compound 3 is shown below. The quinoxa-
line derivative with active methyl group in the side
chain 1 [8] was brominated with N-bromosuccinimide
(NBS) in the presence of benzoyl peroxide as a cata-
lyst in CCl4 to obtain quinoxaline bromomethyl deriva-
2-{[Benzyl(2-cyanoethyl)amino]methyl}-3-
(ethoxycarbonyl)quinoxaline 1,4-dioxide. A solution
of 2 (1.6 g, 0.005 mol) and 3-N-benzylaminopropioni-
trile in ethanol (30 ml), with potassium carbonate (3 g)
added, was refluxed for 4 h. The mixture was poured
into cold water (50 ml), and the precipitate was filtered
off. Recrystallization from ethanol gave pure product 3
(1.1 g), mp 98°C. IR (KBr, ν, cm–1): 2234 (CN) and
1
tive 2 in 73.7% yield. The H NMR spectrum of
bromomethyl derivative 2 reflects the presence of
CH2Br protons at δ 4.75 ppm.
1
1710 (CO, ester). H NMR (CDCl3), δ, ppm: 1.43 t
(3H, J = 7.2 Hz, CH3, ester), 2.23 t (2H, J = 7.3 Hz,
CH2CH2CN), 3.12 t (2H, J = 7.3 Hz, CH2CH2CN),
4.11 q (2H, J = 7.2 Hz, CH2, ester), 4.33 s (2H,
CH2Ph), 4.89 s (2H, QuCH2), 7.65–7.90 m (9H, aro-
matic). Calculated for C22H22N4O4 (M = 406.43):
C 65.01; H 5.46; N 13.78. Found: C 65.34; H 5.75;
N 13.40.
Iodine labeling. 125I-Q3D was prepared by the fol-
lowing procedure: 1 mg of Q3D was dissolved in 1 ml
of DMF with stirring. A 10 : 1 (w/w) solution of
Chloramine T (CAT) in double-distilled water was
prepared, and 50–100 μg was added to 100 μl of Q3D
solution in a dark colored tube, after which approxi-
mately 50–100 MBq of 125I was added at room tem-
perature. After a specified interval of time, the reaction
was stopped by adding a 0.2 N Na2S2O3 solution to
reduce the unchanged iodine before chromatographic
analysis [9]. The product yield and radiochemical pu-
rity were determined by paper electrophoresis. In the
process, free iodide moved toward the anode at the top,
whereas the target compound persisted near the point
of spotting.
Quinoxaline bromomethyl derivative 2 was reacted
with 3-(benzylamino)propionitrile in the presence of
potassium carbonate in ethanol to obtain target com-
pound 3. Compound 3 is hygroscopic and should be
kept under anhydrous conditions. The IR spectrum of 3
contains the cyano group absorption band at 2234 cm–1.
1
Its H NMR spectrum shows the presence of five me-
thylene protons at δ 2.23, 3.12, 4.11, 4.33, and
4.89 ppm. Attempted cyclization of 3 under widely
varied conditions (bases, solvents, temperatures) failed
to give the azepinoquinoxaline ring system, and the
decomposition occurred instead.
Factors affecting labeling yield. With the aim of
optimizing the synthesis conditions, we examined the
effect of the following factors on the labeling yield:
oxidant amount (10, 25, 50, and 100 μg), Q3D amount
2-(Bromomethyl)-3-(ethoxycarbonyl)quinoxaline
1,4-dioxide 2. N-Bromosuccinimide (1.95 g, 0.011 mol)
was added to a solution of 2-(ethoxycarbonyl)-3-
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SYNTHESIS, LABELING, AND BIOLOGICAL EVALUATION OF 2-{[BENZYL-...
397
(10, 25, 50, 100, and 200 μg), pH (2, 4, 7, 9, 11; meas-
ured with a Model 601 A-digital pH meter, Orion Re-
search, USA), and reaction time (1, 5, 10, 30, and
60 min). When varying one of the parameters, the
other parameters were kept constant.
In vitro stability. The target product content was
determined at different time intervals (1, 4, 12, 24, and
48 h) after labeling.
Electrophoresis. Electrophoresis was done with an
EC 3000 p-series 90 programmable power and cham-
ber supply units using cellulose acetate strips (45 cm).
These strips were moistened with 0.05 M phosphate
buffer pH 7 and then introduced in the chamber. Sam-
ples were applied at a distance of 10 cm from the cath-
ode. The strips were kept in the electric field for 1.5 h.
The developed strips were dried and cut into 1-cm seg-
ments, which were counted with a well-type NaI scin-
tillation counter. The radiochemical yield was calcu-
lated as the ratio of the radioactivity of the labeled
product to the total radioactivity [9].
Paper electrophoresis pattern of radioiodinated Q3D.
Biodistribution of 125I-Q3D in ascites tumor
bearing mice. A group of 24 ascites tumor bearing
mice was used for studying the biodistibution of the
labeled drug. Experiments were performed in the same
manner as with normal mice. Ascites fluid was drained
and counted as a whole in a well type NaI(Tl) γ-ray
counter. The results were calculated as percentage of
injected dose (I.D.) per gram of tissue [12].
DNA extraction. Extraction of the DNA from the
tumor helps to study the incorporation rate of radioac-
tivity in the tumor. Ehrlich cells were drained from
ascites bearing mice into RPMI 1640 medium contain-
ing streptomycin and penicillin and were incubated in
vitro for 48 h. The labeled compound was then added.
After 1 h, the medium was centrifuged to separate the
cells. Cells were counted to determine their activity
uptake. DNA was extracted by addition of perchloric
acid, followed by incubation for 1 h and centrifugation
at 5000 rpm. The precipitate was counted in a γ-ray
counter. The experiment was repeated with different
incubation times (2, 4, 6, 16, and 32 h), and the DNA
activity was counted at each time. Also the activity of
cell constituents was counted, and the ratio was calcu-
lated between the DNA-incorporated activity and the
activity in other constituents of the cell [13].
Tumor transplantation in mice. Ehrlich ascites
carcinoma cells (EAC) are a model for studying the
biological behavior of malignant tumors and drugs as-
sumed to produce effect at these sites [10].
A line of Ehrlich ascites carcinoma (EAC) was
maintained in female Swiss Albino mice through
weekly I.P. transplantation of 2.5 × 106 tumor cells per
mouse. EAC cells were obtained by needle aspiration
under aseptic conditions. The ascitic fluid was diluted
with sterile saline so that 0.1 ml contained 2.5 ×
106 cells counted microscopically using a hemocy-
tometer. About 0.2 ml of the solution was then injected
intraperitoneally in the peritoneal cavity to produce
acites tumor [11].
Biodistribution of 125I-Q3D in normal mice.
In vivo biodistribution studies were performed using
four groups of six mice each. Each animal was injected
in the tail vein with 0.2 ml of the solution containing
5–10 kBq of 125I-Q3D. The mice were kept in meta-
bolic cages for the required time. Animals were sacri-
ficed by cervical dislocation at the recommended time
(15 min, 1 h, 4 h, or 24 h) after injection. The organs
or tissues of interest were removed, washed with sa-
line, weighed, and counted. Correction was made for
the background radiation and physical decay during
the experiment. The weights of blood, bone, and mus-
cles were assumed to be 7, 10 and 40% of the total
body weight, respectively [9].
RESULTS AND DISCUSSION
Electrophoresis. The figure illustrates the activity
distribution in electrophoresis. Two main peaks were
formed, one corresponding to the free iodide that
moved toward the anode with 16 cm distance. The sec-
ond peak (125I-Q3D) stayed near the point of spotting
and was similar to that of 125I-iododeoxyuridine under
the same electrophoretic conditions [14].
Factors affecting labeling yield. Effect of oxidant
amount. We found that the electrophilic substitution of
the iodonium ion [I+] in the Q3D molecule occurred
with a high radiochemical yield when using CAT as an
RADIOCHEMISTRY Vol. 54 No. 4 2012

398
IBRAHIM et al.
Table 1. Effect of CAT content on the radiochemical yield
oxidizing agent (Table 1). The radiochemical yield
significantly increased with an increase in the CAT
amount from 10 to 50 μg (optimum content at which
the maximum labeling yield was obtained). At the
CAT amount increased over 50 μg, the yield showed
no significant change. Apparently, at CAT amounts
below 50 μg the CAT concentration is insufficient to
convert all the iodide to iodonium ions, and the yield
decreases [15].
of 125I-Q3Da
Labeled compound
CAT amount, μg
Free I– content, %
yield, %
10
25
50
87.2 ± 0.4
88.6 ± 0.5b
96.6 ± 0.5b,c
12.8 ± 0.3
12.4 ± 0.8
3.4 ± 0.1
3.8 ± 0.4
100
a
Mean ± SEM, n = 6; the same in Tables 3–7.
Significantly different from the initial values using unpaired
Student’s t-test (p < 0.05).
Significantly different from the previous values using unpaired
Student’s t-test (p < 0.05).
b
Effect of substrate content on the labeling yield us-
ing CAT as an oxidizing agent is shown in Table 2.
With an increase in the concentration of the starting
material, the total incorporation of radioiodine usually
increases, because there is a minimum limit to the vol-
ume used [16]. In our case, the yield appreciably in-
creased with an increase in the Q3D amount up to
25 μg, whereas larger amounts did not significantly
affect the labeling yield.
c
Table 2. Effect of Q3D content on the labeling yield
Labeled compound
Q3D amount, μg
Free I– content, %
yield, %
10
25
50
100
200
88.4 ± 0.3
94.5 ± 0.4а,b
94.1 ± 0.4а
95.2 ± 0.3а
94.5 ± 0.3а
11.6 ± 0.4
5.5 ± 0.3
5.9 ± 0.3
4.8 ± 0.4
5.5 ± 0.3
Effect of pH. As shown in Table 3, pH 7 is the opti-
mum pH at which the maximum yield was obtained
(97.3%). The difference between the yields obtained at
all the pH values was significant.
Effect of reaction time. Table 4 shows the relation-
ship between the reaction time and the yield of 125I-
Q3D. The radiochemical yield significantly increased
from 56.9 to 94.8% with an increase in the reaction
time from 1 to 15 min, but at the reaction time ex-
tended to 60 min no significant changes were ob-
served.
In vitro stability of 125I-Q3D. No significant
changes in the relative content of 125I-Q3D were ob-
served for up to 48 h post labeling (Table 5). That is,
the labeled compound is very stable.
Biodistribution of 125I-Q3D. Normal mice. Experi-
ments showed (Table 6) that 125I-Q3D was distributed
rapidly in blood, stomach, heart, and kidneys (15 min
post injection). After 1 h, the 125I-Q3D uptake signifi-
cantly decreased in blood, heart, liver, and spleen but
a
Significantly different from the initial values using unpaired
Student’s t-test (p < 0.05); the same in Tables 3–5.
b
Significantly different from the previous values using unpaired
Student’s t-test (p < 0.05); the same in Tables 3–5.
Table 3. Effect of pH of the reaction medium on the 125I-
Q3D yield
Labeled compound
рН
Free I– content, %
yield, %
2
4
7
9
11
68.4 ± 0.1
90.2 ± 0.4а
97.3 ± 0.3а,b
93.2 ± 0.4а,b
81.7 ± 0.2а,b
31.6 ± 0.2
9.8 ± 0.6
2.8 ± 0.2
6.8 ± 0.5
18.3 ± 0.4
Table 4. Effect of reaction time on the 125I-Q3D yield
Table 5. Effect of time on the stability of 125I-Q3D
Labeled compound
Labeled compound
Free I– content, %
Time, min
Free I– content, %
Time, min
yield, %
content, %
96.3 ± 0.1
95.4 ± 0.7
95.4 ± 0.4
95.1 ± 0.1
95.3 ± 0.5а,b
1
5
10
15
30
60
83.5 ± 0.4
90.6 ± 0.3а
91.3 ± 0.2а
96.5 ± 0.4а,b
96.6 ± 0.5а,b
97.1 ± 0.1а,b
16.5 ± 0.6
9.4 ± 0.9
8.7 ± 0.7
3.5 ± 0.2
3.4 ± 0.4а,b
2.9 ± 0.3
1
4
12
24
48
4.7 ± 0.1
4.6 ± 0.2
4.6 ± 0.2
4.9 ± 0.2
4.7 ± 0.4
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SYNTHESIS, LABELING, AND BIOLOGICAL EVALUATION OF 2-{[BENZYL-...
Table 6. Biodistribution of 125I-Q3D in normal mice (% I.D./g)a
399
Normal mice
1 h 4 h
13.4 ± 0.2а 6.40 ± 0.04а 3.7 ± 0.3а
1.9 ± 0.1а 0.9 ± 0.1а 0.7 ± 0.1а
Ascites bearing mice
Organ, tissue
15 min
24 h
15 min
11.7 ± 1.1
2.1 ± 0.2
1 h
4 h
24 h
Blood
Bones
Muscles
Liver
Lungs
16.0 ± 0.1
1.60 ± 0.05
9.8 ± 0.4b
2.5 ± 0.2b
7.1 ± 0.1b
2.4 ± 0.2
3.2 ± 0.2b
1.8 ± 0.2b
1.30 ± 0.01 1.70 ± 0.02а 1.6 ± 0.1
0.50 ± 0.02а 2.20 ± 0.09 2.70 ± 0.02b 2.10 ± 0.01b 0.70 ± 0.04b
2.40 ± 0.05
5.7 ± 0.1
9.0 ± 0.8
12.2 ± 0.9
6.4 ± 0.5
9.7 ± 0.4
2.4 ± 0.3
0.70 ± 0.02
–
1.8 ± 0.2а 1.10 ± 0.06а 1.00 ± 0.02
8.0 ± 0.1а 3.0 ± 0.2а 1.00 ± 0.01а
4.7 ± 0.3
3.2 ± 0.2b 2.80 ± 0.06b 1.50 ± 0.07b
6.5 ± 0.1 4.20 ± 0.04b 3.1 ± 0.1b
0.5 ± 0.1b
1.4 ± 0.1b
6.0 ± 0.5b
2.9 ± 0.2b
Heart
6.4 ± 0.3а 4.00 ± 0.01а 1.70 ± 0.04а
7.3 ± 0.3
6.1 ± 0.4b
3.1 ± 0.1b
Stomach
Intestine
Kidneys
Spleen
Thyroid
Ascitic fluid
a
16.2 ± 0.6а
5.2 ± 0.3а
8.2 ± 0.6а
9.6 ± 0.2а
5.7 ± 0.2а
9.6 ± 0.3 13.4 ± 0.9b 10.7 ± 0.6b
7.6 ± 0.5 6.40 ± 0.07b 4.4 ± 0.1b
3.5 ± 0.1а 1.50 ± 0.03а
3.1 ± 0.3а 1.50 ± 0.06а
6.1 ± 0.4
3.4 ± 0.1b
2.0 ± 0.1b 1.20 ± 0.06b
1.3 ± 0.1а 1.00 ± 0.02 0.80 ± 0.05а
2.2 ± 0.1 1.70 ± 0.01b 1.10 ± 0.01b 0.30 ± 0.01b
1.0 ± 0.1а
–
4.1 ± 0.2а
–
5.2 ± 0.2
–
2.10 ± 0.02 4.40 ± 0.04b 7.40 ± 0.06b 8.20 ± 0.05
3.5 ± 0.3
5.2 ± 0.4b
7.1 ± 0.1b 5.80 ± 0.05
Significantly different from the previous values using unpaired Student’s t-test (p < 0.05).
Significantly different from the initial values using unpaired Student’s t-test (p < 0.05).
b
125I-Q3D in kidneys may reflect the excretion of the
drug via urine [3]. The observation that the 125I-Q3D
concentration in the thyroid was significantly lower
than in other tissues indicates that the amount of the
free iodide was low, as free iodide is rapidly captured
by thyroid [17]. However, thyroid uptake increased
with time from 4.4% at 1 h to 7.4% at 4 h post injec-
tion due to in vivo deiodination of 125I-Q3D [16, 18].
significantly increased in stomach, bones, muscles, and
thyroid. At 4 and 24 h post injection, the majority of
tissues showed significant decrease in the 125I-Q3D
uptake except the thyroid gland in which the uptake
increased.
Ascites bearing mice. The sites of the highest up-
take of 125I-Q3D at 15 min post injection were the
blood, stomach, heart, and intestine (11.7, 12.3, 7.3,
and 7% I.D./g, respectively). Table 6 shows that the
concentration of 125I-Q3D at 15 min post injection was
the lowest in thyroid, muscles, and spleen. The 125I-Q3D
uptake in ascitic fluid was rapid (3.5% I.D./ml in the
first 15 min). The uptake in ascitic fluid significantly
increased in the first 4 h and then somewhat decreased.
Increased uptake at 1 h post injection was also ob-
served in stomach, kidneys, and thyroid gland, whereas
in blood, heart, and lungs at the same time the uptake
decreased. At 4 h post injection, the majority of organs
showed significant decrease in the 125I-Q3D uptake.
Significant increase was only observed in ascitic fluid
and thyroid gland. Similarly, at 24 h post injection, the
majority of organs showed additional significant de-
crease in the 125I-Q3D uptake. The experiments showed
that ascites was one of the sites of the strongest
125I-Q3D uptake at both l and 24 h post injection. The
overall 125I-Q3D uptake in ascites (fluid volume 3.2 ±
0.7 ml) was about 40% of the injected dose at 4 h post
injection. This result indicates that 125I-Q3D shows
promise for tumor imaging. The high uptake of
DNA extraction. The increase in the incubation
time was associated with significant increase in the
associated activity percentage. More than 60% of the
total activity was associated with DNA (Table 7). This
means that the DNA-associated activity was trans-
ferred from cells to daughter cells in chromosomes.
Table 7. Comparison between DNA-incorporated activity
and activity in other constituent of the cell
Incubation Activity associated
Activity in other
time, h
with DNA, %
12 ± 0.7
constituents of cells, %
1
2
4
88 ± 0.7
18 ± 2а
82 ± 2а,b
24 ± 2а
76 ± 2а,b
8
35 ± 1а
65 ± 1а,b
16
32
45.0 ± 0.8а
55.0 ± 0.8а,b
62.0 ± 0.9а
38.0 ± 0.9 а,b
a
Significantly different from the initial values using unpaired
Student’s t-test (p < 0.05); n = 10.
b
Significantly different from the previous values using unpaired
Student’s t-test (p < 0.05).
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IBRAHIM et al.
Thus, the incorporation of an Auger emitter (125I)
7. Mester, J., DeGoeij, K., and Sluyser, M., Eur. J. Can-
cer, 1996, vol. 32, p. 1603.
into a tumor site was achieved by labeling of Q3D with
125I. The appropriate conditions for labeling of
125I-Q3D (95% yield) are as follows: 50 μg of CAT as
oxidizing agent, 25 μg of Q3D as substrate, pH 7,
room temperature, 15 min. High incorporation of
125I-Q3D in tumor sites (ascites tumor) facilitates tumor
imaging. 125I-Q3D is convenient to transport 125I to the
nucleus of tumor cells. It seems appropriate to further
study this radiolabeled compound in vivo and in vitro
using different cancer cell lines.
8. Issidorides, C.H. and Haddadin, M.J., J. Org. Chem.,
1966, vol. 31, p. 4067.
9. Korde, A., Venkatesh, M., and Sarma, H.D., in Int.
Symp. on Modern Trends in Radiopharmaceuticals for
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April 3, 1998, IAEA, SM-355/13.
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