Production of high antioxidant activity flavonoid monoglucosides from citrus flavanone with immobilised α‐L‐rhamnosidase in one step

Summary The rhamnosyl group of naringin dihydrochalcone, neohesperidin dihydrochalcone, naringin and hesperidin was selectively removed by enzymatic hydrolysis using an immobilised α‐L‐rhamnosidase. Monoglycosylated products, including trilobatin, hesperetin dihydrochalcone‐7‐O‐glucoside, prunin and hesperetin‐7‐O‐glucoside, were isolated and characterised by 1H and 13C NMR and ESI‐MS. To optimise the enzymatic reaction conditions and its process costs, the hydrolysis of neohesperidin dihydrochalcone to produce trilobatin was selected as a model reaction. Using a ratio of neohesperidin dihydrochalcone: immobilised α‐L‐rhamnosidase equal to 1:0.6, the trilobatin yields was over 98%. The recycle of enzyme was also investigated, obtaining trilobatin with a yields of 80% even when the twentieth reaction cycle was conducted. Moreover, antiradical and antimicrobial activities of the obtained flavonoid monoglucosides were examined by DPPH, FRAP and ORAC methods, and compared with the efficacy of parental flavonoid glycosides and their aglycone. The results highlight that some of the obtained flavonoid monoglucosides show significant improvement in the antioxidant activity. The enzymatic hydrolysis of flavonoid diglycosides, selectively removing the rhamnosyl groups, with an immobilised α‐L‐rhamnosidase is able to produce flavonoid monoglucosides that possess better functionalities for further applications. Some of these flavonoid monoglucosides obtained show significant improvement in the antioxidant activity.