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The properties of pectin extracted from mandarin citrus peels by manosonication extraction (MSp) were systematically studied and compared with pectin obtained by the conventional maceration method (CMp). The yield of MSp (25.5%) was significantly higher than that of CMp (18.3%), while MSp exhibited two Mw fraction distributions. Monosaccharide analysis demonstrated that MSp had more branched RG-I regions (78.3 mol%) than CMp (36.6 mol%) with a high content of arabinose and galactose. The branched-chain morphological characteristics of samples were directly imaged by atomic force microscopy. MSp exhibited a significantly lower degree of methoxylation than CMp by FT-IR and NMR analysis, but X-ray diffraction analysis showed little difference in the level of crystallinity. Moreover, MSp and CMp showed non-Newtonian behaviour, and the increasing order of apparent viscosities was 1.0 w/v% MSp < 1.0 w/v% CMp < 2.0 w/v% CMp < 2.0 w/v% MSp. Thermal analysis and weight loss measurements indicated MSp exhibited greater thermal stability. The results also indicated that both MSp and CMp significantly enhanced the emulsion activity at high concentrations; the emulsions containing 1.5 w/v% pectin showed no phase separation over 21 days, suggesting that MSp could be a potential effective stabiliser in the food and beverage industry., (Copyright © 2021 Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2020. Published by Elsevier Ltd.)

To better understanding the potential of manosonication to accelerate the extraction of RG-I pectic polysaccharides from citrus wastes, alkaline-mediated manosonication extraction (MSE) was optimized using a Box-Behnken design, and the extraction kinetics model was analyzed. The single-factor method revealed that NaOH significantly impacted on the yield and RG-I characterizations (Rha mol% and (Gal+Ara)/Rha ratio), whereas other factors were focused on influences of yields. In the developed quadratic polynomial model, the maximum extraction yield of 25.51 ± 0.81 % was obtained with sonication at 42 ℃, 40 % amplitude, and 250 kPa for 20 min. The kinetics study demonstrated that MSE facilitated the extractability, dissolution and degradation of pectin, resulting in the highest extractability of 27.83 % compared with ultrasonic extraction (22.86 %) and alkaline extraction at high (24.71 %) and low temperature (20.21 %). Rheology and thermal analyses verified the change in polymerization by MSE and the potential functional applications of the RG-I pectic polysaccharides., Competing Interests: Declaration of Competing Interest There is no conflicting interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Rhamnogalacturonan I (RG-I) pectin is composed of backbone of repeating disaccharide units →2)-α-L-Rhap-(1→4)-α-D-GalpA-(1→ and neutral sugar side-chains mainly consisting of arabinose and galactose having variable types of linkages. However, since traditional pectin extraction methods damages the RG-I structure, the characteristics and health effects of RG-I remains unclear. Recently, many studies have focused on RG-I, which is often more active than the homogalacturonan (HG) portion of pectic polysaccharides. In food products, RG-I is common to fruits and vegetables and possesses many health benefits. This timely and comprehensive review describes the many different facets of RG-I, including its dietary sources, history, metabolism and potential functionalities, all of which have been compiled to establish a platform for taking full advantage of the functional value of RG-I pectin.

The rhamnogalacturonan I (RG-I) region of pectin shows health benefits and novel gel applications. Commercial pectin is extracted from citrus peel in most instances, whereas they are homogalacturonan (HG)-dominated productions and the methods to extract pectin targeting RG-I are limited. To take full advantage of citrus wastes and upgrading this pectin resources, a new extraction method based on a diluted NaOH assisted by a combination of ultrasound (US) and pressure, namely manosonication (MS), was established for RG-I enriched pectin extraction. MS significantly enhanced the pectin yield (21.47 ± 0.11%) while reducing the use of NaOH reagents (50 mmol/L) and processing time (50 min). Structurally, the MS (300 kPa) resulting products achieved nearly a 2-fold greater RG-I content (58.61 mol%) than that of commercial pectin (30.12 mol%). Moreover, for the investigation of the extraction mechanism, external pressure enhanced the cavitation effect, as the calorimetric intensity increased from 1.28 W/mL (100 kPa) to 3.3 W/mL (350 kPa). A sufficient ultrasonic mechanical action allowed for obtaining RG-I enriched products with large molecular weight (9.506 × 104–2.813 × 105) and low degree of methoxylation. Transmission electron microscopy (TEM) and scanning electron microscopies (SEM) verified the increased disintegration of the cell wall tissue by MS. Raman imaging and immunofluorescence labeling suggested the synergistic effect of pressure and ultrasound on enhancing the yields and RG-I content. This new method provided alternations in functional polysaccharides extraction, and the yield and structure of citrus RG-I enriched pectin strongly indicates the potentials of MS in other RG-I rich vegetables applications. [Display omitted] • Chemical compositions of extracted pectin between different methods were compared. • Manosonication extraction improved pectin yield and RG-I region content. • External pressure enhanced the ultrasonic cavitation effect. • Mechanical action was the dominating factor in cellulose network destruction. • Immunolabeling suggested the synergistic extraction mechanism on RG-I dissolution. [ABSTRACT FROM AUTHOR]

The rhamnogalacturonan I (RG-I) region of pectin revealed functional benefits and novel gel applications. This work investigated the applicability of manosonication extraction (MSE) for RG-I enriched pectin recovery from different citrus peel wastes, including Eureka lemon (LEPp), Guanxi pomelo (POPp), navel orange (ORPp), and grapefruit peels (GRPp). The physicochemical, structural, and macromolecular features of the extractions were systematically evaluated and compared to commercial citrus peel pectin (CCPp). The yields of LEPp (21.76%), POPp (20.17%), and ORPp (20.81%) were significantly higher than GRPp (17.10%). All cultivar pectin samples had lower molecular weight (Mw) than CCPp and showed two fractions, indicating the degradation effect of MSE treatment. Monosaccharide analysis demonstrated that LEPp, POPp, ORPp, and GRPp had more branched RG-I regions (40.50–68.48 mol%) than CCPp (30.74 mol%), with high contents of arabinose (Ara) and galactose (Gal). The lower degree of methoxylation of cultivar pectins was verified by FT-IR and NMR. For the macromolecular features, pectins recovered by MSE showed better functional applications than CCPp. Specifically, LEPp and POPp had superior thermal stability, and GRPp showed a higher viscosity and an enhanced emulsifying activity. In addition, the immunochemical study suggested the pectic epitopes masking phenomenon of citrus particle surface, indicating the linkages between xyloglucan, RG-I, and HG polysaccharides, and confirming the contributions of MSE. The results provided novel knowledge to better understand the manosonication in general targets extraction and proposed fundamental references for cultivars-dependent pectin in industrial applications. [Display omitted] • Manosonication extraction was applicable for citrus RG-I enriched pectin production. • Pectin obtained by manosonication had better thermal stability and higher viscosity. • Structure and properties of pectin were various on citrus cultivars. • Pectin from Navel orange had more RG-I regions with arabinoses and galactoses. • Immunolabeling study suggested the linkages between xyloglucan, RG-I and HG. [ABSTRACT FROM AUTHOR]

• Ultrasonically accelerated NaHCO 3 -H 2 O 2 system was optimized. • Highly active O 2 − generated from HCO 4 - plays the key role in HG domain degradation. • Ultrasound promoted degradation by chemical and mechanical effects. • Degradation fragments have lower degree of methylation (DM) and higher galactose content and anti-cancer activity. The modified pectin (MP) showed the improved functional properties than the native one. The aim of present study was to develop the ultrasonic accelerated bicarbonate-hydrogen peroxide system for pectin modification to generate short fragments with advanced bioactive properties. The depolymerization effects of this system on the physicochemical properties, structural features, and bioactivity of the degraded fragments were studied systematically. The results indicated that the molecular weight of pectin was reduced drastically from 1088 kDa to 33 kDa within 50 min under an optimized condition (M H2O2 -M NaHCO3 = 1:2.5, 50 °C, and ultrasound intensity = 11.4 W/cm3). The resulting fragments also showed lower degree of methoxylation and rheological viscosity. The investigation on the sample structures and active oxygen species demonstrated that the highly active O 2 − species generated from HCO 4 - of NaHCO 3 -H 2 O 2 acted preferentially on the GalA backbone in the HG region, while the RG-I region was maintained; and ultrasound enhanced the degradation efficiency via both chemical effects (increasing the transformation of free radicals) and mechanical effects (disaggregating polysaccharide clusters). The atomic force microscope (AFM) imaging directly verified the branched-chain morphology of pectin and the small-strand degradation fragments. Moreover, ultrasound and NaHCO 3 -H 2 O 2 treatment induced high galactose content in the degraded products, contributing to an improved inhibitory activity against A549 lung cancer cells, as shown by MTT assay. [ABSTRACT FROM AUTHOR]

• Two purified raspberry pectins were extracted using different methods. • Enzyme extraction kept the highly branched structure of raspberry pectin. • Enzyme-extracted pectin exhibited higher anti-inflammatory activity. To characterize the structure of purified raspberry pectin and discuss the impact of different extraction methods on the pectin structure, raspberry pectin was extracted by hot-acid and enzyme method and purified by stepwise ethanol precipitation and ion-exchange chromatography isolation. Enzyme-extracted raspberry pectin (RPE50%-3) presented relatively intact structure with molecular weight of 5 × 104 g/mol and the degree of methylation was 39%. The 1D/2D NMR analysis demonstrated RPE50%-3 was a high-branched pectin mainly containing 50% homogalacturonan, 16% branched α-1,5-arabinan and α-1,3-arabinan, 18% β-1,4-galactan and β-1,6-galactan. Acid-extracted raspberry pectin (RPA50%-3) contained less arabinan than RPE50%-3. Moreover, RPE50%-3 inhibited the nitric oxide (NO), TNF-α, IL-6 production of lipopolysaccharide-induced macrophages by 67%, 22% and 46% at the dosage of 200 ug/mL, while the inhibitory rate of RPA50%-3 were 33%, 9%, and 1%, respectively. These results suggested that enzyme-extracted raspberry pectin contained more arabinan sidechains and exhibited better immunomodulatory effect. [ABSTRACT FROM AUTHOR]