The Protective Effects of Pectic Polysaccharides on Dextran Sulfate Sodium-Induced Colitis in Drosophila melanogaster and Their Structure-Function Relationships.

BACKGROUND

Pectic polysaccharides exhibit therapeutic potential against intestinal inflammation. However, the influence of structural variations on their efficacy remains largely unexplored.

METHODS

This study investigated the structural and anti-inflammatory relationships of okra pectin (OP), citrus pectin (CP), apple pectin (AP), and hawthorn pectin (HP). Based on FT-IR spectra, CP was identified as a high-methoxyl pectin, with a degree of methyl esterification (DM) of 72.07 ± 3.86%. OP, AP, and HP were low-methoxyl pectins with the following DM values: 19.34 ± 3.04%, 32.11 ± 1.71%, and 38.67 ± 2.75%, respectively.

RESULTS

Monosaccharide composition analysis revealed that OP exhibited the highest abundance of RG-I regions among all the samples. Homogalacturonan (HG) was the predominant structural region in AP and HP, while CP contained both of the aforementioned structural regions. Our findings demonstrated that OP and CP significantly ameliorated dextran sulfate sodium (DSS)-induced colitis in the wild-type Drosophila melanogaster strain w1118, as evidenced by improved intestinal morphology, reinforced intestinal barrier function, and enhanced locomotor and metabolic activity. These effects were mediated by the inhibition of JAK/STAT signaling and the activation of the Nrf2/Keap1 pathway. Notably, reducing the molecular weight of CP to 18.18 kDa significantly enhanced its therapeutic efficacy, whereas a reduction in OP molecular weight to 119.12 kDa extended its median lifespan.

CONCLUSIONS

These findings first suggest that abundant RG-I structures and low molecular weight endowed pectins with significant anti-inflammatory activity.