A highly branched RG-I pectin from zucchini and its effects on the intestinal microecology based on a honeybee model.

Due to its superior health benefits, rhamnogalacturonan I (RG-I) pectin has attracted more attention, while the structure-function relationship is ambiguous. Here, a highly branched RG-I rich pectin fraction (ZP) was prepared from zucchini, whose fine structure was identified. The effects of zucchini pectin on the intestinal microecology were compared with commercial citrus pectin (CP) using a honeybee model. ZP has a higher proportion of RG-I structure (67.80 %) and a higher number of branched side chains, which are relatively short. Honeybee model inventions showed that low doses of pectin significantly increased the intestinal length. The gut microbiota strain richness induced by ZP and CP is species specific. ZP significantly enriched the abundance of Bombella, which may possess a higher level of rhamnogalacturonanase. CP resulted in a significant increase in the abundance of Apilactobacillus, which may contain more galacturonidase. Correlation analysis indicated that ZP likely enriched the metabolites (adenosine 5'-monophosphate; adenosine monophosphate) in diabetes-related pathways (mTOR signaling pathway; FoxO signaling pathway), by up-regulating the relative abundance of Bombella, leading to the speculation that ZP may have a role in lowering blood glucose and alleviating diabetes. These results indicated that the biological relevance of RG-I pectin is highly dependent on its detailed branch structure, providing references for the customized utilization of zucchini and RG-I pectin.