Novel 6-O-acylated vitamin C derivatives as hyaluronidase inhibitors with selectivity for bacterial lyases

Previously, we identified ascorbic acid 6-O-hexadecanoate as an up to 1500 times more potent inhibitor of bacterial and bovine hyaluronidases than the parent compound, vitamin C, and determined a crystal structure of hyaluronidase from Streptococcus pneumoniae in complex with the inhibitor. As the alkanoyl chain interacts with a hydrophobic patch of the enzyme we synthesized other 6-O-acylated vitamin C derivatives bearing various lipophilic residues and investigated the inhibition of Streptococcus agalactiae strain 4755 hyaluronidase (SagHyal4755) and of bovine testicular hyaluronidases (BTH) in a turbidimetric assay. All compounds showed selectivity for the bacterial enzyme. Whereas vitamin C 6-O-hexanoate only weakly inhibited SagHyal4755, the inhibition of both enzymes increased with the length of the aliphatic chain. In the case of the 6-O-octadecanoate, IC50 values of 0.9 and 39 μM for SagHyal4755 and BTH, respectively, were determined. Partial replacement of the aliphatic chain with a phenyl, p-phenylene or p-biphenylyl group resulted in inhibitors with activity in the lower micromolar range, too. The title compounds are among the most potent inhibitors of both enzymes known to date.

Based on an X-ray structure of a bacterial hyaluronate lyase in complex with ascorbic acid 6-O-palmitate the title compounds bearing lipophilic substituents were synthesized and investigated for inhibition of bacterial (HylB4755 from Streptococcus agalactiae) and bovine testicular hyaluronidase. Compounds such as 13j are among the most potent hyaluronidase inhibitors known to date.Figure optionsDownload as PowerPoint slide