Background: Strychnos spinosa is a tree whose parts are popularly used in Southeast Nigeria to treat pains, infections, inflammations, hypertension, malaria fever, and ulcers. 
Objectives: This study isolates the bioactive compounds in methanol stembark extract and evaluates the antinociceptive and anti-inflammatory potentials of S. spinosa. 
Methods: Bioactive compounds were isolated using silica gel column chromatography, and their structures were elucidated using Fourier-transform infrared spectroscopy, gas chromatography/mass spectrometry, liquid chromatography/mass spectrometry, and nuclear magnetic resonance spectroscopy apparatus. The antinociceptive activity was determined using the acetic acid-induced writhing mice model, hot plate method, and tail immersion. In contrast, the anti-inflammatory activity was assessed using carrageenan-induced paw-edema in mice. 
Results: The structural elucidation of the major bioactive compounds showed that the compounds are 18-methylnonadecanoate ester, 2-pyridin-3yl-ethanimidamide, 2-ethylformanilide, and acetamide. The extract at the doses of 200, 400, and 800 mg/kg, intraperitoneal significantly decreased (P<0.05) pains in acetic acid-induced writhing in mice, hot plate, and tail immersion assays in a dose-dependent fashion. In the hot plate and tail immersion assays, the extract produced significant pain inhibition of >50% after 120 min at a 400 mg/kg dose. In contrast, the stembark extract of S. spinosa produced the highest inhibition of paw edema formation at a dose of 400 mg/kg in 6 h in the carrageenan-induced paw edema model. 
Conclusion: The results affirmed using S. spinosa stembark extract in traditional medicine to treat pain and inflammation. This was possible due to the presence of the isolated compounds.