Dongmei Wu,Jiaqi Zheng,Weiwei Hu,Xiaoliang Zheng,Qiaojun He,Robert J. Linhardt,Xingqian Ye,Shiguo Chen
Rhamnogalacturonan I (RG-I) pectin are regarded as strong galectin-3 (Gal-3) antagonist because of galactan sidechains. The present study focused on discussing the effects of more structural regions in pectin on the anti-Gal-3 activity. The water-soluble pectin (WSP) recovered from citrus canning processing water was categorized as RG-I pectin. The controlled enzymatic hydrolysis was employed to sequentially remove the α-1,5-arabinan, homogalaturonan and β-1,4-galactan in WSP. The Gal-3-binding affinity KD (kd/ka) of WSP and debranched pectins were calculated to be 0.32 μM, 0.48 μM, 0.56 μM and 1.93 μM. Moreover, based on the more sensitive cell line (MCF-7) model, the IC 30 value of WSP was lower than these of modified pectins, indicating decreased anti-Gal-3 activity. Our results suggested that the total amount of neutral sugar sidechains, the length of arabinan and cooperation between HG and RG-I played important roles in the anti-Gal-3 activity of WSP, not the Gal/Ara ratio or RG-I/HG ratio. These results provided a new insight into structure-activity relationship of citrus segment membrane RG-I as a galectin-3 antagonist and a new functional food.
Pectic oligosaccharides are viewed as excellent immunomodulator, but the specific molecular weight (M w ) range required for anti-inflammatory effects remains unclear. In this study, citrus pectins was depolymerized by the ultrasound/H2O2/Vc system and the pectic mixtures was separated through the superdex 30 chromatography column . Three highly purified pectin fractions (USP1, USP2, USP3) were obtained, with the M w of 2713 g/mol, 3683 g/mol, and 7469 g/mol. All of them were RG-I pectins and USP3 contained more arabinan sidechains than USP1 and USP2. In vitro anti-inflammation assays based on LPS-induced RAW264.7 macrophages indicated that these pectins could suppress the NO release, ROS production and down-regulated the level of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α in a M w -dependent manner. The inhibitory effects increased in the order of USP13KD should be effective as a prophylactic agent against inflammatory diseases in functional food.
The effects RG-І pectin (0.5, 1, 2, 5 and 10%, w/w) on the gelatinization behaviour, gel structure and digestibility of potato starch were characterized by means of rapid viscosity analysis (RVA), rheometry, scanning electron microscopy (SEM) and in vitro digestion. Results indicated that the addition of RG-I pectin significantly decreased the peak and breakdown viscosity and prolonged the pasting temperature of potato starch, but increased the setback viscosity. Meanwhile, the swelling power and amylose leaching of starch granules were restrained because of RG-I pectin adsorption on the starch granules surface. The presence of RG-I pectin also decreased the G’ values of potato starch gel but increased the tan δ values (especially for 1%), indicating that RG-І pectin decreased the 3D network formation of potato starch gel. The microstructure analysis indicated that RG-I pectin decreased the formation of the gel structure, which might place constraints on the relative amylose concentration in the continuous phase. The addition of RG-I pectin also reduced the rapidly digestible starch (RDS) content and increased the slowly digestible starch (SDS) content, while no significant differences of resistant starch (RS) content was observed. Those results indicated that RG-I pectin could affect the physicochemical properties of potato starch and modulate its digestibility and might be a potential option for producing starchy food with lower digestibility.
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