Evaluation of Viola canescens Wall Ex. Roxb. for anti-asthmatic and anti-tussive activity and isolation of bioactive compound

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Folklorically, Viola canescens (VC) is used for the treatment of respiratory disorders, such as cough and asthma. The current study aimed to evaluate VC for anti-asthmatic and anti-tussive activities and isolate the bioactive compound. The plant was collected, extracted, and fractionated, with the isolation of compounds via column chromatography. Solvent extracts of VC were evaluated for anti-asthmatic and anti-tussive activities in animal models. The purified compound obtained from ethyl acetate fraction (EF) via column chromatography was identified by Mass and ¹H-NMR spectroscopic techniques. The EF (at 200 mg/kg/day for 21 days) significantly increased latency to pre-convulsive dyspnea (PCD) as compared to control. Similarly, mucous viscosity of the sensitized group was reduced significantly by EF (at 200 mg/kg). In isolated guinea pig’s ileum preparation, the EF (at 25 μg/ml) exhibited maximum relaxant activity (48.83 ± 1.5% inhibition at 0.8 ml) against histamine-induced contractions (p<0.01). The citric acid-induced cough bouts in guinea pigs were significantly reduced by EF (58.13 ± 3.1% at 200 mg/kg). The EF also significantly inhibited the secretion of phenol red dye (43.02 ± 3.1% at 200 mg/kg). A flavonoid (quercetin) was isolated from the EF that may be probably responsible for anti-asthmatic and anti-tussive activities of the plant.