Abstract
TEMPO-oxidation of neutral polysaccharides has been used to obtain polyuronides displaying improved functional properties. Although arabinoxylans (AX) from different sources may yield polyuronides with diverse properties due to their variable arabinose (Araf) substitution patterns, information of the TEMPO-oxidation of AX on its structure remains scarce. We oxidized AX using various TEMPO:NaClO2:NaOCl ratios. A TEMPO:NaClO2:NaOCl ratio of 1.0:2.6:0.4 per mol of Ara gave an oxidized-AX with high molecular weight, minimal effect on xylose appearance, and comprising charged side chains. Although NMR analyses unveiled arabinuronic acid (AraAf) as the only oxidation product in the oxidized-AX, accurate AraA quantification is still challenging. Linkage analysis showed that > 75 % of the β-(1→4)-xylan backbone remained single-substituted at position O-3 of Xyl similarly to native AX. TEMPO-oxidation of AX can be considered a promising approach to obtain arabinuronoxylans with a substitution pattern resembling its parental AX.
Highlights
Modification of neutral polysaccharides to anionic polymers by the generation of polyuronides may lead to improved/unique functional properties of the polymer (Pierre et al, 2017)
Oxidation of arabinoxylan (AX) using a tetramethylpiperidine-1-oxyl radical (TEMPO)/ sodium hypochlorite (NaOCl) ratio of 1.0 (NaClO2)/NaOCl system at pH 4.6 was performed to investigate if the TEMPO-oxidation will selectively oxidize the Araf side chains of an AX to arabinuronic acid (AraAf), allowing us to yield a polyuronide type structure with a structure resembling the parental AX structure
A preliminary oxidation study on wheat AX indicated that a TEMPO/NaClO2/NaOCl oxidation system using a ratio of 0.2:2.6:0.4 gave preferential results with an oxidizedAX with an apparent molecular weight (Mw) identical to the native AX (Fig. S1) and a degree of Ara oxidation of about 54 (w/w) % (Table S1), based on the Ara content decrease
Summary
Modification of neutral polysaccharides to anionic polymers by the generation of polyuronides may lead to improved/unique functional properties of the polymer (Pierre et al, 2017). The alkaline medium used in the TEMPO/NaOCl/NaBr system can lead to undesirable poly saccharide depolymerization (Spier, Sierakowski, Reed, & de Freitas, 2017) This depolymerization can be overcome by using alternative systems that do not require the use of an alkaline medium, such as Abbreviations: AX, arabinoxylan; AraAf, arabinuronic acid; BAIB, bis(acetoxy)iodobenzene; COSY, homonuclear 1H-1H correlation spectroscopy; DB, degree of branching; DO, degree of oxidation; EI, impact mode; GC–MS, gas chromatography coupled to mass spectrometry; HILIC, hydrophilic interaction chromatography; HPAEC-PAD, High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection; HPSEC, high performance size exclusion chromatography; Hydr_ox-AX1.0:2.6:0.4_H2O, water fraction collected by SPE of the hydrolysate ox-AX1.0:2.6:0.4; Hydr_ox-AX1.0:2.6:0.4_TFA, acetronitrile:water 60:40, containing 0.05 % (v/v) TFA fraction collected by SPE of the hydrolysate ox-AX1.0:2.6:0.4; IS, internal standard; Isugar, 1H-NMR signal integrals derived from each identified sugar; MS, mass spectrometry; Mw, molecular weight; NaBD4, sodium borodeuteride; NaClO2, sodium chlorite; NaOCl, sodium hypochlorite; ox-AX, oxidized-AX; oxAX1.0:2.6:1.5, oxidized-AX with a TEMPO:NaClO2:NaOCl ratio of 1.0:2.6:1.5 per mol of C5-OH of Ara; ox-AX0.2:2.6:1.5, oxidized-AX with a TEMPO:NaClO2:NaOCl ratio of 0.2:2.6:1.5 per mol of C5-OH of Ara; ox-AX1.0:2.6:0.4, oxidized-AX with a TEMPO:NaClO2:NaOCl ratio of 1.0:2.6:0.4 per mol of C5-OH of Ara; ox-product, oxidizedproduct; PMAA, partially methylated alditol acetate; Red-ox-AX1.0:2.6:0.4, carboxyl-reduced ox-AX1.0:2.6:0.4 with carbodiimide/NaBD4; SG, switchgrass; SPE, solid phase extraction; TEMPO, 2,2,6,6-tetramethylpiperidine-1-oxyl radical
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
