Cyclodextrin Glycosyltransferase-Catalyzed Synthesis of Pinoresinol-α-D-glucoside Having Antioxidant and Anti-Inflammatory Activities
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Enzymatic synthesis of pinoresinol-α-glucosides (PGs) was performed through the transglycosylation reaction catalyzed by the recombinant cyclodextrin glycosyltransferase (CGTase) from Bacillus circulans A11 using β-cyclodextrin as the glycosyl donor and pinoresinol as the acceptor molecule. Incubation of 0.5% (wt/vol) β-cyclodextrin with 1.5% (wt/vol) pinoresinol (P) and 80.0 U/mL of CGTase in 20 mM of Tris–HCl buffer (pH 9.0) at 50oC for 60 h was optimal for PGs synthesis. Under these conditions, two PG transfer products with molecular weights of 544 and 682 Da corresponding to pinoresinol monoglucoside (PG1-I and PG1-II) and pinoresinol diglucoside (PG2), respectively, were detected by TLC and MS. The structures of PG1 and PG2 were confirmed as pinoresinol-α-D-glucopyranoside and pinoresinol-α-D-diglucopyranoside, respectively, by 1H-NMR analysis. The free-radical scavenging and anti-inflammatory activities of PG1 and PG2 were reduced as compared with the original P using α,α-diphenyl-β-picrylhydrazyl radical scavenging reactions and the β-glucuronidase inhibition assay. The loss of antioxidant and anti-inflammatory activities might result from the addition of glucose in the position 4-OH of P that may have disturbed its electron rotation. In vivo, PGs are converted to Ps before they are absorbed and so loss of activity may be minimal. Interestingly, the α-glycosylated compounds which showed the change of physicochemical properties such as increase of solubility and sweetness could promote a positive effect on the bioavailability of original P.
Keywords:Antibacterial activity anti-inflammatory activity cyclodextrin glycosyltransferase intermolecular transglycosylation pinoresinol-α-glucoside
We also thank the Drug Discovery and Development Center, and Center of Scientific Equipment for Advanced Research, Thammasat University for special service rate 1 of HPLC.
The authors gratefully acknowledge financial s-upport from the Thammasat University Research Fund under the TU Research Scholar, Contract no. TP 2/26/2559 and the Phramongkutklao College of Medicine Research Fund (Thailand).
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The authors declare that they have no conflict of interest. This article does not contain any studies involving animals or human participants performed by any of the authors.
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