Composition and Structure of Aspen (Pópulus trémula) Hemicelluloses Obtained by Oxidative Delignification

Abstract

In this study, hemicelluloses of aspen wood (Pópulus trémula) were obtained by oxidative delignification in an acetic acid‒water‒hydrogen peroxide medium at temperatures of 70‒100 °C and a process time of 1‒4 h. The maximum polysaccharide yield of up to 9.68 wt% was reported. The composition and structure of the hemicelluloses were studied using a complex of physicochemical methods: gas and gel permeation chromatography, Fourier-transform infrared spectroscopy, 2D nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The xylose, mannose, galactose, and glucose monomer units were identified in the hemicelluloses by gas chromatography. The weight average molecular weight Mw of the products determined by gel permeation chromatography was found to range within 8932‒33,142 g/mol. The reported Fourier-transform spectra of the hemicelluloses contain all the bands characteristic of heteropolysaccharides; a weak lignin absorption signal in the spectra at 1500‒1510 cm−1 is attributed to a minor content of phenolic fragments in the structure of the obtained hemicelluloses. The use of thermogravimetric analysis established that the hemicelluloses isolated from aspen wood are resistant against heating to temperatures of up to 90–100 °C and, upon further heating up to 400 °C, start destructing at an increasing rate. The antioxidant activity of the hemicelluloses was examined using the compounds that mimic free radicals (1,1-diphenyl-2-picrylhydrazyl) and hydroxyl radicals (salicylic acid). It was found that the activity of all polysaccharides in neutralizing DPPH and hydroxyl radicals is lower than the absorption capacity of vitamin C at all the tested concentrations (0.5, 2, and 5 mg/mL) and attains 81.7 and 82.9%, respectively.

Microfibrillated Cellulose with a Lower Degree of Polymerization; Synthesis via Sulfuric Acid Hydrolysis under Ultrasonic Treatment

“…The method based on the free radical scavenging modeling allows one to determine the antiradical activity of potential antioxidants, including polysaccharides. The DPPH solution often used as an analog of free radicals demonstrates the strong absorption at 517 nm [ 27 , 28 ]. The antioxidant can bind to one DPPH electron with the formation of a stable yellow compound diphenylpicrylhydrazine with the absorption decreasing with an increase in the antioxidant concentration.…”

“…The antiradical activity of the MCC and MFC was determined using the method described in [ 27 , 28 ]. To perform the UV measurements, a fresh solution of 1,1-diphenyl-2-picrylhydrazyl (DPPH) (TCI, Tokyo, Japan) in ethanol (0.2 mmol/L) was prepared.…”

Recent advances in the extraction, purification, structural-property correlations, and antiobesity mechanism of traditional Chinese medicine-derived polysaccharides: a review

“…Multiple analytical techniques, including osmometry, viscosity measurement, sedimentation, GPC, HPGPC, HPSEC, and HPLC, are employed to determine the Mw distribution of TCMPOs, of which HPGPC and HPSEC are the most commonly utilized methods ( 38 , 39 , 43 , 44 , 64 ). As mentioned above, polysaccharides are never pure compounds regardless of how many procedures have been applied for purification.…”

Coconut Waste: Discovering Sustainable Approaches to Advance a Circular Economy

“…Hemicellulose is also a polysaccharide in the plant cell wall, but contrary to cellulose, its chain is highly branched and comprises diverse sugar units (pentose and hexoses) [79]. The main sugar units are xylose (the most representative component), glucose, and galactose, which are readily hydrolyzed by dilute acids and soluble in alkaline solutions [80,81]. Thus, hemicelluloses confer to the structure of the lignocellulosic biomass properties such as increased flexibility and a high fiber bonding area, which are essential when processing lignocellulosic materials and make it a desirable resource for applications in coatings and composite materials [82].…”