Enzymatic Synthesis Of Acyclovir-Saccharide Derivatives And Evaluation Of Their Properties

Acyclovir is an acyclic nucleoside analogue that has shown obviously antiviral activity. However,it exhibits low solubility and stability in hydrophilic media,which in turn reduces its biological efficiency.The conjugation of saccharides and drugs offers a lot of opportunities for preparing drug derivatives with bioactivemoieties,enriching the categories of pharmaceuticals and improving drug bioavailability.In particular,the relationship between the solubility of drug-saccharide conjugates and the structure of parent drugs is still a valuable and interesting topic, which would provide available information to further investigate the therapeutic benefit of drugs and their derivatives.In this study,three drug-saccharide derivatives were synthesized by facile enzymatic methods and some properties of these three drug-saccharide derivatives were investigated.Firstly,divinyl dicarboxylates with different carbon length were synthesized from corresponding dicarboxylic acids as the spacer between saccharide and acyclovir.Then sugar vinyl esters were enzymatically synthesized by the transesterification between monosaccharide (D-glucose,D-mannose,D-galactose) and divinylsuccinate,divinyladipate,divinylsebacate. Divinyladipate was the most appropriate spacer to link saccharide with acyclovir from the analysis of the conversion yield and reaction activity.Subsequently,three drug-saccharide derivatives were enzymatically synthesized by esterification of sugar ester with acyclovir were developed.The influence of parameters on the reaction was investigated.The yield can reach 53.4%under the optimal reaction conditions: Alkaline protease from Bacillus subtilis was used as biocatalyst,pyridine was used as reaction medium,enzyme concentration was 20 mg/mL,substrate ratio of sugar ester to acyclovir was 1:2, temperature was 50℃,reaction time was 72 h. Finally,some properties of drug-saccharide conjugates were assayed,including hydrophilic character,in-vitro release and anti-virus ability.The water solubility and in-vitro release of acyclovir-saccharide derivatives were investigated in pH 1.2 and pH 7.4 respectively. Comparing with acyclovir,the water solubility of acyclovir-saccharide derivatives improved more than 100 folds.The releasing trends of derivatives were all fit to the zero order reaction.In addition,acyclovir-glucose had the highest water-solubility and quickest releasing speed.Acyclovir-saccharide derivatives were evaluated for their anti-hepatitis B virus(HBV) activity and cytotoxicity in the HepG 2.2.15 cell line.Cytotoxicity of the derivatives were accessed by MTT assay and HBV antigen secretion levels were measured using an enzyme immunoassay kit.The TI of acyclovir-galactose derivative was the hightest.