Structure and Anti-Inflammatory Activities of Two ι-Carrageenan with Different Molecular Weights During In Vitro Human Intestinal Flora Fermentation

The structure and anti-inflammatory activities of two ι-carrageenan with high molecular weight (HI-CA) and low molecular weight (LI-CA), as well as their fermented products during in vitro human intestinal flora on lipopolysaccharide (LPS)-induced RAW264.7 cells were analyzed. The results suggested that LI-CA had higher uronic acid and reducing sugar contents than HI-CA. Both HI-CA and LI-CA were mainly degraded at the simulated transverse colon fermentation for 36 h, greatly increased short-chain fatty acids (SCFAs) productions, and showed good in vitro anti-inflammatory activities on LPS-induced RAW264.7. Compared with HI-CA, LI-CA had better effects. Especially with LI-CA fermentation at simulated descending colon for 24 h, total butyric acid was up to 422.81 ± 1.62 mM, which was 2.41 times higher than that of HI-CA fermentation. Moreover, the fermented products of LI-CA significantly decreased productions of 66.64–76.19% nitric oxide, 26.42–29.91% reactive oxygen species and 12.38–31.84% tumor necrosis factor-α in LPS-induced RAW264.7, and increased the phosphorylation levels of c-Jun amino-terminal kinase and protein kinase p38 in the LPS-induced mitogen-activated protein kinase (MAPK) signaling pathway. The superior anti-inflammatory activity of ι-carrageenan LI-CA may be related with its lower molecular weight, higher uronic acid and reducing sugar contents, and more SCFAs production fermentation, suggesting the potential application of ι-carrageenan with low molecular weight for anti-inflammatory therapy.