Examining the Isolation of Bioactive Compounds, Antinociceptive, and Anti-inflammatory Activities of Strychnos Spinosa Lam. (Loganiaceae) Stembark Extract

Strychnos spinosa is a tree whose parts are popularly used in Southeast Nigeria to treat pains, infections, inflammations, hypertension, malaria fever, and ulcers. This study isolates the bioactive compounds in methanol stembark extract and evaluates the antinociceptive and anti-inflammatory potentials of S. spinosa. 

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. 

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. 

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.