Synthesis, biological evaluation, molecular docking, and ADMET studies of some isoxazole-based amides Sushama Kauthale, Sunil Tekale, Manoj Damale, Jaiprakash Sangshetti & Rajendra Pawar Medicinal Chemistry Research ISSN 1054-2523 Med Chem Res DOI 10.1007/s00044-017-2070-z
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Author's personal copy MEDICINAL CHEMISTRY RESEARCH
Med Chem Res DOI 10.1007/s00044-017-2070-z
ORIGINAL RESEARCH
Synthesis, biological evaluation, molecular docking, and ADMET studies of some isoxazole-based amides Sushama Kauthale1 Sunil Tekale1 Manoj Damale2 Jaiprakash Sangshetti3 Rajendra Pawar1 ●
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Received: 17 June 2017 / Accepted: 9 September 2017 © Springer Science+Business Media, LLC 2017
Abstract Some isoxazole-based amides were synthesized by the reaction of 3-(2-chlorophenyl)-5-methylisoxazole-4carbonyl chloride with various aliphatic, aromatic and heterocyclic amines; characterized by analysis of spectroscopic data and evaluated for in vivo anti-inflammatory, ulcerogenic, and antimicrobial activity. Compounds A1, A7, and A10 were identified as the potent anti-inflammatory agents in carrageenan-induced albino rat paw edema assay exhibiting 92.85–93.57% edema inhibition after 5 h with lower ulcer index (2.5) than the standard diclofinac sodium (6.15). Antibacterial activity against the bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis was found to be good in comparison with the standard ampicillin in terms of minimum inhibitory concentration values. Anti-inflammatory activity results were supported by molecular docking—possible binding modes, interactions, and docking scores of titled compounds with the active site of cyclooxygenase-2 enzyme. In silico absorption, distribution, metabolism, and excretion–toxicity study was also performed to predict the preliminary pharmacological, pharmacokinetic, and toxicity
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00044-017-2070-z) contains supplementary material, which is available to authorized users. * Rajendra Pawar
[email protected] 1
Department of Chemistry, Deogiri College, Station Road, Aurangabad, MS 431 005, India
2
Department of Pharmaceutical Chemistry, Shri. Bhagwan College of Pharmacy, Aurangabad, MS 431003, India
3
Y. B. Chavan College of Pharmacy, Dr. Rafiq Zakaria Campus, Aurangabad, MS 431001, India
profile of the synthesized anti-inflammatory agents suggesting that these derivatives have good oral drug like behavior and non-toxic nature. Keywords Molecular docking ADMET Anti-inflammatory Ulcerogenic Antibacterial. ●
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Introduction Most of the commercially marketed drugs are small molecules; contributing about 90% of the therapeutics among pharmaceuticals. Small size of drug molecules assists in enhancing possibility of rapid diffusion through cell membranes; so that the drug molecule can reach intracellular sites of receptor. Thus, from pharmacology and molecular microbiology point of view discovery of therapeutically and medicinally active small molecules is highly desirable (Scott et al. 2016). Anti-inflammatory drugs are the compounds used to alleviate inflammation or swelling. These drugs inhibit one or more isoforms of cyclooxygenase (COX) enzyme which catalyzes arachidonic acid present in cell membranes into inflammatory mediators such as prostaglandins (PGs), prostacyclins, and thromboxanes. Unfortunately some of the classical non-steroidal anti-inflammatory drugs induce their action with side effects of ulcer generation, gastric bleeding, and cardiovascular effects as a consequence of inhibition of COX-2 enzyme. Few years back antiinflammatory drugs like valdecoxib and rofecoxib were withdrawn from pharmaceutical market due to such side effects. Consequently design, synthesis, and discovery of non-steroidal anti-inflammatory agents with minimum
Author's personal copy Med Chem Res Fig. 1 Some isoxazole and amide-based commercial drugs N O H2N O
S
O
H N
(1)
F3C
O N
NH
O N H
O
(2)
O
HN
NH2
O R
S
O
N
N
N
Z
(4)
ulcerogenic properties becomes a challenging goal in medicinal chemistry. An antibacterial agent is a compound which kills or inhibits the growth of bacteria. Search for the discovery of new antibacterial agents is essential due to resistance shown by bacteria to existing antibacterial drugs on account of their genetic modifications. Isoxazole ring is an imperative skeleton of many pharmaceutically active ingredients such as valdecoxib (1), isocarboxazid (2), leflunomide (3) etc. (Fig. 1). Valdecoxib is a nonsteroidal anti-inflammatory drug. Isocarboxazid is an antidepressant drug that acts irreversible monoamine oxidase inhibitor and mainly used to treat mood, anxiety, Parkinson’s disease, and dementia-related disorders. Leflunomide; an immunosuppressive antirheumatic drug is used in active moderate-to-severer heumatoid arthritis and psoriatic arthritis (Krensky et al. 2006). Simple amide molecules including pyrazinamide (bacteriostatic antitubercular agent) (4), mepivacaine (5) (local anesthetic) etc. also serve as drugs for the welfare of mankind (Zimhony et al. 2000; Porto et al. 2007). Furthermore studies reveal that benzo[d] thiazol-2-yl-(piperazin-1-yl)methanones (6) act as potent anti-mycobacterial chemo types (Pancholia et al. 2016). Biological potential of isoxazole and amide functionality bearing molecules is reviewed by various researchers (Rajput et al. 2015; Kaur et al. 2014). Recently some novel furancarboxamide derivatives were shown to be potent antifungal targets against Rhizoctonia solani, Botrytis cirerea, Valsa mali, and Sphaceloma ampelimum (Wen et al. 2016). Considering therapeutic potential of isoxazoles, significant biological activities of amide derivatives and mechanism of action of non-steroidal anti-inflammatory drugs, in the present studies we report synthesis of some isoxazole-based amides (Fig. 2a, b). Furthermore, screening of the synthesized isoxazole amides was aimed to explore their potential as non-steroidal anti-inflammatory agents with minimum ulcerogenecity and improved safety profile as an attempt to search for “small drug like” molecules.
N
(3)
N N
O
(5)
(6)
a Cl
O N O
Cl
RNH2
Base, solvent r. t. , 1 h
Cl
O N O
(Scheme 1)
N H
R
(A1-14)
b Cl
O N O
Cl
NH3
Reflux, 100 oC, 1h (Scheme 2)
Cl
O N O
NH2
(A14)
Fig. 2 a Synthesis of isoxazole-based amides A1-13. b Synthesis of isoxazole amides 3-(2-chlorophenyl)-5-methylisoxazole-4-carboxamide (A14)
Molecular docking has given brief insight into strength of molecular complexes, suggesting that the synthesized derivatives have a strong potential to inhibit the prostaglandin precursor. The experimentally observed results of antiinflammatory activity were supported by theoretical predictions of possible interactions and binding modes of these “drug like” molecules with COX-2 enzyme from molecular docking studies. In silico physicochemical and pharmacological properties of the synthesized compounds were preliminarily studied using absorption, diffusion, metabolism, excretion toxicity (ADMET).
Materials and methods Chemicals used were SD fine or Sigma Aldrich made and used without further purification. Reaction progress was monitored using thin layer chromatography (TLC) (30% ethyl acetate: n-hexane) on silica gel precoated aluminum plates. Structures of products were confirmed by analysis of spectroscopic data (1H nuclear magnetic resonance (NMR),
Author's personal copy Med Chem Res 13
C NMR, infrared (IR), and mass spectra). 1H NMR (400 MHz) and 13C NMR (100.6 MHz) spectra of the products were scanned on Brucker Vector 400 MHz spectrophotometer in CDCl3 solvent using tetramethyl silane (TMS) as an internal standard. IR spectra were recorded on a Shimadzu (Prestige IR21) spectrophotometer. Diclofenac sodium (Themis Pharmaceuticals, Mumbai), carrageenin (Sigma Chemical Co, St Louis, MO, USA) were used for screening the biological activity of the synthesized amides.
as monitored by TLC, the contents were cooled to room temperature and the precipitated solid was filtered off under vacuum as the crude product which was washed with icecold water (3 × 5 mL), dried and further recrystallized from ethanol. All the synthesized compounds were characterized by analysis of spectroscopic data—1H NMR, 13C NMR, IR, and mass. Acute toxicity study
Synthesis of isoxazole amides The isoxazole based amides were synthesized by the reaction of various aliphatic, aromatic and heterocyclic amines with 3-(2-chlorophenyl)-5-methylisoxazole-4-carbonyl chloride in presence of triethyl amine or sodium bicarbonate base at 0 °C-room temperature or refluxing with ammonia within 1 h (Fig. 2a, b). Procedure for the synthesis of A1 A solution of thiosemicarbazide (5 mmol) in acetone (5 mL) was reacted with portion wise addition of 3-(2-chlorophenyl)-5-methylisoxazole-4-carbonyl chloride (5 mmol) in the presence of sodium bicarbonate (7.5 mmol) with continuous stirring under ice cold condition. After completion of reaction (monitored by TLC); acetone was evaporated under reduced pressure, poured onto ice-cold water, resulting solid precipitated was filtered, washed (3 × 5 mL) with water and finally recrystallized from ethanol. General procedure for the synthesis of amides A2–A13 Triethyl amine (6 mmol) was added to an ice cold solution of amine (5 mmol) in dichloromethane (5 mL) followed by portion wise addition of 3-(2-chlorophenyl)-5-methylisoxazole-4-carbonyl chloride (5 mmol). The contents were slowly warmed to room temperature and stirred for 1 h. After completion of reaction as monitored by TLC, DCM was evaporated under vacuum on rotary evaporator; the reaction mixture was basified with an ice cold aqueous saturated sodium bicarbonate and extracted with DCM (3 × 10 mL). The combined organic layers was dried over anhydrous sodium sulfate and concentrated to get the crude product which was further recrystallized by triturating with DCM and n-hexane. Procedure for the synthesis of 3-(2-chlorophenyl)-5methylisoxazole-4-carboxamide (A14) 3-(2-Chlorophenyl)-5-methylisoxazole-4-carbonyl chloride (5 mmol) in concentrated ammonia (10 mL) was refluxed at 100 °C for 1 h in a sealed tube. After completion of reaction
Preliminary experiments were carried out on rats (n = 6). Compounds A1–A14 were administered orally in different doses to find out the range of doses which cause zero and 100% mortality of animals. Acute oral toxicity was conducted according to the method of Organization for Economic Co-operation and Development (OECD) (OECD 2001). Animals were kept fasting providing only water. Compounds A1–A14 were given p.o. in doses of 100, 200, 300, and 400 mg/kg/p.o. administered orally for 4 days of six groups of rats (n = 6) and the animals were kept under observation for mortality as well as any behavioral changes for evaluation of a possible anti-inflammatory effect. The minimum lethal dose for our present study was found to be >400 mg/kg per body weight. Anti-inflammatory activity of isoxazole based amides (A1–A14) In vivo anti-inflammatory activity of the synthesized compounds A1–A14 was evaluated using carrageenan induced paw edema bioassay in rats and results were compared with diclofinac sodium as the reference drug. Animal studies were approved by Institutional Animal Ethics Committee (IAEC), constituted for purpose of control and supervision of experimental animals by the Ministry of Environment and Forests, Government of India, New Delhi, India. Wistar rats (150–200 g) were group housed (n = 6) under a standard 12 h light/dark cycle at controlled conditions of temperature and humidity (25 ± 2 °C, 55–65%). Rats received standard rodent chow and water ad libitum. Rats were acclimatized to laboratory conditions for 7 days before carrying the experiments. All experiments were carried out in a noise-free room between 08.00 and 15.00 h. Separate group (n = 6) of rats was used for each set of experiments. Animals were kept fasting providing only water. Compounds A1–A14 were given doses of 10 and 20 mg/kg/p.o. and administered orally for 4 days of six groups of rats (n = 6) and the animals were kept under observation for mortality as well as for any behavioral changes for evaluation of a possible anti-inflammatory effect (Antarkar et al. 1994; Winter et al. 1962; Kasahara et al. 1985; El-Sayed et al. 2010; Abbas et al. 2010).
Author's personal copy Med Chem Res
Carrageenan induced hind paw edema
Table 1 Effect of different isoxazole based amides (A1–A14) on paw edema induced by carrageenan in rats
The animals were divided into five groups of six animals each and were fasted for a period of 24 h prior to study. Group 1 was treated as control (0.1 mL of 1% (w/v) of Carrageenin subcutaneously), Group 2 was received diclofenac sodium 30 mg/kg, p.o. Group 3 were treated with the compounds A1–A14 (10 and 20 mg/kg, p.o.). Edema was induced by injecting 0.1 mL of 1% solution of carrageenan in saline into sub plantar region of right hind paw of the rats. Volumes of edema of injected and contra lateral paws were measured at time interval after induction of inflammation using a plethysomgraph to calculate the percentage of paw edema inhibition using Eq. (1) (Table 1).
Treatment
Dose (mg/kg)
Mean differences in paw volume (mL)
Percentage of inhibition (%)
Normal
0.1 mL of 1% (w/v)
1.40 ± 0.05
–
Diclofenac sodium
30
0.60 ± 0.07*
97.14
A1
10
0.95 ± 0.05
72.14
20
0.65 ± 0.07*
93.57
10
0.97 ± 0.05
70.71
20
0.80 ± 0.06*
82.85
10
0.95 ± 0.05
72.14
20
0.69 ± 0.05*
90.71
10
0.99 ± 0.04
69.28
20
0.82 ± 0.06*
81.42
10
0.98 ± 0.07
70.00
20
0.71 ± 0.05*
89.28
10
0.97 ± 0.06
70.71
20
0.72 ± 0.05*
88.57
10
0.95 ± 0.06
72.14
20
0.66 ± 0.05*
92.85
A8
10
0.97 ± 0.05
70.71
20
0.71 ± 0.06*
89.28
A9
10
0.98 ± 0.05
70.00
20
0.72 ± 0.07*
88.57
A10
10
0.94 ± 0.05
72.85
20
0.66 ± 0.05*
92.85
A11
10
0.96 ± 0.06
71.42
20
0.73 ± 0.07*
87.85
A12
10
0.96 ± 0.05
71.42
20
0.78 ± 0.05*
84.28
A13
10
0.95 ± 0.05
72.14
20
0.76 ± 0.05*
85.71
A14
10
0.95 ± 0.04
72.14
20
0.78 ± 0.06*
84.28
Percentage inhibition ¼
Vc Vt 100 Vc
ð1Þ
A2 A3 A4 A5
where Vc is the Edema volume of control group, Vt the Edema volume of test group Ulcerogenic activity study
A7
Rats were fasted 20 h before drug administration. Compounds A1–A14 and diclofenac sodium were given orally in different doses respectively suspended in 1% Tween; while one group received vehicle (1% Tween). Rats were fasted for 2 h, allowed to feed for 2 h then fasted for another 20 h. Rats were given another two doses on the second and third days. On fourth day, rats were sacrificed, stomach removed, opened along with the greater curvature and rinsed with 0.9% saline. The number of mucosal damage (red spots) was counted and their severity (ulcerogenic severity) was graded from 0 to 4 (Table 2) according to the following score assignment using Eqs. (2) and (3): % Incidence=10 ¼½number of rats showing ulcer of any grade divided by total number of rats in the group 100=10:
ð2Þ Ulcer index ðUIÞ ¼
Total ulcerscore Number of animals ulcerated
A6
ð3Þ
Antimicrobial activity Antibacterial activity was evaluated against four different gram-positive and gram-negative bacterial strains such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis. Minimum inhibitory concentration (MIC) values were determined using standard agar method (Cruickshank et al. 1975; Collins 1976; Khan 1997; Duraiswamy et al. 2006; Saundane et al. 1989). Ampicillin was used as the standard for comparison of
Each data suggests mean ± SEM (n = 6). One-way ANOVA using Dunnett’s test was applied for statistical analysis, treatment groups compared with control group. Significant at *p < 0.01, compared to control group
antibacterial activity. Dimethyl sulfoxide was used as the control. Molecular docking To explore binding affinity, binding mode and possible molecular interactions of the synthesized isoxazole based amides; compounds were docked against active site of COX-2, an isoform of cycloxygenase or prostaglandin endoperoxidase synthease (PGHS) using Surflex-Dock
Author's personal copy Med Chem Res Table 2 Effect of isoxazole based amides (A1–A14) on diclofenac sodium induced ulcer in rats Treatment
Dose (mg/kg)
Normal
0.1 ml of 1% (w/v)
Diclofenac 30 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14
No. of % animals Incidence with ulcer /10
5/5
Ulcer index
0
0.0 ± 0
10
6.15 ± 1.10
10
5/5
10
3.50 ± 0.10
20
5/5
10
2.70 ± 0.10
10
5/5
10
3.80 ± 0.12
20
5/5
10
2.95 ± 0.10
10
5/5
10
3.90 ± 0.13
20
5/5
10
3.00 ± 0.10
10
5/5
10
3.90 ± 0.15
20
5/5
10
3.00 ± 0.10
10
5/5
10
3.80 ± 0.12
20
5/5
10
2.90 ± 0.10
10
5/5
10
3.80 ± 0.15
20
5/5
10
2.90 ± 0.15
10
5/5
10
3.60 ± 0.10
20
5/5
10
2.70 ± 0.10
10
5/5
10
3.90 ± 0.12
20
5/5
10
3.00 ± 0.10
10
5/5
10
3.80 ± 0.10
20
5/5
10
2.90 ± 0.15
10
5/5
10
3.50 ± 0.10
20
5/5
10
2.70 ± 0.15
10
5/5
10
3.80 ± 0.10
20
5/5
10
2.90 ± 0.10
10
5/5
10
3.80 ± 0.12
20
5/5
10
2.90 ± 0.15
10
5/5
10
3.70 ± 0.10
20
5/5
10
2.80 ± 0.15
10
5/5
10
3.90 ± 0.10
20
5/5
10
3.00 ± 0.17
Each data suggests mean ± SEM (n = 5). One-way ANOVA using Dunnett’s test was applied for statistical analysis, treatment groups compared with control group; significant at *p < 0.01, compared to control group
module of Sybyl 2.1.1 package. Post docking analysis was performed in order to validate docking accuracy of the software and ability of docking software for reproducing docking results by analyzing and comparing RMSD values (Table 3). ADMET study In silico pharmacokinetic and pharmacological studies were performed on the basis of absorption, distribution, metabolism and excretion toxicity abbreviated as (ADMET)
which is used to describe disposition of a pharmaceutical compound within an organism. In the present study, ADMET properties of the synthesized isoxazole amides were carried using ADMET predictor FAF Drugs2 which runs on Linux OS. This tool is freely available and used for in silico ADMET filtering.
Results and discussion In case of amides A1–A13, addition of 3-(2-chlorophenyl)5-methylisoxazole-4-carbonyl chloride to thiosemicarbazide or amine was carried out in the presence of appropriate base (NaHCO3 or triethyl amine) under ice-cold condition and then the contents were stirred at room temperature for 1 h. For synthesis of 3-(2-chlorophenyl)-5-methylisoxazole-4carboxamide (A14), starting material 3-(2-chlorophenyl)-5methylisoxazole-4-carbonyl chloride was refluxed with ammonia at 100 °C for 1 h in a sealed tube. Almost all the amines reacted smoothly with the acid chloride to afford corresponding amide derivatives in good to excellent yields. Yields of the products were comparatively higher in case of amines possessing electron donating groups (Entries 5, 12, 14; Table 4). Obtained products were purified by crystallization with ethanol (A1, A14) or by triturating with DCM and n-hexane (A2–A13). Thus no chromatographic technique was required to purify the obtained products. All the compounds were fully characterized by analysis of spectroscopic data 1H, 13C NMR, IR, and mass. A broad signal around 12.5 δ ppm in 1H NMR spectra indicated the formation of amide. In 13C NMR, carbonyl carbon of amide group appeared in the range of 168–175 whereas in IR spectra N–H stretch of amide appeared as an absorption band around between 3200 and 3400 cm−1 confirming the formation of amide. Products were confirmed by presence of molecular ion peaks at appropriate values in the mass spectra. Anti-inflammatory activity All analysis was performed using graph pad prism for Windows. Statistical analysis was expressed as mean ± standard error of the mean (SEM). Data was analyzed by one way ANOVA, where applicable p < 0.05 was considered statistically significant, compared with vehicle followed by Dunnett’s test. Results of experiments for 10 and 20 mg/kg concentrations are summarized in Table 1; Fig. 3. Satisfactory results were observed for 20 mg/kg concentration. Anti-inflammatory activity of synthesized compounds was carried out by carrageenan-induced rat paw edema model using diclofenac sodium as the reference drug. Mean changes in paw edema thickness of animals treated with the
Author's personal copy Med Chem Res Table 3 Effect of different compounds A1–14 on paw edema induced by carrageenan in rats and molecular docking details
Compounds
Inhibition (%)
Molecular docking score Total score (-log Ki)
RMSD Å Crash score
Polar score
A-1
93.57
4.3283
−3.2819
1.6202
0.045
A-2
82.85
3.35
−2.458
1.4119
0.056
A-3
90.71
3.4348
−2.9451
0.8769
0.049
A-4
89.28
2.7991
−0.6882
0.3364
0.057 0.046
A-5
81.42
2.8845
−1.0032
0
A-6
88.57
2.8713
−1.4905
0.0037
0.053
A-7
92.85
3.2007
−1.4473
1.3894
0.052
A-8
89.28
3.1285
−0.4659
0.8413
0.05
A-9
88.57
2.6974
−0.9204
0.065
0.056
A-10
92.85
3.6011
−0.5275
0.8224
0.05
A-11
87.85
2.7763
−1.7416
0.519
0.04
A-12
84.28
2.4909
−0.7506
1.5604
0.044
A-13
85.71
2.4111
−0.546
0.6554
0.052
A-14
84.28
2.4224
−0.9423
1.0196
0.052
Diclofenac
97.14
3.4402
−1.8105
1.4606
0.065
tested compounds from induction of inflammation was measured, together with inhibition percent of edema and results of anti-inflammatory activity are summarized in Table 1 which reveals good results obtained at 20 mg/kg, p.o. dose; comparable with the standard drug. Antiinflammatory activity of the compounds was found in following order: A1 > A7 > A10 > A3 > A5 > A8 > A6 > A9 > A11 > A13 > A12 > A14 > A2 > A4 Thus, the compounds A1, A3, A5, A7, A8, and A10 were found to be more effective than rest of the derivatives. From Table 1, compound A1 with thiosemicarbazide moiety at 20 mg/kg concentration was the most promising anti-inflammatory (93.57% inhibition) agent. In addition, the compound A7 with 2-aminothiazole and A10 with piperidine ring was found to be equipotent in terms of % paw edema inhibition (92.85% inhibition). Compound A3 with 4-fluoroaniline had 90.85% paw edema inhibition had good anti-inflammatory activity as compared with A2 having Cl-atom at the same position which could be probably due to small size of fluorine atom. Similar results were observed in case of A7 and A8 with 2-aminothiazole and 2aminobenzothiazole moieties respectively. However surprisingly, compound A4 with 3-Cl, 4-F substituent had the least anti-inflammatory activity (81.42% inhibition) with higher ulcer index. Further increase in ring size of amine part of the tested compounds had no significant effect on anti-inflammatory activity as in the case of A11 having naphthyl ring. Compounds A7 and A10, A5 and A8, A6 and A9, A12 and A14 were observed to be equipotent antiinflammatory agents in terms of % edema inhibition.
Acute ulcerogenecity study All analysis was performed using graph pad prism for Windows and expressed as mean ± SEM. Data was analyzed by one way ANOVA, wherever applicable p < 0.05 was considered statistically significant, compared with vehicle followed by Dunnett’s test (Finney 1964; Gierse et al. 1999).
Acute ulcerogenicity study Acute ulcerogenicity is usually expressed as a side effect and consequence of anti-inflammatory action. Compounds A1-A14 with best overall outline in animal efficacy model were evaluated for gastric ulcerogenic potential in rats (Table 2; Figs. 4 and 5). Ulcerogenic effect was compared to a classical NSAID, diclofenac sodium (U.I. = 6.15). Interestingly all the synthesized compounds showed mild ulcerogenic potential as they have lower ulcer indices (2.7–3.8) at 20 mg/kg p.o. dose than the standard diclofinac sodium (U. I. = 6.15). Tested compounds showed ulcerogenic activity in the following order: (A1 = A7) < A10 < A13 < (A5 = A11) 100), weight (MW > 500), partition coefficient (logP > 5), number of rotatable bonds (>10) and ratio of H/C(>1). All the above mentioned parameters signify oral bio-availability and good intestinal absorption. Topological polar surface area (TPSA) i.e., surface belonging to polar atoms and molecular weight are the descriptors which correlate with passive molecular transport through membranes that allows prediction of route of transport of drugs through the barrier membranes, intestine and blood-brain barrier (BBB). The percentage of absorption (% ABS) was calculated using TPSA from the formula %ABS = 109 −(0.345 × TPSA) (Winter et al. 1962). All the synthesized compounds exhibited a very good % ABS ranging from 62.93 to 78.64%. Values of partition coefficient (logP > 5), number of rotatable bonds (>10), number of rigid bonds (>25) and ratio of H/C (>1) determine the absorption performance through the lipophilic phospholipid membranes and toxicity. Furthermore, none of the isoxazole amides A1–14 violated Lipinski’s rule of five indicating that these isoxazole derivatives have a potential to be developed as orally active small anti-inflammatory drug candidates with minimum ulcerogenic properties and may be potentially active against COX-2.
Conclusion In conclusion a series of some simple and “small” isoxazolebased amide derivatives has been developed as potent antiinflammatory drug like molecules having less ulcerognic index as compared to the standard diclofinac. Generally newly synthesized compounds show significant consequences. However in the present study, compounds A1, A3, A5, A7, A8 and A10 were observed to exhibit remarkable anti-inflammatory activity with minimum ulcerogenic properties. Results revealed that the isoxazolebased amides derivatives A1 and A10 (92.85–93.5% edema inhibition) showed promising results as non-steroidal antiinflammatory agents with lower ulcer indices as compared to the standard which were supported by computational molecular docking study and thus may be used as alternate therapeutics for inflammation, pain, and subsequent development into potential anti-inflammatory agents with safety profile. The antibacterial activity of A6 was noticeable against P. aeruginosa, S. aureus, and B. subtilis having MIC value (75–125 µg/mL) in comparison with the standard. The isoxazole amides A2, A4, and A13 were found to be highly active against all the tested bacterial strains. In general MIC values of the isoxazole-based amides in case of S. aureus and B. subtilis were comparable with the standard ampicilin and the compounds were less potent antibacterial agents in case of E. coli and P. aeruginosa.
Prediction of in silico pharmacokinetic parameters suggest that the synthesized compounds have potential of high oral drug bio-availability indicating that isoxazole-based amides have new opportunities for the possible modification and future discovery of drug candidates in medicinal chemistry. Acknowledgements Authors are thankful to the Director, Sophisticated Analytical and Instrumentation Facility (SAIF), Panjab University Chandigarh (India) for providing spectral data and to the Director, Scan research laboratory, Bhopal for providing the results of biological activity. Compliance with ethical standards Conflict of interest interests.
The authors declare that they have no competing
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