Phytochemical characterization and pharmacological evaluation of the aqueous bark extract of Pseudobombax simplicifolium A. Robyns: antinociceptive, anti-inflammatory, and antipyretic activities

Abstract Pseudobombax simplicifolium A. Robyns is traditionally used to treat pain, inflammation, and fever, although its chemical composition and pharmacological properties remain poorly investigated. This study characterized the aqueous bark extract of P. simplicifolium (EAPS) and evaluated its antioxidant, antinociceptive, anti-inflammatory, and antipyretic activities. HPLC-DAD analysis identified catechin and epicatechin, and the total phenolic and flavonoid contents were 335.2 ± 0.21 mg GAE/g and 116.0 ± 0.14 mg QE/g, respectively. EAPS exhibited antioxidant activity in the DPPH and ABTS assays, with IC₅₀ values of 58.1 ± 0.17 and 99.6 ± 0.15 µg/mL, respectively. In the acetic acid-induced writhing test, EAPS significantly reduced the nociceptive response in a dose-related manner, with inhibitions of 29.64, 39.43, and 62.10% at 25, 50, and 100 mg/kg, respectively ( p < 0.001). In the formalin test, EAPS significantly reduced paw-licking time at 25, 50, and 100 mg/kg in both the first phase (30.37, 47.48, and 50.50%, respectively) and the second phase (34.21, 46.74, and 55.01%, respectively; p < 0.0001). Naloxone and atropine markedly reversed the antinociceptive effect of EAPS, supporting the involvement of opioidergic and muscarinic cholinergic pathways. EAPS also significantly reduced carrageenan-induced paw edema and decreased total leukocyte and neutrophil recruitment by up to 44.8 and 44.7%, respectively ( p < 0.001). At 100 mg/kg, EAPS reduced TNF-α concentrations from 185.6 ± 12.4 to 91.3 ± 8.8 pg/mL and IL-1β concentrations from 165.3 ± 11.6 to 93.7 ± 6.1 pg/mL ( p < 0.001). In the yeast-induced pyrexia model, 50 and 100 mg/kg EAPS significantly reduced rectal temperature from 30 min onward, with the most pronounced and sustained effect observed at 100 mg/kg ( p < 0.001). Overall, these findings demonstrate that EAPS exhibits in vitro antioxidant, antinociceptive, anti-inflammatory, and antipyretic activities, supporting the traditional use of P. simplicifolium and its potential as a source of bioactive compounds.