Williamson, Ian R.

2018-01-31T11:40:27Z

2018-01-31T11:40:27Z

1952

Mannan A:

1. Mannan A was extracted from delignified ivory nut shavings with 7;., potassium hydroxide solution, and the polysaccharide precipitated by acidification of the extract and addition of methylated spirits.

2. The mannan, purified by means of the copper complex, gave on hydrolysis 97.6% mannose, 1.8% galactose, and o.8% glucose.

3. The reducing power of the mannan determined by oxidation with alkaline hypoiodite gave a degree of polymerisation of 100, and by treatment with 3 :5- dinitrosalicylic acid, 28. The values of the chain length of mannan A obtained by these two methods were different and disagreed with the value obtained by other methods. Values of the chain length of the polysaccharide which are derived from measurement of the reducing power are, therefore, of doubtful validity.

4. A triacetate was prepared which was found by Barger's method to have a degree of polymerisation of 10 -13.

5. The mannan was methylated and the methylated polysaccharide hydrolysed. The hydrolysate was separated on a cellulose column and the following sugars were obtained: 2:3:4:6- tetramethyl Dmannose, 2:3:4 :6- tetramethyl D- galactose, 2:3:6 -trimethyl Dmannose, 2 :3 :4- trimethyl D- mannose, and 2:3- dimethyl D- mannose in the molar ratios of, respectively, 1.0: 0.2: 11.6: 1.0: 0.2. All the galactose present in the purified mannan was accounted for as 2:3:4 :6- tetramethyl galactose.

6. The 2:3 :4- trimethyl mannose fraction crystallised as a disaccharide, which was shown to be 1 -[ 2:3:4 -trimethyl D-mannopyranosido] - 2:3:4 -trimethyl D-mannopyranoside.

7. The degree of polymerisation of the methylated mannan was determined by Barger's method and found to be 9 -11.

8. Periodate oxidation experiments on the mannan showed that 1.6 moles of periodate were consumed per anhydrohexose unit, and one mole of formic acid was liberated per 4 anhydrohexose units.

9. On the basis of these results possible structures for the mannan are proposed.

Mannan B:

1. Mannan B was extracted from the residue left after removal of mannan A from ivory nuts. The residue was extracted with cuprammonium hydroxide and the solution treated with sodium hydroxide. Several fractions were obtained and one which was considered to be mannan B was purified by dissolution in anhydrous formic acid and precipitation with ethanol.

2. Purified mannan B gave on hydrolysis 98.3% mannose, 1.1% galactose, and 0.8% glucose.

3 The reducing power of the mannan was determined by hypoiodite oxidation and colorimetrically by means of 3:5- dinitrosalicylic acid. The first method gave an apparent degree of polymerisation of 12, the second, 130. The values of the Chain length of mannan B obtained by these two methods were different and disagreed with the value obtained by other methods. Values of the chain length of the polysaccharide which are derived from measurement of the reducing power are, therefore, of doubtful validity.

4. Mannan B was meth lated and the methylated polysaccharide hydrolysed. Separation of the mixture of sugars on a cellulose column gave 2:3:4:6 -tetramethyl D- mannose, 2:3 :4 :6- tetramethyl D- galactose, 2:3:6 -trimethyl D- mannose, 2:3:4 -trimethyl D- mannose, and 2:3- dimethyl D-mannose in the molar ratios of, respectively, 1 :1:63 :11 :1. All the galactose present in purified mannan B was accounted for as 2:3:4:6 -tetramethyl galactose.

5. The 2 :3 :4- trimethyl mannose fraction crystallised as a disaccharide, which was shown to be 1 -[2 :3 :4- trimethyl D- mannopyranosido ] - 2:3:4- trimethyl D- mannopyranoside.

6. The degree of polymerisation of methylated mannan B was determined by Barger's method and found to be 35-43.

7. Periodate oxidation experiments on the mannan showed that 0.98 moles of periodate were consumed per anhydrohexose unit, and one mole of formic acid was liberated per 2.4 anhydrohexose units.

8. On the basis of these results possible structures for the mannan are proposed.

http://hdl.handle.net/1842/27687

The University of Edinburgh

Annexe Thesis Digitisation Project 2017 Block 16

Already catalogued

Investigations on the Mannans of Ivory Nut (Phytelephas macrocarpa)

Thesis or Dissertation

PhD Doctor of Philosophy