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/lp/de-gruyter/synthesis-of-coumarin-heterocyclic-derivatives-with-antioxidant-o63rFbsXC7
- Publisher
- de Gruyter
- Copyright
- Copyright © 2009 by the
- ISSN
- 1330-0075
- eISSN
- 1846-9558
- DOI
- 10.2478/v10007-009-0018-7
- pmid
- 19564141
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- See Article on Publisher Site
Abstract
Acta Pharm. 59 (2009) 159170 10.2478/v10007-009-0018-7 Original research paper PARAMESWARAN MANOJKUMAR* THENGUNGAL KOCHUPAPPY RAVI GOPALAKRISHNAN SUBBUCHETTIAR Department of Pharmaceutical Chemistry College of Pharmacy, Sri Ramakrishna Institute of Paramedical Sciences Coimbatore-641044, Tamilnadu, India The aim of the present work was to synthesise coumarinyl heterocycles and to elucidate the potential role of these compounds as antioxidants and cytotoxic agents against Dalton's lymphoma ascites tumour cells (DLA) and Ehrlich ascites carcinoma cells (EAC). The synthesis of coumarin derivatives containing pyrazole, pyrazolone, thiazolidin-4-one, 5-carboxymethyl-4-thiazolidinone and 3-acetyl-1,3,4-oxadiazole ring is reported. 4-Methylcoumarinyl-7-oxyacetic acid hydrazide (1) reacted with arylazopropanes or hydrazono-3-oxobutyrate derivatives to form pyrazole (3a-c) and pyrazolone derivatives (5a-c). Heterocyclisation of Schiff's bases of 1 with thioglycolic acid, thiomalic acid or acetic anhydride afforded novel heterocyclic derivatives 4-thiazolidinones (7a-c), 5-carboxymethyl-4-thiazolidinones (8a-c) and oxadiazoles (9a-c), respectively. Some of the compounds showed promising antioxidant activity in vitro and cytotoxic activity against DLA cells and EAC cells. Keywords: pyrazole, pyrazolone, thiazolidin-4-one, oxadiazole, antioxidant activity Acceptrd April 3, 2009 Coumarin derivatives possess a wide spectrum of biological activities (13). Also, it is well documented that pyrazoles, pyrazolin-5-ones, 4-thiazolidinones and 1,3,4-oxadiazoles display pronounced antioxidant (46) and antineoplastic activity (710). In view of the considerable importance of the coumarins and heterocycles mentioned above, the present work is aimed at the design and synthesis of new heterocyclic compounds bearing coumarin moiety. Moreover, the study includes testing of target compounds for their cytotoxic activity against Dalton's lymphoma ascites (DLA) and Ehrlich ascites carcinoma (EAC) cells. * Correspondence; e-mail: kmano1975@rediffmail.com P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. EXPERIMENTAL Melting points were determined in open capillaries and were uncorrected. IR spectra (KBr discs) were recorded on a JASCO FT/IR-410 spectrophotometer (Japan). 1H NMR spectra were recorded on a Bruker 300 MHz NMR spectrometer (Switzerland). Mass spectra were recorded on LC-MS/MS (API-4000), MDS SCIEX (Canada). Microanalysis was done on a Perkin-Elmer model 2400 CHN analyser (USA). The purity of all compounds was established by single spot on the TLC plates (Merck, Germany). Iodine vapour was used as developing agent. The solvent system used was toluene: methanol (3:7). The starting material 4-methylcoumarinyl-7-oxyacetic acid hydrazide (1) was prepared according to a literature procedure (11). 3-(Arylazo)-2,4-pentanediones (2a-c) and ethyl-2-(substitutedphenyl) hydrazono-3-oxobutyrates (4a-c) were prepared according to reported procedures (1214). Synthetic pathway of newly synthesised compoundsies presented in Scheme 1 and their physicochemical and spectral data are given in Tables I and II. O H2 N O N N AcOH O O NH H 3C O O O O CH3 AcOH 4a-c 2a-c R H 3C N N H 3C N N O O O O R O R O AcOH O N NH H 3C N N O 5a-c O O O 3a-c NH 6a-c R HS O OH AcOH O O S N NH O O O O OH O ( CO)2 O O OH OH O SH R AcOH O O H 3C O S N NH O O O N N O O O 7a-c 9a-c R a: b: H c: F 8a-c Scheme 1 160 P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. Table I. Physico-chemical data of synthesised compounds Elemental analysis Calcd./found (%) C 3a 3b 3c 5a 5b 5c 6a 6b 6c 7a 7b 7c 8a 8b 8c 9a 9b 9c 56 54 72 52 45 60 62 68 83 64 57 72 64 60 72 58 52 70 246248 282284 192194 223225 210212 276278 224226 222224 238240 154155 219220 228230 196197 178179 221223 126128 172174 175177 C24H22N4O4 (430.46) C23H20N4O4 (416.43) C23H19FN4O4 (434.42) C23H20N4O5 (432.44) C22H18N4O5 (418.40) C22H17FN4O5 (436.39) C20H18N2O4 (350.37) C19H16N2O4 (336.34) C19H15FN2O4 (354.33) C22H20N2O5S (424.47) C21H18N2O5S (410.44) C21H17FN2O5S (428.43) C24H22N2O7S (482.51) C23H20N2O7S (468.48) C23H19FN2O7S (486.47) C22H20N2O5 (392.41) C21H18N2O5 (378.38) C21H17FN2O5 (396.37) 66.97 66.94 66.34 65.95 63.59 63.54 63.88 63.65 63.15 63.38 60.55 60.45 68.56 68.38 67.85 67.64 64.40 64.54 62.25 62.19 61.45 61.51 58.87 59.10 59.74 59.51 58.97 59.02 56.79 56.39 67.34 67.57 66.66 66.56 63.63 63.48 H 5.15 5.13 4.84 4.87 4.41 4.50 4.66 4.58 4.34 4.28 3.93 3.91 5.18 5.22 4.79 4.92 4.27 4.37 4.75 4.76 4.42 4.33 4.00 3.95 4.60 4.55 4.30 4.34 3.94 4.02 5.14 5.22 4.79 4.83 4.32 4.25 N 13.02 13.16 13.45 13.34 12.90 12.79 12.96 12.78 13.39 13.28 12.84 12.79 8.00 7.85 8.33 8.56 7.91 7.68 6.60 6.76 6.83 6.78 6.54 6.61 5.81 5.65 5.98 5.93 5.76 5.67 7.14 6.96 7.40 7.54 7.07 7.05 Compd. Yield (%) M.p. (°C) Mol. formula (Mr) P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. Table II. Spectral data of synthesised compounds Compd. 3a IR (n, cm1) 2924, 1721, 1617, 1493, 1439, 1283 2973, 1719, 1615, 1491, 1390, 1283 2934, 1695, 1606, 1521, 1427, 1288 3156, 3055, 2977, 1721, 1623, 1491 3225, 3056, 2966, 1718, 1612, 1388 2927, 1717, 1385, 1263, 1156 3170, 1655, 1686, 1275 1H NMR (d, ppm) (DMSO-d6) / MS 2.41 (s, 3H, CH3 of coumarin), 2.51 (s, 3H, CH3 of phenyl substituent), 3.353.48 (m, 6H, CH3 of pyrazole ring), 4.88 (s, 2H, OCH2), 6.25 (s, 1H, CH of coumarin), 7.237.74 (m, 7H, Ar-H) m/z 431.6 (M+1)+ (14), 219.2 (100), 175.2 (34), 136.9 (61), 123.2 (56) 2.19 (s, 3H, CH3 of coumarin), 2.50 (s, 3H, CH3 at C3 of pyrazole), 3.37 (s, 3H, CH3 at C5 of pyrazole), 4.79 (s, 2H, OCH2), 6.25 (s, 1H, CH of coumarin), 6.857.71 (m, 8H, Ar-H) 2.41 (s, 3H, CH3 of coumarin), 2.51 (s, 3H, CH3 at C3 of pyrazole), 3.37 (s, 3H, CH3 at C5 of pyrazole), 4.79 (s, 2H, OCH2), 6.25 (s, 1H, CH of coumarin), 6.987.73 (m, 7H, Ar-H) 2.27 (s, 3H, CH3 of phenyl substituent), 2.38 (s, 3H, CH3 of coumarin), 3.31(s, 3H, CH3of pyrazolone), 4.73 (s, 2H, OCH2), 6.22 (s, 1H, CH of coumarin), 6.857.74 (m, 7H, Ar-H), 10.32 (s, 1H, NH) m/z 431.6 (M+) (10), 191.2 (26), 123.5 (11), 106.2 (34) 2.52 (s, 3H, CH3 of coumarin), 2.63 (s, 3H, CH3 of pyrazolone), 4.87 (s, 2H, OCH2), 6.38 (s, 1H, CH of coumarin), 7.087.87 (m, 8H, Ar-H), 10.01 (s, 1H, NH) 2.41 (s, 3H, CH3 of coumarin), 2.52 (s, 3H, CH3 of pyrazolone), 4.73 (s, 2H, OCH2), 6.25 (s, 1H, CH of coumarin), 6.867.74 (m, 7H, Ar-H), 10.3 (s, 1H, NH) 2.32 (s, 3H, CH3 of phenyl substituent), 2.41 (s, 3H, CH3 of coumarin), 4.78 (s, 2H, OCH2), 5.12 (s, 1H, CH), 6.24 (s, 1H, CH of coumarin), 7.328.71 (m, 7H, Ar-H), 10.01 (s, 1H, NH) m/z 351.2 (M+1)+ (14), 219.2 (100), 189.0 (42), 175.2 (32) 2.41(s, 3H, CH3 of coumarin), 4.83 (s, 2H, OCH2), 4.98 (s, 1H, CH), 6.36 (s, 1H, CH of coumarin), 7.087.87 (m, 8H, Ar-H), 10.30 (s, 1H, NH) 2.34 (s, 3H, CH3 of coumarin), 4.78 (s, 2H, OCH2), 5.01 (s, 1H, CH), 6.42 (s, 1H, CH of coumarin), 8.248.37 (m, 7H, Ar-H), 10.32 (s, 1H, NH) 2.34 (s, 3H, CH3 of phenyl substituent), 2.41 (s, 3H, CH3 of coumarin), 3.35 (s, 2H, CH2), 4.80 (s, 2H, OCH2), 5.28 (s, 1H, CH), 6.24 (s, 1H, CH of coumarin), 6.977.75 (m, 7H, Ar-H), 10.28 (s, 1H, NH) m/z 425.3 (M+1)+ (10), 291.1 (100), 249.1(80), 177.2 (23), 149.2 (38) 2.41 (s, 3H, CH3 of coumarin), 3.41 (s, 2H, CH2), 4.78 (s, 2H, OCH2), 5.31 (s, 1H, CH), 6.25 (s, 1H, CH of coumarin), 6.997.74 (m, 8H, Ar-H), 8.02 (s, 1H, NH) 2.41 (s, 3H, CH3 of coumarin), 2.50 (s, 2H, CH2), 5.25 (s, 2H, OCH2), 6.25 (s, 1H, CH), 6.87 (s, 1H, CH of coumarin), 7.718.32 (m, 7H, Ar-H), 10.31 (s, 1H, NH) m/z 429.2 (M+1)+ (12), 355.2 (100), 291.1 (64), 249.1 (67), 177.2 (11) 2.33 (s, 3H, CH3 of phenyl substituent), 2.40 (s, 3H, CH3 of coumarin), 2.492.51 (d, 2H, CH2), 4.80 (s, 2H, OCH2), 5.30 (s, 1H, CH-N), 6.24 (s, 1H, CH of coumarin), 6.97.8 (m, 7H, Ar-H), 7.757.98 (t, 1H, CH), 8.30 (s, 1H, NH), 10.30 (s,1H, COOH) m/z 483.2 (M+) (44), 351.2 (85), 291.1 (11), 249.1 (12), 149.2 (64) 3b 3c 5a 5b 5c 6a 6b 6c 7a 3210, 1672, 1685, 1267 3175, 1654, 1692, 1270 2981, 2807, 1716, 1687, 1511, 1273 3178, 3078, 2972, 1713, 1687, 1509 3283, 3087, 2852, 1709, 1509, 1273 3308, 2923, 1713, 1686, 1508 7b 7c 8a P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. 8b 3481, 2922, 1737, 1655, 1459 3408, 2965, 1711, 1686, 1507 3158, 1719, 1660, 1509, 1054 3163, 1720, 1558, 1393, 1078 3120, 1741, 1622, 1509, 1017 2.41 (s, 3H, CH3 of coumarin), 2.502.51 (d, 2H, CH2), 4.70 (s, 2H, OCH2), 5.31 (s, 1H, CH-N), 6.24 (s, 1H, CH of coumarin), 6.978.02 (m, 10H, Ar-H, CH and NH protons), 10.32 (s,1H, COOH) 2.41 (s, 3H, CH3 of coumarin), 2.502.62 (d, 2H, CH2), 4.78 (s, 2H, OCH2), 5.31 (s, 1H, CH-N), 6.25 (s, 1H, CH of coumarin), 6.987.80 (m, 7H, Ar-H), 8.02 (t, 1H, CH), 8.33 (s, 1H, NH), 11.69 (s,1H, COOH) m/z 487.3 (M+1)+ (29), 355.2 (100), 291.1 (26), 249.1 (20), 149.2 (27) 2.4 (s, 3H, CH3 of phenyl substituent), 2.5 (s, 3H, COCH3), 3.4 (s, 3H, CH3 of coumarin), 5.3 (s, 2H, OCH2), 6.2 (s, 1H, CH of coumarin), 7.1 (s, 1H, CH), 7.37.80 (m, 7H, Ar-H) 2.4 (s, 3H, COCH3), 2.5 (s, 3H, CH3 of coumarin), 4.8 (s, 2H, OCH2), 6.2 (s, 1H, CH of coumarin), 6.87.8 (m, 9H, Ar-H and CH) 2.4 (s, 3H, COCH3), 2.5 (s, 3H, CH3 of coumarin), 5.3 (s, 2H, OCH2), 6.2 (s, 1H, CH of coumarin), 7.1 (s, 1H, CH), 7.38.1 (m, 7H, Ar-H) m/z 397.1 (M+1)+ (88), 355.1 (100), 193.3 (6), 163.2 (49), 122.2 (24) 8c 9a 9b 9c Synthesis of 1-(4-methylcoumarinyl-7-oxyacetyl)-3,5-dimethyl-4-(arylazo) pyrazoles (3a-c) A mixture of appropriate 3-(arylazo)-2,4-pentanediones (2a-c) (0.001 mol) and compound 1 (0.248 g, 0.001 mol) in glacial acetic acid (10 mL) was refluxed for 10 h. The resultant solution was cooled and allowed to stand overnight. The resultant solid was collected by filtration, purified by repeated washings with acetic acid and recrystallised from acetic acid. Synthesis of 1-(4-methylcoumarinyl-7-oxyacetyl)-3-methyl-4-(substituted phenyl) hydrazono-2-pyrazolin-5-ones (5a-c) Ethyl-2-(substituted phenyl)hydrazono-3-oxobutyrates (4a-c) (0.02 mol) were dissolved in glacial acetic acid (20 mL) and 4-methylcoumarinyl-7-oxyacetic acid hydrazide (0.496 g, 0.002 mol) dissolved in 20 mL of glacial acetic acid was added. The mixture was refluxed for 4 h, cooled and then allowed to stand overnight. The resultant solid was filtered, dried and then recrystallised from ethanol. The purity of all compounds was established by single spot on the TLC plates as described above. Synthesis of 4-methylcoumarinyl-7-oxyacetic acid [(substituted phenyl) methylene] hydrazides (6a-c) A mixture of compound 1 (2.48 g, 0.01 mol), glacial acetic acid (20 mL) and substituted benzaldehyde (0.01 mol) was refluxed for 8 h. The contents were then poured onto crushed ice. The resultant solid was filtered and recrystallised using glacial acetic acid. P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. Synthesis of 2-(substituted phenyl)-3-(4-methylcoumarinyl-7-oxyacetamido)-4-thiazolidinones (7a-c) A homogenous mixture of compounds 6a-c (0.01 mol) and thioglycollic acid (0.92 g, 0.01 mol) in 20 mL of glacial acetic acid was refluxed for 10 h. The reaction mixture was triturated with sodium bicarbonate solution (10 %). The resultant neutral solid was poured onto crushed ice. The separated product was filtered off, washed with water, dried and recrystallised from ethanol. Synthesis of 2-(substituted phenyl)-3-(4-methylcoumarinyl-7-oxyacetamido)-5-carboxymethyl-4-thiazolidinone (8a-c) A homogenous mixture of compounds 6a-c (0.01 mol) and thiomalic acid (1.52 g, 0.01 mol) in glacial acetic acid (20 mL) was refluxed for 10 h. The reaction mixture was dissolved in sodium bicarbonate solution, reprecipitated by hydrochloric acid (10 %) and recrystallised from ethanol. Synthesis of 3-acetyl-2-(substituted phenyl)-5-(4-methylcoumarinyl-7-oxymethyl)-2,3-dihydro-1,3,4-oxadiazoles (9a-c) A mixture of compounds 6a-c (0.01 mol) and acetic anhydride (5 mL) was refluxed for 2 h. The mixture was cooled, poured onto crushed ice and allowed to stand at room temperature overnight. The separated solid was washed with water, dried and recrystallised from acetone-ethanol (1:1). In vitro cytotoxic activity towards DLA cells and EAC cells The synthesised compounds 3a-c, 5a-c, 7a-c, 8a-c and 9a-c were tested for their cytotoxicity in vitro, in comparison with 5-fluorouracil as reference drug, against DLA cells and EAC cells. Dalton's lymphoma ascites (DLA) and Ehrlich ascite carcinoma (EAC) cells were procured from Adayar Cancer Institute, Chennai, India. DLA and EAC cells (1 ´ 106) were incubated with synthesised compounds at concentrations of 50 mg mL1 and 100 mg mL1, respectively, in 1 mL phosphate buffered saline (incorporated with 10 mL DMSO) at 37 °C for 3 h. Viable cells were counted in a haemocytometer using the trypanblue exclusion method (15). Experiments were carried out in triplicate. Results are given in Table III. Antioxidant activity Free radical scavenging activity of the test compounds 3a-c, 5a-c, 7a-c, 8a-c and 9a-c was studied by the diphenylpicryl hydrazyl (DPPH) assay method (36). Methanolic solution of the synthesised compounds (1.5 mL, 0.2 mmol L1) was added to 1.5 mL (0.2 mmol L1) solution of DPPH radical in methanol (final concentration of DPPH and synthesized compounds was 0.1 mmol L1). The mixture was shaken vigorously allowed to stand for 30 min, absorbance at 517 nm was determined and the percentage of scavenging activity was calculated. P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. Table III. Cytotoxic activity of synthesised compounds Cytotoxicity (%)a Compd. 3a 3b 3c 5a 5b 5c 7a 7b 7c 8a 8b 8c 9a 9b 9c Negative control 5-Fluorouracil a b c DLA cellsb 83.0 48.9 89.1 59.1 90.8 34.9 68.3 62.8 48.4 38.1 42 57.9 49.6 36.5 63.9 98.8 EAC cellsc 11.3 77.9 29.8 12.1 97.5 90.2 14.9 20 9.1 66.8 97.3 43.2 70.1 50.6 46.1 99.5 Results are the mean of three experiments. Compounds were tested at 100 mg mL1 for cytotoxicity against DLA cells. Compounds were tested at 50 mg mL1 for cytotoxicity against EAC cells. Ascorbic acid was used as the reference compound. All tests and analyses were done in three replicates and the results were averaged. Results are presented in Table IV. RESULTS AND DISCUSSION Chemistry Formation of compounds 3a-c and 5a-c was confirmed by the presence of characteristic ring C=N stretching at n between 16061623 cm1 in the IR spectrum. Compound 3a, which was representative of pyrazoles, showed m/z 431.6 (M+1)+ and compound 5a, which represented pyrazolones, showed m/z 431.6 (M+). Similarly, elemental analysis data together with 1H NMR data supported the proposed structure for compounds 3a-c and 5a-c given in Tables I and II. Formation of 4-thiazolidinones (7a-c) and 5-carboxymethyl-4-thiazolidinones (8a-c) was confirmed by IR spectra, which showed ring C=O stretching characteristic of thiazolidinone ring in the range of n 17091737 cm1. 1H NMR for 7a-c showed CH2 protons of the thiazolidinone ring between d 3.353.41 ppm as the singlet signal and d 5.285.31 P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. Table IV. Antioxidant activity of synthesised compounds Compd. No. 3a 3b 3c 5a 5b 5c 7a 7b 7c 8a 8b 8c 9a 9b 9c Negative control Ascorbic acid Scavenging activity (%)a 53 83 31 62 29 36 95 23 60 59 39 96 a Results are mean of three different experiments. Denotes very low antioxidant activity (scavenging activity < 10 %). ppm for CH proton of the thiazolidinone ring as a singlet signal. Compounds 7a and 7c representative of thiazolidine-4-ones showed (M+1)+ peaks at m/z of 425.3 and 429.2, respectively, in mass spectra. 1H NMR for 5-carboxymethyl-4-thiazolidinones (8a-c) showed a singlet in the spectra in the range d 5.305.31 ppm, indicating the presence of CH-N of thiazolidinones. M+ peak and (M+1)+ peak at 483.2 and 487.3 were obtained in the mass spectra of representative compounds 8a and 8c, respectively. IR spectra of compounds 9a-c had different characteristics since they showed no N-H stretching bands, but C-O stretching in the 10541078 cm1 region, which could be attributed to C-O stretching of oxadiazole nucleus. 1H NMR spectra of 9a,b,c showed a singlet in the spectra in the range d 7.10, 7.04, 7.09 ppm indicating CH resonance of the oxadiazoline ring in accord with the literature (10). The mass spectrum of 9c showed the molecular ion peak at m/z 397.1 (M+1)+. Cytotoxicity studies 5-Fluorouracil, which was used as standard cytotoxic agent, exhibited cytotoxicity of 98.8 % against DLA cells at 100 mg mL1 and 99.5 % against EAC cells at a 50 mg mL1 concentration. The results of short term in vitro cytotoxicity studies against DLA cells showed that compounds 3a, 3c, 5a, 5b, 7a, 7b, 8c and 9c exhibited more than 50 % cytotoxicity at a 100 mg mL1 concentration. Compound 5b showed the highest cytotoxicity P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. of 90.8 %. The results of short term in vitro cytotoxicity studies against EAC cells showed that compounds 3b, 5b, 5c, 8a, 8b, 9a and 9b exhibited more than 50 % cytotoxicity at a concentration of 50 mg mL1. Compounds 5b, 5c and 8b showed the highest percentage of cytotoxicity of 97.5, 90.2 and 97.3 %, respectively. Antioxidant activity Concentration of the test compounds and ascorbic acid were of 0.1 mmol L1. Among the pyrazoles, compounds 3a and 3b with p-methyl phenyl substituent and unsubstituted phenyl substituent, respectively, showed more than 50 % antioxidant activity. It was interesting to note that thiazolidine-4-ones showed negligible antioxidant activity of less than 10 % free radical scavenging capacity. Among 5-carboxymethyl-4-thiazolidinones, compound 8b with unsubstituted phenyl substituent showed more than 95 % antioxidant activity which was comparable to that of the standard ascorbic acid (96 %). 3-Acetyloxadiazoles 9a and 9b showed more than 50 % antioxidant activity. Antioxidant activity of pyrazoles and 5-carboxymethyl-4-thiazolidinones followed the following order: unsubstituted phenyl derivative > p-methyl phenyl derivative > p-fluorophenyl derivative. Pyrazolin-5-ones and 3-acetyloxadiazole showed antioxidant activity in the descending order: p-methyl phenyl derivative > unsubstituted phenyl derivative > p-fluorophenyl derivative. Irrespective of the type of heterocyclic nucleus, it was observed that p-fluorophenyl derivatives exhibited the lowest antioxidant activity among compounds in the respective series. Structure activity relation (i) Coumarin derivatives with different heterocyclic nuclei having unsubstituted phenyl group exhibited cytotoxicity against DLA cells in the descending order of potency: pyrazolin-5-one derivative > thiazolidin-4-one derivative > pyrazole derivative > 5-carboxymethyl-4-thiazolidinone derivative > 1,3,4-oxadiazole derivative, as it is evident from the percentage cytotoxicity of 5b, 7b, 3b, 8b and 9b, respectively (Table III). The presence of p-fluorophenyl substituent increased the cytotoxicity of 5-carboxymethyl-4-thiazolidinone derivative, 1,3,4-oxadiazole derivative and azopyrazoles against DLA cells compared to the compounds having unsubstituted phenyl ring or p-methylphenyl substituent in the respective series. The presence of p-fluorophenyl substituent decreased the cytotoxicity of hydrazonopyrazolin-5-ones and thiazolidin-4-one derivatives against DLA cells compared to those having unsubstituted phenyl ring or p-methyl phenyl substituent in the respective series. (ii) Coumarin derivatives with different heterocyclic nuclei having unsubstituted phenyl group exhibited cytotoxicity against EAC cells in the descending order of potency: pyrazolin-5-one derivative > 5-carboxymethyl-4-thiazolidinone derivative > azo pyrazole derivative > 1,3,4-oxadiazole derivative > thiazolidin-4-one derivative, as seen from the cytotoxicity of 5b, 8b, 3b, 9b and 7b, respectively (Table III). The presence of p-fluorophenyl substituent increased the cytotoxicity of azopyrazoles and hydrazonopyrazolin-5-ones against EAC cells compared to the compounds having p-methylphenyl substituent in the respective series. The presence of p-fluorophenyl substituent decreased the cytotoxicity of thiazolidin-4-one derivative, 5-carboxymethyl-4-thiazolidinone derivative and P. Manojkumar et al.: Synthesis of coumarin heterocyclic derivatives with antioxidant activity and in vitro cytotoxic activity against tumour cells, Acta Pharm. 59 (2009) 159170. 1,3,4-oxadiazole derivative against EAC cells compared to those having p-methylphenyl substituent in the respective series. (iii) Coumarin derivatives with different heterocyclic nuclei having unsubstituted phenyl group exhibited antioxidant activity in the descending: 5-carboxymethyl-4-thiazolidinone derivative > pyrazole derivative > 1,3,4-oxadiazole derivative > pyrazolin-5-one derivative > thiazolidin-4-one derivative (Table IV). Substitution of unsubstituted phenyl group at the fourth position of 5-carboxymethyl-4-thiazolidinone derivative (8b) and unsubstituted phenylazo substituent at the third position of pyrazolone derivative (3b) imparted higher antioxidant activity than substitution with p-methylphenyl or p-fluorophenyl group. Substitution of p-fluoro substituent on phenyl ring produced compounds with lower antioxidant activity than the remaining compounds in the respective series, as seen for compounds 3c, 5c, 7c, 8c and 9c. CONCLUSIONS Results of antioxidant activity show that compound 8b (0.1 mmol L1) (phenyl derivative of 5-carboxymethyl-4-thiazolidinone) exhibited the highest free radical scavenging activity (95 %), which was comparable to that of standard ascorbic acid (0.1 mmol L1) (96 %). Cytotoxicity studies against tumour cells showed compound 5b (phenyl derivative of pyrazolin-5-one) to be a good cytotoxic agent against DLA cells at a 100 mg mL1 concentration and compounds 5b and 8b (phenyl derivative of 5-carboxymethyl-4-thiazolidinones) to be potent cytotoxic agents against EAC cells at a 50 mg mL1 concentration. Further studies aimed at development of an effective antioxidant can insolve compound 8b, and compounds 5b and 8b can be subjected to further in vivo anticancer studies. Since antioxidants have a valuable role in the prophylaxis of cancer, it could be concluded that compound 8b can be selected as the lead moiety in the analogue designing process of developing an ideal antineoplastic agent. Acknowledgements. The authors are thankful to Sevaratna Dr. R. Venkatesalu Naidu, Managing Trustee, SNR Sons Charitable Trust, for providing facilities to carry out this research work and Dr. Ramadasankuttan, Research director, Amala Cancer Research Centre, Thrissur, India, for help in carrying out cytotoxicity screening studies. The authors are grateful to Heads, SASTRA University, Suven Life Sciences Limited and Quest Research and Training Institute, India, for providing spectral and analytical data.
Journal
Acta Pharmaceutica – de Gruyter
Published: Jun 1, 2009