The core structure of a Dendrobium huoshanense polysaccharide required for the inhibition of human lens epithelial cell apoptosis

• An active polysaccharide (DHPD1) was isolated from Dendrobium huoshanense.
• DHPD1 was shown to inhibit the apoptosis of human lens epithelial cells.
• The active core domain of DHPD1 was prepared using pectinase hydrolyzation.
• The basic structure features of the core domain of DHPD1 were characterized.
• DHPD1 and its core domain prevent cell apoptosis via alleviating cell inflammation.

The aim of this work was to investigate the core structure of a Dendrobium huoshanense polysaccharide DHPD1 required for the inhibition of lens epithelial cell apoptosis. In order to obtain the fragments containing the core domain, pectinase was employed to hydrolyze DHPD1. After 24 h reaction, it is interesting that the hydrolyzation seemed to be stopped, leading to a final enzymatic fragment DHPD1-24 with molecular weight about 1552 Da. Compared to DHPD1, although the bioactivity is decreased, DHPD1-24 remained the ability to inhibit the H2O2-induced apoptosis of human lens epithelial (HLE) cells via suppressing the MAPK signaling pathways. These results suggested that DHPD1-24 might be the core domain required for DHPD1 to inhibit HLE cell apoptosis. Methylation analysis showed DHPD1-24 was composed of (1 → 5)-linked-Araf, (1 → 3,6)-linked-Manp, 1-linked-Glcp, (1 → 4)-linked-Glcp, (1 → 6)-linked-Glcp, (1 → 4,6)-linked-Glcp, (1 → 6)-linked-Galp and 1-linked-Xylp in a molar ratio of 1.06:1.53:2.11:2.04:0.93:0.91:0.36:1.01. Moreover, the primary structural features of DHPD1-24 were characterized by NMR spectrum.