Synthesis of Azidothymidine-Bound Curdlan Sulfate with Anti-Human Immunodeficiency Virus Activity in vitro

Abstract

Azidothymidine (AZT) was introduced into curdlan by biodegradable ester bond to give AZT-bound curdlan (AZT-curdlan) in order to aim at releasing AZT from the polymer backbone by an enzymatic hydrolysis in living organs. Structure of the AZT-curdlan was analyzed by 13C NMR and 1H-13C COSY-FG 2D-NMR spectroscopy, indicating that AZT was bound to C6 hydroxyl group of curdlan as designed. Subsequently, the AZT-curdlan was sulfated with sulfur trioxide-pyridine complex to give sulfated AZT-curdlans (AZT-curdlan sulfates). AZT-curdlan sulfates, in vitro, exhibited anti-HIV activities in the EC50 range of 0.20 to 0.60 μg ml−1, corresponding to that (EC50=0.50 μg ml−1) of highly active curdlan sulfate. They possessed low cytotoxicities of CC50 more than 1000 μg ml−1 in vitro, indicating that AZT was not released in vitro. However, an increase in the anti-HIV activity and the cytotoxicity was observed when the AZT-curdlan sulfate solution in 90% buffer at pH 7.4 and 10% dimethyl sulfoxide mixture was kept in a refrigerator for a few weeks. The phenomenon indicates that an anti-HIV active AZT was released slowly from the curdlan sulfate carrier. Furthermore, the AZT-curdlan sulfates exhibited low to moderate anticoagulant activities in vitro.