Enzymatic Synthesis and Characterization of Mono-, Oligo-, and Polyglucosylated Conjugates of Caffeic Acid and Gallic Acid.

Glucansucrases can be used to glucosylate various plant-derived phenolic compounds by using sucrose as donor substrate. We applied TMW 1.106 dextransucrase to glucosylate the acceptor substrates caffeic acid and gallic acid. Subsequently, monoglucosylated and in particular oligo- and polyglucosylated conjugates were characterized by using different chromatographic techniques and two-dimensional NMR spectroscopy. Both acceptors were substituted at positions 3 and 4. Under the conditions used, two monoglucosylated products were formed for caffeic acid, whereas only one 3-monosubstituted conjugate was detected for gallic acid. However, both acceptors resulted in 4-substituted oligo- and polyglucosylated conjugates, the amount of which was higher from gallic acid than from caffeic acid. Profile analysis tensiometry suggested that, in contrast to unmodified dextrans, oligo- and polymeric glucoconjugates of gallic acid are highly interfacially active. Overall, we provide the first detailed characterization of enzymatically conjugated oligo- and polymeric dextrans, which may have further potential as functional ingredients.