Effect of Hypericum perforatum aqueous extract on formalin induced pain and inflammation in mice

Introduction: Hypericum perforatum is a medical plant species containing many polyphenolic compounds, specially flavonoids and phenolic acids. A number of studies have shown that polyphenolic compounds have high antioxidant potential and anti inflammatory effects in some of the animal models (but not all the animals). Also in traditional medicine this herb has been used to decrease pain and inflammation. The aim of this study was to investigate the effect of Hypericum perforatum aqueous extract on formalin induced pain and inflammation in mice.

Material & Methods: Animals were pretreated with Hypericum perforatum aqueous extract (0.5g/kg) orally before induction of pain by intrapadly formalin (20µl, 0.5%) injection. The time of licking and biting of injected paw was measured as pain response at 5min intervals for an hour.

Results: The results have shown that formalin induces a biphasic pain response (first phase; 0–5min & second phase; 15–45min after injection) and oral administration of Hypericum perforatum aqueous extract before formalin injection, reduces the second phase of pain response significantly (p<0.05) but it didn't have significant effect on first phase (p≥0.05).

Conclusion: Our results suggest that the effect of Hypericum perforatum aqueous extract is probably because of its high antioxidant, antinociceptive and anti inflammatory properties.

Keywords: Hypericum perforatum, aqueous extract, pain, inflammatory, mice