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• Takeaki Okamoto

  Faculty of Education, Ehime University, Ehime, Japan.

• Sayaka Yokoyama

  Department of Food and Nutritional Environment, Kinjo Gakuin University, Aichi, Japan.
  Graduate School of Bioscience and Biotechnology, Chubu University, Aichi, Japan.

• Hinako Ushimaru

  Graduate School of Bioscience and Biotechnology, Chubu University, Aichi, Japan.

• Mamoru Tanaka

  Graduate School of Bioscience and Biotechnology, Chubu University, Aichi, Japan.
  Department of Food and Nutrition Sciences, College of Bioscience and Biotechnology, Chubu University, Aichi, Japan.

This study aims to investigate the antiallergic effects of Shiikuwasha (Citrus depressaHayata) leaf and peel extracts by examining the regulation of degranulation and inflammatory cytokine production from rat basophilic leukemia (RBL-2H3) cells and antigen-specific antibody production in sensitized mouse spleen lymphocytes.In vivo antiallergic activity was evaluated using the passive cutaneous anaphylaxis (PCA) reaction model. Extracts of Shiikuwasha leaves and peel were prepared using 80% methanol and dissolved in dimethylsulfoxide. The dinitrophenyl-human serum albumin-induced β-hexosaminidase levels in immunoglobulin (Ig) E-sensitized RBL-2H3 cells were assessed using enzymatic assays. Cytokine production was measured by enzyme-linked immunosorbent assay. Antibody production capacity was evaluated using lymphocytes isolated from spleens of type I allergy model mice. Lymphocytes were cultured for 72 h with Shiikuwasha extracts, and ovalbumin-specific IgE, IgG1, and IgG2a levels were measured. Shiikuwasha leaf and peel extract significantly reduced β-hexosaminidase release and suppressed interleukin-4 and tumor necrosis factor-α production from RBL-2H3 cells. Ovalbumin-specific IgE and IgG1 production decreased in Shiikuwasha extract-treated lymphocytes. These extracts also significantly suppressed the PCA reaction. Shiikuwasha leaf and peel extract reduce degranulation in RBL-2H3 cells and antibody production in spleen-derived lymphocytes and therefore exhibit antiallergic effects.