Xylan from birch

Fig. 5 FTIR spectra of commercial xylan from birch wood (line 1) and FTIR spectra of wheat straw hemicellulose extracted with 0.25 mol/1 NaOH/30 °C (tine 2), 0.50 mol/1 NaOH/30 °C (line 3), 0.25 mol/ 1 NaOH/55 °C (line 4), and 0.50 mol/1 NaOH/55 °C (line 5) all the treatments for 2 h...

Xylan from wood has received somewhat less attention from carbohydrate chemists than has the xylan from such rich sources as wheat straw, corn cobs, and esparto grass. However, specific optical rotations of the xylans obtained from the aforementioned sources are of the same general order of magnitude as those of some xylans obtained from wood. Yundt crystallized xylans from paper birch and from barley straw as sphero-crystals, and compared their properties (see Table VII). 

In an attempt to isolate a water-soluble 0-acetyl-(4-0-methylglucurono)-xylan from a birch chlorite holocellulose, Marchessault and coworkers kept the time of contact between the ammonia and the holocellulose at a minimum. Successive extractions of the pretreated holocellulose with water and methyl sulfoxide removed the xylan in yields of 7.1 and 14.6%, respectively, based on the weight of the original wood. The products still contained most of the iironic acid, but only one third of the 0-acetyl groups of the native xylan. 

Glaudemans and Timell also used the system of aqueous alkali-methanol in an attempt to fractionate a (4-0-methylglucurono) xylan from wood of white birch. Very little fractionation according to molecular weight occurred (as had been found previously by Husemann ), and the uronic anhydride content of the 18 fractions isolated ranged from 2.6 to... 

One of the first polymers to be obtained in the form of single crystals was a xylan from wood of white birch reported by Yundt in 1949. The crude xylan was purified by heating in boiling 0.2% oxalic acid solution, to give a highly swollen, water-insoluble fraction in a yield of 7.4% of the wood. Further purification was effected by autoclaving in water at 120° and... 

The FTIR spectra of hemicelluloses extracted from birch wood (commercial xylan, line 1) and wheat straw hemieellulose extracted with 0.25 mol/1 NaOFI/30 °C (line 2),... 

Previous papers have investigated the suitable use of xylan in papermaking [10] and textile printing [21]. In the drug delivery field, xylan extracted from birch wood has been used for the production of nanoparticles after structural modification by the addition of different ester moieties, namely those with furoate and pyroglutamate functions [21]. On the other hand, the esterification of xylan from beech wood via the activation of the carboxylic acid with iV,iV -carbonyldiimidazole has been carried out in order to produce prodrugs for ibuprofen release [10, 21, 22, 37]. 

Figure 7. Positive- (upper) and negative- (lower) ion MALDI mass spectra of the oligosaccharides obtained from birch wood xylan by mild acid hydrolysis. In positive ion mode, both neutral and acidic oligosaccharides are detected, whereas acidic oligosaccharides only are detected by negative-ion MALDI-MS. Reproduced from Reference 6. Copyright 2001 American Chemical Society.

The xylans used were non-substituted linear xylan from beech (Lenzing AG, Austria), 4-0-methylglucuronoxylan from birch (MeGlc-xylan) (Roth, Germany). Hexenuronic acid xylan (HexA-xylan) was alkali treated 4-0-... 

A wood xylan was prepared from birch fibers that had been subjected to acetone extraction and chlorite delignification. The xylan fraction was extracted with a solution of 6.5% KOH in a nitrogen atmosphere at 20 C for 3.7 hours. The extract was acidified and the xylan was precipitated with ethanol. 

We recently reported that cellulose fiber surfaces can be surface modified with glucuronoxylans isolated from birch (14). We have shown in autoclave experiments that it is possible to control the amount of xylan retained on the cellulose surface as well as the surface topography by careful variation of the experimental conditions (time and temperature of the autoclave treatment and pH of the xylan solution). The largest retention of xylan was found at high... 

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