Flavonoids

Dear Colleagues,

Flavonoids are the largest group of polyphenols, plant secondary metabolites arising from the essential aromatic amino acid phenylalanine (or more rarely from tyrosine) via the phenylpropanoid pathway. The flavan nucleus is the basic 15-carbon skeleton of flavonoids (C6-C3-C6), which consists of two phenyl rings (A and B) and a heterocyclic ring (C). The main classes of flavonoids (flavonols, flavanols, flavones, flavanones, isoflavones and anthocyanidins) differ in the level of oxidation and saturation of the C ring, while individual compounds within a class vary in the substitution pattern of the A and B rings. In planta, they exert a plethora of ecological roles as variously colored pigments and signaling molecules, being involved in pollinator attraction and root symbioses, just to name a few examples. In addition, flavonoids protect plant from abiotic and biotic stressors, such as UV radiation and pathogen attack (in this context, they represent a group of phytoalexins). Health-promoting effects of traditional food and medicinal plants have been ascribed to their content in bioactive phytochemicals including flavonoids, also known as nutraceuticals. A huge number of in vitro/in vivo studies on animal and cell experimental models highlighted their preclinical efficacy as antioxidant, antimicrobial, anticancer/chemopreventive, antidiabetic, vasoprotective and vasodilating agents, in addition to their cardio- and neuroprotective effects. The flavonoid mechanism of action is directed toward multiple molecular and biochemical targets in prokaryotic and eukaryotic cells. Therefore, plant foods and herbal remedies are multitarget agents containing hundreds of flavonoids (including aglycones and glycosides) and other different phytochemicals. In this context, given the global threat of antimicrobial resistance, these phytotherapeutics have a low risk of selecting chemoresistant microbial and cancer cells. Flavonoids can also reverse chemoresistance (including multidrug resistance) modulating efflux pumps, and hence they can be used as adjuvant (or chemosensitizer) agents in conventional antimicrobial and anticancer therapies. Not least, flavonoids can mitigate age-associated cellular damage and extend lifespan as epigenetic modulators and by mimicking calorie restriction. Finally, oral bioavailability of flavonoids represents another relevant issue. Indeed, after ingestion, they are metabolized by phase I and II enzymes like other xenobiotics before reaching the target cells and tissues.

In this very wide context, we invite investigators to submit both original research and review articles that explore all these aspects.

Prof. Dr. Marcello Iriti
Dr. Elena Maria Varoni
Prof. Dr. Sara Vitalini
Guest Editors

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