The Enzymatic Esterification Of Sugary Flavonoids In Microreactors And Evaluation Of Their Antibacterial Activity

The new concept of "Green chemistry" was put forward in today’s society,and it is a new field of interdisciplinary research.Enzyme catalyzed reaction is an important means of green synthesis,which has broad application prospects because of its mild reaction condition,high selectivity and yield.On the other hand,Sugar flavonoids are a kind of flavonoid compounds in nature,and have gained prominence in food,cosmetic and pharmaceutical fields because of their physiological activities such as anti-tumor,anti-inflammatory,antibacterial,antiviral.However,their application is limited by their poor solubility and bioavailability.Therefore,the structural modification of flavonoids has become a hot topic for many chemists.In addition,microfluidic technology is popular in the micro-analysis,which has advantages of fast mass and heat transfer,high conversion rate,safe operation and easy to enlarge.With the rapid development of micro-processing technology,It was found that the enzymatic reaction can be realized in microfluidic rapidly and efficiently,and gained a breakthroughs in the field of biocatalysis.Based on these,in this paper we utilized lipase to catalyze esterification of sugary flavonoids in a continuous-flow microreactor for the first time,and synthesized a series of novel sugary flavonoid derivatives.Furthermore,the antimicrobial activity of the derivatives of sugary flavonoids was evaluated.In the paper,we report the esterification of sugary flavonoids catalysed by lipase RM IM in microreactors.Three kinds of sugary flavonoids(hesperidin,neohesperidin,neohesperidin dihydrochalcone)and three types of vinyl esters(vinyl acetate,vinyl laurate,vinyl palmitate)were employed as the substrate for the esterification reaction.Finally,six kinds of sugary flavonoid derivatives were obtained and all these products were thin layer analysis analyzed and proved by 1H –NMR,13C-NMR,HPLC,ESI-MS.The effects of substrate structure,substrate molar ratio,reaction time and other factors on enzymatic esterification of sugary flavonoids were investigated.The results indicated that most excellent solvent is a mixture of DMSO/ Tert amyl alcohol =1:4,best molar ratio of the substrates is 1:8,the optimal reaction temperature is 52℃,the optimum reaction time is 35 min.Finally,we studyed in microfluidic reactor and shaking reactor for esterification reaction,and the results showed that the reaction can get better conversion rate in microreactors.In addition,the effect of substrate structure on the performance of this reaction was investigated,the results indicated that the technology has high regioselectivity for flavonoids,and the selectivity can reach 99%.Moreover,the technology has higher esterification efficiency for long chain vinyl ester compounds.In this paper,we investigated the antibacterial activity of the synthesized sugary flavonoid derivatives.The results show that antibacterial effect of the derivatives was obviously enhanced.