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. Keywords: Laggera aurita, anti-inflammatory, analgesic, acute toxicity

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