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Alam M, Richards GN. Polysaccharides of tropical pasture herbage. V. A galactoglucomannan from Townsville lucerne (Stylosanthes humilis). Aust J Chem 1971. [DOI: 10.1071/ch9712411] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
After removal of pectic
substances, lignin, and hemicelluloses from Townsville lucerne stems, the
residual ?α-cellulose? contained significant amounts of mannose. Further
extraction with a mixture of sodium hydroxide and sodium borate gave a
galactoglucomannan which was partly purified by precipitation with barium
hydroxide to give a crude yield of 0.35% based on the α-cellulose or 0.12%
based on the original plant dry weight. Further purification by chromatography
on QAE- Sephadex gave a polymer which showed only one component on free
boundary electrophoresis in borate buffer. Its structure was determined by
periodate oxidation, Smith degradation, and methylation-hydrolysis. The
backbone of the polymer consists of glucose and mannose units, linked 1,4, but their
order within the chain is not known. The non- reducing end-groups are
glucopyranose and galactopyranose units in the ratio 1 : 4. The galactose may
be present as single unit substituents at a frequency of 1 galactose per 14 main-chain
units and all such substitution occurs at mannose units with none at glucose
units. The similarity of the optical rotation to that of galactoglucomannans
previously isolated from wood suggests that the majority of the glycosidic
linkages are β-oriented.
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502
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Alam M, Richards GN. Polysaccharides of tropical pasture herbage. IV. A pectic acid from Townsville lucerne (Stylosanthes humilis). Aust J Chem 1971. [DOI: 10.1071/ch9711049] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Pectic acid, extracted from
the stems of Townsville lucerne in 4% yield, has been fractionated by
precipitation with sodium acetate. The product contains two components as
revealed by electrophoresis in phosphate buffer, but the major structural
characteristics have been determined by partial hydrolysis. The pectic acid is
esterified to a very small extent (1% OCH3) and consists
predominantly of 1,4-a-linked D-galacturonic acid units with L-arabofuranose
units as the major neutral constituent.
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