Anti-nociceptive and anti-inflammatory effects of hydroalcoholic extract and essential oil of Pinus eldarica in animal models

Abstract

Objective: Several species of Pinus have shown anti-nociceptive and anti-inflammatory properties. This study was aimed to evaluate anti-nociceptive and anti-inflammatory effects of hydroalcoholic extract of bark and essential oil of leaves of P. eldarica in animal models.

Materials and methods: Hydroalcoholic extract of bark and essential oil of leaves of P. eldarica were prepared and phenolic content and essential oil composition were analyzed using Folin-Ciocalteu method and GC/MS, respectively. Anti-nociceptive effect was assessed using acetic acid, formalin and hot plate tests in male Swiss mice (25-30 g) and for evaluation of anti-inflammatory activity, carrageenan test in male Wistar rats (180-200 g) and croton oil-induced ear edema in male mice, were used. Involvement of opioid, α2-adrenergic, 5-HT3 receptors and adenosine triphosphate (ATP)-dependent K+ channels in pain relief was tested using naloxone, ondansetron, yohimbine and glibenclamide.

Results: The total phenolic content of the extract in terms of gallic acid equivalent was 404.9±7.7 mg/g of the extract powder. P. eldarica hydroalcoholic extract (200 and 400 mg/kg) and essential oil (100 and 200 µl/kg) significantly (all, p<0.001) decreased pain behavior in acetic acid and formalin tests but not in hot plate test. The extract and essential oil suppressed edema in carrageenan and croton tests. Glibenclamide partially reversed the anti-nociceptive effect of hydroalcoholic extract while the other antagonists were ineffective.

Conclusion: Hydroalcoholic extract of bark and essential oil of leaves of P. eldarica significantly decreased acute and chronic pain as well as inflammation. ATP-dependent K+ channels mediate a part of the observed anti-nociceptive effect.

Keywords: Analgesic; Anti-inflammation; Herbal medicine; Pinus eldarica.

Figure 1

Effect of P. eldarica bark hydroalcoholic extract in acetic acid test in mice (n=6). Vehicle (10 ml/kg tween 80 0.5% in saline), hydroalcoholic extract (100, 200 and 400 mg/kg) and indomethacin (10 mg/kg) were injected i.p. 30 min before acetic acid injection (10 ml/kg, i.p.) and after 10 min, the number of abdominal contractions was counted in a 10 min interval. *p<0.05; **p<0.01 and ***p<0.001 compared with the control

Figure 2

Effect of P. eldarica leaves essential oil in acetic acid test in mice (n=6). Vehicle (10 ml/kg tween 80 0.5% in saline), essential oil (50, 100 and 200 µl/kg) and indomethacin (10 mg/kg) were injected i.p. 30 min before acetic acid injection (10 ml/kg, i.p.) and after 10 min, the number of abdominal contractions was counted in a 10 min interval. ***p<0.001 compared with the control

Figure 3

Effect of P. eldarica bark hydroalcoholic extract in formalin test in mice (n=6). Vehicle (10 ml/kg tween 80 0.5% in saline), hydroalcoholic extract (100, 200 and 400 mg/kg) and indomethacin (10 mg/kg) were injected i.p. 30 min before subcutaneous injection of formalin (20 µl, 2.5% v/v) into the right hind paw of animals. Licking time was measured 0-5 and 20-40 min after formalin injection and respectively considered as acute and chronic phases. ***p<0.001 compared with the control

Figure 4

Effect of P. eldarica leaves essential oil in formalin test in mice (n=6). Vehicle (10 ml/kg tween 80 0.5% in saline), essential oil (50, 100 and 200 µl/kg) and indomethacin (10 mg/kg) were injected i.p. 30 min before subcutaneous injection of formalin (20 µl, 2.5% v/v) into the right hind paw of animals. Licking time was measured 0-5 and 20-40 min after formalin injection and respectively considered as acute and chronic phases. **p<0.01 and ***p<0.001 compared with the control

Figure 5

Effect of different antagonists on antinociceptive effect of P. eldarica hydroalcoholic extract. Four groups of mice (n=6) were pretreated with naloxone (5 mg/kg), ondansetron (0.5 mg/kg), yohimbine (5 mg/kg) and glibenclamide (10 mg/kg) and one group received vehicle (10 ml/kg tween 80 0.5% in saline). Thirty minutes later, the hydroalcoholic extract (400 mg/kg, i.p.) was administered to all animals and after 30 min, acetic acid (10 ml/kg, i.p.) was injected. The control group received only acetic acid. The number of abdominal contractions was counted in a 10-min period started 10 min after acetic acid injection. ***p<0.001 compared with the control. #p<0.05 compared with the hydroalcoholic extract group

Figure 6

Effect of different antagonists on antinociceptive effect of P. eldarica essential oil. Four groups of mice (n=6) were pretreated with naloxone (5 mg/kg), ondansetron (0.5 mg/kg), yohimbine (5 mg/kg) and glibenclamide (10 mg/kg) and one group received vehicle (10 ml/kg tween 80 0.5% in saline). Thirty minutes later, the essential oil (200 µl/kg, i.p.) was administered to all animals and after 30 min, acetic acid (10 ml/kg, i.p.) was injected. The control group received only acetic acid. The number of abdominal contractions was counted in a 10-min period started 10 min after acetic acid injection. ***p<0.001 compared with the control