Abstract
Allergic rhinitis (AR) is a common inflammatory condition of the nasal mucosa and it is an immunoglobulin E–mediated disease. The incidence and prevalence of AR globally have been escalating over recent years. Antihistamines, intranasal corticosteroids, decongestants, intranasal anticholinergics, intranasal cromolyn, leukotriene receptor antagonists and immunotherapy have been used in the treatment of AR. However, there is a need to search for more effective and safer remedies as many of the current treatments have reported side effects. Medicinal plants have been used traditionally to relief symptoms of AR but their efficacy and safety have not been scientifically proven. In this review, up-to-date reports of studies on the anti-allergic rhinitis of several medicinal plants and their bioactive metabolites through suppression of the immune system are compiled and critically analyzed. The plant samples were reported to suppress the productions of immunoglobulin E, cytokines and eosinophils and inhibit histamine release. The suppression of cytokines production was found to be the main mechanistic effect of the plants to give symptomatic relief. The prospect of these medicinal plants as sources of lead molecules for development of therapeutic agents to treat AR is highlighted. Several bioactive metabolites of the plants including shikonin, okicamelliaside, warifteine, methylwarifteine, luteolin-7-O-rutinoside, tussilagone, petasin, and mangiferin have been identified as potential candidates for development into anti-allergic rhinitis agents. The data collection was mainly from English language articles published in journals, or studies from EBSCOHOST, Medline and Ovid, Scopus, Springer, and Google Scholar databases from the year 1985–2020. The terms or keywords used to find relevant studies were allergic rhinitis OR pollinosis OR hay fever, AND medicinal plant OR single plant OR single herb OR phytotherapy. This comprehensive review serves as a useful resource for medicinal plants with anti-allergic rhinitis potential, understanding the underlying mechanisms of action and for future exploration to find natural product candidates in the development of novel anti-allergic rhinitis agents.
Highlights
Allergic rhinitis (AR) is one of the common allergic diseases affecting 30% of the world population (Tohidinik et al, 2019)
There’s a significant decrease at p < 0.001, p < 0.01, p < 0.05 in IL5, related orphan receptor gamma t (RORc), IL-13 levels respectively compared with the OVA group when 200 mg/kg/ml of P. nigrum was given to the subject
Current conventional treatment administers antihistamine drugs as first-line therapy. Other mechanistic effects such as suppression of immunoglobulin E (IgE), inhibition of cytokines production and suppression of eosinophil production have been used as targets in efforts to search for bioactive principles from medicinal plants with strong anti-allergic rhinitis activity
Summary
Allergic rhinitis (AR) is one of the common allergic diseases affecting 30% of the world population (Tohidinik et al, 2019). The search for new therapeutic agents from medicinal plants to treat AR is definitely needed especially plants which have shown positive outcomes in exerting anti-allergic properties, toward AR animal models Medicinal plants and their bioactive metabolites possess different mechanisms of action in combating the mediators or immune system involved in AR inflammatory cascades or allergic reaction pathways. Some of these phytochemicals have anti-allergic properties as well as antiinflammatory properties which may be useful to treat different types of allergic diseases and symptoms. AR is one of the types of allergy that manifest an abnormal regulation of the immune system
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