Flavonoids and their glycosides are abundant in many plant-based foods. The (de)glycosylation of flavonoids by retaining glycoside hydrolases has recently attracted much interest in basic and applied research, including the possibility of altering the glycosylation pattern of flavonoids. Research in this area is driven by significant differences in physicochemical, organoleptic, and bioactive properties between flavonoid aglycones and their glycosylated counterparts. While many flavonoid glycosides are present in nature at low levels, some occur in substantial quantities, making them readily available low-cost glycosyl donors for transglycosylations. Retaining glycosidases can be used to synthesize natural and novel glycosides, which serve as standards for bioactivity experiments and analyses, using flavonoid glycosides as glycosyl donors. Engineered glycosidases also prove valuable for the synthesis of flavonoid glycosides using chemically synthesized activated glycosyl donors. This review outlines the bioactivities of flavonoids and their glycosides and highlights the applications of retaining glycosidases in the context of flavonoid glycosides, acting as substrates, products, or glycosyl donors in deglycosylation or transglycosylation reactions.

• Keywords
• Glucosidase, Glycoside hydrolase, Glycosyl donor, Glycosynthase, Hydrolysis, Rutinosidase, Transglycosylation,
• MeSH
• Flavonoids * chemistry   MeSH
• Glycoside Hydrolases * metabolism   MeSH
• Glycosides chemistry   MeSH
• Glycosylation MeSH
• Catalysis MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Flavonoids * MeSH
• Glycoside Hydrolases * MeSH
• Glycosides MeSH

Quercetin is a flavonoid largely employed as a phytochemical remedy and a food or dietary supplement. We present here a novel biocatalytic methodology for the preparation of quercetin from plant-derived rutin, with both substrate and product being in mostly an undissolved state during biotransformation. This "solid-state" enzymatic conversion uses a crude enzyme preparation of recombinant rutinosidase from Aspergillus niger yielding quercetin, which precipitates from virtually insoluble rutin. The process is easily scalable and exhibits an extremely high space-time yield. The procedure has been shown to be robust and was successfully tested with rutin concentrations of up to 300 g/L (ca 0.5 M) at various scales. Using this procedure, pure quercetin is easily obtained by mere filtration of the reaction mixture, followed by washing and drying of the filter cake. Neither co-solvents nor toxic chemicals are used, thus the process can be considered environmentally friendly and the product of "bio-quality." Moreover, rare disaccharide rutinose is obtained from the filtrate at a preparatory scale as a valuable side product. These results demonstrate for the first time the efficiency of the "Solid-State-Catalysis" concept, which is applicable virtually for any biotransformation involving substrates and products of low water solubility.

• Keywords
• Aspergillus niger, quercetin, rutin, rutinose, rutinosidase, “solid-state biocatalysis”,
• MeSH
• Aspergillus niger enzymology   genetics   MeSH
• Biocatalysis * MeSH
• Disaccharides chemistry   metabolism   MeSH
• Fungal Proteins genetics   metabolism   MeSH
• Glycoside Hydrolases genetics   metabolism   MeSH
• Pichia genetics   metabolism   MeSH
• Industrial Microbiology methods   MeSH
• Quercetin chemistry   metabolism   MeSH
• Rutin chemistry   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• beta-rutinosidase MeSH Browser
• Disaccharides MeSH
• Fungal Proteins MeSH
• Glycoside Hydrolases MeSH
• Quercetin MeSH
• Rutin MeSH
• rutinose MeSH Browser

Natural flavonoids, especially in their glycosylated forms, are the most abundant phenolic compounds found in plants, fruit, and vegetables. They exhibit a large variety of beneficial physiological effects, which makes them generally interesting in a broad spectrum of scientific areas. In this review, we focus on recent advances in the modifications of the glycosidic parts of various flavonoids employing glycosidases, covering both selective trimming of the sugar moieties and glycosylation of flavonoid aglycones by natural and mutant glycosidases. Glycosylation of flavonoids strongly enhances their water solubility and thus increases their bioavailability. Antioxidant and most biological activities are usually less pronounced in glycosides, but some specific bioactivities are enhanced. The presence of l-rhamnose (6-deoxy-α-l-mannopyranose) in rhamnosides, rutinosides (rutin, hesperidin) and neohesperidosides (naringin) plays an important role in properties of flavonoid glycosides, which can be considered as "pro-drugs". The natural hydrolytic activity of glycosidases is widely employed in biotechnological deglycosylation processes producing respective aglycones or partially deglycosylated flavonoids. Moreover, deglycosylation is quite commonly used in the food industry aiming at the improvement of sensoric properties of beverages such as debittering of citrus juices or enhancement of wine aromas. Therefore, natural and mutant glycosidases are excellent tools for modifications of flavonoid glycosides.

• Keywords
• catechin, enzymatic hydrolysis, hesperetin, icariin, naringenin, puerarin, quercetin, rhamnosidase, rutinosidase, transglycosylation,
• MeSH
• Flavonoids metabolism   MeSH
• Glycoside Hydrolases metabolism   MeSH
• Isoflavones metabolism   MeSH
• Catechin metabolism   MeSH
• Humans MeSH
• Quercetin metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Flavonoids MeSH
• Glycoside Hydrolases MeSH
• Isoflavones MeSH
• Catechin MeSH
• puerarin MeSH Browser
• Quercetin MeSH