Neuraminic acid — Structure, Chemistry, Biological Activity

Abstract

Abstract The interest in the sialic acids chemistry has rapidly increased in last years, especially since their involvement in the regulation of a great variety of biological phenomena was recognised. In this paper we are interested in the biological function of sialic acid that it is able to interact with biomolecules, as well as viruses are. In particular, during influenza infection, the virus attaches cell surface receptors containing sialic acids. Haemagglutinin (HA) and neuraminidase (NA) are two major surface glycoproteins expressed by both influenza A and B viruses. HA is knownto mediate binding of viruses to target cells via terminal sialic acid residues in glycoconjugates. This binding is the first step of viral infection. In contrast to HA activity, the NA catalyses removal of terminal sialic acids linked to glycoproteins and glycolipids. The NA activity is necessary in the elution of newly formed viruses from infected cells and may also promote viralmovement through respiratory tract mucus, thus enhancing viral infectivity. Therefore, HA and NA have been considered to be a suitable target for developing agents against influenza infection. The first approach in the design of high affinity inhibitors has been to use sialic acid as a scaffolding, modifying its functional groups in order to increase the affinity of the sialic acid cell receptor analogue to the HA; a second approach has concerned the partial and total syntheses of sialic acid analogues potentially able to inhibit the receptor — destroying activity of NA.