Anti-Asthmatic Activity of Caesalpinia pulcherrima in Guinea Pigs

Background: Asthma is a chronic inflammatory respiratory disease affecting over 300 million individuals globally, with limited treatment efficacy and significant adverse effects associated with conventional pharmacotherapy. Plant-based therapeutic agents have emerged as promising alternatives warranting systematic evaluation. Objective: This study evaluated the anti-asthmatic, antihistaminic, and bronchoprotective potential of ethanolic leaf extract of Caesalpinia pulcherrima (Caesalpiniaceae) through complementary in vitro and in vivo approaches in guinea pig models. Methods: In vitro antihistaminic activity was assessed using histamine-induced contraction in isolated guinea pig ileum preparations, with responses compared against chlorpheniramine maleate (standard control). In vivo bronchoprotective efficacy was evaluated in an acute histamine aerosol-induced bronchospasm model in guinea pigs. Test groups received vehicle (0.1% carboxymethyl cellulose), chlorpheniramine maleate (2 mg/kg), or ethanolic leaf extract (200 and 400 mg/kg, p.o.). Preconvulsive dyspnoea time (PCT) was measured at baseline, 1 hour, 4 hours, and 24 hours post-drug administration. Percentage protection was calculated and analyzed. Results: In vitro studies demonstrated dose-dependent inhibition of histamine-induced ileal contractions by the extract, achieving 74.05% inhibition at maximum histamine concentration (3.2 ml), comparable to chlorpheniramine effects. In vivo studies showed significant bronchoprotection with peak efficacy at 4 hours post-administration; the 400 mg/kg extract dose yielded 67.44% protection versus 73.73% for chlorpheniramine maleate. The 400 mg/kg extract group exhibited preconvulsive dyspnoea time of 21.50 ± 0.43 seconds at 4 hours, significantly extended compared to vehicle control (p