Leonurus japonicus Houtt. extract containing isoquercitrin reduces airway inflammation in mice with allergic asthma

Leonurus japonicus Houtt. (Lamiaceae) has traditionally been used to treat respiratory disorders, including cough and dyspnea. The aim of this study was to investigate the therapeutic potential of a standardized hydroalcoholic extract from the aerial parts of L. japonicus in an in vivo model of allergic asthma.

Balb/c mice were sensitized and challenged with ovalbumin (OVA) and then treated intraperitoneally with L. japonicus (at doses of 100, 200, or 400 mg/kg), dexamethasone (at a dose of 2 mg/kg), or saline for seven consecutive days during intranasal OVA challenges. Bronchial hyperresponsiveness, lung cytokine levels (IL-4, IL-5, IL-10, and IFN-γ), inflammatory cells in bronchoalveolar lavage fluid (BAL), lung inflammation, and mucus production were evaluated. The chemical profile of the extract was determined by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS).

Leonurus japonicus significantly reduced bronchial hyperresponsiveness, eosinophil infiltration, peribronchial inflammation and mucus secretion at all tested doses. The 200 mg/kg dose reduced IL-4 and IL-10 levels, and the 400 mg/kg dose decreased IL-5 and IL-10 levels. Isoquercitrin was identified as the major constituent of the extract.

These findings support the traditional use of L. japonicus and suggest its potential as an anti-inflammatory and immunomodulatory agent for treating allergic asthma.