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The enzymatic deglycosylation of the plant flavonoid rutin (quercetin-3- O- (6- O -α- l -rhamnopyranosyl-β- d -glucopyranoside) is usually assessed by means of high performance liquid chromatography (HPLC). We have developed a spectrophotometric method for the quantification of the released quercetin. After the enzymatic reaction, quercetin is extracted with ethyl acetate, and subsequently oxidized under basic conditions. The absorbance of quercetin autooxidation products at 320 nm was correlated with the quercetin concentration by linear regression (molar extinction coefficient 23.2 (±0.3) × 10 3 M −1 cm −1 ). With this method, rutin-deglycosylation activity in buckwheat flour and a commercial naringinase was measured, and showed no significant differences with the results obtained by HPLC. The convenience of this method resides on the enzymatic activity quantification using the natural substrate by UV–visible spectrometry. Moreover, the simplicity and speed of analysis allows its application for a large number of samples. [ABSTRACT FROM AUTHOR]

An intracellular naringinase from Bacillus amyloliquefaciens 11568 isolated from soil was purified, identified, and characterized. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the purified enzyme gave a single protein band corresponding to a molecular mass of 32 kDa. The optimum pH and temperature for naringinase and its α - l -rhamnosidase and β - d -glucosidase activities were pH 7.5 and 45 °C, respectively. The enzymes were stable below 45 °C between pH 3.5 and 8.5. The K m and the V max of the isolated naringinase were 0.95 mmol/L and 3847.3 mmol/(L·min), respectively. The isolated naringinase was capable of hydrolyzing naringin, neohesperidin, and other glycosides. Additionally, a concentration of 4 U/mL of the enzyme in citrus juice was sufficient to remove the naringin and alleviate the bitterness of the juice. These results provide an in-depth insight into the structure of the naringinase and the hydrolysis of naringin and other flavonoids. [ABSTRACT FROM AUTHOR]

Abstract: Hesperetin-7-O-glucoside (Hes-7-G) was produced by the enzymatic conversion of hesperidin by Aspergillus sojae naringinase due to the removal of the terminal rhamnose. Extracts from orange juice and peel containing the hesperidin were so treated by this enzyme that the hesperidin could also be converted to Hes-7-G. The solubility of Hes-7-G in 10% ethanol was enhanced 55- and 88-fold over those of hesperidin and hesperetin, respectively, which may make Hes-7-G more bioavailable. Hes-7-G was 1.7- and 2.4-fold better than hesperidin and hesperetin, respectively, in the inhibition of human intestinal maltase. Hes-7-G was more potent by 2- and 4-fold than hesperidin in the inhibition of human HMG-CoA reductase. Additionally, Hes-7-G exhibited more effective inhibition of the growth of Helicobacter pylori than hesperetin, while its effectiveness was similar to that of hesperidin. Therefore, the results suggest that bioconverted Hes-7-G is more effective and bioavailable than hesperidin, as it has enhanced inhibitory and solubility properties. [Copyright &y& Elsevier]

Abstract: Antioxidant capacity, radical scavenging activity, as well as protective effect on lipoperoxidation, glutathione oxidation and DNA damage, were evaluated in grapefruit juice subjected to bitterness removal by naringinase or by physical adsorption with Amberlite®IRA-400. The results showed a reduction in naringin content for the naringinase-treated juice (N-PJ) and those processed with the exchange resin (R-PJ), which made both juices acceptable to consumers. Total antioxidant capacity, measured by ABTS and FRAP assays, was lower in R-PJ samples. The highest superoxide and hydroxyl radical scavenger activity was observed in N-PJ. With regard to inhibitory effect of juice samples on lipoperoxidation, N-PJ also provided the greatest effectiveness. In addition, R-PJ showed the lowest levels of GSH. The results showed a protective effect on DNA oxidative damage for all juice samples tested. In summary, enzymatic technology was more effective than physical adsorption in preserving the antioxidant and biomolecule protection capacity of fresh grapefruit juice. [ABSTRACT FROM AUTHOR]

Abstract: Aspergillus sojae isolated from a traditional Korean fermented soybean product exhibited strong naringinase activity. The naringinase enzyme was purified and had a molecular weight of 70kDa. The α-l-rhamnosidase activity of this enzyme was optimal at pH 6.0 and stable in the pH range of 5.5–8.0. The purified enzyme also had β-d-glucosidase activity, but the activity was relatively weak compared to the activity of the naringinase from Penicillium decumbens. The enzymatic bioconversion by A. sojae naringinase of naringin to prunin was efficiently performed with a 91% yield and a negligible amount of naringenin. The bioconversion was achieved by repetitive batch reactions with enzyme recycling. Prunin exhibited a markedly enhanced solubility compared to naringenin and naringin while maintaining the in vitro inhibition of HMG-CoA reductase. The results reported in this paper show that the naringinase produced by A. sojae will be useful in enhancing the potential bioavailability of naringin by efficiently converting it to prunin as a food component in citrus. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was the modelling, under high pressure, of naringin hydrolysis by naringinase. Response surface methodology (RSM) was used to compare the effects of the selected variables on the bioconversion under study. The combined action of temperature (13–61°C) and pressure (80–216MPa) on the catalytic activity of naringinase was investigated at pH 4.0 using naringin as the substrate. The choice of experimental domains resulted from preliminary studies. Naringinase activity, for naringin hydrolysis at pH 4.0, could be described by a convex surface with a maximum of 0.13mMmin−1, at 41°C and 158MPa. After 1h of reaction time, reducing sugars production could also be described by a convex surface, with a maximum reducing sugars concentration of 8mM at 38°C and 168MPa. The interaction temperature–pressure had a significant effect on both naringinase activity and reducing sugar formation after 1h. Under the optimized conditions, the naringin hydrolysis by naringinase was evaluated. [Copyright &y& Elsevier]

Abstract: Naringinase, induced from Aspergillus niger CECT 2088 cultures, was immobilized into a polymeric matrix consisting of poly(vinyl alcohol) (PVA) hydrogel, cryostructured in liquid nitrogen, to obtain biocatalytically active beads. The effects of matrix concentration, enzyme load and pH on immobilization efficiency were studied. Between 95% and 108% of the added naringinase was actively entrapped in PVA cryogel, depending on the conditions of immobilization used. The optimal conditions were: 8% (w/v) PVA at pH 7 and 1.6–3.7Uml−1 of enzyme load. The pH/activity profiles revealed no change in terms of shape or optimum pH (4.5) upon immobilization of naringinase. However, the optimum temperature was shifted from 60°C to 70°C and the activation energy of reaction, E a, was decreased from 8.09kJmol−1 to 6.36kJmol−1 by immobilization. The entrapped naringinase could be reused through six cycles (runs of 24h at 20°C), retaining 36% efficacy for the hydrolysis of naringin in simulated juice. [Copyright &y& Elsevier]

Abstract: Initially exploited in chemistry and physics, high-pressure technology has gained importance in various fields. Flavonoids, namely naringin and naringenin, from citrus, are functional chemicals with important properties in the fields of healthcare, food and agriculture. Naringin, the principal bitter flavonone glycoside and the primary bitter component in grapefruit juice, can be hydrolysed by naringinase into tasteless naringenin. The temperature of 303K was ideal for maximizing the activity of the naringinase at 160MPa when compared to atmospheric pressure. The pressure had a positive effect on the reaction rate, with a value of −15.0±1.8cm3 mol−1 for the activation volume. Kinetic parameters, k M and V max for naringinase were evaluated, the maximum initial rate at 160MPa (V max =2.7mMmin−1) was higher than that at atmospheric pressure (V max =0.06mMmin−1). This is a promising result for future application of enzymatic hydrolysis of naringin at high pressure, in the citrus juice industry. [Copyright &y& Elsevier]