Studies on tracheorelaxant and anti-inflammatory activities of rhizomes of Polygonatum verticillatum

Background: The present study describes the tracheorelaxant and anti-inflammatory effects of Polygonatum verticillatum which may support its medicinal use in hyperactive airway complaints and inflammatory disorders.Methods: The tracheorelaxant activity of crude extract of the rhizomes of P. verticillatum (PR) was assessed in isolated guinea-pig tracheal tissues immersed in tissue organ bath filled with Tyrode's solution and a continuous supply of carbogen gas (95% O₂ and 5% CO₂). The contractile and relaxant responses of the tissue were measured using isometric transducers coupled with Power-Lab data acquisition system. The anti-inflammatory effect was evaluated in carrageenan-induced rat paw edema model, while the lipoxygenase inhibitory activity was performed in the in-vitro assay. Various chromatographic and spectroscopic techniques were used for the isolation and characterization of pure molecules.Results: In isolated guinea-pig tracheal preparations, PR caused complete inhibition of the high K⁺ (80 mM) and carbachol-induced contractions however, it was more potent against K⁺ than CCh, similar to verapamil. Pretreatment of the tissue with PR, displaced the Ca²⁺ concentration-response curves to the right, similar to that induced by verapamil, indicating the presence of Ca²⁺ channel blocking like activity. When tested on carrageenan-induced rat paw edema, PR demonstrated a marked reduction in edema with 65.22% protection at 200 mg/kg, similar to aspirin. In the in-vitro assay, PR showed lipoxygenase inhibitory activity (IC₅₀: 102 ± 0.19 μg/mL), similar to baicalein. Bioactivity-guided fractionation led to the isolation of 2-hydroxybenzoic acid and β-sitosterol.Conclusions: These results indicate that the plant possesses tracheorelaxant, mediated possibly through a Ca²⁺ channel blockade mechanism, and anti-inflammatory activities, which may explain the medicinal use of this plant in airway disorders and inflammation.