Impact of Seasonal Changes on the Phytochemical Composition, Analgesic and Anti-Inflammatory Properties of Ethanol Extract from the Aerial Parts of Waltheria indica L. in Rodents

Background and Objective: Seasonal changes significantly influence the phytochemical compositions and therapeutic potentials of medicinal plants. This study seeks to examine the influence of seasonal changes on the phytochemical composition and the analgesic and anti-inflammatory effects of ethanol extracts from the aerial parts of Waltheria indica L. in rodents. Materials and Methods: Samples collected during the wet and dry seasons were subjected to standard extraction and spectrophotometric methods to quantify their phytochemical levels. The extract’s analgesic and anti-inflammatory properties were evaluated using established experimental methods. Results: Phytochemical screening of the ethanol extract from the aerial parts confirmed the presence of alkaloids, flavonoids, tannins, saponins and terpenes. The winter extract demonstrated significant (p<0.05) analgesic and anti-inflammatory effects, as evidenced by the inhibition of acetic acid-induced writhing in mice and a reduction in carrageenan-induced paw edema in rats, compared to controls. At doses of 200 and 400 mg/kg, the summer extract significantly (p<0.05) reduced acetic acid-induced writhing by 48.05 and 57.41%, respectively, against control values. Both extracts reduced carrageenan-induced rat paw edema, with the summer extract showing a 64.52% reduction and the winter extract achieving a 79.60% reduction at a 400 mg/kg dose, 4 hrs post-carrageenan injection. Comparative analysis revealed that the winter extract produced a higher inhibition of carrageenan-induced paw edema than the summer extract (79.60 vs 64.52%). Conclusion: The ethanol extract of W. indicaaerial parts collected in winter exhibited superior analgesic and anti-inflammatory activity, suggesting that winter may be the optimal season for harvesting W. indica for medicinal purposes.