Investigation of the antitussive activity of Phyllanthus amarus extract on in vitro and in vivo models

Background Cough caused by Streptococcus pyogenes is commonly associated with throat infections and inflammation, often leading to discomfort and complications. Herbal medicines such as Phyllanthus amarus have been traditionally used for treating respiratory symptoms, but scientific validation of their antitussive potential remains limited. ObjectiveThis study aimed to investigate the antitussive activity of Phyllanthus amarus extract (PAE), using both in vitro and in vivo models.Materials and methodsAntibacterial activity against S. pyogenes was evaluated by agar well diffusion and broth microdilution methods. Anti-inflammatory effects were assessed via nitric oxide (NO) production inhibition in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Cytotoxicity was tested using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The in vivo antitussive effect was evaluated in an ammonia-induced cough model in mice by measuring latency to first cough and cough frequency.Results and conclusionPAE exhibited strong antibacterial activity against S. pyogenes, with an inhibition zone of 16.8 mm and a minimum inhibitory concentration (MIC) value of 0.5 mg/mL. The extract significantly inhibited NO production in a dose-dependent manner with IC₅₀ value of 217.3 µg/mL without inducing cytotoxicity. Moreover, PAE at 1.0 g/kg prolonged cough latency and reduced cough frequency compared to the control in vivo model. As the result, P. amarus extract demonstrates promising antitussive activity, potentially mediated through its antibacterial and anti-inflammatory activities. These findings support its potential use as a natural remedy for cough management.