Enzymatic transformation of flavonoids

There is a growing interest in natural pharmacologically active compounds with either healthprotecting or therapeutic properties to be used in medicine, pharmaceutical, cosmetic or food industry. Flavonoids are excellent candidates for this role due to their potent beneficial biological activities. However, many of dietary flavonoids are glycosylated, and therefore their use in certain fields is limited, especially due to their low solubility in lipophilic systems. An effective method of resolving this disadvantage has been introduced, i.e. enzyme-mediated acylation of sugar moieties of flavonoid glycosides with either aliphatic or aromatic molecules. Moreover, specific modifications of a flavonoid skeleton may confer several beneficial characteristics to the parental molecule. Additionally, it can be interesting to increase natural flavonoid diversity and produce potentially bioactive derivatives by enzymatic conversion. This review summarizes to-date knowledge on flavonoid biotransformations. The key factors affecting enzyme-mediated acylation of flavonoids, such as the type and origin of the biocatalyst, the structure and concentration of the substrates (acyl donor, acyl acceptor and their ratio), the reaction media, and the reaction temperature, are being discussed relating to the reaction rate and the performance of the biocatalytic process.