We previously found that persimmon leaf extract contains antiallergic substances that inhibit histamine release by human basophilic cell line KU812 in response to cross-linkage of FcepsilonRI.
The purpose of this study was to identify substances in the persimmon leaf extract that are responsible for the effect and to examine their in vivo effects on the allergic mouse model.
HPLC analysis of persimmon leaf extract was done to measure its content. Inhibitory activity of persimmon leaf extract or its major constituent of flavonoids (astragalin) on the histamine release by KU812 cells was examined. To investigate the effects of these substances in vivo, models of passive cutaneous anaphylaxis and atopic dermatitis mice (NC/Nga) were used.
Persimmon leaf extract or astragalin inhibited histamine release from KU812 in response to cross-linkage of FcepsilonRI. Oral intake of both substances dose dependently inhibited passive cutaneous reactions. Moreover, oral administration of these substances to NC/Nga atopic dermatitis-model mice led to a striking suppression of the development of dermatitis, scratching behavior, and serum IgE elevation. Histologic analyses revealed that infiltration of inflammatory cells, especially degranulated mast cells, thickening of the epidermis, and prominent hyperkeratosis, were significantly reduced. Immunologic studies showed that the capacity of spleen T cells to produce both IL-4 and IL-13, but not IFN-gamma, was downregulated by means of oral intake of these substances.
This study demonstrates a novel activity of astragalin and the dramatic effect of persimmon leaf extract and astragalin on atopic dermatitis-model mice.
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