Pharmacological Investigation of Calotropis gigantea L. for Anti-asthmatic and Anti-inflammatory Activities
Abstract
Background: Asthma is a chronic inflammatory airway disease characterized by airflow obstruction, bronchial hyperresponsiveness, and excessive mucus production. Although current therapies improve symptom control, long-term management remains challenging, encouraging the search for plant-based alternatives. Calotropis gigantea L. (Asclepiadaceae) has been traditionally used to treat respiratory and inflammatory disorders. Aim: To evaluate the anti-asthmatic and anti-inflammatory activities of root bark extracts of C. gigantea and identify the principal bioactive constituent through bioactivity-guided fractionation. Methods: Petroleum ether, chloroform, ethanolic, and aqueous root bark extracts (100 and 150 mg/kg, i.p.) were evaluated using milk-induced leukocytosis and eosinophilia, egg albumin-induced mast cell degranulation, and carrageenan-induced paw oedema models. The most active ethanolic extract was fractionated by silica gel column chromatography into six fractions (F1–F6). Fractions were screened using the clonidine-induced catalepsy model in mice with chlorpheniramine maleate as the reference. The most active fraction was purified, and the isolated compound was characterized by UV, IR, MS, and 1H/13C NMR spectroscopy. Results: The ethanolic extract exhibited the strongest anti-asthmatic and anti-inflammatory activity, significantly reducing leukocytosis, eosinophilia, mast cell degranulation, and paw oedema. Fraction F4 showed the highest activity, producing inhibition of clonidine-induced catalepsy comparable to chlorpheniramine. Phytochemical characterization identified stigmasterol as the major bioactive constituent. Conclusion: C. gigantea root bark possesses significant anti-asthmatic and anti-inflammatory properties, validating its traditional use. The pharmacological effects are primarily attributed to stigmasterol, highlighting its potential as a natural therapeutic candidate for asthma and inflammatory disorders. Major Finding: Bioactivity-guided fractionation identified Fraction F4 as the most active fraction, and stigmasterol was isolated as the principal compound responsible for the anti-asthmatic and anti-inflammatory effects.