Anti-Allergic Effect of Oroxylin A from Oroxylum indicum Using in vivo and in vitro Experiments

Oroxylum indicum has long been used in Asian traditional medicine to prevent and treat respiratory diseases, diabetes, diarrhea and other conditions. Oroxylin A is a flavone that is present in Oroxylum indicum and in Scutellaria baicalensis. Because the root extracts of both plants have been shown to have anti-allergic effects, the authors investigated whether oroxylin A is likely to have beneficial effects on allergic asthma using female Balb/c mice and rat RBL-2H3 mast cells. Antigen-induced degranulation was measured in vitro by measuring β-hexosaminidase activity. A murine ovalbumin-induced allergic asthma model was used to test the in vivo efficacy of oroxylin A. Sensitization and challenge of ovalbumin induced allergic asthma responses, the accumulations of eosinophils and Th2 cytokine levels in bronchoalveolar lavage fluid and lung tissues. Oroxylin A administration decreased numbers of inflammatory cells, especially eosinophils, and reduced the expression and secretion of Th2 cytokines, including IL-4 and IL-13, in lung tissues and bronchoalveolar lavage fluid. Histologic studies showed oroxylin A reduced inflammatory signs and mucin production in lungs. These findings provide evidence that oroxylin A has potential use as an anti-allergic therapeutic.