Synthesis of mono Mannich bases of 2-(4-hydroxybenzylidene)-2,3-dihydroinden-1-one and evaluation of their cytotoxicities

Article abstract of DOI:10.3109/14756366.2015.1070263

Chalcones and Mannich bases are a group of compounds known for their cytotoxicities. In this study restricted chalcone analogue, compound 2-(4-hydroxybenzylidene)-2,3-dihydroinden-1-one MT1, was used as a starting compound to synthesize new mono Mannich b

Full text of DOI:10.3109/14756366.2015.1070263

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J Enzyme Inhib Med Chem, Early Online: 1–6
2015 Taylor & Francis. DOI: 10.3109/14756366.2015.1070263
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RESEARCH ARTICLE
Synthesis of mono Mannich bases of 2-(4-hydroxybenzylidene)-2,3-
dihydroinden-1-one and evaluation of their cytotoxicities
Mehtap Tugrak1, Cem Yamali1, Hiroshi Sakagami2, and Halise Inci Gul1
2
1Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Ataturk University, Erzurum, Turkey and Division of Pharmacology,
Meikai University School of Dentistry, Sakado, Saitama, Japan
Abstract
Keywords
Chalcones and Mannich bases are a group of compounds known for their cytotoxicities. In this
study restricted chalcone analogue, compound 2-(4-hydroxybenzylidene)-2,3-dihydroinden-1-
one MT1, was used as a starting compound to synthesize new mono Mannich bases since
Mannich bases may induce more cytotoxicity than chalcone analogue that they are derived
from by producing additional alkylating center for cellular thiols. In this study, cyclic and acyclic
amines were used to synthesize Mannich bases. All compounds were tested against Ca9–22
(gingival carcinoma), HSC-2, HSC-3 and HSC-4 (oral squamous cell carcinoma) as tumour cell
lines and HGF (gingival fibroblasts), HPC (pulp cells) and HPLF (periodontal ligament fibroblasts)
human normal oral cells as non tumour cell lines. Cytotoxicity, selectivity index (SI) values and
potency selectivity expression (PSE) values expressed as a percentage were determined for the
compounds. According to data obtained, the compound MT8 with the highest PSE value
bearing N-methylpiperazine moiety seems to be a good candidate to develop new cytotoxic
compounds and is suited for further investigation.
Chalcone analogue, cytotoxicity,
dihydroinden-1-one, 1-indanone, Mannich
bases, phenol, selectivity index, MTT,
synthesis
History
Received 11 February 2015
Revised 12 June 2015
Accepted 25 June 2015
Published online 6 August 2015
Introduction
shape of molecule which is responsible for the cytotoxicity is
not possible. The aim of the present study was to synthesize
conformationally restricted chalcone analogue, 2-(4-hydroxy-
benzylidene)-2,3-dihydroinden-1-one, and its Mannich bases
(MT8-MT15). Different amines having different pKa values
such as N-methyl piperazine (MT8), morpholine (MT9),
piperidine (MT10), pyrrolidine (MT11), dimethylamine
(MT12), diethylamine (MT13), dipropylamine (MT14) and
dibenzylamine (MT15) were considered. Different pKa values
can direct the deamination ratio and alkylation ratio of the
compounds. It was also aimed to evaluate the cytotoxicities of
the compounds against human tumour cell lines [gingival
carcinoma (Ca9–22), oral squamous cell carcinoma (HSC-2,
HSC-3 and HSC-4)] and human normal oral cells [gingival
fibroblasts (HGF), periodontal ligament fibroblasts (HPLF) and
pulp cells (HPC)].
Styryl ketones which have a,b-unsaturated ketone moiety are
known as potential cytotoxic and anticancer compounds1. These
compounds showed remarkable affinity for thiol groups and did
not react with amino or hydroxy groups2,3. Amino and hydroxy
groups are available in nucleic acids, and hence a,b-unsaturated
ketones may not have the genotoxic effects which are associated
with various alkylating agents used in cancer chemotherapy4.
Mannich bases are a group of compounds having various
biological activities such as cytotoxic5–15 anti-inflammatory16,17
and anticonvulsant18,19 activities.
a,b-Unsaturated ketone/s available in the chemical structure of
Mannich bases or produced from Mannich bases by deamination
process is/are responsible for their cytotoxicities. a,b-Unsaturated
ketones alkylate cellular thiols to produce cytotoxicity20. It was
reported that Mannich bases of styryl ketones have increased
cytotoxicity comparing to its styryl ketone analogue21.
The cytotoxic and anticancer properties of chalcone (1,3-
diphenyl-2-propenone) and related compounds have been
reported7,8,15,22–28. Conferring Mannich bases to phenolic chal-
cones increased their cytotoxicity7,8,15,26,27. Chalcones are con-
jugated molecules and sufficiently flexible to permit a wide
variety of conformations. Hence, discernment of the optimal
Materials and methods
Melting points were determined using an Electrothermal 9100
(IA9100; Bibby Scientific Limited, Staffordshire, UK) instrument
and are uncorrected. 1H-NMR (400 MHz) and 13C-NMR
(100 MHz) spectra were obtained using a Varian Mercury Plus
spectrometer (Varian Inc., Palo Alto, CA). Chemical shifts (ꢀ)
were reported in parts per million. Mass spectra were undertaken
on an HPLC-TOF Waters Micromass LCT Premier XE (Waters
Corporation, Milford, MA) mass spectrometer using an electro-
spray ion source (ESI). All reactions were carried out in CEM
Address for correspondence: Prof. Dr. H. Inci Gul, Department of
Pharmaceutical Chemistry, Faculty of Pharmacy, Ataturk University,
Erzurum, Turkey. Tel: +90-442-231-5219. Fax: +90-442-231-5201.
E-mail: incigul1967@yahoo.com

2
M. Tugrak et al.
J Enzyme Inhib Med Chem, Early Online: 1–6
OH
Scheme 1. Synthesis of MT1.
O
H
EtOH
HO
+
NaOH
10%
O
O
MT1
Discover Microwave Synthesis Systems (CEM Corporation, 126.8, 126.0, 124.3, 121.6, 116.9, 61.3, 54.8, 52.5, 45.8 and 32.5;
Mass spectrum: 349.19 (M+ + 1); HRMS (ESI-MS) Calcd:
349.1916 for C22H25N2O2 [M+H+], found: 349.1902.
Matthews, NC; 908010).
Synthesis of 2-(4-hydroxybenzylidene)-2,3-dihydroinden-
1-one (MT1)
2-(4-Hydroxy-3-(morpholinomethyl)benzylidene)-2,3-
dihydroinden-1-one (MT9)
A solution of the 4-hydroxybenzaldehyde (0.02 mol) in ethanol
1
(6 ml) was added into a stirred solution of 1-indanone (0.02 mol) Yield: 11.3%. m.p.: 171–174 ꢀC. H-NMR (CDCl3) ꢀ 2.62 (4H,
in aqueous solution of sodium hydroxide (10 ml, 10%). Stirring bs, CH2-morpholine), 3.79 (6H, s, CH2-morpholine, CH2–N),
was maintained at room temperature overnight. The reaction 4.00 (2H, s, indeno H-3), 6.91 (1H, d, phenyl H-5,
mixture was then poured onto water (100 ml) and neutralized with J ¼ 8.4 Hz),7.31 (1H, s, phenyl H-2), 7.41 (1H, t, indeno H-6,
hydrochloric acid (10%, w/v). The precipitated solid product J ¼ 7.3 Hz), 7.54–7.62 (4H, m, ¼CH–, indeno H-4, H-5, phenyl
was filtered, washed with water, and crystallized from water– H-6), 7.89 (1H, d, indeno H-7, J ¼ 7.7 Hz); 13C-NMR 194.6,
ethanol22,29 (Scheme 1).
159.8, 149.6, 138.5, 134.5, 134.2, 132.4, 132.1, 132.0, 127.8,
127.3, 126.3, 124.5, 121.4, 117.2, 66.9, 62.0, 53.1 and 32.7; Mass
spectrum: 336.15 (M+ + 1); HRMS (ESI-MS) Calcd: 336.1600 for
C21H22NO3 [M+H+], found: 336.1590.
General synthesis of Mannich bases (MT8–MT15)
The mixture of the compound MT1 (21 mmol), paraformaldehyde
(25 mmol) and suitable secondary amine (21 mmol) [MT8 (N-
methyl piperazine), MT9 (morpholine), MT10 (piperidine), MT11
(pyrrolidine), MT12 (dimethylamine), MT13 (diethylamine),
2-(4-Hydroxy-3-(piperidin-1-ylmethyl)benzylidene)-2,3-
dihydroinden-1-one (MT10)
1
MT14 (dipropylamine) and MT15 (dibenzylamine)] was heated Yield: 6.1%. m.p.: 163–166 ꢀC. H-NMR (CDCl3) ꢀ 1.66 (10H,
in 15 ml of acetonitrile (120 ꢀC, 200 Watt, 13.8 barr) for 15 min bs, CH2-piperidine), 3.74 (2H, s, CH2–N), 3.99 (2H, s, indeno H-
(MT8, MT10, MT13, MT14 and MT15) or 30 min (MT9, MT11 3), 6.88 (1H, d, phenyl H-5, J ¼ 8.4 Hz), 7.28 (1H, d, phenyl H-2,
and MT12). Reactions were monitored by TLC. When the J ¼ 1.8 Hz), 7.41 (1H, t, indeno H-6, J ¼ 6.8 Hz), 7.54–7.62 (4H,
reaction was stopped, reaction solvent was removed under m, ¼CH–, indeno H-4, H-5, phenyl H-6), 7.89 (1H, d, indeno H-7,
vacuum. The compounds MT8, MT15 and MT10 were purified J ¼ 7.7 Hz); 13C NMR 194.3, 160.4, 149.4, 138.4, 134.3, 134.2,
by crystallization. It was EtOH (MT8 and MT15) or MeOH/ 131.9, 131.5, 131.4, 127.5, 126.5, 126, 124.2, 122.1, 116.9, 62.0,
aseton (MT10). On the other hand, the compounds MT9, MT11, 53.9, 32.5, 25.7 and 23.8; Mass spectrum: 334.18 (M+ + 1);
MT12, MT13 and MT14 were purified by column chromatog- HRMS (ESI-MS) Calcd: 334.1807 for C22H24NO2 [M+H+],
raphy on silica gel (SiO2) using suitable solvent system. It was found: 334.1804.
CHCl3:MeOH (98:2) for MT9, CHCl3:MeOH:NH3 (98:2:2) for
MT11, MT13, MT14 and CHCl3:MeOH:NH3 (90:10:2) for MT12
(Scheme 2).
2-(4-Hydroxy-3-(pyrrolidin-1-ylmethyl)benzylidene)-2,3-
dihydroinden-1-one (MT11)
1
Yield: 22.2%. m.p.: 152–154 ꢀC. H-NMR (CDCl3) ꢀ 1.81–1.86
(4H, m, CH2-pyrrolidine), 2.62 (4H, s, CH2-pyrrolidine), 3.84
2 -(4-Hydroxy-benzylidene)-indan-1-one (MT1)
Yield: 76.3%. Melting point (m.p.): 227–229 ꢀC, 235–236 ꢀC29.
(2H, s, CH2–N), 3.90 (2H, s, indeno H-3), 6.84 (1H, d, phenyl H-
1H-NMR (CD3OD) ꢀ 4.04 (2H, s, indeno H-3), 6.88–6.91 (2H, m,
5, J ¼ 8.4 Hz), 7.24 (1H, s, phenyl H-2), 7.34 (1H, t, indeno H-6,
phenyl H-3, H-5), 7.44–7.50 (2H, m, ¼CH–, indeno H-6), 7.57–
7.69 (4H, m, phenyl H-2, H-6, indeno H-4, H-5), 7.80 (1H, d,
indeno H-7, J ¼ 7.7 Hz), 7.90 (1H, s, phenyl 4-OH); 13C-NMR
195.5, 159.9, 150.5, 137.9, 134.9, 134.7, 133.1, 131.7, 127.5,
126.8, 126.5, 123.6, 115.9 and 32.15; mass spectrum: 235.08
[M ꢁ H]+; HRMS (ESI-MS) Calcd: 235.0759 for C16H11O2
[M ꢁ H]+, found: 235.0758.
J ¼ 6.6 Hz), 7.47–7.54 (4H, m, ¼CH–, indeno H-4, H-5, phenyl
H-6), 7.83 (1H, d, indeno H-7, J ¼ 7.7 Hz); 13C-NMR 194.2,
160.4, 149.4,138.3, 134.2, 134.1, 131.5, 131.4, 131.2, 127.4,
126.3, 126.1, 124.1, 122.9, 116.7, 58.7, 53.4, 32.5 and 23.7; Mass
spectrum: 318.14 (M+ + 1); HRMS (ESI-MS) Calcd: 318.1494 for
C21H20NO2 [M+H+], found: 318.1484.
2-(4-Hydroxy-3-((4-methylpiperazin-1-yl)methyl)
benzylidene)-2,3-dihydroinden-1-one (MT8)
2-(4-Hydroxy-3-(dimethylaminomethyl)-benzylidene)
-2,3-dihydroinden-1-one (MT12)
1
1
Yield: 51%. m.p.: 152–154 ꢀC. H-NMR (CDCl3) ꢀ 2.31 (3H, s, Yield: 7.4%. m.p.: 166–169 ꢀC. H-NMR (CDCl3) ꢀ 2.38 (6H,s,
N–CH3), 2.32–2.60 (8H, m, CH2-piperazin ring), 3.79 (2H, s, 2 ꢂ CH3), 3.74 (2H, s, CH2–N), 4.00 (2H, s, indeno H-3), 6.91
CH2–N), 3.99 (2H, s, indeno H-3), 6.90 (1H, d, phenyl H-5, (1H, d, phenyl H-5, J ¼ 8.4 Hz), 7.30 (1H, s, phenyl H-2), 7.43
J ¼ 8.8 Hz), 7.31 (1H, s, phenyl H-2), 7.41 (1H, t, indeno H-6, (1H, t, indeno H-6, J ¼ 7.0 Hz), 7.54–7.62 (4H, m, ¼CH–, indeno
J ¼ 7.2 Hz), 7.54–7.61 (4H, m, ¼CH–, indeno H-4, H-5, phenyl H-4, H-5, phenyl H-6), 7.89 (1H, d, indeno H-7, J ¼ 7.6 Hz); 13C-
H-6) 7.89 (1H, d, indeno H-7, J ¼ 7.7 Hz); 13C-NMR 194.3, NMR 194.3, 160.3, 149.4, 138.4, 134.2, 131.8, 131.7, 131.6,
159.8, 149.4, 138.3, 134.2, 134.1, 131.9, 131.8, 131.7, 127.5, 127.5, 126.6, 126.1, 124.2, 122.2, 116.9, 62.7, 44.4 and 32.5;

DOI: 10.3109/14756366.2015.1070263
Cytotoxicities of new phenolic mono-Mannich bases
3
*
OH
OH
CH3CN
O
Secondary
Amine
+
+
H
H
13.8 barr, 200 Watt
120°C
O
O
MT 1
MT 8 - MT 15
C H
6
5
,
,
,
N
,
N
,
N
,
,
*:
N
N
N
N
CH
N
O
N
3
C H
6
5
MT8
MT9
MT10
MT11
MT12
MT13
MT14
MT15
Scheme 2. Synthesis of MT8–MT15.
Mass spectrum: 294.14 (M+ + 1); HRMS (ESI-MS) Calcd: Biological activity
294.1494 for C19H20NO2 [M+H+], found: 294.1480.
Cytotoxicity evaluation
The cytotoxicity of the compounds MT1 and MT8-MT15 was
assayed towards human tumour cell lines [gingival carcinoma
(Ca9–22), oral squamous cell carcinoma (HSC-2, HSC-3, HSC-
4)] and human normal oral cells [gingival fibroblasts (HGF),
periodontal ligament fibroblasts (HPLF) and pulp cells (HPC)] as
described30 with some minor modifications. In brief, all cells
were cultured in DMEM supplemented with 10% fetal bovine
serum (FBS). The following concentrations of the compounds in
dimethylsulfoxide (DMSO) were added to the medium and
incubated at 37 ꢀC for 48 h: MT1 and MT8-MT15 (0.32, 1, 3.2,
10, 31.6, 100, 316 and 1000 mmol/L), melphalan (3.12, 6.25, 12.5,
25. 50, 100, 200 and 400 mmol/L) and 5-FU (7.8, 15.6, 31.3, 62.5,
125, 250, 500 and 1000 mmol/L). The media that contained the
same concentration of DMSO (0.0078, 0.156, 0.03125, 0.0625,
0.125, 0.25, 0.5 or 1%) were used as controls, since DMSO above
0.25% is cytotoxic. The viable cell numbers were determined by
the MTT method. The CC50 values were determined from dose-
response curves.
2-(4-Hydroxy-3-(diethylaminomethyl)-benzylidene)-2,3-
dihydroinden-1-one (MT13)
Yield: 23.5%. m.p.: 138–141 ꢀC. 1H-NMR (CDCl3) ꢀ 1.13 (6H, t,
2 ꢂ CH3, J ¼ 7.1 Hz), 2.66 (4H, q, 2 ꢂ CH2, J ¼ 7.3 Hz), 3.84 (2H,
s, CH2–N), 3.99 (2H, s, indeno H-3), 6.87 (1H, d, phenyl H-5,
J ¼ 8.4 Hz), 7.29 (1H, s, phenyl H-2), 7.41 (1H, t, indeno H-6,
J ¼ 7.1 Hz), 7.54–7.61 (4H, m, ¼CH–, indeno H-4, H-5, phenyl
H-6), 7.90 (1H, d, indeno H-7, J ¼ 7.3 Hz); 13C-NMR 194.6,
160.9, 149.7, 138.6, 134.6, 134.4, 132.1, 131.6, 127.7, 126.7,
126.3, 124.5, 122.8, 177.2, 94.6, 57.1, 46.6, 32.8 and 11.3; Mass
spectrum: 322.18 (M+ + 1); HRMS (ESI-MS) Calcd: 322.1807 for
C21H24NO2 [M+H+], found: 322.1805.
2-(4-Hydroxy-3-(dipropylaminomethyl)-benzylidene)-2,3-
dihydroinden-1-one (MT14)
Yield: 10.4%. m.p.: 113–115 ꢀC. 1H-NMR (CDCl3) ꢀ 0.90 (6H, t,
2 ꢂ CH3, J ¼ 7.3 Hz), 1.54–1.63 (4H, m, 2 ꢂ CH2), 2.51 (4H, t,
2 ꢂ CH2, J ¼ 7.7 Hz), 3.83 (2H, s, CH2–N), 4.00 (2H, s, indeno H-
3), 6.88 (1H, d, phenyl H-5, J ¼ 8.4 Hz), 7.28 (1H, s, phenyl H-2),
7.41 (1H, t, indeno H-6, J ¼ 7.1 Hz), 7.54–7.61 (4H, m, ¼CH–,
indeno H-4, H-5, phenyl H-6), 7.90 (1H, d, indeno H-7,
J ¼ 7.3 Hz); 13C-NMR 194.6, 160.8, 149.7, 138.6, 134.6, 134.4,
132.2, 131.7, 127.7, 126.7, 126.3, 124.5, 122.9, 117.1, 58.4, 55.6,
32.8, 19.6 and 11.9; Mass spectrum: 350.21 (M+ + 1); HRMS
(ESI-MS) Calcd: 350.2120 for C23H28NO2 [M+H+], found:
350.2103.
Results and discussion
In this study, 2-(3-((amino)methyl)-4-hydroxybenzylidene)-2,3-
dihydroinden-1-one types of mono Mannich bases MT8-MT15
were designed and synthesized starting from MT1 [2-(4-hydroxy-
benzylidene)-indan-1-one]. N-methyl piperazine (MT8), morpho-
line (MT9), piperidine (MT10), pyrrolidine (MT11), dimethyla-
mine (MT12), diethylamine (MT13), dipropylamine (MT14) and
dibenzylamine (MT15) were used as an amine compound. All
Mannich bases MT8–MT15 reported here are new. The chemical
1
structures of the compounds were confirmed by H-NMR, 13C-
2-(4-Hydroxy-3-(dibenzylaminomethyl)-benzylidene)-2,3-
dihydroinden-1-one (MT15)
1
NMR and HRMS. The H NMR and 13C NMR data of MT1,
which is starting compound for Mannich bases and known
Yield: 21.2%. m.p.: 188–190 ꢀC. 1H-NMR (CDCl3) ꢀ 3.66 (4H, s, compounds, are in accordance with literature29.
2 ꢂ CH2–C6H5), 3.74 (2H, s, CH2–N), 3.98 (2H, s, indeno H-3),
The cytotoxicities of these synthesized compounds were tested
7.24–7.63 (17H, m, phenyl H-2, H-5, H-6, ¼CH–, indeno H-4, H- against Ca9–22, HSC-2, HSC-3 and HSC-4 human tumour cell
5, H-6, protons of dibenzylamine), 7.91 (1H, d, indeno H-7, lines and also against HGF, HPLF and HPC human normal oral
J ¼ 7.3 Hz); 13C-NMR 194.7, 188.3, 182.6, 167.5, 165.5, 162.6, cells. The cytotoxicity results were reported at Table 1.
158.1, 156.1, 149.8, 146.6, 145.9, 140.9, 138.7, 138.3, 136.9,
The first question to be answered is whether there is the
134.9, 134.4, 131.8, 131.7, 129.8, 129.3, 128.9, 128.7, 127.7, antineoplastic property of the compounds or not. Except com-
127.6, 126.8, 126.3, 124.7, 124.5, 58.3, 54.0 and 32.9; Mass pound MT15, which is dibenzylamine derivative, CC50 values
spectrum: 446.20 (M+ + 1); HRMS (ESI-MS) Calcd: 446.2080 for (the concentration of the compound that kills 50% of the cells as
C26H28N3O4 [M+H+], found: 446.2096.
mmol/L) were in 6.8 to41000 micromolar range towards Ca9–22,

4
M. Tugrak et al.
J Enzyme Inhib Med Chem, Early Online: 1–6
HSC-2, HSC-3 and HSC-4, which are cancer lines (Table 1). The
cytotoxic potencies of MT1 and its Mannich bases MT8–MT15
towards cell lines used were compared with clinically used
anticancer drugs: melphalan (alkylating agent) and 5-fluorouracil
(5-FU, pyrimidine antagonist). Only compound MT8 was more
cytotoxic than melphalan and 5-FU towards HSC-2 and HSC-4
cell lines.
The second aspect of these compounds to be considered is
whether they are tumour-specific cytotoxins since tumours are
surrounded by different types of normal cells in oral cavity.
Selectivity index (SI) value, which is the quotient of the average
CC50 value of the non-malignant cells and the CC50 value of a
compound towards a specific malignant cell line, was generated.
The compounds, which have SI values of41, can be considered as
tumour-specific antineoplastic agents (Table 1). Accordingly it
can be said that the compounds MT8–MT14 have shown
remarkable tumour specificity against all cancer cell lines
except MT10 towards Ca9–22 and HSC-4 cell lines (Table 1).
However, MT10 showed the highest SI value against HSC-3 cells
(SI ¼ 10.39).
When MT1 was converted to some Mannich bases, increased
cytotoxicity was observed in MT8 (6.33 times), MT9 (2.45 times),
MT11 (5.53 times), MT12 (2.51 times), MT13 (1.62 times) and
MT14 (3.45 times) towards Ca9–22 cancer cell line compared
with MT1. But, only compounds MT9 (41.68 times), MT11 (1.77
times) and MT14 (3.43 times) showed increased selectivity
against Ca9–22 cell line, as compared with MT1.
Increased cytotoxicities were observed at Mannich bases
MT8 (21.80 times), MT9 (2.54 times), MT11 (1.49 times),
MT12 (1.68 times), MT13 (1.09 times) and MT14 (2.28 times),
compared with MT1 towards HSC-2 cancer cell line. When the
increases in SI of the compounds compared with MT1 were
considered, increased SI was observed at MT8 (1.69 times),
MT9 (41.75 times), MT14 (2.26 times) towards HSC-2 cell line.
On the other hand, except MT15, the increases in cytotoxicities
of all Mannich bases were observed towards HSC-3 cancer cell
line compared with MT1. MT8 (11.39 times), MT9 (5.04 times),
MT10 (3.40 times), MT11 (8.18 times), MT12 (2.49 times),
MT13 (2.59 times) and MT14 (3.12 times) were more cytotoxic
than MT1 against HSC-3. When SI of Mannich bases was
compared with that of MT1 against the same cell line, MT9
(43.46 times), MT10 (3.92 times), MT11 (2.63 times), MT13
(1.15 times) and MT14 (3.09 times) showed remarkably
increased selectivity against HSC-3 cell line.
Additionally, increases in cytotoxicities of Mannich bases
compared with MT1 were observed against HSC-4 cell lines.
These compounds were MT8 (27.35 times), MT9 (1.04 times),
MT11 (1.79 times), MT12 (2.29 times), MT13 (1.09 times) and
MT14 (2.09 times). But when the increase in SI value was
considered, compared with that of MT1 against HSC-4 cell lines,
only MT8 (2.11 times) and MT14 (2.07 times) showed increased
SI values. It is quite natural to observe different cytotoxicity levels
for compounds which have different chemical structures towards
different cell lines, since the mechanism of action for any
compound can be different towards each cell line. That is why
cytotoxicity value and selectivity index can be found different for
any compound.
Lead compound/s should possess both marked cytotoxic
potency and also selective toxicity for tumours. In order to
identify such molecule/s, a potency selectivity expression (PSE)
was devised which is the product of the reciprocal of average
CC50 values towards Ca9–22, HSC-2, HSC-3 and HSC-4 cells
(that reflects cytotoxic potential, the column E, Table 1) and the
average SI values towards these cell lines (that reflects the
tumour-selectivity, the column J, Table 1) and expressed as a
percentage. The PSE data are also shown in Table 1. When PSE

DOI: 10.3109/14756366.2015.1070263
Cytotoxicities of new phenolic mono-Mannich bases
5
values were considered, all compounds had lower PSE values than Declaration of interest
the reference compounds melphalan and 5-FU. It was clear that
The authors report no conflict of interest. The authors alone are
responsible for the content and writing of this article.
This research work was supported by Ataturk University Research
except compounds MT10 and MT15 (PSE ꢃ 0.0051,40.001), the
other Mannich bases had higher PSE values than MT1
(PSE ¼ 0.0144). MT8, which has the N-methylpiperazine moiety Found, Turkey (Project No. BAP: 2010/166, 2011/289 and 2012/75). The
HRMS spectra and Ataturk University, Faculty of Science, Department of
Organic Chemistry for NMR spectra.
authors are thankful to Dr Murat Sukuroglu (from Gazi University) for
in its chemical structure had the highest PSE value
(PSE ¼ 0.2262) (15.7-fold increase as compared with MT1),
followed by MT14 (PSE ¼ 0.1035) (7.2-fold increase). It can
be said that MT8 having N-methylpiperazine moiety in its
References
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new tumour selective cytotoxins and is suited for further
investigation.
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The only difference in chemical structure of Mannich bases
synthesized was the difference of amine part. Amines used have
different pKa values which may govern the cytotoxicity by
affecting the deamination ratio. The compound MT8 has second
nitrogen atom while the others has only one nitrogen atom.
When six-membered cyclic amine compounds MT8 (N-methyl-
piperazine), MT9 (morpholine), MT10 (piperidine), MT11
(pyrrolidine) and acyclic amine compounds MT12 (dimethyla-
mine), MT13 (diethylamine), MT14 (dipropylamine) and MT15
(dibenzylamine) were compared in terms of PSE value obtained,
it was noticed that PSE values was in the order of
MT84MT94MT10. It means that the contribution of different
atom available in the cyclic amines into PSE value was in the
order of N4O4C. PSE value of MT9 (0.0566) was ꢄ1/4 of
MT8 (0.2262) while MT10 (5 0.0051) had 1/11 PSE value of
MT9. When five-membered cyclic amine was used for MT11
instead of six-membered cyclic amine, the PSE value of MT11
(0.0517) was similar to that of MT9. On the other hand, when
acyclic amines were used instead of cyclic amines such as
dimethylamine, diethylamine and dipropylamines in MT12,
MT13 and MT14, respectively, PSE values of MT12–MT14
(0.00145–0.1035) were quite lower than the compounds having
six-membered cyclic amines.
2. Mutus B, Wagner JD, Talpas CJ, et al. 1-Para-chlorophenyl-4,4-
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bis Mannich bases derived from acetophenone in brine shrimp
bioassay. Drug Res 2002;52:840–3.
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piperidinomethylchalcone derivatives and their cytotoxicity against
PC-3 cell lines. Archiv Der Pharmazie 2007;340:195–201.
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When MT14, which has dipropylamine, was considered, its
PSE value was more than five times of MT12 and MT13, and it
was approximately two times higher than those of compounds
MT9, which has six-membered cyclic amine morpholine, and
MT11, which has five-membered cyclic amine pyrrolidine. It is
quite natural to observe increased PSE values in MT14 compared
with MT12 and MT13 because it has higher log P value than the
other homologues MT12 with dimethylamine and MT13 with
diethylamine (Table 1). Increased log P value may increase
membrane permeability of the compounds. On the other hand,
although MT13 and MT10 had similar log P values as 3.74 and
3.79, respectively; PSE value of MT13 was approximately three
times of MT10. This suggests that log P value may not be the sole
determinant of PSE value of the compound. In addition, when
PSE values of MT15 having dibenzylamine and MT12 having
dimethylamine were compared, addition of two phenyl rings
increased the log P values 1.5 times but caused the loss of activity
and selectivity, supporting that cytotoxicity and PSE value of the
compounds are not directly related to their log P value. The
activity of the compounds may be related to their chemical
structure, their stability, their mechanism of action and the cell
type used.
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buthylamino-1-propanone hydrochlorides against Jurkat and L6
cells. Drug Res 2009;59:364–9.
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bases and corresponding piperidinols on DNA topoisomerase I.
Drug Res 2008;58:686–91.
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bases with dimethylamine and their hydrazones and evaluation of
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13. Mete E, Gul HI, Canturk P, et al. Biological activity of 1-aryl-3-
phenethylamino-1-propanone hydrochlorides and 3-aroyl-4-aryl-1-
phenethyl-4-piperidinols on PC-3 cells and DNA topoisomerase I
enzyme. Zeitschr Naturforschung Sect C 2010;65:647–52.
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Pyrrolidine and diethylamine are non-classical bioisoster with
each other. MT11 having pyrrolidine ring had 3.6 times higher
PSE value than that of MT13 having diethylamine. In this case,
better selectivity was observed in conformationally restricted
amine compound MT11.
In conclusion, the compound MT8 with the highest PSE value
bearing N-methylpiperazine moiety seems to be a good candidate
to develop new cytotoxic compounds and is suited for further
investigation.
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