Ayman R. Baiuomy

Studies on the anti-inflammatory and anti-nociceptive effects of melatonin in the rat

The present study aimed to evaluate the anti-inflammatory and anti-nociceptive effects of melatonin in the rat. Acute inflammation was induced by sub-plantar injection of carrageenan (1%) in the rat hind paw. The rats received vehicle or drug 30 min before carrageenan administration and were evaluated for paw oedema at 1, 2, 3, and 4 h post-carrageenan. The induced inflammation and the formation of oedema were determined by measurement of the paw thickness. Nociception was tested by determining vocalization following electrical stimulation of the tail. Given intraperitoneally (i.p.) 30 min before carrageenan, melatonin caused significant and a dose-dependent reduction of hind paw swelling induced by carrageenan. At doses of 0.5 and 1 mg kg(-1), melatonin inhibited the carrageenan-induced oedema by 20.5 and 29.6% versus control values at 4 h post-carrageenan, respectively. Melatonin (0.5 and 1 mg kg(-1), i.p.) 30 min beforehand displayed anti-nociceptive effect in the electric stimulation of the rat tail test, increasing nociceptive thresholds to electrically-induced pain at 4 h post-treatment by 29.6 and 39.5%, respectively. Melatonin given simultaneously with the non-selective COX-1 and COX-2 inhibitor indomethacin (5 mg kg(-1), i.p.) 30 min prior to carrageenan, enhanced the anti-inflammatory effect of the latter in the carrageenan-induced paw oedema model by 23%. Melatonin (0.5 mg kg(-1), i.p.) increased the anti-nociceptive effect of indomethacin (5 mg kg(-1), i.p.). Meanwhile, the anti-inflammatory and anti-nociceptive effect of the highly selective COX-2 inhibitor rofecoxib (2.25 mg kg(-1), i.p.) was only slightly increased by melatonin administration at 0.5 mg kg(-1). Melatonin enhanced the anti-inflammatory effect of cysteamine (300 mg kg(-1), s.c.) in the carrageenan-induced paw oedema. Melatonin (20 and 40 microg per paw) given prior to carrageenan into the rat hind paw was devoid of anti-inflammatory effect. These results indicate that melatonin possesses anti-inflammatory and anti-nociceptive properties in the rat and enhance those of indomethacin. This effect is likely to be centrally mediated.

The anti-inflammatory effects of the phosphodiesterase inhibitor pentoxifylline in the rat

The present study aimed to evaluate the anti-inflammatory effects of pentoxifylline (PTX), a non-specific phosphodiesterase inhibitor in the rat. Acute inflammation was induced by subplantar injection of carrageenan (1%) in the rat hind paw. Results showed that intraperitoneal (i.p.) administration of PTX (36 or 72 mg kg(-1)) 30 min prior to carrageenan reduced the paw oedema response in dose-dependent manner with a maximal effect of 18.9 and 40.1%, respectively, at 2h post-carrageenan (P<0.001 and <0.001 at respective doses). Theophylline given at equimolar doses (29.9 or 45.8 mg kg(-1), i.p.) did not reduce the oedema response. With higher doses of PTX (144-300 mg kg(-1), i.p.) the anti-oedema effect of the drug was more pronounced, but mainly confined to the first 2h following carrageenan injection and decreasing rapidly thereafter. PTX (72 mg kg(-1), i.p.) given 30 min after carrageenan challenge reduced the oedema response by 24.7 and 26.2% at 1 and 2h after dosing (P<0.05 and <0.05, respectively). PTX (36 or 72 mg kg(-1), i.p.) co-administered with indomethacin (5 mg kg(-1), i.p.) 30 min before carrageenan had little modulatory effect on the anti-oedema effect of indomethacin, but the higher dose of PTX (144 mg kg(-1), i.p.) reduced the anti-inflammatory effect of indomethacin by 24% at 4h post-carrageenan. PTX (72 mg kg(-1), i.p.) enhanced the anti-oedema effect of the selective COX-2 inhibitor celecoxib (33 mg kg(-1), i.p.) by 55.1% at 4h post-carrageenan. In contrast, the higher dose of PTX (144 mg kg(-1), i.p.) reduced the anti-oedema effect of celecoxib by 46.8% at 4h post-carrageenan. PTX (36 or 72 mg kg(-1)) enhanced the anti-oedema effect of dexamethasone (0.1 mg kg(-1)) with maximal effect of 76 and 104.8% at 2h post-carrageenan (P<0.01 and <0.01 for respective doses). PTX (0.6 mg per paw) given with carrageenan into the rat hind paw reduced the oedema response with a maximal effect of 33.4% at 1h following carrageenan. PTX (0.6 mg per paw) given in the contralateral hind paw reduced the carrageenan-induced paw oedema for 1h by 32.2%. Thus, PTX, when given at doses comparable to those used in man for treatment of circulatory disorders displayed anti-inflammatory in vivo and enhanced the anti-inflammatory effect of a selective COX-2 inhibitor or dexamethasone. PTX may have therapeutic potential as anti-inflammatory agent either alone or in combination with non-steroidal anti-inflammatory drugs or with steroids. There is also an intriguing possibility for the use of topical preparations for the management of local inflammatory conditions.

Synthesis and biological evaluation of some novel fused thiazolo[3,2-a]pyrimidines as potential analgesic and anti-inflammatory agents

Some novel bicyclic thiazolopyrimidine derivatives bearing various substituents have been synthesized through one-pot three-component method. Structures of the target compounds were confirmed by elemental analysis and spectral data. Some selected members of the newly synthesized compounds were investigated for their analgesic and anti-inflammatory activities and revealed pronounced anti-inflammatory activity greater than that of indomethacin (reference drug).

Structure-Based Design of Benzimidazole Sugar Conjugates: Synthesis, SAR and In Vivo Anti-inflammatory and Analgesic Activities

A series of 2-methyl-N-substituted-benzimidazoles, bearing hydroxypyrrolidinon-5-yl or hydroxypyrrolidin-2-yl, 2,3:5,6-di-O-isopropylidene-alpha-D-mannofuranoside, 2,3,5,6-tetrahydroxy-alpha-D-mannofuranoside, 1:2,5:6-di-O-isopropylidene-alpha-D-gluco-furanose,3-O-benzyl-6,7-dideoxy-1:2-O-isopropylidene-alpha-D-xylo-heptofuranos-5-ulose, 3-O-benzyl-6,7-dideoxy-1,2-dihydroxy-alpha-D-xylo-heptofuranos-5-ulose, 1,2,5,6-tetrahydroxy-alpha-D-glucofuranose sugar moieties, were obtained in good yields from 2-methyl N-(trichloroacetamidomethyl)benzimidazole as a donor and carbohydrate residues as acceptor precursors in the presence of catalytic amount of trimethylsilyl trifluoromethanesulfonate (TMSOTf) as Lewis acid. Compounds 6, 7, 10, 13, 15, and 16 showed significant anti-inflammatory and analgesic activities.

Effect of spironolactone on pain responses in mice

The effects of spironolactone, a non-selective aldosterone antagonist, were examined on thermally-induced pain using the hot-plate and tail-flick tests, on chemogenic pain induced by intraplantar capsaicin, on electrically-induced pain, on visceral nociception induced by intraperitoneal acetic acid injection and on haloperidol-induced catalepsy in mice. Spironolactone significantly shortened response latency in the mouse tail-flick test but produced modest decreases in response latencies in the mouse hot plate test. The drug reduced the antinociceptive effect of tramadol in the hot plate test. Spironolactone in addition decreased nociceptive thresholds of electrically-induced pain in mice. In contrast, spironolactone elicited significant antinociceptive actions in the mouse acetic-acid-induced writhing assay and at doses of 20-160 mg/kg decreased capsaicin-induced chemogenic pain. Spironolactone at doses of 40 or 80 mg/kg reduced spontaneous activity and produced a significant impairment on the rotarod test in mice. The drug (10-80 mg/kg) increased the duration of catalepsy induced by haloperidol by 56.3-188.5 %. In conclusion, spironolactone increased pain behavior in a dose-dependent manner in models of thermal and electrical pain, but decreased inflammatory visceral pain due to intraperitoneal acetic acid and chemogenic pain due to intraplantar capsaicin. The effect of spironolactone on various types of pain needs further evaluation.

Evaluation of anti-inflammatory, anti-nociceptive, and anti-ulcerogenic activities of novel synthesized thiazolyl and pyrrolyl steroids.

Developing new therapeutic agents that can overcome gastrointestinal injury and at the same time could lead to an enhanced anti‐inflammatory effect becomes an urgent need for inflammation patients. Thiazolyl and pyrrolyl steroids were synthesized via straight forward and efficient methods and their structures were established based on their correct elemental analysis and compatible IR, 1H‐NMR, 13C‐NMR, and mass spectral data. The dihydrothiazolyl‐hydrazonoprogesterone 12 and the aminopyrrolylprogesterone 16a showed anti‐inflammatory, antinociceptive, and anti‐ulcerogenic activity with various intensities. Edema were significantly reduced by both doses of tested compounds (25 and 50 mg/kg) at 2, 3, and 4 h post‐carrageenan. The high dose of compound 16a was the most effective in alleviating thermal pain. Gastric mucosal lesions, caused in the rats by the administration of ethanol or indomethacin (IND), were significantly inhibited by each of the two tested compounds. These results provide a unique opportunity to develop new anti‐inflammatory drugs which devoid the ulcerogenic liabilities associated with currently marketed drugs.

Design, synthesis, anti-inflammatory, analgesic screening, and molecular docking of some novel 2-pyridyl (3H)-quinazolin-4-one derivatives

A novel series of 6-bromo-2-(4-pyridyl)-quinazolin-4(3H)-ones were synthesized by reacting 5-bromo anthranilic acid with isonictinoly chloride in the presence of acetic anhydride, which were further reacted with p-amino acetophenone to obtain 3-(4-acetylphenyl)-6-bromo-2-(pyridin-4-yl)quinazolin-4(3H)-one (3). Compound 3 underwent further reactions with different aldehydes to afford chalcone derivatives 4–10, which in turn underwent various cyclization reactions to afford cyclized products 15–18. 2-aminothiazole derivatives 12 obtained by reaction of 3 with bromine then with thiourea. Compound 14 obtained by treatment of 11 with KSCN followed by cyclization. Some of the synthesized compounds 4, 5, 12, 14, 15 and 18 were screened for both analgesic and anti-inflammatory activities. All tested compounds showed good analgesic and anti-inflammatory activity in comparison to the reference standard indomethacin. Compounds 4 and 5 showed the highest anti-inflammatory activity, while compounds 14 and 15 showed the highest analgesic activity among all the tested compounds.

Synthesis and antidepressant evaluation of five novel heterocyclic tryptophan-hybrid derivatives.

This study aimed at evaluating the reactivity of L‐Tryptophan (TRP) 1 towards various chemical reagents to produce new bi‐ and tri‐heterocyclic systems providing basic pharmacological activities. Indol‐3‐yl hydroxyoxazol‐2‐yl acetonitrile derivatives 5 and 6, indol‐3‐yl‐hydroxyoxazol‐2‐yl‐1,2,4‐triazine derivatives 8 and 9, indol‐3‐yl‐hydroxyoxazol‐2‐yl‐aminopyrazole derivatives 11a, b, and indol‐3‐yl‐hydroxyoxazol‐2‐yl‐aminoisoxazole derivative 12 were synthesized via straightforward and efficient methods. The structures were characterized by spectral data (IR, 1H‐NMR, 13C‐NMR, and MS) and the purity was ascertained by microanalysis. Also, this work was extended to study the potential role of the novel synthesized TRP derivatives 5, 6, 9, 11a, and 12 as antidepressant and sedative agents in comparison with TRP. All compounds showed significant antidepressant activity in the forced‐swimming test at two doses (50 or 100 mg/kg). Also, all tested compounds (at 50 or 100 mg/kg) produced a significant decrease in locomotor activity of mice during a 30 min observation period. The most potent antidepressant and sedative effect was produced by the tri‐heterocyclic compounds 9 and 12, followed by 11a and TRP.

Citric acid strongly inhibits visceral pain response in mice

Citric acid introduced into the stomach of mice at increasing concentrations of 0.1, 1 or 10 % (4.8 μM-0.48 mM; 95 μmol/kg-9.5 mmol/kg, 0.5 ml) caused dose-dependent inhibition of abdominal constrictions induced 1 h later by i. p. acetic acid injection by -51 % to -69.5 %. When administered at 10 % (0.48 mM, 0.5 ml) 15 min before nociceptive challenge, citric acid inhibited the nociceptive response by 96.8 %. Inhibition of the acetic acid-induced ab- dominal constrictions was also observed when lower doses of citric acid were introduced into the stomach (0.2 ml of 0.1-1 %; 38.1 μmol/kg-0.38 mmol/kg). The effect was evident as early as 5 min after administration of citric acid into the stomach and with the maximal effect being at 15-30 min after dosing. Lidocaine given orally 5 min prior to citric acid (1 %, 48 μM; 0.38 mmol/kg, 0.2 ml) prevented antinociception by citric acid, but lidocaine given 15 min before oral introduction of citric acid enhanced the citric acid-induced inhibition of the no- ciceptive response to acetic acid. The antinociceptive effect of orally administered citric acid (1 %, 48 μM; 0.38 mmol/kg, 0.2 ml) was increased by pre-treatment with propranolol (4 mg/kg, s. c.), yohimbine (4 mg/kg, s. c.), guanethidine (32 mg/kg, s. c.), but reduced after treatment with atropine (3 mg/kg, s. c.), which itself increased the nociceptive behavior. Simi- lar inhibition of the acetic acid-induced nociceptive behavior was also observed when sodium citrate (pH 7.21) or 0.1 N HCl (pH 3) or 1 % sucrose solution (0.2 ml) was intragastrically given. It is suggested that citric acid might act to stimulate sensory afferents and that trans- mission of nociceptive information centrally leads to the activation of descending antinocicep- tive mechanism to a noxious stimulus.

Design, Synthesis, In Vivo Anti-inflammatory, Analgesic Activities andMolecular Docking of Some Novel Pyrazolone Derivatives

A novel series of 1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one derivatives were synthesized. The synthesis started with the important building block 3, which was prepared via coupling of from 2-(bis (methylthio) methylene) malononitrile 1 with 4-amino-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one 2. The 5-aminopyrazole derivatives 4-8 were prepared from the cyclocondensationof 3 with the appropriate sulfonohydrazides and pyridine- 4-carbohydrazide respectively. Cyclocondensation of 1 or 9 with pyridine-4-carbohydrazide and 4-methylbenzene sulfonohydrazide corresponding pyrazole derivatives 10, 11, 12 and 13. Condensation 2 and 1-isothiocyanato-4- methylbenzene 14 yielded 15 which was refluxed with malonic acid to yielded1-(1,5-dimethyl-3-oxo-2-phenyl-2,3- dihydro-1H-pyrazol-4-yl)-2-thioxo-3-(2methylphenyl) dihydropyrimidine-4,6(1H,5H)-dione (16). All tested compounds showed analgesic and anti-inflammatory activities in comparison to the reference standard drugs tramadol, acetyl salicylic acid and indomethacin. Maximum protection against the thermal stimulus was observed at 90 min following the administration of the compound (5) (105.8%), which was statistically significant comparable to the reference drug tramadol (148.7%). Compounds (5, 6, 11 and 13) revealed their maximal analgesic effect after 60 min (68.5%, 77.5%, 84.6% and 89.7%, respectively), then their effect started to decrease. In addition, derivatives 10, 12 and 16 showed anti-inflammatoryactivity after 4 hours, which was greater than that of the reference drug indomethacin and reached the maximum effect at the 2nd h. Additionally, a molecular docking study was performed against the COX enzyme using the Molsfot ICM 3.8 software.