Abstract
BackgroundTransglycosylation represents one of the most promising approaches for obtaining novel glycosides, and plant phenols and polyphenols are emerging as one of the best targets for creating new molecules with enhanced capacities. These compounds can be found in diet and exhibit a wide range of bioactivities, such as antioxidant, antihypertensive, antitumor, neuroprotective and anti-inflammatory, and the eco-friendly synthesis of glycosides from these molecules can be a suitable alternative for increasing their health benefits.ResultsTransglycosylation experiments were carried out using different GH3 β-glucosidases from the fungus Talaromyces amestolkiae. After a first screening with a wide variety of potential transglycosylation acceptors, mono-glucosylated derivatives of hydroxytyrosol, vanillin alcohol, 4-hydroxybenzyl alcohol, and hydroquinone were detected. The reaction products were analyzed by thin-layer chromatography, high-pressure liquid chromatography, and mass spectrometry. Hydroxytyrosol and vanillyl alcohol were selected as the best options for transglycosylation optimization, with a final conversion yield of 13.8 and 19% of hydroxytyrosol and vanillin glucosides, respectively. NMR analysis confirmed the structures of these compounds. The evaluation of the biological effect of these glucosides using models of breast cancer cells, showed an enhancement in the anti-proliferative capacity of the vanillin derivative, and an improved safety profile of both glucosides.ConclusionsGH3 β-glucosidases from T. amestolkiae expressed in P. pastoris were able to transglycosylate a wide variety of acceptors. Between them, phenolic molecules like hydroxytyrosol, vanillin alcohol, 4-hydroxybenzyl alcohol, and hydroquinone were the most suitable for its interesting biological properties. The glycosides of hydroxytyrosol and vanillin were tested, and they improved the biological activities of the original aglycons on breast cancer cells.
Highlights
Transglycosylation represents one of the most promising approaches for obtaining novel glyco‐ sides, and plant phenols and polyphenols are emerging as one of the best targets for creating new molecules with enhanced capacities
Many Glycosyl hydrolases (GHs) can catalyze this kind of reaction, and numerous strategies have been developed in order to obtain added-value compounds by transglycosylation [18,19,20,21,22,23]
In order to test the transglycosylation activity of the GH3 β-glucosidases BGL-2, BGL-2T and BGL-3, we first performed a screening of potential acceptors, according to the methodology previously developed [24]
Summary
Transglycosylation represents one of the most promising approaches for obtaining novel glyco‐ sides, and plant phenols and polyphenols are emerging as one of the best targets for creating new molecules with enhanced capacities These compounds can be found in diet and exhibit a wide range of bioactivities, such as antioxi‐ dant, antihypertensive, antitumor, neuroprotective and anti-inflammatory, and the eco-friendly synthesis of glycosides from these molecules can be a suitable alternative for increasing their health benefits. Retaining glycosyl hydrolases act through a double-displacement mechanism involving the formation of a covalent glycosyl-enzyme intermediate, which is subsequently cleaved upon nucleophilic attack by water (hydrolysis reactions) They can produce new glycosidic bonds when alternative nucleophiles to water participate as acceptors, through a mechanism named transglycosylation [3]. As a result of the latter reaction, a new glycoside is synthesized by the transfer of a sugar unit (e.g.: glucose, galactose, xylose, fructose...) to the nucleophilic acceptor
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