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An acidic d -xylan from the Siberian apricot (Armeniaca siberica L.) fruit
Carbohydrate Research, 198 (1990) 163-167 Elsevier Science Publishers B .V., Amsterdam
163 - Printed
in The Netherlands
Note
An acidic o-xylan from the Siberian apricot (Armeniaca siberica L.) fruit PILZEGIJN ODONMAZIG, DAGVIJN BADGAA,
Institute of Chemistry, Mongolian Academy of Sciences, UIan-Bator (Mongolia) ANNA EBRINGEROVA* , VINCENT MIHALOV, AND JURAJ ALFOLDI
Institute of Chemistry, Slovak Academy of Sciences, 842 38 Bratislava (Czechoslovakia) (Received
April 7th, 1989; accepted
for publication,
August
14th, 1959)
The fruit of the wild Siberian apricot (Armeniaca siberica L.), which grows near Ulan-Bator (Mongolia), is an important potential raw material for the food and pharmaceutical industry’. The isolation of various organic acids2 and phlorizin3 therefrom has been reported, and the fractional extraction of the carbohydrate components of the ripe fruit and their general characteristics have been described4. Xylan-type hemicelluloses were major constituents of the cell-wall polysaccharides, and we now report on the structure of an acidic xylan from the ammoniacal extract of the cell-wall material. The water-insoluble, nitrogen-free hemicellulose fraction 4, isolated4 from the chlorite-delignified cell-wall material of the ripe apricot fruit, gave a single peak on ultracentrifugation and was assumed to be an L-arabino-(4-O-methyl-D-glucurono)D-xylan. However, on fractional precipitation of the xylan with CetavlorG, a minor proportion (A-l) was precipitated but the major part (A-2) remained in solution (Table I). A-2 appeared to be homogeneous in free-boundary electrophoresis, had a substantially diminished content of arabinose, but an almost unchanged molar ratio of xylose to uranic acid of 14:l. Uranic acids were present mainly as 4-0methyl-D-glucuronic acid (detected by p.c.) with traces of D-galacturonic acid. A single-step methylation6 of A-2 gave a product with [aID -51” (chloroform), indicative of p linkages. When methylated A-2 was reduced by lithium aluminium hydride and then hydrolysed, g.1.c. and g.l.c.-m.s. (Table II) of the products, as the partially methylated alditol acetates, revealed 2,3,4-&O-methylxylose, 2,3-di-0-methylxylose, mono-0-methylxylose, and 2,3,4-tri-O-methylglucase in the molar ratios 1.2:84.4:6.9:5.9. Identification of the 2- and 3-O-methylxylose was not possible on SP 2340, but fragmentation analysis’ of the alditol acetates obtained by borodeuteride reduction gave a ratio of 7:37. The preponder*Author
for correspondence.
000%6215/90/$03.50
@ 1990 Elsevier Science Publishers
B.V.
164 TABLE
NOTE
I
ANAI.YTICAL
CHARACTERISTICS
OF APRICOT
HEMICELLULOSES
Fraction A-I
No. 44
[ffl$O
-
0.5 0 1.6 94.2 1.3 2.4 22.9
9.8 0.8 14.2 16.6 12.3 46.3 -
2.4 7.1 7.8 71.3 7.9 3.5 23.9
Rhamnose (%) Fucose Arabinose Xylose Glucose Galactose ;i?. x IO-3
3.0 9.2d -66.0”
0.2 l.ld
3.9 9.2” -79.50
Yield (%) Uranic acid (%)*
A-2
“Per cent of starting apricot (dry-weight basis)“. bExpressed as “anhydro-(4-0-methyl-D-glucuronic acid)“.
ante of 2,3-di-0-methylxylose and the similar proportions of 3-0-methylxylose and 2,3,4-tri-0-methylglucose suggest that A-2 contained a backbone of (l-+4)-linked xylopyranosyl residues and single 4-0-methyl-D-glucopyranosyluronic acid units as side chains attached to position 2 of the xylose residues. Moreover, 2-0-(4-0methyl-a-D-glucopyranosyluronic acid)-D-xylose was isolated after partial hydrolysis of A-2 and identified by r3C-n.m.r. spectroscopy*. These results are in agreement with the uptake of periodate (0.97 moY132 g). In the r3C-n.m.r. spectrum of A-2 (Fig. l), the (1+4)-P-D-xylan backbone gives rise to characteristic main signals at 6 101.78, 72.66, 74.04, 75.45, and 63.28 related to the C-l 72 ?3 ,4 75 resonances 9Jo. The signals at 6 97.31, 71.91 (doublet), 81.84, 69.62, 173.78 (not shown), and 59.28 clearly indicate the presence of 4-0TABLE
II
METHYLATION
ANALYSIS
Methylared alditol acetate’
2,3,5-Me,-Ara 2,3,4-Me,-Xyl 2,3-Me,-Xyl Z-Me-Xyl 3-Me-Xyl 2,3,6-Me,-Gal 2,3,4-Me,-Glc
OF
A-2 (A)
AND
CARBOXYL-REDUCED
A-2 (B) I____-
Deduced linkage
Araf-( l+ Xylp-( l_, +4)-Xylp-(l-+ +3,4)-Xylp-(l-_, -+2,4)-Xylp-(l-+ +4)-Galp-(l-+ GlcpA-(la
Tb
0.63 0.82 1.44 2.14 2.14 2.01 1.92
Mole % A
B
trace 1.5 88.7 1.2 6.4 2.2 0
0 1.3 84.3 1.0 5.9 1.6 5.9
“2,3,5-Me,-Ara = 2,3,5-tri-O-methylarabinose, etc. bRetention times of the acetates on SP 2340 relative to that of 1,5-di-O-acetyl-2,3,4,6-tetra-0-methylglucitol.
corresponding
alditol
NOTE
105
95
100
Fig. 1. I%-N.m.r.
WL
h
A 90
85
p_p.m.
80
75
1. 70
65
60
spectrum for A-2.
methyl-cu-D-glucuronic acid groups and belong to C-1,2,3,4,5,6 and MeO-4. The location of the uronosyl residues at position 2 of the xylose residues is confirmediOJ1 by the signals of C-1,2,4,5 shifted to 101.30,76.55,76.22, and 42.72 p.p.m., respectively. A slight branching of the xylan chain indicated by the methylation analysis (Table II) can be deduced also from the occurrence of i3C signals with similar low intensities at 65.87 and 69.75 p.p.m., corresponding to C-5 and C-4, respectively, of the terminal xylopyranosyl residueslo. The formation of a small proportion (~0.5%) of 2,3,5-tri-O-methylarabinose from A-2 is indicative of terminal arabinofuranosyl groups, but their content is too low to be identified by 13C-n.m.r. spectroscopy. It is likely that both arabinosyl and galactosyl residues found in the purified xylan come from pectic polymers12 that were co-purified with A-2. An arabinose-cleavage effect of the delignification method can be excluded since such an effect was not observed during the isolation of arabinoxylans from sodium chlorite-holocellulose of rye bran13. The above data allow the conclusion that A-2 is a typical, slightly branched 4-O-methyl-D-glucurono-D-xylan, which constitutes a substantial part of the apricot tissue and bears a close resemblance in its structural features to that reported for woody tissues of angiosperms 14. The structure of A-2 differs greatly from that15 of an acidic xylan from pear cell-wall which had D-glucuronic acid residues attached at position 3 of a slightly branched xylan backbone. EXPERIMENTAL Generul. - Descending p.c. was performed on Whatman paper No. 1 with A, l-butanol-pyridine-water (6:4:3); B, ethyl acetate-acetic acid-formic acidwater (18: 3 : 1: 4); and detection with aniline hydrogenphthalate. The procedures
for total hydrolysis, quantitative
analysis of sugars, and determination
of uranic
166
NOTE
acid and optical rotation have been described 4~*3 . Free-boundary electrophoresis was performed with a Zeiss 35 apparatus (Jena) on a 1% solution of the polysaccharide in 0.05~ sodium borate buffer (pH 9.2). The number-average mol. wt. (M,) was determined by osmometry with a Knauer Osmometer on solutions in methyl sulfoxidc. The 13C-n.m.r. (75 MHz) spectrum was recorded on a 3% solution in (CD&O at 70”, using a Bruker AM-300 Spectrometer. 1.r. spectra were recorded with a Perkin-Elmer G983 spectrophotometer. Isolation and purification of the polysaccharide. - The crude xylan was the water-insoluble material (fraction 4) extracted by aq. 5% sodium hydroxide from delignified apricot cell-wal14. A solution of the crude xylan (1.44 g) in aq. 4% sodium hydroxide (80 mL) was treated5 with Cetavlon. From the precipitate, after washing with water and acidification, fraction A-l (81 mg) was obtained. The supernatant solution, after acidification and precipitation with ethanol, yielded fraction A-2 (1.08 g), Both fractions were dried by solvent exchange (ethanol, acetone, and ether). Partial hydrolysis of A-2. - A-2 (200 mg) was hydrolysed with aq. 0.2% oxalic acid (4 mL) at 100” for 2 h, and the products were separated into neutral and acidic sugar fractions, using the ion-exchange technique16. P.c. (solvent A) of the neutral fraction revealed xylose, traces of arabinose and galactose, and xylo-oligosaccharides (R,,t 0.66, 0.37, 0.17, and 0.06), identified by comparison with the synthetic componentsg. The first member of the series was isolated (18 mg) by preparative p.c. (solvent A). P.c. (solvent B) of the acidic fraction revealed two main components (Rx,, 1.48 and 0.68), the second of which was isolated (11 mg) by preparative p.c. (solvent B). The compounds isolated above were identified by ‘“Cn.m.r. spectroscopy as 4-0-P-D-xylopyranosyl-D-xylose and 2-O-(4-O-methyl-a-Dglucopyranosyluronic acid)-D-xylose*l”. Linkage analysis. - To a solution of A-2 (100 rug) in methyl sulfoxide (4 mL) was added6 dry, powdered sodium hydroxide (400 mg). After stirring the mixture under nitrogen for 1 h, methyl iodide (3 mL) was added slowly with external cooling. The methylation was allowed to proceed for 1 h at 40” and the mixture was then worked-up as described 13.The resulting methylated polysaccharide (90.8 mg) exhibited no i.r. absorption for hydroxyl. The methylated product (15 mg) was hydrolysed with aq. 90% oxalic acid (2 mL) at 100” for 1 h, then with 2~ trifluoroacetic acid (3 mL) at 100” for 3 h. To a solution of another portion (40 mg) in dry tetrahydrofuran (15 mL) was added lithium aluminium hydride (150 mg), and the mixture was boiled under reflux for 6 h, then worked-up in the usual way. The resulting reduced methylated A-2 had an i.r. band at 3600 cm-l (OH) but not at 1735 cm-l (ester C-O). Each methylated product was subjected to hydrolysis, as described above, and borodeuteride reduction, and the products were analysed by g.1.c. and g.l.c.-m.s.7,13. Periodate oxidation. - A- 2 (10 mg) was treated with 1LhM sodium periodate (10 mL) at room temperature in the dark. The periodate consumption was monitored spectrophotometrically17.
NOTE!
167
REFERENCES 1 P. ODONMAZIG, D. BADGAA, A. EBRINGEROVA,AND F. JANECEK, Tr. Inst. Chim. AN MNR (MongoZfa), (1984) 91-98. 2 B. MOELLERAND K. HERRMANN,J. Chromatogr., 2451 (1982) 371. 3 B. PROKSA,D. UHR~N,P. ODONMAZIG,AND D. BADGAA, Pharmazia, 43 (1988) 658. 4 P. ODONMAZIG,D. BADGAA, A. EBRINGEROVA, AND F. JANE~EK, .I. Sci. Food Agric., 35 (1985) 575-582. 5 E. SC~, Methods Carbohydr. Chem., 5 (1965) 38-44. 6 I. CILICANOAND F. KEREK, Carbohydr. Res., 131 (1987) 209-217. 7 P.-E. JANSSON,L. KENNE, H. LIEDGREN,B. LINDBERG,AND J. L~NNGREN, Chem. Commun. Univ. Stockholm, 8 (1976) l-75. 8 P. KovAC, E. PETRAKOVA, AND P. KoCrS, Carbohydr. Res., 93 (1981) 144-147. 9 J. HIRSCH,P. KovAt, AND E. PETRAKOVA, Carbohydr. Res., 106 (1982) 203-216. 10 P. KovAC, J. ALF~LDI, P. KoCIS, E. PETRAKOVA,AND J. HIRSCH,Cellul. Chem. TechnoL, 16 (1982) 261-269. 11 J.-P. UTILLE, P. KovAc, F. SAURIOL,AND A. S. PERLIN, Carbohydr. Res., 154 (1986) 2X-258. 12 K. W. TALMADGE, K. KEEGSTRA,W. D. BAUER, AND P. ALBERSHEIM,Plant Physiol., 51 (1973) 158-173. 13 Z. HROMADKOVA,A. EBRINGEROVA,E. PETRAKOVA.AND J. SCHRAML,Carbohydr. Res., 136 (1987) 73-79. 14 T. E. TIMELL, Adv. Carbohydr. Chem., 19 (1964) 247-302. 15 S. K. CHANDA, E. L. HIRST, AND E. G. V. PERCIVAL,J. Chem. Sot., 21 (1967) 74-77. 16 A. EBFUNGEROVA, A. KRAMAR, F. RENDOS,AND R. DOMANSKY,Holzforschung, 21 (1967) 74-77. 17 G. 0. ASPINALLAND R. J. FERRIER, Chem. Ind. (London), (1957) 819.
163 - Printed
in The Netherlands
Note
An acidic o-xylan from the Siberian apricot (Armeniaca siberica L.) fruit PILZEGIJN ODONMAZIG, DAGVIJN BADGAA,
Institute of Chemistry, Mongolian Academy of Sciences, UIan-Bator (Mongolia) ANNA EBRINGEROVA* , VINCENT MIHALOV, AND JURAJ ALFOLDI
Institute of Chemistry, Slovak Academy of Sciences, 842 38 Bratislava (Czechoslovakia) (Received
April 7th, 1989; accepted
for publication,
August
14th, 1959)
The fruit of the wild Siberian apricot (Armeniaca siberica L.), which grows near Ulan-Bator (Mongolia), is an important potential raw material for the food and pharmaceutical industry’. The isolation of various organic acids2 and phlorizin3 therefrom has been reported, and the fractional extraction of the carbohydrate components of the ripe fruit and their general characteristics have been described4. Xylan-type hemicelluloses were major constituents of the cell-wall polysaccharides, and we now report on the structure of an acidic xylan from the ammoniacal extract of the cell-wall material. The water-insoluble, nitrogen-free hemicellulose fraction 4, isolated4 from the chlorite-delignified cell-wall material of the ripe apricot fruit, gave a single peak on ultracentrifugation and was assumed to be an L-arabino-(4-O-methyl-D-glucurono)D-xylan. However, on fractional precipitation of the xylan with CetavlorG, a minor proportion (A-l) was precipitated but the major part (A-2) remained in solution (Table I). A-2 appeared to be homogeneous in free-boundary electrophoresis, had a substantially diminished content of arabinose, but an almost unchanged molar ratio of xylose to uranic acid of 14:l. Uranic acids were present mainly as 4-0methyl-D-glucuronic acid (detected by p.c.) with traces of D-galacturonic acid. A single-step methylation6 of A-2 gave a product with [aID -51” (chloroform), indicative of p linkages. When methylated A-2 was reduced by lithium aluminium hydride and then hydrolysed, g.1.c. and g.l.c.-m.s. (Table II) of the products, as the partially methylated alditol acetates, revealed 2,3,4-&O-methylxylose, 2,3-di-0-methylxylose, mono-0-methylxylose, and 2,3,4-tri-O-methylglucase in the molar ratios 1.2:84.4:6.9:5.9. Identification of the 2- and 3-O-methylxylose was not possible on SP 2340, but fragmentation analysis’ of the alditol acetates obtained by borodeuteride reduction gave a ratio of 7:37. The preponder*Author
for correspondence.
000%6215/90/$03.50
@ 1990 Elsevier Science Publishers
B.V.
164 TABLE
NOTE
I
ANAI.YTICAL
CHARACTERISTICS
OF APRICOT
HEMICELLULOSES
Fraction A-I
No. 44
[ffl$O
-
0.5 0 1.6 94.2 1.3 2.4 22.9
9.8 0.8 14.2 16.6 12.3 46.3 -
2.4 7.1 7.8 71.3 7.9 3.5 23.9
Rhamnose (%) Fucose Arabinose Xylose Glucose Galactose ;i?. x IO-3
3.0 9.2d -66.0”
0.2 l.ld
3.9 9.2” -79.50
Yield (%) Uranic acid (%)*
A-2
“Per cent of starting apricot (dry-weight basis)“. bExpressed as “anhydro-(4-0-methyl-D-glucuronic acid)“.
ante of 2,3-di-0-methylxylose and the similar proportions of 3-0-methylxylose and 2,3,4-tri-0-methylglucose suggest that A-2 contained a backbone of (l-+4)-linked xylopyranosyl residues and single 4-0-methyl-D-glucopyranosyluronic acid units as side chains attached to position 2 of the xylose residues. Moreover, 2-0-(4-0methyl-a-D-glucopyranosyluronic acid)-D-xylose was isolated after partial hydrolysis of A-2 and identified by r3C-n.m.r. spectroscopy*. These results are in agreement with the uptake of periodate (0.97 moY132 g). In the r3C-n.m.r. spectrum of A-2 (Fig. l), the (1+4)-P-D-xylan backbone gives rise to characteristic main signals at 6 101.78, 72.66, 74.04, 75.45, and 63.28 related to the C-l 72 ?3 ,4 75 resonances 9Jo. The signals at 6 97.31, 71.91 (doublet), 81.84, 69.62, 173.78 (not shown), and 59.28 clearly indicate the presence of 4-0TABLE
II
METHYLATION
ANALYSIS
Methylared alditol acetate’
2,3,5-Me,-Ara 2,3,4-Me,-Xyl 2,3-Me,-Xyl Z-Me-Xyl 3-Me-Xyl 2,3,6-Me,-Gal 2,3,4-Me,-Glc
OF
A-2 (A)
AND
CARBOXYL-REDUCED
A-2 (B) I____-
Deduced linkage
Araf-( l+ Xylp-( l_, +4)-Xylp-(l-+ +3,4)-Xylp-(l-_, -+2,4)-Xylp-(l-+ +4)-Galp-(l-+ GlcpA-(la
Tb
0.63 0.82 1.44 2.14 2.14 2.01 1.92
Mole % A
B
trace 1.5 88.7 1.2 6.4 2.2 0
0 1.3 84.3 1.0 5.9 1.6 5.9
“2,3,5-Me,-Ara = 2,3,5-tri-O-methylarabinose, etc. bRetention times of the acetates on SP 2340 relative to that of 1,5-di-O-acetyl-2,3,4,6-tetra-0-methylglucitol.
corresponding
alditol
NOTE
105
95
100
Fig. 1. I%-N.m.r.
WL
h
A 90
85
p_p.m.
80
75
1. 70
65
60
spectrum for A-2.
methyl-cu-D-glucuronic acid groups and belong to C-1,2,3,4,5,6 and MeO-4. The location of the uronosyl residues at position 2 of the xylose residues is confirmediOJ1 by the signals of C-1,2,4,5 shifted to 101.30,76.55,76.22, and 42.72 p.p.m., respectively. A slight branching of the xylan chain indicated by the methylation analysis (Table II) can be deduced also from the occurrence of i3C signals with similar low intensities at 65.87 and 69.75 p.p.m., corresponding to C-5 and C-4, respectively, of the terminal xylopyranosyl residueslo. The formation of a small proportion (~0.5%) of 2,3,5-tri-O-methylarabinose from A-2 is indicative of terminal arabinofuranosyl groups, but their content is too low to be identified by 13C-n.m.r. spectroscopy. It is likely that both arabinosyl and galactosyl residues found in the purified xylan come from pectic polymers12 that were co-purified with A-2. An arabinose-cleavage effect of the delignification method can be excluded since such an effect was not observed during the isolation of arabinoxylans from sodium chlorite-holocellulose of rye bran13. The above data allow the conclusion that A-2 is a typical, slightly branched 4-O-methyl-D-glucurono-D-xylan, which constitutes a substantial part of the apricot tissue and bears a close resemblance in its structural features to that reported for woody tissues of angiosperms 14. The structure of A-2 differs greatly from that15 of an acidic xylan from pear cell-wall which had D-glucuronic acid residues attached at position 3 of a slightly branched xylan backbone. EXPERIMENTAL Generul. - Descending p.c. was performed on Whatman paper No. 1 with A, l-butanol-pyridine-water (6:4:3); B, ethyl acetate-acetic acid-formic acidwater (18: 3 : 1: 4); and detection with aniline hydrogenphthalate. The procedures
for total hydrolysis, quantitative
analysis of sugars, and determination
of uranic
166
NOTE
acid and optical rotation have been described 4~*3 . Free-boundary electrophoresis was performed with a Zeiss 35 apparatus (Jena) on a 1% solution of the polysaccharide in 0.05~ sodium borate buffer (pH 9.2). The number-average mol. wt. (M,) was determined by osmometry with a Knauer Osmometer on solutions in methyl sulfoxidc. The 13C-n.m.r. (75 MHz) spectrum was recorded on a 3% solution in (CD&O at 70”, using a Bruker AM-300 Spectrometer. 1.r. spectra were recorded with a Perkin-Elmer G983 spectrophotometer. Isolation and purification of the polysaccharide. - The crude xylan was the water-insoluble material (fraction 4) extracted by aq. 5% sodium hydroxide from delignified apricot cell-wal14. A solution of the crude xylan (1.44 g) in aq. 4% sodium hydroxide (80 mL) was treated5 with Cetavlon. From the precipitate, after washing with water and acidification, fraction A-l (81 mg) was obtained. The supernatant solution, after acidification and precipitation with ethanol, yielded fraction A-2 (1.08 g), Both fractions were dried by solvent exchange (ethanol, acetone, and ether). Partial hydrolysis of A-2. - A-2 (200 mg) was hydrolysed with aq. 0.2% oxalic acid (4 mL) at 100” for 2 h, and the products were separated into neutral and acidic sugar fractions, using the ion-exchange technique16. P.c. (solvent A) of the neutral fraction revealed xylose, traces of arabinose and galactose, and xylo-oligosaccharides (R,,t 0.66, 0.37, 0.17, and 0.06), identified by comparison with the synthetic componentsg. The first member of the series was isolated (18 mg) by preparative p.c. (solvent A). P.c. (solvent B) of the acidic fraction revealed two main components (Rx,, 1.48 and 0.68), the second of which was isolated (11 mg) by preparative p.c. (solvent B). The compounds isolated above were identified by ‘“Cn.m.r. spectroscopy as 4-0-P-D-xylopyranosyl-D-xylose and 2-O-(4-O-methyl-a-Dglucopyranosyluronic acid)-D-xylose*l”. Linkage analysis. - To a solution of A-2 (100 rug) in methyl sulfoxide (4 mL) was added6 dry, powdered sodium hydroxide (400 mg). After stirring the mixture under nitrogen for 1 h, methyl iodide (3 mL) was added slowly with external cooling. The methylation was allowed to proceed for 1 h at 40” and the mixture was then worked-up as described 13.The resulting methylated polysaccharide (90.8 mg) exhibited no i.r. absorption for hydroxyl. The methylated product (15 mg) was hydrolysed with aq. 90% oxalic acid (2 mL) at 100” for 1 h, then with 2~ trifluoroacetic acid (3 mL) at 100” for 3 h. To a solution of another portion (40 mg) in dry tetrahydrofuran (15 mL) was added lithium aluminium hydride (150 mg), and the mixture was boiled under reflux for 6 h, then worked-up in the usual way. The resulting reduced methylated A-2 had an i.r. band at 3600 cm-l (OH) but not at 1735 cm-l (ester C-O). Each methylated product was subjected to hydrolysis, as described above, and borodeuteride reduction, and the products were analysed by g.1.c. and g.l.c.-m.s.7,13. Periodate oxidation. - A- 2 (10 mg) was treated with 1LhM sodium periodate (10 mL) at room temperature in the dark. The periodate consumption was monitored spectrophotometrically17.
NOTE!
167
REFERENCES 1 P. ODONMAZIG, D. BADGAA, A. EBRINGEROVA,AND F. JANECEK, Tr. Inst. Chim. AN MNR (MongoZfa), (1984) 91-98. 2 B. MOELLERAND K. HERRMANN,J. Chromatogr., 2451 (1982) 371. 3 B. PROKSA,D. UHR~N,P. ODONMAZIG,AND D. BADGAA, Pharmazia, 43 (1988) 658. 4 P. ODONMAZIG,D. BADGAA, A. EBRINGEROVA, AND F. JANE~EK, .I. Sci. Food Agric., 35 (1985) 575-582. 5 E. SC~, Methods Carbohydr. Chem., 5 (1965) 38-44. 6 I. CILICANOAND F. KEREK, Carbohydr. Res., 131 (1987) 209-217. 7 P.-E. JANSSON,L. KENNE, H. LIEDGREN,B. LINDBERG,AND J. L~NNGREN, Chem. Commun. Univ. Stockholm, 8 (1976) l-75. 8 P. KovAC, E. PETRAKOVA, AND P. KoCrS, Carbohydr. Res., 93 (1981) 144-147. 9 J. HIRSCH,P. KovAt, AND E. PETRAKOVA, Carbohydr. Res., 106 (1982) 203-216. 10 P. KovAC, J. ALF~LDI, P. KoCIS, E. PETRAKOVA,AND J. HIRSCH,Cellul. Chem. TechnoL, 16 (1982) 261-269. 11 J.-P. UTILLE, P. KovAc, F. SAURIOL,AND A. S. PERLIN, Carbohydr. Res., 154 (1986) 2X-258. 12 K. W. TALMADGE, K. KEEGSTRA,W. D. BAUER, AND P. ALBERSHEIM,Plant Physiol., 51 (1973) 158-173. 13 Z. HROMADKOVA,A. EBRINGEROVA,E. PETRAKOVA.AND J. SCHRAML,Carbohydr. Res., 136 (1987) 73-79. 14 T. E. TIMELL, Adv. Carbohydr. Chem., 19 (1964) 247-302. 15 S. K. CHANDA, E. L. HIRST, AND E. G. V. PERCIVAL,J. Chem. Sot., 21 (1967) 74-77. 16 A. EBFUNGEROVA, A. KRAMAR, F. RENDOS,AND R. DOMANSKY,Holzforschung, 21 (1967) 74-77. 17 G. 0. ASPINALLAND R. J. FERRIER, Chem. Ind. (London), (1957) 819.