CS231686B1 - A method for preparing 4-O-methyl-D-glucurone-D-xylanes - Google Patents

Abstract

The invention relates to a method for preparing 4-0-methyl-D-glucurono-D-xylans. The essence of the preparation consists in that after removing contaminating polysaccharides from delignified sawdust of deciduous trees using 1 to 5% aqueous ammonium hydroxide solution, D-xylans are extracted in two subsequent extraction stages with 3 to 8 and 10 to 18% aqueous sodium hydroxide solutions or 3 to 12% and 15 to 24% aqueous potassium hydroxide solutions at a temperature of 15 to 30 °C for 1 to 5 h. ® D-xylans are isolated from alkaline extracts by precipitation in a double volume amount of ethyl alcohol and neutralized only after the first decantation. The invention has applications in the pulp and paper, food, chemical and pharmaceutical industries.

Description

1,231,686

The present invention relates to a process for preparing 4-O-methyl-D-glucurone-D-xylanes.

Processes for preparing D-xylans from plant materials are! a complex set of operations involving delignification of the underlying raw material, multi-stage extraction with various chemistry, and isolation of the polysaccharides from the extracts. The obtained prodrugs are contaminated with other polysaccharides present in the aqueous medium. Technically demanding purification methods, e.g., short-term thermal pretreatment of the base material, using a nitrogen atmosphere during extraction, or repeated reprecipitations with various reagents, will result in greater purity of the D-xylan preps, but often at the expense of their yield. E. Timell; Adv. Carbohydrate Chem.255, (1964); AO 195,527J. The preparation of D-xylans in these ways is not only simple for chemicals and energy, but also for time and technical equipment, which adversely affects the production process economy.

The above drawbacks are substantially eliminated by the method of the present invention for preparing 4-O-methyl-D-glucurone-D xylans, wherein contaminating polysaccharides are removed from delignified sawdust sawdust using 1-5% aqueous hydroxide solution ammonium at 15 to 30 ° C for 1 to 5 h. D-xylanes are extracted in two successive extraction steps using 3 to 8% and 10 to 18% aqueous sodium hydroxide or 3 to 12% and 15 to 24%, respectively. aqueous potassium hydroxide solutions at 15 to 30 ° C for 1 to 5 h with stirring. From the alkaline extracts, the D-xylanes are isolated by precipitation in twice the volume of ethyl alcohol and after the first decantation, the suspension is neutralized with acetic acid or saline.

The precipitated D-xylanes are washed with 75 to 80% regenerated 2 231 686 alcohols, dried either by subsequent washing with 96% ethyl alcohol and acetone, lyophilization or other means. The advantage of the proposed method for the preparation of 4-O-methyl-D-glucose-D-xylans over the prior art is that it is economically more efficient because D-xylanes are isolated by aqueous sodium or potassium hydroxide solutions already in the two extraction stages. chemically pure, differing in the content of 4-O-methyl-D-glucuronic acid and in molecular weight, in yields of 60 to 85% of pentosane floods present without the use of a nitrogen atmosphere and thermal pre-treatment. The process is also less demanding in terms of chemicals, time, and operation, and can be applied to sawdust and woody wood of various deciduous trees, with high hemicellulose content on semi-cellulose. The extracted sawdust residue is a cellulosic material having properties suitable for use in the paper industry. Example 1

A suspension of air-dried beechwood sawdust (30 kg) of 27.5% pentose in 330 l of water is heated to 50 ° C with stirring in 500 L of reactor and 4.5 L of 98% acetic acid and 20 L are added successively in three equal portions. kg of chlorite sodium. The reaction mixture is heated to 70 ° C and held for 1 hour at this temperature by cooling with water. After the addition of 100 L of water, the reaction was quenched, the solution was evaporated and the delignified material was washed four times with 300 L of water. Then, damp sawdust is extracted with 200 l of a 1% aqueous solution of ammonium hydroxide at 20 ° C for 2 h with stirring, then extracted and drained. To the extraction residue was added 200 L of 5% aqueous sodium hydroxide solution and the suspension was stirred at 20 ° C for 2 h. The extract was evaporated and the pilin was washed with 200 L of 5% aqueous sodium hydroxide solution and the combined extracts were filtered after filtration on earthenware. through silo fabric precipitate to 800 l of 96% ethyl alcohol. After a first decantation of the aqueous alcoholic solution, the rapidly sedimenting precipitate is filtered in earthenware and washed with regenerated 75-80% ethyl alcohol containing 2% acetic acid to neutralize the alkali present and then washed with 80% ethyl alcohol to a constant ash content. The precipitate is suspended in water and lyophilized. There was obtained 4-0- 3 231 686 methyl-D-glucurone-O-xylan I in 16.9 mg yield. sawdust which contains 98% D-xyloyl and 19.3% uronic acids from neutral sugars and has an average molecular weight (M) of 18,610.

Π * 1 "Z was confirmed by methylation analysis and C-NMR spectroscopy. The extracted sawdust was subsequently mixed with 200 µl of aqueous sodium hydroxide solution at 20 ° C for 2 h. The extract obtained was treated as in the previous step. The recovered 4-O-methyl-D-glucurone-D-xylan II (5.6% yield from aspirin contains 93% of D-xylose and 13.4% of neutral sugars). uro acid and has an average molecular weight (Mp) of 19,460. The deho chemical structure was confirmed by methylation analysis and C-NMR spectroscopy.

The procedure is as in Example 1, except that the earthing material is used with sawdust filings (26.5% pentosans) and as extraction agents in the second and third step diffraction extracts of 3% and 10% aqueous sodium hydroxide, the extractions are carried out at 15 ° C for 5 h. The yield of 4-O-methyl-O-glucurone-D-xylan I is 13.9% and the fraction II is 7.4% related to α sawdust. Example 3

The procedure is as in Example 1 except that birch wood sawdust (30.6% pentosan) is used as the starch material, 5% aqueous hydroxamic ammonium solution, 8% and 18% aqueous sodium hydroxide solution are used as extraction agents, and extraction is performed at 30 ° C for 1 h. The yield of 4-O-methyl-D-glucurone-D-xylan is 15.3% and fraction II 7.2%, respectively. sawdust. Example 4

The procedure is as in Example 1 except that poplar wood sawdust (25.1% pentosans) is used as the starting material. The extractants used were 1% aqueous ammonium hydroxide, 3% and 15% aqueous potassium hydroxide solutions, and the extractions were carried out at 15 ° C for 231,686 for 5 h. Yield of 4-O-methyl-D-glucurone-D -xylan I is 7.6% and fraction II is 9.3% related to as sawdust. Example 5

The procedure is as in Example 1, except that the stock material used is sawdust of a mixture of deciduous trees (26.6% pentosans) and 5% aqueous ammonium hydroxide solution, 12% and 24% aqueous potassium hydroxide solutions as extraction agents. The extractions are carried out at 30 ° C for 1 h. The yield of 4-O-methyl-D-glucurone-D-xylan I is 10.1% of affraction II is 9.5% related to a.s. sawdust. O-xylans have wide application possibilities in various industries. In the pulp and paper industry, it can be used as an additive to improve pulping grinding, in the food industry as a neutral filler in the production of low-calorie foods, in the chemical industry as a raw material in the production of D-xylose, D-xylite fural as well as various derivatives. -makable in the pharmaceutical industry, in the production of laundry detergents, detergents, flocculants and the like.

Claims (1)

OBJECT OF THE INVENTION 231 686 Process for preparing 4-O-methyl-D-glucuron-D-xylans, characterized in that D-xylanes are extracted from the delignified sawdust of deciduous tree species after removal of contaminating polysaccharides using 1 to 5% aqueous ammonium hydroxide solution in two successive stages of 3 to 8 K and 10 to 18% aqueous sodium hydroxide solutions or 3 to 12% and 15 to 24% aqueous potassium hydroxide solutions at 15 to 30 ° C for 1 to 5 haz alkaline extracts are isolated by precipitation in twice the volume of ethyl alcohol and neutralized the first decantation.