7. MONOSACCHARIDES AND OLIGOSACCHARIDES
323
glycosidic derivatives it is largely confined to the higher plants. In
extracts of the latter trace amounts of the free sugar have been found.
2. Combined
Xylans (123), which may be composed entirely of D-xylose or which
may contain minor amounts of other sugars, are plentiful in the woody
tissues of all kinds of higher plants. The marine alga Rhodymenia
palmata (124, 125) contains a xylan in which the units are arranged
somewhat differently from those in the polysaccharides of terrestrial
origin.
Plant gums from Astragalus spp. (genus Leguminosae) (gum tragacanth) (126); from wheat grain (127); from members of the Rosaceae,
peach (128), almond (129), egg plum (130), and cherry (131); from
the cactus Opuntia fulgida (cholla gum) (132); and from the leaves of
Phormium tenax (New Zealand flax) (133)—all have been shown to
contain moieties of D-xylose. Damson gum contains a much smaller
proportion (134). These gums (135), which are exudates from the surfaces of the plant, may possibly be pathological manifestations and may
vary in composition in a single plant (136).
From a number of different higher plants mucilages have been obtained that contain a proportion of D-xylose. Among Phntago spp.
xylose-containing mucilages are found in P. lanceolata (137), P. arenaria
(138), P. ovata (139), and P. fastigiata (140). Mucilages from quince
seed (141), flaxseed (linseed) (142), and seeds from Tamarindus indica
(143) also yield some D-xylose on hydrolysis.
In contrast with its prevalence in the higher plants, D-xylose is rare
as a component of simple glycosides. The disaccharide primeverose,
XßßG, glycosidically bound to alizarin, seems to be the sole example;
it occurs in Primula officinalis (145), in madder Rubia tinctorum
(146). Primeverose has also been found in the carob bean (Ceratonia
siliqua) (147). Many years ago a nonreducing D-glucosyl-D-xyloside
was described as occurring (as a dibenzoate) in the leaves of Daviesia
latifolia (148). The exact structure of this substance does not appear
to have been established.
The only example of a D-xylose-containing substance elaborated by
a microorganism is afforded by the capsular slime of the human pathogen Cryptococcus neoformans (formerly Torulopsis histolyticum)
(149).
This ill-defined material contains also D-mannose, D-galactose, and a
uronic acid.
H. L-FUCOSE
In combination, this sugar occurs in a wide variety of situations.
Members of the Phaeophyceae, e.g., Fucus, Laminaria,
Ascophyllum,
323
glycosidic derivatives it is largely confined to the higher plants. In
extracts of the latter trace amounts of the free sugar have been found.
2. Combined
Xylans (123), which may be composed entirely of D-xylose or which
may contain minor amounts of other sugars, are plentiful in the woody
tissues of all kinds of higher plants. The marine alga Rhodymenia
palmata (124, 125) contains a xylan in which the units are arranged
somewhat differently from those in the polysaccharides of terrestrial
origin.
Plant gums from Astragalus spp. (genus Leguminosae) (gum tragacanth) (126); from wheat grain (127); from members of the Rosaceae,
peach (128), almond (129), egg plum (130), and cherry (131); from
the cactus Opuntia fulgida (cholla gum) (132); and from the leaves of
Phormium tenax (New Zealand flax) (133)—all have been shown to
contain moieties of D-xylose. Damson gum contains a much smaller
proportion (134). These gums (135), which are exudates from the surfaces of the plant, may possibly be pathological manifestations and may
vary in composition in a single plant (136).
From a number of different higher plants mucilages have been obtained that contain a proportion of D-xylose. Among Phntago spp.
xylose-containing mucilages are found in P. lanceolata (137), P. arenaria
(138), P. ovata (139), and P. fastigiata (140). Mucilages from quince
seed (141), flaxseed (linseed) (142), and seeds from Tamarindus indica
(143) also yield some D-xylose on hydrolysis.
In contrast with its prevalence in the higher plants, D-xylose is rare
as a component of simple glycosides. The disaccharide primeverose,
XßßG, glycosidically bound to alizarin, seems to be the sole example;
it occurs in Primula officinalis (145), in madder Rubia tinctorum
(146). Primeverose has also been found in the carob bean (Ceratonia
siliqua) (147). Many years ago a nonreducing D-glucosyl-D-xyloside
was described as occurring (as a dibenzoate) in the leaves of Daviesia
latifolia (148). The exact structure of this substance does not appear
to have been established.
The only example of a D-xylose-containing substance elaborated by
a microorganism is afforded by the capsular slime of the human pathogen Cryptococcus neoformans (formerly Torulopsis histolyticum)
(149).
This ill-defined material contains also D-mannose, D-galactose, and a
uronic acid.
H. L-FUCOSE
In combination, this sugar occurs in a wide variety of situations.
Members of the Phaeophyceae, e.g., Fucus, Laminaria,
Ascophyllum,