Docosanoic Acid, Quercetin, and Vitexin from Dennettia tripetala Bak. f.: Isolation, Characterization, and Evaluation of their In-vivo Anti-inflammatory and Analgesic Effects

Abstract

Among the medicinal plants that have found usefulness in ethnomedicine and attracted scientific interests is Dennettia tripetala Baker f. (Annonaceae). D. tripetala is widely used in African traditional medicine for managing diabetes, inflammation, pain, and other ailments. This study aimed to isolate and characterize bioactive compounds from the root and stem bark of D. tripetala and evaluate their anti-inflammatory and analgesic properties through in vivo models. The stem bark and root of D. tripetala were collected from Itak Ikot Akap village in Ikono Local Government Area, Akwa Ibom State, Nigeria. The plant materials were extracted using 70% aqueous methanol, and the extracts were partitioned into n-hexane, dichloromethane, ethyl acetate, and n-butanol fractions. Compounds were isolated through open-column chromatography and thin layer chromatography and characterized using ¹H NMR, ¹³C NMR, and FTIR spectroscopy. Anti-inflammatory activity was evaluated using egg albumin and xylene-induced oedema models, while analgesic activity was assessed using formalin-induced paw licking and hot plate tests, respectively. Data were analyzed using one-way ANOVA, with significance level set at p<0.05. The dichloromethane and ethyl acetate fractions exhibited the highest anti-inflammatory activity, with the root extract at 447 mg/kg significantly inhibiting egg albumin-induced oedema by 81% at 5 hours, compared to 77% for aspirin. In the xylene-induced oedema model, the root extract at 670 mg/kg achieved 76% inhibition, comparable to the standard drug. Analgesic effects were most pronounced in the formalin test, where the root extract reduced paw licking duration by 85% in the late phase. ¹H NMR, ¹³C NMR, and FTIR spectroscopy were utilized in identification of compounds. Docosanoic acid showed ester signals (C=O at 1736 cm^-¹, 174.0 ppm). Quercetin had hydroxyl signals (12.5–9.3 ppm) and a carbonyl at 175.9 ppm, while vitexin displayed glycosidic signals (3.85–3.24 ppm) and a carbonyl at 182.6 ppm, confirming their bioactive potential. These findings validate the traditional use of D. tripetala and highlight its potential as a source of natural therapeutic agents.