Therapeutic Efficacy of Flavonoids in Allergies: A Systematic Review of Randomized Controlled Trials

Abstract

Objective. To assess the clinical efficacy of flavonoid supplements on allergic diseases. Design. Systematic review. Data Sources. MEDLINE/PubMed, Scopus, Web of Science, and Embase databases were searched from inception to September 2021. Eligibility Criteria for Selecting Studies. Eligible study designs were randomized controlled trials that investigated the effect of flavonoids applied to allergic diseases. Results. This review included 15 randomized controlled trials, including allergic rhinitis/cedar pollinosis ( n = 10 ), asthma ( n = 3 ), and atopic dermatitis ( n = 2 ). A total of 990 participants aged 6 to 69 years were included in these studies. Globally, 12 studies (80%) revealed some benefits of flavonoids (isolate or combined with other compounds) in allergic patients, while three studies (20%) reported no statistically significant impact on symptom scores and/or lung function. No severe adverse events related to treatment were reported. According to the GRADE system, the outcomes evaluated were of low to moderate quality of evidence. Conclusions. Overall, this review suggests that the administration of flavonoids may provide a viable strategy for mitigating allergic symptoms. Future trials with high methodological quality are needed to establish definitive conclusions. This trial is registered with PROSPERO registration no. CRD42021237403.

Allergic Inflammation: Effect of Propolis and Its Flavonoids

“…Propolis showed inhibitory effects on myeloperoxidase activity, ornithine decarboxylase, tyrosine-protein-kinase, NADPH-oxidase, and hyaluronidase from guinea pig mast cells. This anti-inflammatory activity can be explained by the presence of active flavonoids and cinnamic acid derivatives such as acacetin, quercetin, naringenin and CAPE and CA [ 69 , 70 , 71 , 105 , 106 , 107 , 108 , 109 , 110 ]. Conversely, Ahangari et al [ 57 ] demonstrated that the ethanolic extract of propolis (3, 10, 30, and 100 µg/mL) did not show significant effects on the histamine release induced by ionophore A23187 and ovalbumin.…”

“…These results indicate that CAPE is effective in the systemic anaphylaxis model, indicating that CAPE-mediated anti-allergic effects may be the result of its protective effects against IgE-mediated allergy [ 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 100 ]. CAPE effectively reduced the infiltration of monocytes and neutrophils and inhibited the activation of TLR by interrupting interaction of the ligand (LPS) with the receptor complex (TLR4/MD2) [ 108 , 109 ]. CAPE successfully affects several cellular oxidative processes: (1) inhibits myeloperoxidase activity (MPO) by PMN infiltration; (2) reduces respiratory burst of human PMN; and (3) forms oxide-base in epidermal DNA isolated in mice treated in vivo [ 109 ].…”

“…CAPE effectively reduced the infiltration of monocytes and neutrophils and inhibited the activation of TLR by interrupting interaction of the ligand (LPS) with the receptor complex (TLR4/MD2) [ 108 , 109 ]. CAPE successfully affects several cellular oxidative processes: (1) inhibits myeloperoxidase activity (MPO) by PMN infiltration; (2) reduces respiratory burst of human PMN; and (3) forms oxide-base in epidermal DNA isolated in mice treated in vivo [ 109 ]. Inhibition of LOX and leukotriene production in peritoneal macrophages was also successfully inhibited by CAPE and CA.…”

“…EEP-treated skin samples exhibited slight hyperkeratosis, absence of parakeratosis, mild acanthosis, absence of elongated rete ridges, and mild dermal inflammation. In addition, flavonoids present in propolis can inhibit the degranulation of mast cells basophils, reduce histamine, tryptase, IL-4, IL-5 IL-6, IL-8, IL13 and other inflammatory mediators released from cultured mast cells and macrophages [ 18 , 69 , 70 , 71 , 100 , 109 , 110 , 111 , 112 , 113 ]. Several flavonoids were found to inhibit the release of histamine, leukotrienes, prostaglandin D2, and granulocyte macrophage-colony stimulating factor (GM-CSF) from mast cells in a concentration-dependent manner [ 70 , 97 ].…”

Clinical Associations of Bitter Taste Perception and Bitter Taste Receptor Variants and the Potential for Personalized Healthcare

“…129 Future clinical research studies may want to consider comparing differences in the efficacy of bitter among patients with varying TAS2R SNPs, as inconsistencies and heterogeneity in therapeutic efficacy of flavonoids for asthma have been noted across several studies. 130 Similarly, MP-AzeFlu (Dymista ® ; spray of azelastine/fluticasone propionate) is a drug used for allergic rhinitis and its dilatory effects on pre-contracted airways are thought to be enhanced by T2R activation rather than through blocking histamine receptors. 131 Investigations can be conducted on the specific receptor isoforms that MP-AzeFlu activates and whether its efficacy is affected by T2R polymorphisms of the host.…”