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
