Entinociceptive effects of Euphorbia helioscopia extract on Balb/c mice

Euphorbia helioscopia has multiple pharmacological activities, such as antibacterial, antiviral, antifungal,anticancer and/or antitumor, allelopathic, anti-allergic and anti-asthmatic, antioxidant, antinociceptive effect. The aim of the study was to evaluate the antinociceptive activities of Euphorbia helioscopia extract in Balb/c mice, as well as the total flavonoids, phenolic contents, and antioxidant activities of the extract.

In this study, 90 Balb/c mice were randomly designated into 9 groups. Group 1 received normal saline, groups 2 to 7 received different doses of the E. helioscopia hydroethanolic extract (i.e., 0.05, 0.1, 0.2, 0.4, 2, & 8 mg/kg, i.p.).In addition, groups 8 and 9 received naloxone (1 mg/kg) and extract (8 mg/kg) plus naloxone (1 mg/kg), respectively (Naloxone was injected 15 minutes after extract administration). Then, pain response was evaluated for 30 minutes after the injection of 20 µL formalin (1.5%) in the plantar surface of the mice foot. Further, the beta-carotene-linoleate method was used for measuring antioxidant capacity. Finally, total phenolic and flavonoid content were measured based on Folin-Ciocalteu colorimetric and aluminum chloride colorimetric methods, respectively.

Total phenol and flavonoid content were 49.43 ± 1.8 mg GAE/g dried extract and 30.19 ± 1.96 mg rutin/g dried extract, respectively. Our results showed that during the first 5 minutes (the acute pain step), a significant difference (P<0.05) was observed between the control group and the group which received the E. helioscopia hydroethanolic extract (8 mg/kg). In the next 25 minutes (the chronic pain step), a significant difference (P<0.05) was found between the control group and the group which received 0.1 and 8 mg/kg doses of the extract. Based on the results, naloxone was unable to reverse the antinociceptive effects of the extract and the maximum antioxidant activity of the extract was 1.641 mg/g of rutin equivalent.

In general, this study supports the use of the E. helioscopia extract in folk medicine as the analgesic agent and calls for further investigations regarding elucidating its mechanism of action. Eventually, our findings revealed that the extract of E. helioscopia possessed either antinociceptive or anti-oxidative activities.