Isolation and Characterisation of Docosanoic Acid, Quercetin and Vitexin from Dennettia tripetala Bak. f. Root and Stem Bark and their In-vivo Anti-inflammatory and Analgesic Activities

Abstract

Dennettia tripetala Baker f. (Annonaceae) is widely used in African traditional medicine for managing diabetes, inflammation, pain, and other ailments due to its diverse phytochemical composition. 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 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. Ethical approval was obtained from the University of Uyo Health Research Ethics Committee for animal studies. 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. Isolated compounds, including quercetin, vitexin, and docosanoic - nonacosyl ester acid were carried out using spectroscopic methods. These findings validate the traditional use of D. tripetala and highlight its potential as a source of natural therapeutic agents.