Pentafluorophenyl Substitution of Natural Di(indol-3-yl)methane Strongly Enhances Growth Inhibition and Apoptosis Induction in Various Cancer Cell Lines

Article abstract of DOI:10.1002/cbdv.201900028

Di(indol-3-yl)methane (=3,3′-methanediyldi(1H-indole), DIM, 1) is a known weakly antitumoral compound formed by digestion of indole-3-carbinol (=1H-indol-3-ylmethanol), an ingredient of various Brassica vegetables. Out of a series of nine fluoroaryl deriv

Full text of DOI:10.1002/cbdv.201900028

Title: Pentafluorophenyl substitution of natural di(indol-3-yl)methane
strongly enhances growth inhibition and apoptosis induction in
various cancer cell lines
Authors: Aamir Ahmad, Prasad Dandawate, Sebastian Schruefer,
Subhash Padhye, Fazlul H. Sarkar, Rainer Schobert, and
Bernhard Biersack
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To be cited as: Chem. Biodiversity 10.1002/cbdv.201900028
Link to VoR: http://dx.doi.org/10.1002/cbdv.201900028

10.1002/cbdv.201900028
Chemistry & Biodiversity
Chem. Biodiversity
Pentafluorophenyl substitution of natural di(indol-3-yl)methane strongly
enhances growth inhibition and apoptosis induction in various cancer cell lines
Aamir Ahmad,a Prasad Dandawate,b,c Sebastian Schruefer,d Subhash Padhye,b,c Fazlul H. Sarkar,e Rainer
Schobert,d and Bernhard Biersack*,d
a Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604, USA
b Department of Cancer Biology, School of Medicine, KU Medical Center, Kansas City, Kansas 66160, USA
c ISTRA, Abeda Inamdar Senior College, Pune 411001, India
d Organic Chemistry Laboratory, University of Bayreuth, 95447 Bayreuth, Germany, e-mail: bernhard.biersack@yahoo.com
e Retired as Distinguished Professor, Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
Di(indol-3-yl)methane (DIM, 1) is a known weakly antitumoral compound formed by digestion of indole-3-carbinol, an ingredient of various Brassica
vegetables. Out of a series of nine fluoroaryl derivatives of 1, three pentafluorophenyl derivatives 2c, 2h and 2i were identified that exhibited a two to five
times greater anti-proliferative effect and an increased apoptosis induction when compared with 1 in the following carcinoma cell lines: BxPC-3 pancreas,
LNCaP prostate, C4-2B prostate, PC3 prostate and the triple-negative MDA-MB-231 breast carcinoma. Compound 2h was particularly efficacious against
androgen-refractory C4-2B prostate cancer cells (IC50 = 6.4 µM) and 2i against androgen-responsive LNCaP cells (IC50 = 6.2 µM). In addition, 2c and 2h
exhibited distinct activity in three cancer cell lines resistant to 1.
Keywords: indole • fluorine • 3,3’-diindolylmethane • anticancer drugs • prostate cancer • apoptosis
Introduction
Indole-3-carbinol (I3C) is an ingredient of Brassica vegetables such as broccoli, cabbage, sprouts and cauliflower. Upon digestion of these plants I3C gets
converted to the condensation product di(indol-3-yl)methane (DIM, 1) (Figure 1). Both compounds show moderate efficacy against various cancer cell
lines and tumors with a focus on prostate cancer.[1,2] The biological targets and modes of action of these compounds are largely known by now. Identified
targets of I3C include p21, p27, cyclin-dependent kinases, Bax/Bcl-2, cytochrome P-450, and GADD153. Downstream cellular responses to dietary I3C
were also explained by assuming a modification of nuclear transcription factors such as Sp1, the estrogen receptor, and the aryl hydrocarbon receptor.[3]
Compound 1 displayed androgen antagonist activity and down-regulated platelet-derived growth factor D in prostate carcinoma cells[4-6]. Special
formulations of 1 led to a stabilization of the level of the prostate tumor marker protein PSA and to a partial response in prostate cancer patients.[7] In
breast cancer cells 1 inhibited the nuclear translocation of NF-κB, and it induced the formation of pro-apoptotic p27kip. 1 also augmented the efficacy of
taxotere against breast cancer via NF-κB inactivation and downregulation of FoxM1.[8-11] New drugs against cancer are still sought for.[12] Safe et al.
investigated a series of para-substituted phenyl-di(indol-3-yl)methane derivatives for their anticancer activity. The 4-fluorophenyl derivative 2a (Scheme
1) showed a significantly increased efficacy and it initiated stress-mediated apoptosis in pancreatic cancer.[13] Indole-related benzimidazole derivatives
were also tested for biological activities.[14] In this study we harnessed fluoroarenes as shuttle and amplifier groups for insufficiently active bis-indole
´´nutraceuticals´´. We prepared a series of fluorophenyl substituted analogues of 1 and evaluated their apoptosis induction and anti-proliferative effects
in various human cell lines including pancreatic, prostate and breast carcinoma cell lines. In addition, docking calculations were carried out for 1 and the
most active new derivatives bound to putative protein targets. We have chosen COX-2 and androgen receptor because the activity of both proteins was
already reported to be suppressed by 1.[4,15] Such computational studies are customarily applied for the initial investigation of the affinity of new
compounds for various protein targets.[16]
OH
N
HN
NH
H
I3C
DIM (1)
Figure 1. Chemical structures of indole-3-carbinol and di(indol-3-yl)methane 1.
1
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Results and Discussion
Chemistry
The compounds 2a-c were reported previously.[13,17,18] However, we used a different procedure by Gruber et al. for the synthesis of all derivatives 2a-i.[19]
These were obtained as solids upon heating indoles 3a-c with half an equivalent of the corresponding fluorobenzaldehyde in water in the presence of a
catalytic amount of sulfuric acid (Scheme 1). The compounds 2a-i were characterized by NMR, IR and MS. The signal of the methine proton in the 1H NMR
spectra of the pentafluoro derivatives 2c (δ = 6.38 ppm), 2h (δ = 6.32 ppm) and 2i (δ = 6.21 ppm) was shifted downfield compared with the corresponding
signals in the 1H NMR spectra of the other derivatives (δ = 5.81-5.89 ppm). The observed de-shielding can be explained by the formation of a H-bond with
the neighboring fluorine atoms in the molecules of 2c, 2h and 2i. Conversely, large highfield shifts were observed for the methine carbon signals in the 13
C
NMR spectra of 2c (δ = 29.1 ppm), 2h (δ = 29.8 ppm) and 2i (δ = 29.2 ppm) compared to those of the other derivatives 2 (δ = 39.2-40.1 ppm). The observed
shielding of the methine carbons of 2c, 2h and 2i can be explained by the high electron-density of the fluorine atoms of the phenyl ring, in particular, by
the 2- and 6-F atoms.
R5
R4
R3
R6
R7
2a: R1-R7 = H
2b: R1-R3, R7 = H; R4-R6 = F
R2
R2
R2
2c: R1, R2 = H; R3-R7 = F
(i)
R1
2d: R1-R3, R6, R7 = H; R4 = F; R5 = OMe
2e: R1-R3, R6, R7 = H; R4 = F; R5 = OEt
2f: R1-R3, R7 = H; R4, R6 = F; R5 = OMe
2g: R1-R3, R7 = H; R4 = F; R5, R6 = OMe
2h: R1 = Me; R2 = H; R3-R7 = F
2i: R1 = H; R2 = OMe; R3-R7 = F
N
H
N
N
H
R1R1
3a: R1, R2 = H
3b: R1 = Me, R2 = H
3c: R1 = H, R2 = OMe
H
Scheme 1. Reagents and conditions: (i) Fn(OR)mC6H5-(n+m)CHO (0.5 equiv.), H2SO4 (cat.), H2O, 1-3 h, 90 °C, 37-93%.
Biological evaluation
The anti-proliferative activity of 1 and 2a-i was first tested on cells of the triple-negative MDA-MB-231 breast cancer and the BxPC-3 pancreas cancer
(Table 1). The pentafluorophenyl derivatives 2c, 2h and 2i were most active against MDA-MB-231 cells with IC50(72 h) = 11.2-13.2 µM which is a distinct
improvement over 1 (IC50 = 37.8 µM). Against BxPC-3 cells, 2c reached an IC50(72 h) value of 8.4 µM and 2i displayed an IC50(72 h) value of 7.5 µM and, thus,
these new compounds are about four times more active than 1 (IC50 = 32.1 µM) in this cancer cell line. In addition, compounds 1 and 2a-i were inactive
against non-malignant MCF-10A mammary and HPDE pancreas cells up to doses of 200 µM (72 h). Hence, compounds 2c, 2h and 2i are also highly
selective for tumor cells.
Table 1. Inhibitory concentrations IC50 (72 h) [µM] of compounds 1 and 2a-i in MTT tests against cells of MDA-MB-231 breast and BxPC-3 pancreas carcinomas
Compd./cell line
MDA-MB-231
BxPC-3
1
37.8 ± 1.1
19.8 ± 0.8
14.2 ± 0.4
12.9 ± 0.4
27.8 ± 0.9
17.4 ± 0.6
22.3 ± 1.0
17.8 ± 0.8
13.2 ± 0.6
11.2 ± 0.4
32.1 ± 1.2
17.8 ± 0.7
12.8 ± 0.5
8.4 ± 0.3
24.1 ± 0.9
15.1 ± 0.6
18.9 ± 0.7
15.4 ± 0.5
11.8 ± 0.4
7.5 ± 0.3
2a
2b
2c
2d
2e
2f
2g
2h
2i
2
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Encouraged by these results we selected the pentafluorophenyl compounds 2c, 2h and 2i for additional MTT tests on further human cancer cell lines
(Table 2). Three prostate cancer cell lines LNCaP (AR+, androgen-responsive), the bone metastatic LNCaP derivative C4-2B (AR+, androgen-refractory),
and PC3 (AR-) as well as aggressive and/or drug-resistant cancer cell lines 518A2 (melanoma), KB-V1/Vbl (vinblastine-resistant cervix carcinoma) and HT-
29 (colon carcinoma) were selected for these tests. The latter three cell lines are highly resistant to 1 (IC50 > 100 µM). In all cell lines the pentafluorophenyl
derivatives 2c, 2h and 2i performed generally better than 1. Compound 2h was even five times more efficacious than 1 with IC50 = 6.4 µM against the C4-
2B cancer cells. Both 2c and 2h were also about twice as active as 1 against LNCaP (AR+) cells (IC50 = 8.1 µM) and against PC3 (AR-) cells (IC50 ca. 13 µM).
Compound 2i exhibited comparable activity against LNCaP cells. Further to this, the anticancer active derivatives 2c, 2h and 2i were tested in the
aggressive and/or drug-resistant human cancer cell lines 518A2, KB-V1/Vbl and HT-29. In contrast to 1, the pentafluorophenyl derivatives 2c, 2h and 2i
displayed distinct growth inhibition in all three cancer cell lines (IC50 = 9.6-16.5 µM) and, thus, were able to overcome the pronounced resistance of these
cancer cells towards 1.
Table 2. Inhibitory concentrations IC50 (72 h) [µM] of compounds 1, 2c, 2h and 2i in MTT tests against cells of LNCaP, C4-2B, and PC3 prostate carcinomas, 518A2 melanoma,
vinblastine-resistant KB-V1/Vbl cervix carcinoma, and HT-29 colon carcinoma (n.d., not determined).
Compd./cell line
1
2c
2h
2i
LNCaP
C4-2B
PC3
18.9 ± 0.5
32.4 ± 1.0
25.2 ± 0.9
> 100
8.1 ± 0.3
8.1 ± 0.2
6.4 ± 0.1
13.1 ± 0.3
10.7 ± 0.3
10.9 ± 2.4
9.6 ± 0.3
6.2 ± 0.2
n.d.
13.1 ± 0.5
12.9 ± 0.2
12.6 ± 0.3
11.3 ± 1.2
11.7 ± 2.8
n.d.
518A2
KB-V1/Vbl
HT-29
16.5 ± 0.9
11.7 ± 0.8
10.7 ± 2.1
> 100
> 100
Finally, the compounds 1, 2c and 2h were selected for the evaluation of apoptosis induction in the three prostate cancer cell lines (Figure 2). Histone/DNA
ELISA assays were carried out in order to determine the apoptosis rates of these three compounds. The apoptosis rates obtained for 2c and 2h were
distinctly higher than the respective rates for 1 in all three cell lines. This correlates fairly well with the IC50 values obtained from the MTT assays.
Figure 2. Apoptosis induction by 1, 2c, 2h, and 2i in LNCaP, C4-2B, and PC3 prostate carcinoma cells as detected by histone/DNA ELISA assay.
3
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Docking studies
The anti-proliferative activities of compound 1 and of its congeners 2a-i, in particular those against prostate cancer cells, are likely related to the
inhibition of crucial cellular proteins such as the androgen receptor (AR), and/or COX-2. Docking calculations with 1 and the derivatives 2a-i were carried
out in order to identify new protein-drug interactions and binding modes of 2a-i after binding to AR or COX-2 which might explain their enhanced
anticancer activity. While in both proteins 1 revealed the highest calculated binding energies (-9.0 kcal/mol for AR, -8.9 kcal/mol for COX-2) with one
hydrogen bond (H-bond) established to Leu704 (AR) and two H-bonds to Tyr355 and Met522 (COX-2), the active derivative 2c also bound with
considerable energies (-8.3 kcal/mol for AR, -8.2 kcal/mol for COX-2). In contrast, docking of the active compounds 2h and 2i resulted in reduced binding
energies (2h: -7.2 kcal/mol for AR, -7.4 kcal/mol for COX-2; 2i: -7.2 kcal/mol for AR, -7.8 kcal/mol for COX-2) when compared with the other derivatives
(Table 3 and 4). Interestingly, 2e bound with a slightly higher energy than 2c when docked to AR, while 2a and 2f reached or exceeded the binding energy
of 2c when docked to COX-2. Two H-bonds of 2c (via both indole-NH moieties) to Thr755 and Pro682 of the AR were observed that might explain its high
binding energy (Figure 3). In contrast, 2e interacts with the AR (Arg752) via the ethoxy group of the phenyl ring. In the case of COX-2, compound 2c bound
to Gly350 via an H-bond to the NH of one indole moiety, while 2a was anchored by one H-bond to Gln203 via its indole-NH. Compound 2f bound by two
H-bonds to Thr62 and Thr60 via the indole-NH and methoxyphenyl-O moieties. It is likely that the methyl groups at the indole scaffolds of 2h impair a
tight binding to the AR and to COX-2. A similar effect can be assumed for the methoxy groups at the indole moieties of compound 2i. Yet, it is possible
that an improved permeability of the cellular membranes due to the additional methyl groups of 2h and the methoxy groups of 2i can compensate for the
reduced AR and COX-2 binding and so lead to stronger tumor cell growth inhibition when compared with 2c and the other tested derivatives.
Table 3. Docking of 1 and derivatives 2a-i into the binding cavity of the androgen receptor (AR). BE = binding energy (kcal/mol); bond length in Å.
Compd.
BE
No of H-bonds
Amino acid residues involved
Bond length
1
-9.0
-7.1
1
LEU704
2.3
2a
2
SER782
GLN783
2.5
2.5
2b
2c
-7.7
-8.3
2
2
THR755
PRO682
2.9
2.5
THR755
PRO682
2.4
2.9
2d
2e
2f
-8.4
-8.4
-8.0
1
1
2
PHE876
ARG752
2.2
2.5
THR755
ARG752
1.9
2.8
2g
-7.5
3
ASN756
GLY683
2.0 and 3.2
2.0
2h
2i
-7.2
-7.2
1
GLU678
GLU681
2.4
2
2.6 and 2.8
4
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Table 4. Docking of 1 and derivatives 2a-i into the binding cavity of COX-2. BE = binding energy (kcal/mol); bond length in Å.
Compd.
1
BE
No of H-bonds
Amino acid residues involved
Bond length
-8.9
2
TYR355
MET522
2.3
2.0
2a
2b
2c
2d
-8.6
-7.8
-8.2
-7.9
1
1
1
2
GLN203
THR62
2.8
2.5
2.6
GLY350
THR62
THR60
2.4
3.4
2e
2f
-7.7
-8.2
-8.1
2
2
2
THR62
THR60
2.5
3.5
THR62
THR60
2.5
3.4
2g
PHE580
SER579
2.1
2.4
2h
2i
-7.4
-7.8
1
3
TYR355
1.9
GLN192
ASN581
GLN350
3.4
3.2
2.5
Figure 3. Proposed binding mode of 1, 2c, 2h and 2i into the binding pockets of the androgen receptor (AR) or COX-2. Hydrogen bonds are indicated by dashed lines.
The nitrogen of the indole ring is mainly involved in the drug interaction with the protein cavities of COX-2 and AR. However, the binding sites of 2c, 2h
and 2i differ significantly from the binding sites of 1 in both COX-2 and AR protein structures (Figure 4). The presence of the aromatic ring in compounds 2
is responsible for this alternative binding to both proteins. The different binding sites can explain the different activities against cancer cells.
5
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Figure 4. Overlay images of 1, 2c, 2h and 2i into the binding pockets of the androgen receptor (AR) or COX-2. Red: 1; green: 2c; blue: 2h; magenta: 2i.
Conclusions
A series of fluoroaryl derivatives 2 of di(indol-3-yl)methane 1 were prepared by a simple one-step protocol starting from indole derivatives 3a-c and
appropriately substituted benzaldehydes. All those fluorinated compounds 2 that were tested on a panel of human cancer cell lines were more efficacious
than 1. The pentafluorophenyl derivatives 2c, 2h and 2i, differing only in the substitution of the indole scaffold, were the most active compounds against
the tested cancer cells. Compounds 2c and 2h were also strong inducers of apoptosis in prostate cancer cells. In addition, compounds 2c, 2h and 2i
breached the resistance of three aggressive and drug-resistant cancer cell lines (518A2, KB-V1/Vbl, HT-29) towards 1. This, and the obvious room for
further structural fine-tuning renders the compounds 2 a promising class of test compounds.
Experimental Section
Chemistry
Melting points were recorded using a Gallenkamp apparatus and are uncorrected. IR: Perkin-Elmer Spectrum One FT-IR spectrophotometer equipped
with an ATR sampling unit. NMR: Bruker Avance 300 spectrometer; chemical shifts are given in parts per million (δ) downfield from Me4Si as internal
standard; coupling constant (J) are given in Hz; MS: Varian MAT 311A (EI). Microanalyses indicated by the symbols of the elements were within ± 0.2% of
the theoretical values for all new compounds. The starting compounds and pure solvents were purchased from the usual sources and were used without
further purification. Compound 1 was provided by Dr. Michael Zeligs (BioResponse) and analysed (NMR, IR, MS) leading to the identification of
compound 1 as pure di(indol-3-yl)methane. Merck silica gel 60 (230-400 mesh) was used for column chromatography.
Synthesis
General procedure for the preparation of bisindoles 2.
3,3’-Diindolyl(4-fluorophenyl)methane (2a). Indole (586 mg, 5.0 mmol) was suspended in water (25 mL) and 4-fluorobenzaldehyde (276 µL, 2.5 mmol)
was added. A catalytic amount of conc. sulfuric acid (3 drops) was added to the mixture before stirring at 90 °C for 2.5 h. Ethyl acetate was added to
dissolve the formed precipitate, the organic phase was separated, dried over Na2SO4, filtered, and the filtrate was concentrated in vacuum. The residue
thus obtained was purified by column chromatography (silica gel 60; ethyl acetate / n-hexane 1:2, v/v). Yield: 800 mg (2.35 mmol, 84 %); νmax (ATR)/cm-1
1
3406, 1601, 1504, 1455, 1417, 1337, 1214, 1155, 1123, 1092, 1038, 1009, 853, 816, 793, 782, 738; H NMR (300 MHz, CDCl3) δ 5.89 (1 H, s), 6.5-6.6 (2 H, m),
6.9-7.1 (4 H, m), 7.2-7.3 (6 H, m), 7.4-7.5 (2 H, m), 7.73 (2 H, s); 13C NMR (75.5 MHz, CDCl3) δ 39.3, 111.1, 114.7, 15.0, 119.2, 119.3, 119.7, 121.9, 123.5, 126.8,
129.9, 130.0, 136.6, 139.6, 159.7, 162.9; MS (EI) m/z 340 [M+] (100%), 245 (62) 223 (26) 122 (15).
6
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Biological studies
Cell lines and culture conditions. BxPC-3 pancreas cancer (gemcitabine-sensitive) and MDA-MB-231 breast cancer cells (triple-negative) were purchased
from the American Type Culture Collection (Manassas, VA) and maintained in Dulbecco’s modified Eagle’s medium (DMEM; Invitrogen, Carlsbad, CA)
supplemented with 10% fetal calf serum (FCS), 100 U/mL of penicillin, and 100 µg/mL of streptomycin. Prostate cancer cell lines PC3 (AR-), LNCaP (AR+,
androgen-sensitive) and C4-2B (AR+, androgen-refractory) were obtained from the American Type Culture Collection (Manassas, VA) and maintained in
RPMI 1640 (Invitrogen, Carlsbad, CA) supplemented with 10% fetal bovine serum (FBS), 100 U/mL of penicillin and 100 µg/mK of streptomycin. All cells
were cultured in a humidified 5% CO2 atmosphere at 37 °C. The human melanoma cell line 518A2 (Department of Radiotherapy and Radiobiology,
University Hospital Vienna), the human colon adenocarcinoma cell line HT-29 (German Center of Biological Materials, Braunschweig, Germany), and the
KB-V1/Vbl cervix cancer cell line (German Center of Biological Materials, Braunschweig, Germany) were grown in DMEM or RPMI (HT-29) medium,
supplemented with 10% fetal bovine serum (FBS), 1% Antibiotic-Antimycotic solution (both from Gibco) and 250 µg/mL gentamycin (SERVA). MCF-10A
breast epithelial cells were obtained from ATCC and maintained in DMEM-F12 medium supplemented with 0.1 µg/mL cholera toxin, 0.02 µg/mL
epidermal growth factor, 10 µg/mL insulin, 0.5 µg/mL hydrocortisone, 100 U/mL penicillin, 100 µg/mL streptomycin and 5% horse serum in a humidified
5% CO2 atmosphere at 37 °C. HPDE human pancreatic ductal epithelial cells were obtained from the M. D. Anderson Cancer Center of the University of
Texas and maintained in RPMI-1640 media supplemented with 10% fetal bovine serum and 1% penicillin and streptomycin.
MTT assay. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (ABCR) was used to identify viable cells which reduce it to a violet
formazan. Cells (3x103/well) were seeded and cultured for 24 h on 96-well microplates. Incubation (5% CO2, 95% humidity, 37 °C) of cells following
treatment with the test compounds (dilution series from 5-40 µM in DMSO) was continued for 72 h. 25 µL of an MTT stock solution, containing 5 mg/mL
in phosphate-buffered saline (PBS), was added to a final concentration of 0.05% and incubated for further 2 h at 37 °C. The supernatant was withdrawn
and the formazan was dissolved in isopropanol or DMSO (100 µL). The absorbance at 595 nm was measured on an Ultra Multifunctional Microplate
Reader (Tecan, Durham, NC). All experiments were repeated at least three times with quadruplet observations in every repeat.
Histone/DNA-ELISA apoptosis assay. The Cell Death Detection Kit (Roche, Palo Alto, CA) was used to detect apoptosis in LNCaP, C4-2B and PC3 prostate
cancer cells treated with test compounds as described previously.[20] Briefly, cells were treated with test compounds for 72 h. The cytoplasmic
histone/DNA fragments from these cells were extracted and incubated in microtiter plate modules coated with anti-histone antibodies. Subsequently, the
peroxidase-conjugated anti-DNA antibodies were used for the detection of immobilized histone/DNA fragments followed by color development with
2,20-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) substrate for peroxidase. The absorbance of the samples was determined with the microplate
reader at 405 nm.
Docking studies. All the docking calculations were performed with AutoDock Vina software to study interactions of compounds with the binding site of
COX-2 (PDB ID: 6COX) and androgen receptor (PDB ID: 1E3G).[21] The 3D molecular structures of the compounds were generated by CORINA software.
Compounds were energy minimized to obtain stable conformation of bonds and angles in MGL tools. The molecular docking was performed to obtain a
population of possible conformations and orientations for the ligands at the binding site. All molecular docking studies were carried out in AutoDock Vina
software by creating grid with 60x60x60 and grid center defined with x, y and z axis by implementing Lamarckian Genetic Algorithm (LGA). The best
conformation was chosen with the most negative binding energy after docking. The interactions of compounds with COX-2 and androgen receptor
binding sites including hydrogen bonds and the bond lengths were analyzed using PyMOL software.[22]
Supplementary Material
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/MS-number.
Author Contribution Statement
A. A. and S. S. designed and performed the biological assays. B. B. synthesized the test compounds and wrote the article. P. D. performed the docking
calculations. S. P., F. H. S. and R. S. contributed to the study design, interpretation of the data and the drafting of the manuscript.
7
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References
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10.1002/cbdv.201900028
Chemistry & Biodiversity
Chem. Biodiversity
Entry for the Graphical Illustration
F
F
F
F
F
R2
R2
- Pentafluorophenyl analogs 2c, 2h, and 2i of
3,3'-diindolylmethane (DIM)
- 2c, 2h, and 2i break resistance to DIM in
various cancer cells
R1R1
N
N
H
H
2c: R1, R2 = H
2h: R1 = Me, R2 = H
2i: R1 = H, R2 = OMe
9
This article is protected by copyright. All rights reserved.