Analgesic Activity of 5-Acetamido-2-Hydroxy Benzoic Acid Derivatives and an In-Vivo and In-Silico Analysis of Their Target Interactions.

The design, synthesis, and evaluation of novel non-steroidal anti-inflammatory drugs (NSAIDs) with better activity and lower side effects are big challenges today. In this work, two 5-acetamido-2-hydroxy benzoic acid derivatives were proposed, increasing the alkyl position (methyl) in an acetamide moiety, and synthesized, and their structural elucidation was performed using 1H NMR and 13C NMR. The changes in methyl in larger groups such as phenyl and benzyl aim to increase their selectivity over cyclooxygenase 2 (COX-2). These 5-acetamido-2-hydroxy benzoic acid derivatives were prepared using classic methods of acylation reactions with anhydride or acyl chloride. Pharmacokinetics and toxicological properties were predicted using computational tools, and their binding affinity (kcal/mol) with COX-2 receptors (Mus musculus and Homo sapiens) was analyzed using docking studies (PDB ID 4PH9, 5KIR, 1PXX and 5F1A). An in-silico study showed that 5-acetamido-2-hydroxy benzoic acid derivates have a better bioavailability and binding affinity with the COX-2 receptor, and in-vivo anti-nociceptive activity was investigated by means of a writhing test induced by acetic acid and a hot plate. PS3, at doses of 20 and 50 mg/kg, reduced painful activity by 74% and 75%, respectively, when compared to the control group (20 mg/kg). Regarding the anti-nociceptive activity, the benzyl showed reductions in painful activity when compared to acetaminophen and 5-acetamido-2-hydroxy benzoic acid. However, the proposed derivatives are potentially more active than 5-acetamido-2-hydroxy benzoic acid and they support the design of novel and safer derivative candidates. Consequently, more studies need to be conducted to evaluate the different pharmacological actions, the toxicity of possible metabolites that can be generated, and their potential use in inflammation and pain therapy.

Chemical composition, antinociceptive and anti-inflammatory activities of the curzerene type essential oil of Eugenia uniflora from Brazil.

ETHNOPHARMACOLOGICAL RELEVANCE: The Eugenia uniflora leaf infusion is widely used in folk medicine to treat gastroenteritis, fever, hypertension, inflammatory and diuretic diseases. AIM OF THE STUDY: This work evaluated the acute oral toxic, antinociceptive, and anti-inflammatory activities of the curzerene chemotype of Eugenia uniflora essential oil (EuEO). MATERIAL AND METHODS: EuEO was obtained by hydrodistillation and analyzed by GC and GC-MS. The antinociceptive action in mice was evaluated for the peripheral and central analgesic activity using abdominal contortion and hot plate tests (50, 100, and 200 mg/kg); xylene-induced ear swelling was carried out for the nociception test, and carrageenan-induced cell migration test. Spontaneous locomotor activity was assessed in the open field test to rule out any nonspecific sedative or muscle relaxant effects of EuEO. RESULTS: The EuEO displayed a yield of 2.6 ± 0.7%. The major compounds classes were oxygenated sesquiterpenoids (57.3 ± 0.2%), followed by sesquiterpene hydrocarbons (16.4 ± 2.6). The chemical constituents with the highest concentrations were curzerene (33.4 ± 8.5%), caryophyllene oxide (7.6 ± 2.8%), ß-elemene (6.5 ± 1.8%), and E-caryophyllene (4.1 ± 0.3%). Oral treatment with EuEO, at doses of 50, 300, and 2000 mg/kg, did not change the behavior patterns or mortality of the animals. EuEO (300 mg/kg) did not cause a reduction in the number of crossings in the open field compared to the vehicle group. The aspartate aminotransferase (AST) level was higher in EuEO-treated groups (50 and 2000 mg/kg) when compared to the control group (p < 0.05). EuEO, at doses of 50, 100, and 200 mg/kg, reduced the number of abdominal writhings by 61.66%, 38.33%, and 33.33%. EuEO did not show increased hot plate test time latency in any of the intervals analyzed. At 200 mg/kg, EuEO decreased paw licking time, with inhibition of 63.43%. In formalin-induced acute pain, EuEO decreased paw licking time at doses of 50, 100, and 200 mg/kg in the first phase, with inhibition of 30.54%, 55.02%, and 80.87%. The groups treated with EuEO at doses of 50, 100, and 200 mg/kg showed ear edema reduction of 50.26%, 55.17%, and 51.31%, respectively. Moreover, EuEO inhibited leukocyte recruitment only at a dose of 200 mg/kg. The inhibitory values of leukocyte recruitment after 4 h of carrageenan application were 4.86%, 4.93%, and 47.25% for 50, 100, and 200 mg/kg of essential oil, respectively. CONCLUSION: The EuEO, curzerene chemotype, has significant antinociceptive and anti-inflammatory activities and low acute oral toxicity. This work confirms the antinociceptive and anti-inflammatory of this species as the traditional use.

Chemical composition and antinociceptive and anti-inflammatory activity of the essential oil of Hyptis crenata Pohl ex Benth. from the Brazilian Amazon.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaf tea of Hyptis crenata has its practical use in the Brazilian Amazon for treating gastrointestinal and liver disorders, sweating induction, and as an anti-inflammatory. AIM OF THE STUDY: Evaluation of the chemical composition, acute oral toxicity, and antinociceptive and anti-inflammatory activities of the H. crenata essential oil. MATERIAL AND METHODS: The essential oil was hydrodistilled and analyzed by GC and GC-MS. The antinociceptive action in mice was evaluated for the peripheral and central analgesic activity (abdominal contortion and hot plate tests), and the xylene-induced ear swelling was carried out for the nociception test. RESULTS: Oxygenated monoterpenes (53.0%) and monoterpene hydrocarbons (38.9%) predominated in the H. crenata oil, being 1,8-cineo1e (35.9%), α-pinene (20.8%), camphor (10.0%), and ß-pinene (7.3%) their primary constituents. The oral oil administration in the mice did not display changes in behavior patterns or animal mortality at 300 and 2000 mg/kg doses. The control group's biochemical parameters (ALP, AST, ALT) displayed a statistical difference from the treated group, unlike the renal parameters, which showed no variation between the groups. Oil reduced the abdominal contortions at doses of 100 (79.5%) and 300 mg/kg (44.4%), while with endodontacin, the dose was 5 mg/kg (75.2%). In addition, the oil could not decrease the paw licking/biting time at doses of 30, 100, and 300 mg/kg. However, it showed a significant antinociceptive effect on the second phase in the formalin test inhibiting licking time, with a reduction of 50.8% (30 mg/kg), 63.4% (100 mg/kg), 58.0% (300 mg/kg), and morphine (4 mg/kg, 78.3%). The oil administration produced significant inhibition of ear edema at all tested doses, with a better effect produced at 30 mg/kg (64.0% inhibition). CONCLUSION: The oil of Hyptis crenata, rich in 1,8-cineole, camphor, α-pinene, and ß-pinene, totaling 74%, displayed low acute toxicity and significant anti-inflammatory activity, with peripheral and no central antinociceptive action. Thus, these results show an actual perspective on using H. crenata oil in developing a phytotherapeutic product.

Antinociceptive Activity and Toxicity Evaluation of the Fatty Oil from Plukenetia polyadenia Mull. Arg. (Euphorbiaceae).

Seed oil (Pp-oil) of Plukenetia polyadenia is used by native people of the Brazilian Amazon against arthritis and rheumatism, spreading it on the arms and legs to reduce the pain and inflammation. Pp-oil was obtained by pressing dried seeds at room temperature to give a 47.0% yield of oil. It was then subjected to fatty acid composition analysis. The principal fatty acids were linoleic acid (46.5%), α-linolenic acid (34.4%) and oleic acid (13.9%). Then, it was evaluated for its antinociceptive activity in mice, using the acetic acid-induced abdominal writhing, hot plate and formalin test models. Additionally, its toxicity was determined. The Pp-oil proved to have no toxicological effects, showing dose-dependent antinociceptive effect under chemical stimulation. At oral doses of 25-100 mg/kg, Pp-oil significantly reduced the abdominal writhes in the writhing test. A higher oral dose of 200 mg/kg did not induce alterations in the latency time of the hot plate test when compared to the control, suggesting an analgesic activity of peripheral origin. At oral doses of 50 and 100 mg/kg, the Pp-oil significantly reduced the second phase of the algic stimulus in the formalin test. In addition, the antinociception of Pp-oil was reversed by naloxone in the evaluation of its mechanism of action. Therefore, the Pp-oil proved to be safe at very high doses and to show significant analgesic properties. The role of Pp-oil is still being investigated with respect the mechanism of action, but the results suggest that opiod receptors could be involved in the antinociception action observed for the oil of P. polyadenia.

Antinociceptive activity of 1-nitro-2-phenylethane, the main component of Aniba canelilla essential oil.

Aniba canelilla (H.B.K.) Mez is a medicinal plant used in the Amazon folk therapeutic as antispasmodic, antidiarreic, carminative, tonic agent and a stimulant of the digestive and central nervous system. Our preliminary studies showed that the plant essential oil has analgesic activity in mice. Now, we are reporting the antinociceptive effect of the compound 1-nitro-2-phenylethane (97.5%), the main component of the essential oil of Aniba canelilla, which was obtained by column chromatographic purification. In the writhing test this compound was dosed at 15, 25 and 50 mg/kg reducing the abdominal writhes in a significant manner; in the hot plate test it was assayed at 50, 100 and 200 mg/kg producing no alterations in the latency time when compared to the control; and in the formalin test the 1-nitro-2-phenylethane was tested at 50 and 25 mg/kg decreasing significantly the second phase of the algic stimulus. The study suggests that the 1-nitro-2-phenylethane has analgesic activity, probably of peripheral origin. The mechanism involved is not completely understood, however, the results suggest that the opioid receptors are involved in the antinociceptive action observed to 1-nitro-phenylethane.