EHOOPrAHH^ECKAa XHMH3, 2015, moM 41, № 1, c. 102-111
ANTI-INFLAMMATORY ACTIVITIES OF SOME NEWLY SYNTHESIZED PYRIDINYL- AND INDAZOLYL BENZAMIDE DERIVATIVES
© 2015 Azza A. Hussain1, *, Mohamed M. Abdulla2, Abd El-Galil E. Amr3, 4, Mohamed A. Al-Omar3, Ahmed F. A. Shalaby1
1 Chemistry Department, Faculty of Science, Cairo University, Egypt 2Research Unit, Saco Pharm. Co., 6th October City 11632, Egypt 3Pharmaceutical Chemistry Department, Drug Exploration & Development Chair (DEDC), College of Pharmacy,
King Saud University, Riyadh 11451, Saudi Arabia 4Applied Organic Chemistry Department, National Research Center, Dokki, Cairo, Egypt Received 27.02.2014; in final form 29.04.2014
A series of substituted (pyridin-4-yl)phenyl-2-methoxybenzamide and their derivatives were prepared and screened for their anti-inflammatory activities. Initially the acute toxicity of the compounds was assayed via the determination of their LD50. Some of the newly synthesized compounds exhibited better pharmacological and biological responses than the reference controls with low concentrations. The structures of newly synthesized compounds were confirmed by chemical, elemental and spectroscopic evidences.
Keywords: 5-chloroanisic acid, aldehydes, N-substituted benzamides, anti-inflammatory activities
In our previous work, some of substituted heterocyclic benzamide derivatives were studied as anti-an-drogenic , and antimicrobial agents . The androgenic, anabolic, and anti-inflammatory activities of many heterocyclic steroidal derivatives have been reported . On the other hand, cyanopyridone and cy-anopyridine derivatives have promising antimicrobial properties , as well as anticancer activities . Recently, some new heterocyclic compounds containing pyridine moiety have been reported as anticancer and anti-inflammatory agents [6, 7]. Synthesis of the heterocyclic ring system and its derivatives occupy an important place in the realm of synthetic organic chemistry, due to possible therapeutic and pharmacological properties of such compounds [8—10]. They have emerged as integral backbones of over 7000 existing drugs [11, 12]. The pyridine ring is also an integral part of anticancer and anti-inammatory agents [13, 14]. In addition, pyridines are known to possess a range of biological activities such as analgesic, antifungal, anti-malarial, antibacterial, anti-HIV, phytotoxic, anti-tumor and antiviral properties [15—21]. In view of these observations and in continuation of our previous work in pyridine chemistry, we synthesized some new het-erocyclic compounds containing pyridine, thiopyri-
* Corresponding author (e-mail: email@example.com).
done, pyridine rings and tested their anti-inflammatory activities.
RESULTS AND DISCUSSION
The continuation of our previous work, a series of substituted pyridine and cyclohexanone derivatives (III)-(VIII) were synthesized by using N-[4-(substi-tuted acryloyl)phenyl] -5-chloro-2-methoxybenza-mide derivatives (IIa—f) as starting materials, which were synthesized according to our reported methods [22-24] (Scheme 1).
Cyclocondensation of (IIc, e, f) with malononitril in sodium methoxide or sodium ethoxide solution afforded the corresponding cyanomethoxy- and ethoxy pyridine derivatives (IIIa—c) and (IVa—c), respectively. Rebenson Annulations' Reaction of derivatives (IIa—f) with ethyl acetoacetate in the presence of sodium ethoxide gave the corresponding ethyl 4-(4-(5-chloro-2-methoxybenzamido)phenyl)-2-oxo-6-(sub-stituted phenyl)cyclohex-3-enecarboxylate derivatives (Va—f), respectively. The latter compounds (Va, e) were cyclized by action ofhydrazine derivatives to give the corresponding derivatives (VIa—e), respectively (Scheme 2).
Additionally, reaction of chalcone derivatives (IIa—f) with acetyl acetone in the presence of sodium ethoxide afforded the corresponding acetyl cyclohexanone derivatives (VIIa—f), respectively. Finally, compounds
Cl Ar =
Y^-rr Mixed anhydride CH3 Method
a, X = H; b, X = 4-Br; c, X = 4-Cl
d, X = 2-NO2; e, X = 4-NO2; f, X = 4-OCH3
Scheme 1. Synthetic route for starting materials (IIa—f).
CU Ar =
a, X = R = H; b, X = H, R = CH3; c, X = H, R = Ph d, X = 4-NO2, R = CH3; e, X = 4-NO2, R = Ph
Scheme 2. Synthetic route for compounds (IIIa—c), (I\&—c), (Va—f) and (Via—e).
Ar N H
a, X = H; b, X = 4-Br; c, X = 4-Cl
d, X = 2-NO2; e, X = 4-NO2; f, X = 4-OCH3
Ar N H
Ar N H
(VlIa, b, e)
a, X = H; b, X = 4-Br; c, X = 4-NO2
Scheme 3. Synthetic route for compounds (Vila—f) and (VlIIa—c).
(Vila, b, e) were cyclized with hydrazine hydrate into the corresponding cyclized products (Vllla—c), respectively (Scheme 3).
Pharmacological Activities Antiinflammatory activity
All the tested compounds showed potent anti-inflammatory activities against Carrageenan-induced edema (rats paw test) model (Table 1). For more confirmation of the Carrageenan-induced edema (rats paw test) model it was resorted to measuring Inhibition of plasma PGE2 and the obtained results confirmed those obtained with those of Carrageenan-in-duced edema (rats paw test) model (Table 1). Searching the exact mechanism of action of tested derivatives on COX-1 and COX-2 enzyme inhibitory activity were measured and the tested derivatives showed COX-1 and COX-2 enzyme inhibitory activities but inhibitory effects on COX-2 enzyme are more than those on COX-1 enzyme (Table 2).
Structure Activity Relationship (SAR)
Careful analysis of the relations of the chemical structure with the obtained results of pharmacological bioassays leads to the following conclusions about the features of structural activity relationship.
1. Belonging to the groups or atoms on the aromatic part the descending order of activities places in the following manner F, Cl, Br, H, 2-NO2, 4-NO2, OCH3.
2. Belonging to the moiety attached to N atom of pyrazoline the phenyl one alters the activities more than the methyl and the methyl more than hydrogen.
3. Ester form increases the activities more than ke-tonic one.
4. Building extra pyrazoline ring increases the activity.
All the tested compounds showed potent anti-inflammatory activities with high percentage of inhibition of plasma PGE2 and the mechanism of action depends mainly on inhibition of COX-2 activities with good safety margins for these newly synthesized compounds.
All melting points are uncorrected and were measured using an Electrothermal capillary melting point apparatus. The IR spectra were recorded on a Shimad-zu FT-IR 8101 PC infrared spectrophotometer in the KBr tablet. The 1H- and 13C-NMR spectra were determined in CDCl3 with Bruker AM-200 MHz spec-
trometer. The chemical shifts (5, ppm) were measured using TMS as internal standard. Mass spectra (EI) were recorded on Finnigan SSQ operating at 70 eV. Elemental analysis determined on a Perkin Elmer 240 (microanalysis), Microanalysis Center, Cairo University, Cairo, Egypt.
Synthesis of ^-(4-(6-(aryl)-3-cyano-2-methoxy-pyridin-4-yl)phenyl)-5-chloro-2-methoxybenzamides (Illa—c). A mixture of one of compound (IIc, e, f) (2 mmol), malononitril (0.16 g, 2.4 mmol) and sodium methoxide (0.108 g, 2 mmol) in methanol (25 mL) was refluxed for 3 hrs. The reaction mixture was evaporated under reduced pressure, washed with water, dried and crystallized from methanol to give the corresponding compounds (Illa—c), respectively.
Yield 82%, mp. 196-198°C. IR: 3518 (NH), 2238 (CN), 1680 (amide I), 1624 (amide II) cm-1. 1H-NMR: 5 3.45, 4.12 (2s, 6H, 2OCH3), 7.18 (s, 1H, py-rid-H), 7.23-8.15 (m, 11H, Ar-H), 11.75 (s, 1H, NH exchangeable with D2O). 13C-NMR: 5 55.54, 56.00 (2OCH3), 119.24 (CN), 163.25 (CONH), 156.12, 114.72, 147.11, 136.11, 155.82 (5C, pyrid-C), 133.96, 132.70, 133.72, 125.93, 114.97, 155.18, 134.18, 117.61, 131.90, 145.10, 140.71, 128.83, 128.71, 130.28 (18C, Ar-C). MS: m/z 504 (24%) [M+]. Anal. C27H19Cl2N3O3 (504.36): Calcd. C, 64.30; H, 3.80; Cl, 14.06; N, 8.33. Found: C, 64.18; H, 3.72; Cl, 14.00; N, 8.27.
Yield 75%, mp. 204-206°C. IR: 3524 (NH), 2235 (CN), 1680 (amide I), 1625 (amide II) cm-1. 1H-NMR: 5 3.40, 4.14 (2s, 6H, 2OCH3), 7.12 (s, 1H, pyrid-H), 7.26-8.18 (m, 11H, Ar-H), 11.86 (s, 1H, NH exchangeable with D2O). 13C-NMR: 5 55.52, 56.01 (2OCH3), 119.23 (CN), 163.26 (CONH), 156.10, 114.70, 147.10, 136.10, 155.83 (5C, pyrid-C), 142.10, 146.68, 133.77, 125.93, 114.93, 155.20, 134.18, 117.63, 131.90, 145.10, 140.71, 121.62, 128.71, 130.20 (18C, Ar-C). MS: m/z 515 (12%) [M+]. Anal. C27H19ClN4O5 (514.92): Calcd. C, 62.98; H, 3.72; Cl, 6.89; N, 10.88. Found: C, 62.90; H, 3.66; Cl, 6.82; N, 10.82.
Yield 68%, mp. 242-244°C. IR: 3528 (NH), 2234 (CN), 1682 (amide I), 1625 (amide II) cm-1. 1H-NMR: 5 3.40, 3.65, 4.14 (3s, 9H, 3OCH3), 7.15 (s, 1H, pyrid-H), 7.22-7.86 (m, 11H, Ar-H), 11.84 (s, 1H, NH exchangeable with D2O). 13C-NMR: 5 55.52, 55.85, 56.01 (3OCH3), 119.25 (CN), 163.25 (CONH), 155.98, 114.74, 147.12, 136.17, 155.80 (5C, pyrid-C), 128.10, 158.76, 133.75, 125.90, 114.92, 155.21, 134.19, 117.65, 131.92, 145.10, 140.70, 114.62,
Table 1. Anti-inflammatory and inhibition of plasma PGE2 for synthesized compounds (IIIa—c), (I\&—c), (\k—f), (VIa-e), (VIIa—f), (VIIIa-c)
Com- Dose, Protection Inhibition
pound mg/kg against edema, % of plasma PGE2, %
(Ilia) 2.5 81.20 ± 0.6 84.89 ± 0.6
5 90.42 ± 0.4 88.74 ± 0.7
(IIIb) 2.5 80.47 ± 0.3 84.12 ± 0.6
5 89.61 ± 0.2 87.94 ± 0.5
(IIIc) 2.5 79.02 ± 0.5 82.62 ± 0.6
5 88.00 ± 0.6 86.37 ± 0.5
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