Quercetin’s physical characteristics include its yellow crystalline form, a melting point of approximately 316°C, and practical insolubility in water, although it dissolves in organic solvents and aqueous alkaline solutions. It is highly abundant in foods such as capers, red onions, kale, apples, and berries like cranberries and blueberries. Quercetin’s content in these foods varies depending on factors such as cultivation conditions, storage, and processing methods.
In plants, quercetin is synthesized via the phenylpropanoid pathway, beginning with the amino acid phenylalanine. Phenylalanine is converted into 4-coumaroyl-CoA, which undergoes a series of enzymatic reactions involving chalcone synthase and flavonol synthase to produce quercetin. This pathway not only highlights the complexity of plant metabolism but also underscores quercetin’s role in plant defense mechanisms, such as UV protection and pathogen resistance.
Quercetin’s antioxidant properties stem from its ability to scavenge free radicals, chelate metal ions, and inhibit lipid peroxidation, thus mitigating oxidative stress. These properties are pivotal in reducing the risk of chronic diseases like cardiovascular diseases, diabetes, neurodegenerative disorders, and certain types of cancer. Recent studies have also suggested quercetin’s potential role in modulating the immune response and reducing inflammation, making it a subject of interest in combating viral infections, including SARS-CoV-2. Preliminary research indicates that quercetin may inhibit viral entry and replication, though more clinical studies are required to substantiate these findings.
Quercetin’s bioavailability, however, is relatively low due to poor absorption, rapid metabolism, and systemic elimination. To address this, various strategies, such as using quercetin glycosides or nanoformulations, are being explored to enhance its effectiveness as a dietary supplement and therapeutic agent.
Quercetin: Structure, Properties, and Therapeutic Potential
