Structural characterization and in vitro fermentation of the polysaccharide from fruits of Gardenia jasminoides

In the current, the polysaccharide (GFP-40) from fruits of Gardenia jasminoides was obtained by water extraction and ethanol precipitation, further to characterize the structure features by the high performance gel permeation chromatography (HPGPC), high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), methylation combined with gas chromatography - mass spectrometry (GC–MS), and nuclear magnetic resonance spectroscopy (NMR). Subsequently, GFP-40 was enzymatically degraded into several fractions with different molecular weight, and further evaluated the prebiotic potentials by in vitro fecal fermentation. Results showed that GFP-40 had molecular weight of 253 kDa, mainly consisted of GalA (82.03 %). Structure analysis indicated that GFP-40 was the mainly high-methoxyl homogalacturonan (HG) pectin (79.61 %) with alternately linked 1,4-Gal p A and 1,4-Gal p A (OMe) as backbone. Additionally, GFP-40 and its degraded fractions (55.6 kDa, 14.2 kDa, 4.7 kDa and 2.0 kDa) showed no significant difference in monosaccharide composition. The OD 600 of each group gradually increased during fermentation, while the pH value, neutral sugar, and uronic content decreased. After fermentation, degraded fractions with lower molecular weight (4.7 kDa and 2.0 kDa) significantly increased the production of short chain fatty acids (SCFAs). GFP-40 and its enzymatic degraded fractions significantly increased the relative abundance of probiotics (such as Firmicutes and Actinobacteriota ) and decreased the relative abundance of pathogens (such as Proteobacteria ). These findings indicated that molecular weight of polysaccharide was related to the probiotic effect, with lower molecular weight showed better activities, and polysaccharide from fruits of Gardenia jasminoides could be potentially used as a functional substance to improve human health.