Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that promotes the inflammatory response and is involved in inflammatory diseases. Vascular endothelial growth factor (VEGF) is involved in TNF-alpha-mediated diseases. Scientists from the Seoul National University investigated the inhibitory effects of myricetin on TNF-alpha-induced VEGF upregulation and found that the flavonol inhibited TNF-alpha-induced VEGF expression in cultured mouse epidermal cells by targeting mitogen-activated protein kinase 4 (MKK4) and extracellular signal-regulated kinase kinase 1 (MEK1). They concluded that myricetin may have potent chemopreventive effects against TNF-alpha-related diseases [1].
Bee pollen are traditionally used to alleviate allergic reactions and myricetin may be one of the active components. Researchers of the Universidade Federal da Paraíba, Brasil, investigated the anti-allergic effect of bee pollen extract and pure myricetin on mice with ovalbumin-induced allergy [2]. They found that treatment with bee pollen extract inhibited the paw edema, IgE and IgG production, leukocyte migration and EPO activity in lungs. The extract partially protected against anaphylactic shock. Treatment of the mice with myricetin also inhibited cell migration and IgE and IgG production. They concluded that myricetin may be one of the phytochemicals in bee pollen extract that is responsible for the anti-allergic effect.
A study by Hiermann and co-workers of the Institute of Pharmacognosy, University of Graz, Austria, investigated the anti-inflammatory effect of myricetin glucuronide, and structurally-related compounds in carrageenan-induced rat paw edema [3]. They found that myricetin glucuronide is a inhibitor of lipoxygenase 5-LOX and cyclooxygenases COX-1 and Cox-2. They also found that small changes in the molecular structure of myricetin resulted in a lower anti-inflammatory activity.
[1] MKK4 is a novel target for the inhibition of tumor necrosis factor-alpha-induced vascular endothelial growth factor expression by myricetin. Biochem Pharmacol. 2009 Feb 1;77(3):412-21.
[2] Anti-allergic effect of bee pollen phenolic extract and myricetin in ovalbumin-sensitized mice. J Ethnopharmacol. 2008 Sep 2;119(1):41-6.
[3] Anti-inflammatory activity of myricetin-3-O-beta-D-glucuronide and related compounds. Inflamm Res. 1998 Nov;47(11):421-7.
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