Fisetin glycosides synthesized by cyclodextrin glycosyltransferase from Paenibacillus sp. RB01: characterization, molecular docking, and antioxidant activity

Abstract

Fisetin is a flavonoid that exhibits high antioxidant activity and is widely employed in the pharmacological industries. However, the application of fisetin is limited due to its low water solubility. In this study, glycoside derivatives of fisetin were synthesized by an enzymatic reaction using cyclodextrin glycosyltransferase (CGTase) from Paenibacillus sp. RB01 in order to improve the water solubility of fisetin. Under optimal conditions, CGTase was able to convert more than 400 mg/L of fisetin to its glycoside derivatives, which is significantly higher than the previous biosynthesis using engineered E. coli. Product characterization by HPLC and LC-MS/MS revealed that the transglycosylated products consisted of at least five fisetin glycoside derivatives, including fisetin mono-, di- and triglucosides, as well as their isomers. Enzymatic analysis by glucoamylase and α-glucosidase showed that these fisetin glycosides were formed by α-1,4-glycosidic linkages. Molecular docking demonstrated that there are two possible binding modes of fisetin in the enzyme active site containing CGTase-glysosyl intermediate, in which O7 and O4’ atoms of fisetin positioned close to the C1 of glycoside donor, corresponding to the isomers of the obtained fisetin monoglucosides. In addition, the water solubility and the antioxidant activity of the fisetin monoglucosides were tested. It was found that their water solubility was increased at least 800 times when compared to that of their parent molecule while still maintaining the antioxidant activity. This study revealed the potential application of CGTase to improve the solubility of flavonoids.

Fisetin—In Search of Better Bioavailability—From Macro to Nano Modifications: A Review

“…The concentrations required to scavenge 50% of DPPH radical were comparable for fisetin-7-O-glucoside (2.28 µM), fisetin-4 -O-glucoside (2.52 µM) and fisetin (2.72 µM). Transglycosylation did not affect antioxidant activity in this case, unlike in the previous example [134].…”

“…The concentrations required to scavenge 50% of DPPH radical were comparable for fisetin-7-O-glucoside (2.28 µM), fisetin-4′-O-glucoside (2.52 µM) and fisetin (2.72 µM). Transglycosylation did not affect antioxidant activity in this case, unlike in the previous example[134].These two studies show that incorporating glucosyl moiety into the fisetin compound significantly improves its solubility, but further evaluation of fisetin derivative properties is needed.…”

Fisetin derivatives exhibit enhanced anti-inflammatory activity and modulation of endoplasmic reticulum stress

“…Low solubility in water and poor bioavailability may be limiting the use of this molecule in the pharmacological context [9,16]. For this reason, it is important to tailor this molecule into safer, more stable and active derivatives that can aid in the development of FST-based pharmacological strategies and also add to the current understanding of its bioactivities.…”