Isoquercitrin: Pharmacology, toxicology, and metabolism

doi:10.1016/j.fct.2014.03.018

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Highlights

•: Isoquercitrin = quercetin-3-O-glucoside = quercetin-3-O-β-d-glucopyranoside.
•: Isoquercitrin can be obtained by enzymatic hydrolysis of rutin.
•: Isoquercitrin shows higher bioavailability than quercetin.
•: Acceptable daily intake ca 5 mg/kg/day; but may cause some drug interactions.
•: Isoquercitrin exerts chemoprotective activities in vitro and in vivo.

Abstract

The flavonoid isoquercitrin (quercetin-3-O-β-d-glucopyranoside) is commonly found in medicinal herbs, fruits, vegetables and plant-derived foods and beverages. This article reviews the occurrence, preparation, bioavailability, pharmacokinetics, toxicology and biological activity of isoquercitrin and “enzymatically modified (α-glucosylated) isoquercitrin” (EMIQ). Pure isoquercitrin can now be obtained on a large scale by enzymatic rutin hydrolysis with α-l-rhamnosidase. Isoquercitrin has higher bioavailability than quercetin and displays a number of chemoprotective effects both in vitro and in vivo, against oxidative stress, cancer, cardiovascular disorders, diabetes and allergic reactions. Although small amounts of intact isoquercitrin can be found in plasma and tissues after oral application, it is extensively metabolized in the intestine and the liver. Biotransformation of isoquercitrin includes deglycosylation, followed by formation of conjugated and methylated derivatives of quercetin or degradation to phenolic acids and carbon dioxide. The acceptable daily intake of (95%) isoquercitrin and of EMIQ was estimated to be 5.4 and 4.9 mg/kg/day, respectively. Adverse effects of higher doses in rats included mostly (benign) chromaturia; nevertheless some drug interactions may occur due to the modulation of the activity and/or expression of drug metabolizing/transporting systems. With respect to the safety, affordability and beneficial pharmacological activities, highly pure isoquercitrin is a prospective substance for food supplementation.

Graphical abstract

Keywords

Quercetin-3-glucoside;
Quercetin-3-O-β-d-glucopyranoside;
Enzymatically modified isoquercitrin;
Bioavailability;
Safety;
Biological activity

: Corresponding author at: Laboratory of Biotransformation, Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídeňská 1083, Prague 4 CZ-142 20, Czech Republic. Tel.: +420 296 442 766.

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