Antioxidant, Anti‑inflammatory, Analgesic Properties, and Phytochemical Characterization of Stem Bark Extract and Fractions of Anthocleista nobilis

Background: Anthocleista nobilis (Loganiaceae) is used by Mbano people of Imo State, Nigeria, for the treatment of various ailments. Objective: The aim of this study is to evaluate the antioxidant, anti‑inflammatory, and analgesic properties of the methanol extract, fractions, and subfractions of A. nobilis. Materials and Methods: The powdered stem bark was extracted with methanol and sequentially fractionated into n‑hexane, ethyl acetate, and butanol fractions. The constituents of the fractions were analyzed using high‑pressure liquid chromatography (HPLC), and the components were identified by dereplication. Antioxidant potential of the extracts and fractions was investigated using 2,2‑diphenyl‑1‑picrylhydrazyl free‑radical scavenging method. Anti‑inflammatory and analgesic activities of the extract and fractions were also investigated using xylene‑induced inflammation and acetic acid‑induced writhing models, respectively. Results: A total of five compounds isovitexin (R_t = 18.77 min), isovitexin‑2’’‑O‑xyl (R_t = 19.68 min), p‑Hydroxybenzoic acid (Rt = 11.88 min), Sarasinoside L (R_t = 19.64 min), isovitexin (R_t = 18.77), and apigenin monoglycoside (R_t = 19.64 min) were identified by HPLC analysis and dereplication. The ethyl acetate fraction and subfraction elicited the best anti‑inflammatory activity. The ethyl acetate subfraction also inhibited acetic acid‑induced pain by 79% and 85.0% at the doses of 100 mg/kg and 200 mg/kg, respectively, which was better than 71.1% and 81.3% observed for diclofenac at similar doses. Conclusion: A. nobilis could be a potential source of anti‑inflammatory and analgesic lead compounds.