Acute Toxicological, Analgesic and Anti-inflammatory Effects of Methanol Extract of Laggera Aurita Linn F (Compositae) in Mice and Rats

Abstract

Background: The plant Laggera aurita is an annual or biannual plant belonging to the family Compositae that has been used for management of pain related conditions locally.  It reportedly has anti-oxidant as well as antimicrobial properties.

Objectives: To conduct LD₅₀ and phytochemical studies, evaluate the analgesic and anti-inflammatory properties of the methanol extract of L. aurita and determine possible mechanism of action.

Methodology: Analgesic and anti-inflammatory properties of the extract were investigated using acetic acid induced writhing, thermally-induced pain, and formalin induced inflammation in rats and mice. Phytochemical and acute toxicological screenings were also conducted.

Results: The LD₅₀ was found to be above 5000 mg/kg with slight changes in histological architecture observed in the kidney, liver, lungs and stomach. The extract at dose 200, 400 and 800 mg/kg significantly (p<0.05) inhibited acetic acid induced writhes in mice and increased mean reaction time in the thermal pain model, both dose dependently. The effect on thermally induced pain was blocked by naloxone, a non-specific opioid antagonist, suggesting opioid receptor involvement in analgesia. The extract also significantly (p<0.05) decreased formalin induced paw edema dose dependently.

Conclusion: These findings suggest that the methanol extract of L. aurita possesses analgesic and anti-inflammatory properties that justify its ethnomedicinal use in management of pain and inflammation.