Quercetin: Difference between revisions

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 === Absorption and Bioavailability ===
-Quercetin's bioavailability is notably limited due to its poor water solubility. It is usually metabolized extensively in the intestines and liver, with only a small fraction reaching systemic circulation. Various formulations and delivery systems, like quercetin phytosomes, have been developed to enhance its bioavailability.
+=== Absorption and Bioavailability ===
+Quercetin's bioavailability is complex, influenced largely by its poor water solubility, which results in low absorption and extensive metabolism, hence reducing its availability to exert biological effects. It is predominantly found in foods as glycosides, bound to sugar molecules, which impacts its absorption and subsequent bioavailability.
+Absorption Process:
+Quercetin, when consumed, undergoes an absorption process primarily in the small intestine. The glycosidic form of quercetin needs to be hydrolyzed by β-glucosidase to its aglycone form before absorption. Once hydrolyzed, it is absorbed through enterocytes via passive diffusion or through active transport mechanisms. The overall absorption of quercetin is estimated to be relatively low, varying between individuals and dependent on dietary matrix and presence of other flavonoids.
+Enhancing Bioavailability:
+Due to inherent limitations in bioavailability, several strategies have been explored to enhance the absorption and stability of quercetin. These include the development of various formulations and delivery systems such as:
+{| class="wikitable" style="width:70%; text-align:center;"
+|-
+! Formulation !! Enhancement in Bioavailability !! Notes
+|-
+| Quercetin Phytosomes || Up to 20 times || Significantly increases oral bioavailability compared to unformulated quercetin.
+|-
+| Nanoparticle Formulations || Several-fold increase || Includes liposomal encapsulations; increased solubility and cellular uptake.
+|-
+| Complexation with Cyclodextrins || Up to 10 times || Improves water solubility significantly, enhancing therapeutic effects.
+|-
+| Co-administration with Piperine || Approximately 20% || Inhibits metabolism of quercetin, improving its bioavailability.
+|}
+Metabolism and Bioavailability:
+Once absorbed, quercetin undergoes extensive first-pass metabolism in the liver and intestines, where it is converted into various metabolites through glucuronidation, sulfation, and methylation. The extensive metabolism significantly reduces the concentrations of free quercetin in the plasma, limiting its bioavailability. The metabolites, however, may retain some biological activity and contribute to the overall effects of quercetin in the body.
+Implications of Low Bioavailability:
+The low bioavailability of quercetin raises questions about the clinical relevance of its potential health benefits observed in vitro and in animal studies. It necessitates the need for effective delivery systems and formulations to realize its therapeutic potential in humans. Additionally, understanding the biological activities of its metabolites is crucial, as they are the predominant forms present in systemic circulation.
 === Metabolism and Elimination ===