Influence of eugenol on oxidative stress biomarkers in the liver of carrageenan-induced arthritis rats

Exploring the anti-inflammatory potential of Colocasia esculenta root extract in in-vitro and in-vivo models of inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Colocasia esculenta (CE) (L.) Schott is an annual herbaceous tropical plant from the family of Araceae which has been traditionally used for the healing of various ailments such as asthma, arthritis, internal hemorrhage, diarrhea, and neurological disorders. The plant is reported to have potential anti-microbial, anti-fungal, antimetastatic, anti-hepatotoxic, and anti-lipid peroxidative activities.

AIM OF THE STUDY

The present study is designed to explore the potential anti-inflammatory property of Colocasia esculenta methanolic root extract (CEMRE) on carrageenan-induced rat paw edema and lipopolysaccharide (LPS) stimulated RAW264.7 cells.

MATERIALS AND METHODS

Carrageenan-induced rat paw edema model was used to investigate the in vivo anti-inflammatory action of CEMRE. Adult male Wistar rats (180-220 g; n = 6) were pre-treated with CEMRE (100, 200, and 400 mg/kg BW) orally before 1 h of injection of 1% carrageenan. Indomethacin (10 mg/kg BW) was given orally as the standard drug. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), nitric oxide (NO), prostaglandinE2 (PGE2), and cytokines levels were measured. Liquid chromatography-mass spectrometry (LC-MS) was done to identify the phytoconstituents present in CEMRE. The inhibitory activity of CEMRE was investigated against cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in in vitro assessment of LPS-stimulated RAW264.7 cells. The RAW 264.7 cells were pre-treated with Indomethacin (5 μM and 10 μM) and CEMRE (17 μg/ml and 34 μg/ml) followed by induction of LPS (1 μg/ml) for 24 h. Docking analyses were also performed to explore the interaction of important phytoconstituents (Sinapic acid, Acetylsalicylic acid, L-fucose, Salicylic acid, Quinic acid, Zingerone, and Gingerol) of CEMRE with COX-2 and iNOS.

RESULTS

Pre-treatment with CEMRE (400 mg/kg) could inhibit the paw inflammation significantly which was elevated due to carrageenan induction. The inhibition is comparable to that of the standard drug Indomethacin. The concentration of serum AST, ALT, ALP, NO, PGE2 and cytokines were also considerably lowered in the CEMRE-treated group as compared to the carrageenan-induced group. CEMRE (34 μg/ml) inhibited the LPS-stimulated relative expression of mRNA of COX-2 and iNOS and significantly reduced the expression of nitric oxide and prostaglandin E2. Docking analyses revealed promising interaction with low binding energies between Sinapic acid with both the target proteins COX-2 and iNOS.

CONCLUSION

Collectively, our results suggested that CEMRE exhibited effective anti-inflammatory actions on carrageenan-induced rat paw edema and LPS-treated RAW 264.7 cells by reducing the in vivo paw edema inhibition, inhibiting the serum NO, PGE2, cytokines and also reduced the in vitro production of NO, PGE2 along with expressions of mRNA COX-2 and iNOS. Molecular docking demonstrated good binding affinities among the target proteins and ligand Sinapic acid. Thus the bioactive compound from CE need to be isolated and purified.

Pulegone and Eugenol Oral Supplementation in Laboratory Animals: Results from Acute and Chronic Studies

Essential oils are natural compounds used by humans for scientific purposes due to their wide range of properties. Eugenol is mostly present in clove oil, while pulegone is the main constituent of pennyroyal oil. To guarantee the safe use of eugenol and pulegone for both humans and animals, this study addressed, for the first time, the effects of these compounds, at low doses (chronic toxicity) and high doses (acute toxicity), in laboratory animals. Thirty-five FVB/n female mice were randomly assigned to seven groups (n = 5): group I (control, non-additive diet); group II (2.6 mg of eugenol + 2.6 mg of pulegone); group III (5.2 mg of eugenol + 5.2 mg of pulegone); group IV (7.8 mg of eugenol + 7.8 mg of pulegone); group V (7.8 mg of eugenol); group VI (7.8 mg of pulegone); and group VII (1000 mg of eugenol + 1000 mg of pulegone). The compounds were administered in the food. Groups I to VI were integrated into the chronic toxicity study, lasting 28 days, and group VII was used in the acute toxicity study, lasting 7 days. Animals were monitored to assess their general welfare. Water and food intake, as well as body weight, were recorded. On the 29th day, all animals were euthanized by an overdose of ketamine and xylazine, and a complete necropsy was performed. Blood samples were collected directly from the heart for microhematocrit and serum analysis, as well as for comet assay. Organs were collected, weighed, and fixed in formaldehyde for further histological analysis and enzymatic assay. Eugenol and pulegone induced behavioral changes in the animals, namely in the posture, hair appearance and grooming, and in mental status. These compounds also caused a decrease in the animals’ body weight, as well as in the food and water consumption. A mortality rate of 20% was registered in the acute toxicity group. Both compounds modulated the serum levels of triglycerides and alanine aminotransferase. Eugenol and pulegone induced genetic damage in all animals. Eugenol increased the activity of the CAT enzyme. Both compounds increased the GR enzyme at the highest dose. Moreover, pulegone administered as a single compound increased the activity of the GST enzyme. Histopathological analysis revealed inflammatory infiltrates in the lungs of groups II, III, and IV. The results suggest that eugenol and pulegone may exert beneficial or harmful effects, depending on the dose, and if applied alone or in combination.

Apoptotic Inducement of Neuronal Cells by Aluminium Chloride and the Neuroprotective Effect of Eugenol in Wistar Rats

Aluminium is known to accelerate oxidative stress, amyloid beta (Aβ) deposition, and plaque formation in the brain of rats. Objective. The present study is aimed at studying the neuroprotective effects of eugenol following aluminium-induced neurotoxicity on caspase-3, apoptotic proteins (Bcl-2 and Bax), and oxidative stress markers in Wistar rats such as superoxide dismutase (SOD), glutathione peroxidase (GPx), nitric oxide (NO), and assay oxidative stress to mitochondrial DNA (mtDNA) by measuring the levels of 8-hydroxy-2-deoxyguanosine (8-OHdG). Materials and methods. Twenty (20) adult Wistar rats were randomly divided into four (4) groups with five animals in each group. Route of administration was oral throughout the duration of this study and this study lasted for 21 days. Rats were sacrificed 24 hours after administration of the last dose (i.e., day 22) with 0.8 mg/kg ketamine as an anaesthetic agent. Results. Exposure to AlCl₃ resulted in a significant (p < 0.01) elevation in the levels of nitric oxide and 8-hydroxy-2-deoxyguanosine (8-OHdG), enhanced the activity of caspase-3, increased the level of proapoptotic protein Bax and reduced the levels of antiapoptotic protein Bcl-2, and significantly (p < 0.01) reduced the levels of SOD and GPx. However, treatment with eugenol resulted in a significant reduction (p < 0.01) in the levels of nitric oxide (NO) and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels, inhibited the activity of caspase-3, increased levels of Bcl-2 and significantly (p < 0.05) reduced levels of Bax protein, respectively, and also significantly (p < 0.05) increased the levels of SOD and GPx. Our results would hereby suggest that eugenol would provide a therapeutic value against aluminium-induced oxidative stress as related to antioxidant and antiapoptotic activities.