Characterization of two pectic polysaccharides from Rosa roxburghii Tratt fruit and their protection on Bifidobacterium against antibiotic damage

This study aimed to investigated the structural and physicochemical properties of two pectic polysaccharide fractions (RTFP1-2 & RTFP2) isolated from Rosa roxburghii Tratt fruit by anion-exchange and size-exclusion chromatography purification, as well as their protection on Bifidobacterium spp. against antibiotic damage. RTFP1-2 had a relatively lower molecular weight of 1.12 × 10⁵ Da and RTFP2 had a higher molecular weight of 5.06 × 10⁵ Da. Chemical composition analysis revealed that both RTFP1-2 and RTFP2 consisted of galacturonic acid (53.13 %, 64.73 %), galactose (27.26 %, 20.04 %), arabinose (3.57 %, 2.94 %), rhamnose (2.32 %, 1.67 %) and glucose (13.73 %, 10.62 %), respectively. These two pectic polysaccharides mainly contained homogalacturonan and rhamnogalacturonan I domain. RTFP1-2 and RTFP2 were resistant to in vitro gastrointestinal digestion with no more than 18 % (w/w) hydrolysis. Minimum inhibitory and bactericidal concentration (MIC and MBC) determination showed RTFPs could notably promote bifidobacterial survivals against three commonly used antibiotics with MIC increasing to ≥ 64 μg/mL and MBC to ≥ 512 μg/mL. The protection attributed to the viscous layers formed by the RTFPs surrounding the bacterial cells to prevent antibiotics from accessing to the bacteria. The viscous RTFP1-2 and RTFP2 also promoted the cohesion among bacterial cells and enhanced bacterial biofilm formation. The results suggested that RTFPs could be potential prebiotic additives used alone or supplemented with probiotic bacteria.