Screening and quantification of the enzymatic deglycosylation of the plant flavonoid rutin by UV-visible spectrometry

Abstract

Rutin is a plant flavonoid constituted by the flavonol quercetin 3-O-linked to the disaccharide rutinose (quercetin 3-O-(6-O-α-L-rhamnopyranosyl-β-D-glucopyranoside)). The enzymatic deglycosylation of rutin is usually assessed by means of the standard method for flavonoid quantification (high performance liquid chromatography, HPLC). In this work, 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 26.5 (± 0.3) × 103 M-1 cm-1). The convenience of this method relies on the enzymatic activity quantification using the natural substrate by UV-visible spectrometry. Moreover, the simplicity and speed of analysis allows its application for the assay of a large number of samples.