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PubMed1985

[High performance liquid chromatographic determination of organic acids, sugars, glycerin and alcohol in wine on a cation exchange resin].

The main constituents of wine (ethanol, glycerol, glucose, fructose, tartrate, malate, lactate, succinate, acetate and citrate) were separated by HPLC in one run and determined quantitatively in a time of 25 min. The stationary phase was the cation exchange resin HPX 87H and the mobile phase was dilute sulfuric acid. The results of the HPLC analysis of several wines are presented. Good agreement is observed with the results obtained by conventional methods.

Acids↗
PubMed1984

Effect of age-dependent changes on jejunal and ileal amino acid-sugar interaction in vivo.

The effects of L-leucine on jejunal and ileal D-galactose absorption have been studied at three different ages in rats using a perfusion system in vivo. Both, D-galactose and L-leucine have been perfused through the jejunum and the ileum at two concentrations, 5mM (low) and 20 mM (high). L-leucine induced a reversible inhibition of D-galactose absorption at the three ages studied and in both intestinal segments. The inhibition was higher at 20 mM when carriers were saturated. A lineal correlation exits between the inhibition percentage and the age of animals, increasing with growth in the jejunum and decreasing in the ileum. Attention is called to the possibility of different transport mechanisms at low concentration (5 mM), one of low affinity in the jejunum and the other of high affinity in the ileum.

Absorption↗
PubMed1990

Central action of endogenous sugar acid (2-buten-4-olide): comparison with local anesthesia in hypothalamus.

Rats were trained to discriminate cue tone stimuli (CTS) predicting reward (CTS+) [juice or intracranial self-stimulation (ICSS)], or aversion (CTS-) (mild electric shock or tail pinch). Unit activity in the lateal hypothalamus (LHA) and lateral preoptic-anterior hypothalamic area (lPOA-AHA) of the rat was recorded during CTS learning. The effects of local anesthesia of the amygdala (AM), ventral tegmental area (VTA) or LHA by procaine hydrochloride, and the effects of intraperitoneal or intravenous 2-buten-4-olide (2-B4O) on LHA neural activity and licking behavior were compared. LHA neurons differentiated between rewarding and aversive stimuli, and acquired corresponding discrimination of CTS+ and CTS-. In the lPOA-AHA, neurons responded similarly to CTS+, rewarding stimuli, CTS- and aversive stimuli. Procainization of the AM suppressed LHA neural responses to CTS1+ predicting juice, and stopped licking for juice. Procainization of the VTA suppressed LHA neural responses to CTS2+ predicting ICSS, and stopped licking for ICSS. LHA procainization suppressed both licking for juice and ICSS. Both intraperitoneal and intravenous 2-B4O stopped licking for juice and ICSS, but did not influence LHA responses to CTS1+ or CTS2+. The results suggest that dynamic interaction of AM-LHA-VTA are important for CTS+ learning, and 2-B4O acts directly on LHA neurons while maintaining afferent sensory inputs to the LHA.

4-Butyrolactone↗
PubMed1988

A novel endogenous sugar acid depolarizes ventromedial hypothalamic neurons in vitro.

2-Buten-4-olide (2-B-4-O) has been identified in the serum of fasted rats and proved to act as a feeding suppressant. The effect of 2-B-4-O on neurons in the ventromedial hypothalamic (VMH) nucleus was investigated with intracellular recordings in brain slice preparations of rats. 2-B-4-O, applied by perfusion (0.1-10 mM) or drops (50-100 mM), dose dependently depolarized 30% of the VMH neurons tested. The depolarization by 2-B-4-O application persisted after complete elimination of synaptic inputs during perfusion with Ca2+-free/high-Mg2+ solution. The depolarization, accompanied by a decrease in membrane conductance, reversed polarity around -95 mV and was dependent on extracellular K+ concentration. The VMH neurons depolarized by 2-B-4-O had some specific electrophysiological properties corresponding with those of glucoreceptor neurons. The results suggest that 2-B-4-O directly excites VMH neurons, presumed to be glucoreceptor neurons, by decreasing K+ conductance, and this effect may participate in the feeding suppressive action of 2-B-4-O.

4-Butyrolactone↗
PubMed2005

Acidic sugar degradation pathways: an ab initio molecular dynamics study.

Ab initio molecular dynamics (MD) simulations were employed to elucidate xylose and glucose degradation pathways. In the case of xylose, a 2,5-anhydride intermediate was observed leading to the formation of furfural through elimination of water. This pathway agrees with one of the mechanisms proposed in the literature in that no open chain intermediates were found. In the case of glucose, a series of intermediates were observed before forming the 2,5-anhydride intermediate that eventually leads to hydroxymethylfurfural (HMF). One of these intermediates was a very short-lived open-chain form. Furthermore, two novel side-reaction pathways were identified, which lead to degradation products other than HMF.

Anhydrides↗