Evaluation of In Vivo Analgesic Properties of Stigmasterol Isolated from Sida ovata Forssk Root Extract

Pain is a major global health concern, particularly in developing countries where access to conventional analgesics is often limited. This limitation has contributed to the widespread traditional use of medicinal plants such as Sida ovata Forssk. (Malvaceae) for pain management. While S. ovata is commonly used in Ethiopian folk medicine for analgesic purposes, its phytochemical constituents and analgesic properties have not been investigated. The present study aimed to evaluate the analgesic activity of the roots of S. ovata andto isolate and characterize the bioactive compound(s) responsible for its pain-relieving effects. Root extracts were prepared using 80% methanol, followed by solubility-based fractionation and purification through silica gel column chromatography. This process led to the isolation of a sterol, which was identified as stigmasterol using 1H-NMR, 13C-NMR, and DEPT-135 spectroscopic techniques. The analgesic activity of the crude hydroalcoholic extract, its solvent fractions, and the isolated stigmasterol was assessed using the acetic acid-induced writhing test in mice. The results demonstrated significant, dose-dependent inhibition of writhing responses. The 80% methanol root extract exhibited inhibition rates of 56.84%, 63.16%, and 72.63% at doses of 100, 200, and 400 mg/kg, respectively. Among the solvent fractions, the methanol fraction showed the highest analgesic activity, from which stigmasterol was isolated as the major bioactive component. Remarkably, stigmasterol displayed potent analgesic effects at lower doses, with inhibition rates of 64.57%, 70.88%, and 73.33% at 25, 50, and 100 mg/kg, respectively. These findings provide scientific validation for the traditional use of S. ovata roots in pain management and identify stigmasterol as a key active compound.