Degradation Products Fromed from Glucosamine in Water

Article abstract of DOI:10.1021/jf970812n

An aqueous solution of glucosamine hydrochloride was heated to 150 °C for 5 min under different pH conditions. The reaction product mixture obtained was analyzed by GC/MS. It was found that the major products formed were furfurals, especially at pH = 4 and 7. At pH = 8.5, additional flavor components were generated, including pyrazines, 3-hydroxypyridines, pyrrole-2-carboxaldehyde, furans, acetol, and several other compounds. Of the components identified, it is worthwhile to note the formation of pyrazine and methylpyrazine as major components at pH = 8.5. It is proposed that a retro-aldol condensation plays an important role in the formation of the intermediates, α-aminoacetaldehyde (I) and α-amino propanal (II). As a result, self-condensation of I generates pyrazine and combination of I and II generates methylpyrazine. In addition, it is also interesting to note the formation of 3-hydroxypyridines and pyrrole-2-carboxaldehyde. It is suggested that both groups of compounds are derived from furfurals. As the ammonia is liberated from glucosamine, it initiates the ring-opening of furfurals to form 5-amino-2-keto-3-pentenals. Intramolecular condensations of these intermediates between the amino group and the carbonyl groups lead to the formation of 3-hydroxypyridines and pyrrole-2-carboxalhyde.

Full text of DOI:10.1021/jf970812n

J. Agric. Food Chem. 1998, 46, 1129−1131
1129
Degr a d a tion P r od u cts F or m ed fr om Glu cosa m in e in Wa ter
Chi-Kuen Shu
Bowman Gray Technical Center, R. J . Reynolds Tobacco Company, Winston-Salem, North Carolina 27105
An aqueous solution of glucosamine hydrochloride was heated to 150 °C for 5 min under different
pH conditions. The reaction product mixture obtained was analyzed by GC/MS. It was found that
the major products formed were furfurals, especially at pH ) 4 and 7. At pH ) 8.5, additional
flavor components were generated, including pyrazines, 3-hydroxypyridines, pyrrole-2-carboxalde-
hyde, furans, acetol, and several other compounds. Of the components identified, it is worthwhile
to note the formation of pyrazine and methylpyrazine as major components at pH ) 8.5. It is
proposed that a retro-aldol condensation plays an important role in the formation of the
intermediates, R-aminoacetaldehyde (I) and R-amino propanal (II). As a result, self-condensation
of I generates pyrazine and combination of I and II generates methylpyrazine. In addition, it is
also interesting to note the formation of 3-hydroxypyridines and pyrrole-2-carboxaldehyde. It is
suggested that both groups of compounds are derived from furfurals. As the ammonia is liberated
from glucosamine, it initiates the ring-opening of furfurals to form 5-amino-2-keto-3-pentenals.
Intramolecular condensations of these intermediates between the amino group and the carbonyl
groups lead to the formation of 3-hydroxypyridines and pyrrole-2-carboxaldehyde.
Keyw or d s: Glucosamine; retro-aldol condensation; R-amino acetaldehyde; R-amino propanal; GC/
MS
INTRODUCTION
It is well-known that the first step of the amino acid-
reducing sugar reaction is a sugar amine condensation,
leading to an N-substituted Amadori or Heyns inter-
mediate, from which the flavor compounds are gener-
ated via subsequent rearrangements and/or degradation
reactions. Similarly, when the amino acid is replaced
with ammonia, the sugar amine condensation also
occurs, initially forming the simple sugar amine instead
of an Amadori or Heyns intermediate. Previous studies
on the flavor formation from Amadori and Heyns
compounds are abundant (Vernin and Parkanyi, 1982;
Finot et al., 1990; Labuza et al., 1994), but the informa-
tion on flavor formation from simple sugar amines is
limited. The objective of this study was to identify the
degradation products formed from glucosamine in water
at different pH values and to propose the formation
F igu r e 1. Mechanism proposed for the formation of pyrazine
and methylpyrazine.
mechanism of some of the products identified.
EXPERIMENTAL PROCEDURES
furfural (1 g), diammonium hydrogen phosphate (2 g), and
water (70 mL) was performed.
Ma ter ia ls. Glucosamine hydrochloride, sodium hydroxide,
anhydrous sodium sulfate, furfural, and diammonium hydro-
gen phosphate were purchased from Aldrich Chemical Co.
(Milwaukee, WI). A DB-Wax fused silica column was pur-
chased from J &W Scientific, Inc. (Folsom, CA).
P r ep a r a tion of th e Rea ction Mixtu r es. In an enclosed
reaction vessel (Parr Instrument Co., Moline, IL), each solution
of glucosamine hydrochloride (5 g) and water (70 mL) was
heated at 150 °C for 5 min under different pH conditions (4,
7, and 8.5). The pH of the original solution was 4, while that
of the other two solutions was adjusted to 7 and 8.5 by adding
5% NaOH. Each reaction mixture obtained was adjusted to
pH 7 with NaOH and extracted with ethyl acetate (50 mL ×
3). The combined extracts were dried over anhydrous Na2-
SO4 and concentrated by a rotary evaporator to 25 mL prior
to the GC/MS analysis.
GC/MS An a lysis. The concentrated extracts were analyzed
by GC/MS on a DB-Wax fused silica column (30 m × 0.32
mm, 0.15 µm film thickness) with splitless injection. The oven
temperature was programmed from 50 to 200 °C at 3 °C/min;
a mass selective detector (EI; 70 eV) was used. The NBS
library was used for MS search.
Qu a n tita tive Estim a te. The internal standard, ethyl
undecanoate, was added to each concentrated extract, which
was then analyzed under the same chromatographic conditions
except a flame ionization detector was used. The response
factor of the internal standard was used for those of the
mixture components. The quantitative results obtained were
reported as parts per million (ppm) parts of glucosamine used.
RESULTS AND DISCUSSION
The components identified from the three glucosamine
reaction mixtures along with the quantitative data were
Rea ction of F u r fu r a l a n d Dia m m on iu m Hyd r ogen
P h osp h a t e. Under the above conditions, the reaction of
S0021-8561(97)00812-1 CCC: $15.00 © 1998 American Chemical Society
Published on Web 02/12/1998

1130 J. Agric. Food Chem., Vol. 46, No. 3, 1998
Shu
Ta ble 1. Com p on en ts Id en tified fr om th e Rea ction s Hea ted a t 150 °C for 5 m in a n d th e Qu a n tities Estim a ted (p p m )
component identified
pH ) 4
pH ) 7
pH ) 8.5
component identified
pH ) 4
pH ) 7
pH ) 8.5
pyrazine
methylpyrazine
acetoin
trace
trace
371
517
trace
97
11
30
21
132
18
furan-2,5-dicarboxaldehyde
quinaxoline
2-(2-furyl)pyrazine
17
22
11
16
trace
166
181
127
acetol
2-(hydroxyacetyl)furan
pyrrole-2-carboxaldehyde
2-(hydroxyethyl)pyrazine
3-hydroxy-4,5-dihydro-2(3H)-
furanone
trace
16
12
9
2,6-dimethylpyrazine
ethylpyrazine
2,3-dimethylpyrazine
vinylpyrazine
acetic acid
trace
hydroxymaltola
30
furfural
46
123
72
25
3-hydroxy-2-methylpyridine
3-hydroxy-6-methylpyridine
3-hydroxypyridine
(hydroxymethyl)pyridine isomer
5-(hydroxymethyl)furfural
2-acetyl-5-(hydroxymethyl)furan
trace
trace
180
141
488
240
2-acetylfuran
1-hydroxy-3-butanone
5-methylfurfural
2-acetylpyrazine
furfuryl alcohol
cyclotene
trace
trace
trace
187
trace
trace
2283
trace
460
trace
trace
trace
a
2,3-Dihydro-3,5-dihydroxy-6-methylpyran-4-one.
F igu r e 2. Mechanism proposed for the formation of 3-hydroxypyridines and pyrrole-2-carboxaldehydes.

Degradation of Glucosamine in Water
J. Agric. Food Chem., Vol. 46, No. 3, 1998 1131
compiled in Table 1. These results revealed that the
major products formed from the thermal degradation
of glucosamine in water were furfurals, especially at pH
) 4 or 7. At pH ) 8.5, additional flavor components
were generated, which included pyrazines (pyrazine and
methylpyrazine were the major components), 3-hy-
droxypyridines, pyrrole-2-carboxaldehyde, furans, hy-
droxy ketones, and several other compounds.
formation of pyrrole-2-carboxaldehydes. To support the
proposed mechanism, the reaction of furfural and di-
ammonium hydrogen phosphate (used as an ammonia
source) was performed under similar conditions. As
expected, both 3-hydroxypyridine and pyrrole-2-carbox-
aldehyde were generated as the major components,
providing further substantiation for the proposed for-
mation mechanism.
Of the components identified, it is worthwhile to note
the formation of the unsubstituted pyrazine, meth-
ylpyrazine, 3-hydroxypyridines, and pyrrole-2-carbox-
aldehyde. For the formation of these two major pyra-
zines, these data suggest that a retro-aldol condensation
plays an important role in the formation of the inter-
mediates, R-aminoacetaldehyde (I) and R-amino propa-
nal (II). As a result, self-condensation of I generates
pyrazine and combination of I and II generates meth-
ylpyrazine (Figure 1). It is also proposed that both
groups, 3-hydroxypyridines and pyrrole-2-carboxalde-
hyde may be derived from furfurals. Mechanistically,
the ammonia, liberated from glucosamine, initiates the
ring-opening of furfurals to form 5-amino-2-keto-3-
pentenals, as shown in Figure 2. Intramolecular con-
densation of these intermediates between the amino
group and the aldehyde group leads to the formation of
3-hydroxypyridines, while a similar condensation be-
tween the amino group and the keto group leads to the
LITERATURE CITED
Finot, P. A., Aeschbacher, H. U., Hurrell, R. F., Liardon, R.,
Eds. The Maillard Reaction in Food Processing, Human
Nutrition and Physiology; Birkhauser Verlag: Basel, Swit-
zerland, 1990.
Labuza, T. P., Reineccius, G. A., Monnier, V. M., O’Brien, J .,
Baynes, J . W., Eds. Maillard Reactions in Chemistry, Food,
and Health; The Royal Society of Chemistry: Cambridge,
England, 1994.
Vernin, G.; Parkanyi, C. Mechanisms of formation of hetero-
cyclic compounds in Maillard and pyrolysis reactions. In The
Chemistry of Heterocyclic Flavouring and Aroma Com-
pounds; Vernin, G., Ed.; Ellis Horwood: Chichester, U.K.,
1982, pp 151-207.
Received for review September 18, 1997. Revised manuscript
received December 15, 1997. Accepted December 17, 1997.
J F970812N