2.1. General
All chemicals and solvents in this project were purchased from Merck AG and Aldrich Chemical. Thomas-Hoover capillary apparatus was used to determine melting points. Infrared spectra were obtained using a Perkin Elmer Model 1420 spectrometer, and 1H-NMR spectra were acquired by a Bruker FT-500 MHz instrument (Brucker Biosciences, USA) with TMS as the internal standard. Chloroform-D and DMSO-D6 were used as solvents. Coupling constant (J) values were measured in hertz (Hz), and spin multiples are presented as s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), and br (broad). A 6410Agilent LCMS triple quadrupole mass spectrometer (LCMS) with an electrospray ionization (ESI) interface was used to perform mass spectral measurements, and there was a Costech 4010 elemental analyzer to perform the C, H, and N elemental analyses. The microanalysis values of C and H were within ± 0.4% of the theoretical values.
2.2. Synthesis of Ethyl 4-Hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carboxylate (10)
Isatoic anhydride (9) (10 g, 61.5 mmol) and diethyl malonate (49 mL, 300 mmol) were reacted in dry DMF (100 mL) and warmed at 85°C for 5 hours. TLC (thin-layer chromatography) was used to monitor the reaction completion. When the reaction was completed, the mixture was cooled. The reaction mixture was added to a mixture of ice and water; the obtained precipitate was filtered and washed with water: Yield: 40%, pale brown powder, mp: 134°C; IR (KBr): 1750, 1730 (C=O), 2700-3200 (OH) cm-1; LC-MS (ESI): m/z 234 [M+H]+.
2.3. Synthesis of 4-Hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (11)
Compound 10 (20 g, 55.7 mmol) was suspended in ethanol (30 mL), to which hydrazine hydrate (10 mL, 33 mmol) was added and stirred under reflux for 2 hours. When the reaction was completed, the white suspension was filtered. The precipitate was washed with ethanol and dried under a vacuum: Yield: 90%, white powder, mp: 152°C; IR (KBr): 1750, 1740 (C=O), 2800 (NH) cm-1; LC-MS (ESI): m/z 220 [M+H]+.
2.4. General Procedure for the Synthesis of Compound 12a-o
A solution of Compound 11 (1 mmol) in absolute ethanol (5 mL) was prepared, and one drop of 98% H2SO4 was then added to the solution. After that, the reaction continued by adding benzaldehyde derivatives (1.1 mmol) to the mixture and refluxed for 2 hours. When the reaction was completed (monitored with TLC), the reaction temperature was lowered in an ice bath, and the obtained precipitates were filtered. After washing with cold ethanol, the precipitate was crystallized in absolute ethanol (average yield: 90%).
2.5. Benzylidene- 4-hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12a)
mp: 225°C; IR (KBr): 1400 - 1600 (aromatic), 1645 (C=O),1659 (C=O), 2700 - 3200 (OH) cm-1; LCMS (ESI): m/z 306 [M-H]-; 1H-NMR (400 MHz, DMSO-d6): δ 7.32 (t, J = 8 Hz, 1H, quinoline H7), 7.39 (d, J = 8 Hz, 1H, quinoline H8), 7.47 - 7.49 ( m, 3H, benzylidene H3 & H4 & H5), 7.72 (t, J = 8 Hz, 1H, quinoline H6), 7.78 (m, 2H, benzylidene H2 & H6), 8.00 (d, J = 8 Hz, 1H, quinoline H5), 8.49 (s, 1H, = CH), 12.08 (s, 1H, NH), 13.33 (s, 1H, NH), 16.67 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 96.43, 114.57, 116.45, 123.12, 124.47, 128.03, 129.34, 131.14, 134.22, 137.73, 139.32, 151.33, 162.84, 167.95, 173.25; Anal. Calcd. for C17H13N3O3: C, 66.44; H, 4.26; N, 13.67; Found: C, 66.48; H, 4.31; N, 13.60.
2.6. 2-Chlorobenzylidene- 4-hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12b)
mp: 187°C; IR (KBr): 1400 - 1600 (aromatic), 1644 (C=O), 1669 (C=O), 2500 - 3300 (OH) cm-1; LCMS (ESI): m/z 340 [M-1]-; 1H-NMR (400 MHz, DMSO-d6): δ 7.33 (m, 1H, quinoline H7), 7.41 - 7.58 (m, 4H, quinoline H8 & 2-chlorobenzylidene H3 & H4 & H5), 7.74 (t, J = 8 Hz, 1H, quinoline H6), 8.04 (m, 2H, quinoline H5 & 2-chlorobenzylidene H6), 8.70 (brs, 1H, = CH), 12.10 (s, 1H, NH), 13.42 (s, 1H, NH), 16.52 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 94.60, 116.60, 118.09, 123.54, 124.65, 129.13, 129.94, 131.68, 134.50, 139.30, 141.09, 142.17, 142.38, 157.31, 163.22, 167.94, 172.83; Anal. Calcd. for C17H12ClN3O3: C, 59.75; H, 3.54; N, 12.30; Found: C, 59.71; H, 3.59; N, 12.33.
2.7. 3-Chlorobenzylidene- 4-hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12c)
mp: 198°C; IR (KBr): 1400 - 1600 (aromatic), 1658 (C=O),1683 (C=O), 2500 - 3300 (OH) cm-1; LCMS (ESI): m/z 340 [M-H]-; 1H-NMR (400 MHz, DMSO-d6): δ 7.33 (t, J = 8Hz, 1H, quinoline H7), 7.40 (d, J = 8Hz, 1H, quinoline H8), 7.49 - 7.53 (m, 2H, quinoline H6 & 3-clorobenzylidene H5), 7.71 - 7.76 (m, 2H, 3-chlorobenzylidene H4 & H6), 7.81 (s, 1H, 3-chlorobenzylidene H2), 8.01 (d, J = 8 Hz, 1H, quinoline H5), 8.49 (s, 1H, = CH), 12.11 (s, 1H, NH), 13.39 (s, 1H, NH), 16.54 (s, 1H, OH) ); 13C-NMR (100 MHz, DMSO-d6): δ 96.46, 114.52, 116.48, 123.19, 124.51, 126.58, 127.32, 130.76, 131.31, 134.10, 134.85, 136.44, 139.36, 149.78, 162.84, 168.12, 173.29; Anal. Calcd. for C17H12ClN3O3: C, 59.75; H, 3.54; N, 12.30; Found: C, 59.72; H, 3.57; N, 12.27.
2.8. 4-Chlorobenzylidene- 4-hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12d)
mp: 241°C; IR (KBr): 1400 - 1600 (aromatic), 1658 (C=O), 1683 (C=O), 2500 - 3300 (OH) cm-1; LCMS (ESI): m/z 340 [M-H]-; 1H-NMR (400 MHz, DMSO-d6): δ 7.33 (t, J = 8 Hz, 1H, quinoline H7), 7.39 (d, J = 8 Hz, 1H, quinoline H8), 7.54 (d, J = 8.4Hz, 2H, 4-chlorobenzylidene H3 & H5), 7.73 (t, J = 8 Hz, 1H, quinoline H6), 7.79 (d, J = 8.4Hz, 2H, 4-chlorobenzylidene H2 & H6), 8.00 (d, J = 8 Hz, 1H, quinoline H5), 8.49 (s, 1H, = CH), 12.10 (s, 1H, NH), 13.36 (s, 1H, NH), 16.60 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 96.44, 114.55, 116.47, 123.17, 124.49, 129.49, 129.63, 133.18, 134.82, 135.62, 139.35, 150.14, 162.84, 168.03, 173.27; Anal. Calcd. for C17H12ClN3O3: C, 59.75; H, 3.54; N, 12.30; Found: C, 59.79; H, 3.60; N, 12.26.
2.9. 2-Fluorobenzylidene- 4-hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12e)
mp: 195°C; IR (KBr): 1400 - 1600 (aromatic), 1647 (C=O), 1668 (C=O), 2660 - 3200 (OH) cm-1; LCMS (ESI): m/z 326 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 7.31 - 7.36 (m, 3H, quinoline H7 & 2-fluorobenzylidene H3 & H5), 7.40 (d, J = 8 Hz, 1H, quinoline H8), 7.51 - 7.57 (br s, 1H, 2-fluorobenzylidene H6), 7.73 (t, J = 8.4 Hz, 1H, 2-fluorobenzylidene H4), 7.95 (t, J = 8 Hz, 1H, quinoline H6), 8.01 (d, J = 8 Hz, 1H, quinoline H5), 8.60 (s, 1H, = CH), 12.09 (s, 1H, NH), 13.38 (s, 1H, NH), 16.56 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 94.58, 116.90, 118.13, 123.64, 124.55, 129.23, 130.04, 131.78, 134.60, 139.35, 141.04, 142.07, 142.37, 151.31, 158.09, 163.12, 167.84, 172.93; Anal. Calcd. for C17H12FN3O3: C, 62.77; H, 3.72; N, 12.92; Found: C, 62.72; H, 3.68; N, 12.99.
2.10. 3-Fluorobenzylidene- 4-hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12f)
mp: 237°C; IR (KBr): 1400 - 1600 (aromatic), 1648 (C=O), 1671 (C=O), 2800 - 3300 (OH) cm-1; LCMS (ESI): m/z 326 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 7.30 - 7.34 (m, 2H, quinoline H7 & 3-fluorobenzylidene H6), 7.39 (d, J = 8.4 Hz, 1H, quinoline H8), 7.51 - 7.57 (m, 2H, 3-fluorobenzylidene H2 & H5), 7.62 (d, J = 7.6 Hz, 1H, 3-fluorobenzylidene H4), 7.73 (t, J = 8.4 Hz, 1H, quinoline H6), 8.00 (d, J = 8.4 Hz, 1H, quinoline H5), 8.60 (s, 1H, = CH), 12.09 (s, 1H, NH), 13.38 (s, 1H, NH), 16.56 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 96.46, 113.88, 114.10, 114.52, 116.47, 117.79, 118.01, 123.18, 124.32, 124.50, 131.45, 131.53, 134.84, 136.70, 136.78, 139.35, 150.02, 161.57, 162.85, 163.99, 168.09, 173.28; Anal. Calcd. for C17H12FN3O3: C, 62.77; H, 3.72; N, 12.92; Found: C, 62.83; H, 3.64; N, 12.88.
2.11. 4-Fluorobenzylidene- 4-hydroxy- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12g)
mp: 212°C; IR (KBr): 1400 - 1600 (aromatic), 1649 (C=O),1667 (C=O), 2200 - 3400 (OH) cm-1; LCMS (ESI): m/z 326 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 7.30 - 7.35 (m, 3H, quinoline H7 & 4-fluorobenzylidene H2 & H6), 7.39 (d, J = 8.4 Hz, 1H, quinoline H8), 7.72 (t, J = 8.4 Hz, 1H, quinoline H6), 7.83 - 7.86 (m, 2H, 4-fluorobenzylidene H3 & H5), 8.00 (d, J = 8.4 Hz, 1H, quinoline H5), 8.50 (s, 1H, = CH), 12.09 (s, 1H, NH), 13.32 (s, 1H, NH), 16.65 (s, 1H, OH) ); 13C-NMR (100 MHz, DMSO-d6) : δ 96.41, 114.56, 116.37, 116.46, 116.59, 123.14, 124.47, 130.22, 130.31, 130.86, 134.75, 139.32, 150.25, 162.68, 162.84, 165.15, 167.94, 173.24; Anal. Calcd. for C17H12FN3O3: C, 62.77; H, 3.72; N, 12.92; Found: C, 62.71; H, 3.78; N, 12.96.
2.12. 4-Hydroxy-N'- (2-methylbenzylidene)- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12h)
mp: 203°C; IR (KBr): 1400 - 1600 (aromatic), 1632 (C=O),1658 (C=O), 2200 - 3200 (OH) cm-1; LCMS (ESI): m/z 322 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 2.50 (s, 3H, CH3), 7.27 - 7.37 (m, 4H, quinoline H7 & 2-methylbenzylidene H3 & H4 & H5), 7.40 (d, J = 8.4 Hz, 1H, 2- methylbenzylidene H6), 7.73 (d, J = 7.2 Hz, 1H, quinoline H8), 7.85 (t, J = 7.2 Hz, 1H, quinoline H6), 8.01 (d, J = 7.2 Hz, 1H, quinoline H5), 8.67 (s, 1H, = CH), 12.04 (s, 1H, NH), 13.26 (s, 1H, NH), 16.77 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 22.54, 94.65, 116.60, 118.09, 123.54, 124.60, 129.13, 129.83, 131.94, 134.38, 139.30, 141.09, 142.17, 142.50, 154.31, 163.12, 167.68, 172.94; Anal. Calcd. for C18H15N3O3: C, 67.28; H, 4.71; N, 13.08; Found: C, 67.22; H, 4.76; N, 13.01.
2.13. 4-Hydroxy-N'- (4-methylbenzylidene)- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12i)
mp: 181°C; IR (KBr): 1400 - 1600 (aromatic), 1662 (C=O), 2500 - 3300 (OH) cm-1; LCMS (ESI): m/z 322 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 2.35 (s, 3H, CH3),7.28 (d, J = 8.4 Hz, 2H, 4-methylbenzylidene H3 & H5), 7.32 (t, J = 7.6 Hz, 1H, quinoline H7), 7.39 (d, J = 7.6 Hz, 1H, quinoline H8), 7.67 (d, J = 8.4 Hz, 2H, 4-methylbenzylidene H2 & H6), 7.72 (t, J = 7.6 Hz, 1H, quinoline H6), 8.00 (d, J = 7.6 Hz, 1H, quinoline H5), 8.44 (s, 1H, = CH), 12.07 (s, 1H, NH), 13.27 (s, 1H, NH), 16.73 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 21.58, 96.41, 114.60, 116.45, 123.12, 124.47, 128.03, 129.95, 131.51, 134.72, 139.31, 141.11, 151.36, 162.84, 167.83, 173.23. Anal. Calcd. for C18H15N3O3: C, 67.28; H, 4.71; N, 13.08; Found: C, 67.33; H, 4.65; N, 13.15.
2.14. 4-Hydroxy-N'- (2-methoxybenzylidene)- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12j)
mp: 122°C; IR (KBr): 1400 - 1600 (aromatic), 1599 (C=O),1660 (C=O), 2700 - 3200 (OH) cm-1; LCMS (ESI): m/z 338 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 3.89 (s, 3H, OCH3), 7.05 (t, J = 7.6 Hz, 1H, 2-methoxybenzylidene H5), 7.13 (t, J = 8 Hz, 1H, quinoline H7), 7.32 (d, J = 8 Hz, 1H, quinoline H8), 7.40 (d, J = 7.6 Hz, 1H, 2-methoxybenzylidene H6), 7.47 (t, J = 8 Hz, 1H, quinoline H6), 7.73 (t, J = 7.6 Hz, 1H, 2-methoxybenzylidene H4), 7.87 (d, J = 7.6 Hz, 1H, 2-methoxybenzylidene H3), 8.00 (d, J = 8 Hz, 1H, quinoline H5), 8.58 (s, 1H, = CH), 12.08 (s, 1H, NH), 13.33 (s, 1H, NH), 16.67 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 56.24, 96.43, 111.44, 114.58, 116.45, 121.27, 121.94, 123.12, 124.46, 126.39, 132.84, 134.72, 139.30, 146.14, 158.57, 162.82, 167.79, 173.21; Anal. Calcd. for C18H15N3O4: C, 64.09; H, 4.48; N, 12.46; Found: C, 64.03; H, 4.44; N, 12.50.
2.15. 4-Hydroxy-N'- (3-methoxybenzylidene)- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12k)
mp: 190°C; IR (KBr): 1400 - 1600 (aromatic), 1641 (C=O), 1664 (C=O), 2600 - 3200 (OH) cm-1; LCMS (ESI): m/z 338 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 3.81 (s, 3H, OCH3), 7.02 (t, J = 8 Hz, 1H, quinoline H7), 7.29 - 7.41 (m, 5H, quinoline H8 & 3-methoxybenzylidene H2 & H4 & H5 & H6), 7.71 (t, J = 8 Hz, 1H, quinoline H6), 7.99 (d, J = 8 Hz, 1H, quinoline H5), 8.44 (s, 1H, = CH), 12.08 (s, 1H, NH), 13.33 (s, 1H, NH), 16.63 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 55.64, 96.44, 112.24, 114.56, 116.45, 117.27, 120.86, 123.14, 124.47, 130.46, 134.75, 135.59, 139.32, 151.22, 159.95, 162.85, 167.93, 173.23; Anal. Calcd. for C18H15N3O4: C, 64.09; H, 4.48; N, 12.46; Found: C, 64.04; H, 4.53; N, 12.51.
2.16. 4-Hydroxy-N'- (4-methoxybenzylidene)- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12l)
mp: 240°C; IR (KBr): 1400 - 1600 (aromatic), 1650 (C=O),1663 (C=O), 2500 - 3200 (OH) cm-1; LCMS (ESI): m/z 338 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 3.82 (s, 3H, OCH3), 7.07 (d, J = 8.4 Hz, 2H, 4-methoxybenzylidene H3 & H5), 7.32 (t, J = 8 Hz, 1H, quinoline H7), 7.39 (d, J = 8 Hz, 1H, quinoline H8), 7.70 - 7.75 (m, 3H, quinoline H6 & 4-methoxybenzylidene H2 & H6), 8.00 (d, J = 8Hz, 1H, quinoline H5), 8.41 (s, 1H, = CH), 12.06 (s, 1H, NH), 13.24 (s, 1H, NH), 16.80 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 55.82, 96.39, 114.63, 114.86, 116.44, 123.10, 124.45, 126.72, 129.75, 134.67, 139.27, 151.17, 161.78, 162.85, 167.64, 172.20; Anal. Calcd. for C18H15N3O4: C, 64.09; H, 4.48; N, 12.46; Found: C, 64.13; H, 4.44; N, 12.42.
2.17. 4-Hydroxy-N'- (2-hydroxybenzylidene)- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12m)
mp: 228°C; IR (KBr): 1400 - 1600 (aromatic), 1643 (C=O), 1663 (C=O), 2300 - 3300 (OH) cm-1; LCMS (ESI): m/z 322 [M-H]-; 1H-NMR (400 MHz, DMSO-d6): δ 6.92 (m, 2H, quinoline H7 & 2-hydroxybenzylidene H3), 7.29 - 7.36 (m, 2H, quinoline H8 & 2-hydroxybenzylidene H5), 7.39 (d, J = 8 Hz, 1H, quinoline H6), 7.58 (d, J = 7.6 Hz, 1H, 2-hydroxybenzylidene H6),7.72 (t, J = 7.6 Hz, 1H, 2-hydroxybenzylidene H4), 7.99 (d, J = 8Hz, 1H, quinoline H5), 8.68 (s, 1H, = CH), 11.00 (s, 1H, OH), 12.11 (s, 1H, NH), 13.36 (s, 1H, NH), 16.36 (s, 1H, OH). ); 13C-NMR (100 MHz, DMSO-d6): δ 96.39, 114.47, 116.47, 116.93, 118.86, 119.95, 123.13, 124.47, 130.10, 132.56, 134.78, 139.36, 151.25, 158.07, 162.77, 167.51, 173.04; Anal. Calcd. for C17H13N3O4: C, 63.16; H, 4.05; N, 13.00; Found: C, 63.12; H, 4.12; N, 12.89.
2.18. 4-Hydroxy-N'- (4-hydroxybenzylidene)- 2-oxo- 1,2-dihydroquinoline- 3-carbohydrazide (12n)
mp: 220°C; IR (KBr): 1400 - 1600 (aromatic), 1636 (C=O),1660 (C=O), 2600 - 3300 (OH) cm-1; LCMS (ESI): m/z 322 [M-H]-; 1H-NMR (400 MHz, DMSO-d6): δ 6.85 (d, J = 7.6 Hz, 2H, 4-hydroxybenzylidene H3 & H5), 7.31 (t, J = 8 Hz, 1H, quinolone H7), 7.39 (d, J = 8 Hz, 1H, quinolone H8), 7.63 (d, J = 7.6 Hz, 2H, 4-hydroxybenzylidene H2 & H6), 7.71 (t, J = 8 Hz, 1H, quinoline H6), 7.99 (d, J = 8 Hz, 1H, quinoline H5), 8.44 (s, 1H, = CH), 10.07 (s, 1H, OH), 12.04 (s, 1H, NH), 13.19 (s, 1H, NH), 16.86 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 96.35, 114.64, 116.20, 116.40, 122.99, 124.38, 125.14, 129.94, 134.52, 139.22, 151.39, 160.44, 162.82, 167.50, 173.14; Anal. Calcd. for C17H13N3O4: C, 63.16; H, 4.05; N, 13.00; Found: C, 63.10; H, 4.11; N, 13.04.
2.19. 4-Hydroxy-N'- (4-(methylthio) benzylidene)- 2-oxo- 1,2-dihydroquinoline- 3 -carbohydrazide (12o)
mp: 231°C; IR (KBr): 1400 - 1600 (aromatic), 1611 (C=O), 1671 (C=O), 2500 - 3200 (OH) cm-1; LCMS (ESI): m/z 354 [M+H]+; 1H-NMR (400 MHz, DMSO-d6): δ 2.52 (s, 3H, SCH3), 7.31 - 7.36 (m, 3H, quinolone H7 & 4-methylthiobenzylidene H3 & H5), 7.39 (d, J = 8Hz, 1H, quinolone H8), 7.71 (m, 3H, quinolone H6 & 4-methylthiobenzylidene H2 & H6), 8.00 (d, J = 8 Hz, 1H, quinolone H5), 8.44 (s, 1H, = CH), 12.08 (s, 1H, NH), 13.29 (s, 1H, NH), 16.72 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d6): δ 14.61, 96.43, 114.60, 116.46, 123.14, 124.48, 125.99, 128.42, 130.52, 134.74, 139.31, 142.38, 150.98, 162.84, 167.79, 173.23; Anal. Calcd. for C18H15N3O3S: C, 61.18; H, 4.28; N, 11.89; Found: C, 61.13; H, 4.31; N, 11.85.
2.20. Antibacterial Activity
The antibacterial activity of the compounds was evaluated by the broth microdilution method (
21). The following strains were used in this study:
Staphylococcus aureus PTCC 6538,
Micrococcus luteus PTCC 9341
Bacillus cereus PTCC 6633,
Escherichia coli PTCC 8739,
Salmonella Typhi PTCC 14028, and
Pseudomonas aeruginosa PTCC 9027. All strains were cultured in Soybean Casein Digest Agar (SCDA) and, after 24 hours of incubation, were diluted by 0.5 McFarland turbidity standards.
Different concentrations of the synthesized compounds (10 µL of each) were poured into the 96 well plates, to which80 µL of Muller Hinton Broth (MHB) medium and 10 µL of microbial suspensions were added. The final concentration of the microbial suspensions in each well was 1.5 × 107 cfu/mL. The plates were sealed to lower the solvent evaporation and then incubated at 35°C for 24 h. An ELISA reader spectrophotometer (TECAN-SP) was used to read the optical density of the wells at 580 nm. The inhibitory concentration (IC) in each well was measured by the following equation:
In this equation, ODa, ODb, and ODc determine the optical density of the solutions containing microorganisms and test compounds, only test compounds, and only microorganisms, respectively. Moreover, IC50 is defined as the lowest concentration of the test compound, at which the bacterial growth was disrupted. The standard antibiotics were ciprofloxacin and nalidixic acid. Each assay was performed as duplicates.
2.21. Molecular Docking Study
Autodock Vina software was used to perform a molecular modeling study (
22). In this study, 3OYA was used to analyze the binding mode of the compounds in the IN active site. Autodock tools 1.5.6 from the MGL Tools package were utilized to prepare the protein and ligands’ structures (
23). First, the co-crystallized raltegravir and water molecules were removed from the protein structure. Then Kollman charges were calculated, nonpolar hydrogens were removed, and AutoDock4 atom type was assigned to the protein structure. HyperChem 8.0 was used to create and optimize the ligand molecule (
24). The Grid box with 20 × 20 × 20 dimensions was defined around the crystallographic ligand, raltegravir, and regarded as the active site. Autodock Vina was used to dock the molecule in the active site and produce the bioactive conformations.