Structural Elucidation of Polysaccharide Extract

The crude extract of polysaccharide ESM-C sample (15 mg) and the purifier fraction ESM-C-A sample (5 mg) were each dissolved in 400 μL deuterium oxide (99.9 atom% D, Sigma-Aldrich, Inc.) for data collection. The ¹H chemical shift spectrum was referred to D₂O at δ_H 4.49 ppm (313 K) as an internal standard. For structural elucidation of ESM-C-A, ¹H and ¹³C spectra were recorded on Bruker AVII-500 MHz and Bruker AVIII-800 instruments, respectively. In the ¹³C NMR spectra measurement, a relaxation delay and acquisition time of 3.5 and 1.3 s, respectively. And 13312 scans per spectrum were accumulated. A standard spectrum of HA at 300 MHz ¹H-NMR was used as reported^{29 (link)}.