Structure and Anti-Tumor Activities of Exopolysaccharides from Alternaria mali Roberts

In this study, an extracellular polysaccharide from Alternaria mali Roberts (AMEP) was extracted, and its structure was characterized, in addition to its antitumor activity in vitro. Neutral polysaccharide AMEP-1 and anionic polysaccharide AMEP-2 were isolated from AMEP, and their monosaccharide compositions consisted of mannose (Man), glucose (Glc), and galactose (Gal) but at different ratios. The linking mode of both AMEP-1 and AMEP-2 is Manp-(1→4) and Glcp-(1→6), and the branched chains are connected to the main chain through O-6. AMEP-2 inhibited the proliferation of BGC-823 cells in a time- and concentration-dependent manner. AMEP-2 also induced the apoptosis of BGC-823 cells, and showed anti-tumor effects by inducing cell cycle arrest in the S phase, reactive oxygen species production, and mitochondrial membrane potential reduction in BGC-823 cells. Therefore, AMEP-2 shows potential for further development as a novel anti-tumor agent.