Anti-allergic activity of an ethanol extract of bunching onion (Allium fistulosum), a traditional vegetable from Osaka

Abstract

Introduction: The incidences of allergic diseases such as allergic rhinitis, atopic dermatitis, asthma, and food allergies are rising in developed countries. Mast cells play critical roles in various biologic processes related to allergic diseases, including expressing the high-affinity receptor for immunoglobulin (Ig) E on their surface. The interaction of multivalent antigens with surface-bound IgE causes the secretion of granule-stored mediators, as well as the de novo synthesis of cytokines. These mediators and cytokines precede the development of allergic diseases. In Osaka Prefecture, Japan, certain locally cultivated crops have received 'Naniwa-yasai', a designation that certifies the significance of traditional vegetables in supporting Osaka's agriculture and cuisine for over a century. In this study, we investigated the anti-allergic effects of four traditional vegetables from Osaka. Methods: Vegetables were obtained from Research Institute of Environment, Agriculture and Fisheries, Osaka Prefecture. Vegetables (100g) were extracted using 60% aqueous ethanol (1litter) for 1h. After cooling and filtration, the filtrate was concentrated in vacuo and lyophilized to give an extract. Rat basophilic leukemia RBL-2H3 cells, which are used as a mast cell model, were obtained from the American Type Culture Collection (ATCC; Manassas, VA, USA). The degranulation of mast cells was determined using a β-hexosaminidase release assay. Results: The anti-allergic activity of extracts made from Tanabe radish, Moriguchi radish, bunching onion (Allium fistulosum), and mizu eggplant were examined. Various concentrations of each extract were added to RBL-2H3 mast cells prior to stimulation with the calcium ionophore A23187. β-hexosaminidase release was markedly and dose dependently decreased in mast cells following the addition of A. fistulosum, demonstrating its anti-allergic activity. None of the other vegetables had an anti-allergic effect on RBL-2H3 cells. Conclusion: An Osakan traditional vegetable, bunching onion (Allium fistulosum), exhibited anti-allergic activity, and should be explored further as a possible treatment for allergic diseases.