Potential Therapeutic Actions of Flavonoids Present in Propolis That Modulate Vascular Endothelial Growth Factor Signaling to Regulate Angiogenesis.

Propolis is a plant-derived substance collected by honeybees that has a range of potential therapeutic applications. Propolis consists of resins, waxes, and fatty acids, as well as essential oils and other organic compounds. The pharmacologically active components of propolis include phenols and flavonoids, among others. Flavonoids that are found in propolis include chrysin, quercetin, galangin, kaempferol, and apigenin. Angiogenesis is the growth of new blood vessels from endothelial cell precursors. Angiogenesis is important in normal physiology and development. Pathological angiogenesis is widely implicated in human diseases, such as retinal diseases, cancers, and inflammatory diseases; currently, many of these conditions lack effective treatments. The process of angiogenesis is modulated by pro-angiogenic factors, in particular, Vascular Endothelial Growth Factor (VEGF). Flavonoids, including several that are present in propolis, have been found to inhibit angiogenesis by attenuating VEGF signaling. Although promising, such findings are primarily based on preclinical studies, and few clinical studies have evaluated the efficacy and toxicity of flavonoids in vivo. This review outlines the therapeutic potential of essential flavonoids from propolis that may have value as anti-angiogenic agents by modulating VEGF signaling. Overall, the findings suggest that flavonoids that are present in propolis are potential agents for the treatment of human diseases in which pathological angiogenesis is activated.