Citation: Kitamura, Y.; Nishi, K.; Ishida, M.; Nishimoto, S.; Sugahara, T. Anti-Allergic Effect of Aqueous Extract of Coriander (Coriandrum sativum L.) Leaf in RBL-2H3 Cells and Cedar Pollinosis Model Mice. Nutraceuticals 2022, 2, 170–180. https://doi.org/10.3390/ nutraceuticals2030013 Academic Editors: Ivan Cruz- Chamorro and Luisa Tesoriere Received: 22 June 2022 Accepted: 22 July 2022 Published: 26 July 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Anti-Allergic Effect of Aqueous Extract of Coriander (Coriandrum sativum L.) Leaf in RBL-2H3 Cells and Cedar Pollinosis Model Mice Yurika Kitamura 1 , Kosuke Nishi 1,2 , Momoko Ishida 1 , Sogo Nishimoto 3 and Takuya Sugahara 1,2, * 1 Department of Bioscience, Graduate School of Agriculture, Ehime University, Matsuyama 790-8566, Japan; e652005y@mails.cc.ehime-u.ac.jp (Y.K.); nishi.kosuke.mx@ehime-u.ac.jp (K.N.); ishida.momoko.vb@ehime-u.ac.jp (M.I.) 2 Food and Health Sciences Research Center, Ehime University, Matsuyama 790-8566, Japan 3 Department of Food Science, Faculty of Bioresources and Environmental Sciences, Ishikawa Prefectural University, Nonoichi 921-8836, Japan; niss@ishikawa-pu.ac.jp * Correspondence: mars95@agr.ehime-u.ac.jp; Tel.: +81-89-946-9863 Abstract: Coriander (Coriandrum sativum L.) is classified in the Apiaceae family and used as an herb. Coriander leaf has been reported to possess various health functions. Here, we report the anti-allergic effect of aqueous coriander leaf extract (ACLE). ACLE with 1.0 mg/mL or higher concentration significantly inhibited degranulation of RBL-2H3 cells in a concentration-dependent manner with no cytotoxicity. ACLE suppressed the increase in the intracellular Ca 2+ concentration in response to antigen-specific stimulation. Immunoblot analysis demonstrated that ACLE significantly downregu- lates phosphorylation of phosphatidylinositol 3-kinase and tends to downregulate phosphorylation of Syk kinase in the signaling pathways activated by antigen-mediated stimulation. Oral administration of ACLE did not alter the sneezing frequency of pollinosis model mice stimulated with cedar pollen, but significantly reduced the serum IgE level. Our data show anti-allergic effects of coriander leaf in both cultured cells and pollinosis mice. These results suggest that coriander leaf has the potential to be a functional foodstuff with anti-allergy effects. Keywords: anti-allergy; Coriandrum sativum L.; cedar pollen; degranulation; RBL-2H3 cell; coriander leaf 1. Introduction An allergy means to immunize excessively against antigens invading from the outside of the body. Allergy falls into four types, among which type I allergy, including allergic rhinitis, asthma, atopic dermatitis, and hay fever, is increasing in the number of patients in recent years worldwide. The number of patients with pollinosis is approximately 30% of the population and is still increasing in Japan [1,2]. Type I allergy, also called immedi- ate hypersensitivity or anaphylactoid type, is attributed to immunoglobulin E (IgE) [3]. Antigen-specific IgE antibodies are secreted by plasma cells and bind to FcεRI receptor on mast cells. Upon crosslinking of antigens to IgE antibody bound on FcεRI, various chemical mediators contained in granules are released from the cells. This phenomenon is called degranulation, and the secreted chemical mediators cause smooth muscle contraction, hypervascular permeability, hyperactivity, etc. Suppressing degranulation can therefore be an effective strategy for relieving allergy symptoms, and the research on the substance that alleviates allergic symptoms is considered crucially important. Coriander (Coriandrum sativum L.), an aromatic herb commonly used for cooking in southeast Asia thanks to its unique aroma and flavor, belongs to the Apiaceae family. Coriander is well known to possess several biological activities [4–8]. For example, an- timicrobial activities of C. sativum essential oil have been well reported [9–11]. C. sativum seeds exhibit antidiabetic effects in streptozotocin-induced diabetic mice [12,13], in rats fed Nutraceuticals 2022, 2, 170–180. https://doi.org/10.3390/nutraceuticals2030013 https://www.mdpi.com/journal/nutraceuticals