Background and aims:
Euphorbia helioscopia has multiple pharmacological activities, such as antibacterial, antiviral, antifungal,anticancerand/or antitumor, allelopathic, anti-allergic and anti-asthmatic, antioxidant, antinociceptive effect. The aim of the study was to evaluate theantinociceptive activities of
Euphorbia helioscopia extract in Balb/c mice, as well as the total flavonoids, phenolic contents, and antioxidantactivities of the extract.Methods: In this study, ۹۰ Balb/c mice were randomly designated into ۹ groups. Group ۱ received normal saline, groups ۲ to ۷ receiveddifferent doses of the E. helioscopia hydroethanolic extract (i.e., ۰.۰۵, ۰.۱, ۰.۲, ۰.۴, ۲, & ۸ mg/kg, i.p.).In addition, groups ۸ and ۹received naloxone (۱ mg/kg) and extract (۸ mg/kg) plus naloxone (۱ mg/kg), respectively (Naloxone was injected ۱۵ minutes after extractadministration). Then, pain response was evaluated for ۳۰ minutes after the injection of ۲۰ μL formalin (۱.۵%) in the plantar surface of themice foot. Further, the beta-carotene-linoleate method was used for measuring antioxidant capacity. Finally, total phenolic and flavonoidcontent were measured based on Folin-Ciocalteu colorimetric and aluminum chloride colorimetric methods, respectively.Results: Total phenol and flavonoid content were ۴۹.۴۳ ± ۱.۸ mg GAE/g dried extract and ۳۰.۱۹ ± ۱.۹۶ mg rutin/g dried extract, respectively.Our results showed that during the first ۵ minutes (the acute pain step), a significant difference (P < ۰.۰۵) was observed between the controlgroup and the group which received the E. helioscopia hydroethanolic extract (۸ mg/kg). In the next ۲۵ minutes (the chronic pain step), asignificant difference (P < ۰.۰۵) was found between the control group and the group which received ۰.۱ and ۸ 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 theextract was ۱.۶۴۱ mg/g of rutin equivalent.Conclusion: In general, this study supports the use of the E. helioscopia extract in folk medicine as the analgesic agent and calls for furtherinvestigations regarding elucidating its mechanism of action. Eventually, our findings revealed that the extract of E. helioscopia possessedeither antinociceptive or anti-oxidative activities.