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PubMed2001

Effect of xanthurenic acid on infectivity of Plasmodium falciparum to Anopheles stephensi.

Terminally differentiated malarial gametocytes remain in the vertebrate circulation in a developmentally arrested state until they are taken up by the mosquito. The gametocytes then undergo gametogenesis in the mosquito mid-gut within minutes after ingestion of the infected blood meal. The male gametogenesis (exflagellation) can be triggered by the combination of a decrease in temperature of at least 5 degrees C and a simultaneous increase in pH between 8.0 and 8.3. Xanthurenic acid, which is present in mosquito mid-gut as well as in mosquito head, had been shown to induce exflagellation in vitro at a non-permissible pH. Here we report for the first time that with the increasing concentration of exogenous xanthurenic acid, there is a gradual increase in the number of oocysts in the mid-gut of infected mosquitoes. The concentration of xanthurenic acid for optimum infection in the membrane feeding assay was determined to be 100 microM. Three different strains of Plasmodium falciparum, viz. 3D7, 7G8 and W2 were tested in different experiments and similar findings hold true for all of them. These results demonstrate that xanthurenic acid not only induces exflagellation of male gametocytes but also promotes infectivity of Plasmodium falciparum to mosquito vectors.

Animals↗
PubMed1997

Transamination of 3-hydroxykynurenine to produce xanthurenic acid: a major branch pathway of tryptophan metabolism in the mosquito, Aedes aegypti, during larval development.

An electrochemically active compound was detected in the larvae of Aedes aegypti mosquitoes and progressive accumulation of this compound was observed during larval development. The compound was purified from mosquito larvae using various chromatographic techniques and spectral analysis of the purified compound resulted in its identification as xanthurenic acid. Production of xanthurenic acid results from the transamination of 3-hydroxykynuorenine, and analysis of the biochemical pathway in xanthurenic acid production revealed the presence of a particular transaminase that has a much higher specific activity to 3-hydroxykynurenine than to kynurenine in the mosquito larvae. Concentration of xanthurenic acid is closely related to the level of this transaminase activity. Results suggest that this particular transaminase plays an important role in regulating the level of 3-hydroxykynurenine in the mosquito, A. aegypti during larval development.

Aedes↗
PubMed2001

The gametocyte-activating factor xanthurenic acid stimulates an increase in membrane-associated guanylyl cyclase activity in the human malaria parasite Plasmodium falciparum.

Sex is an obligate step in the life cycle of the malaria parasite and occurs in the midgut of the mosquito vector. With both Plasmodium falciparum and Plasmodium berghei, the tryptophan metabolite xanthurenic acid induces the release of motile male gametes from red blood cells (exflagellation), a prerequisite for fertilization. The addition of cGMP or phosphodiesterase inhibitors to cultures of mature gametocytes has also been shown to stimulate exflagellation. Here, we demonstrate that there is a guanylyl cyclase activity associated with mature P. falciparum gametocyte membrane preparations, which is dependent on the presence of Mg(2+)/Mn(2+) but is inhibited by Ca(2+). Significantly, this activity is increased on addition of xanthurenic acid. In contrast, a xanthurenic acid precursor (3-hydroxykynurenine), which is not an inducer of exflagellation, does not induce this guanylyl cyclase activity. These results therefore suggest that xanthurenic acid-induced exflagellation may be mediated by activation of the parasite cGMP signalling pathway.

Animals↗
PubMed1989

Kynurenine metabolism and xanthurenic acid formation in vitamin B6-deficient rat after tryptophan injection.

Normal and vitamin B6-deficient rats received an intraperitoneal injection of 30 mg/100g of body wt, and the contents of metabolites in kidney or plasma and the related enzyme activities in kidney were determined. The contents of kynurenine and 3-hydroxykynurenine in B6-deficient rat plasma and kidney were much higher than those in normal rat. The changes of those contents in plasma were parallel to those in kidney, but not in liver. The contents of kynurenic acid and xanthurenic acid in B6-deficient liver, plasma, and kidney were also much higher than those in normal rats. However, the changes of those contents in plasma were parallel to those in liver, but not in kidney. Xanthurenic acid and kynurenic acid accumulated to a much greater extent in kidney than in plasma and liver. Kidney kynureninase activity was very low, but kynurenine aminotransferase activities were very high. These observations indicated that the production of xanthurenic acid after tryptophan injection was favorable in B6-deficient kidney with respect to enzyme activities and substrate concentrations, and suggested that kidney took up kynurenine or 3-hydroxykynurenine from blood and after conversion of them it excreted xanthurenic or kynurenic acid into urine.

Animals↗
PubMed2001

Identification of a novel fluorophore, xanthurenic acid 8- O -beta-D-glucoside in human brunescent cataract.

We have identified the chemical structure of a novel protein-unbound fluorescent glucoside (Fl-Glc), found to be far more abundant in the human brunescent cataractous lens nuclei than in non-brunescent ones. Our earlier experiments showed that long-term incubation of the protein-free filtrate of non-brunescent cataractous nuclei generated increasing amounts of a particular yet to be characterized fluorophore (Fl-X). High performance liquid chromatography (HPLC) analyses revealed Fl-X and Fl-Glc to be identical. HPLC-electrospray ionization-mass spectrometry (HPLC-ESI-MS) disclosed the molecular weights (MW) of Fl-X and its beta-glucosidase-digest (Fl-X-aglycon) to be 367 and 205, respectively. Fl-X-aglycon and authentic xanthurenic acid (MW = 205) not only eluted at exactly the same retention time on HPLC but also revealed their protonated ions at the same m/z of 206.1 by positive ion analysis on HPLC-ESI-MS. These results suggest that Fl-X ( = Fl-Glc) is a beta-glucoside of xanthurenic acid. Fl-Glc was finally identified as xanthurenic acid 8- O -beta- D -glucoside because the retention times of both completely agreed with three kinds of HPLC conditions.

Cataract↗
PubMed1983

Antagonism of kynurenine-induced seizures by picolinic, kynurenic and xanthurenic acids.

Picolinic, kynurenic, xanthurenic and anthranilic acids are metabolites of L-kynurenine which, when administered intraperitoneally (i.p.) antagonized (in descending order of potency) the seizures induced by intracerebroventricular (i.c.v.) injections of l-kynurenine sulfate in SHR and C57BL/6 mice. Picolinic and anthranilic acids were also effective after oral administration. Picolinic acid completely prevented seizures. Kynurenic acid, when injected i.c.v. prior to l-kynurenine sulfate, appeared to be more effective than after i.p. administration while picolinic and anthranilic acids were less effective. This suggest that the antikynurenine effect of metabolites of kynurenine (kynurenines) is related to different brain structures, i.e. kynurenic acid predominantly affects structures adjacent to ventricles (e.g. hippocampus, caudate nucleus) while picolinic and anthranilic acids act on other brain structures or the periphery. Xanthurenic, kynurenic and picolinic acids merely prolonged the latency of seizures induced by i.c.v. quinolinic acid (another metabolite of kynurenine) or by subcutaneous strychnine sulfate and i.p. pentylenetetrazole, and did not modify seizures induced by i.p. caffeine and thiosemicarbazide. This selective antagonism of the tested kynurenines against kynurenine might be an important anticonvulsant factor in kynurenine-dependent seizures. It is suggested that increased excretion of xanthurenic, kynurenic and picolinic acids in patients with convulsive states may be manifestations of compensatory processes.

Animals↗
PubMed1998

Identification of xanthurenic acid as the putative inducer of malaria development in the mosquito.

Malaria is transmitted from vertebrate host to mosquito vector by mature sexual blood-living stages called gametocytes. Within seconds of ingestion into the mosquito bloodmeal, gametocytes undergo gametogenesis. Induction requires the simultaneous exposure to at least two stimuli in vitro: a drop in bloodmeal temperature to 5 degrees C below that of the vertebrate host, and a rise in pH from 7.4 to 8.0-8.2. In vivo the mosquito bloodmeal has a pH of between 7.5 and 7.6. It is thought that in vivo the second inducer is an unknown mosquito-derived gametocyte-activating factor. Here we show that this factor is xanthurenic acid. We also show that low concentrations of xanthurenic acid can act together with pH to induce gametogenesis in vitro. Structurally related compounds are at least ninefold less effective at inducing gametogenesis in vitro. In Drosophila mutants with lesions in the kynurenine pathway of tryptophan metabolism (of which xanthurenic acid is a side product), no alternative active compound was detected in crude insect homogenates. These data could form the basis of the rational development of new methods of interrupting the transmission of malaria using drugs or new refractory mosquito genotypes to block parasite gametogenesis.

Animals↗
PubMed1981

Xanthurenic acid excretion in urine after oral intake of 5 grams L-tryptophan by healthy volunteers: standardisation of the reference values.

The excretion of xanthurenic acid in urine after oral intake of 5 grams of L-tryptophan was studied and correlated with test and test-person parameters. The xanthurenic acid was determined by a colorimetric method, which gives reliable and reproducible results. Two groups, of 11 healthy volunteers each, participated. The first group started the test at 08.00 hours and the second group at 22.00 hours. Both groups repeated the same test, within one weed of the first test, at 22.00 hours. The xanthurenic acid excretion in the 24-hour urine correlated significantly (p = 0.04) with urine volume, but did not correlated with age, sex, height, body-weight, urine pH and urinary output of creatinine or 17-hydroxysteroids. The intraindividual variability of the test is not significant. The test should be started in the evening and the urine should be collected over 24 hours. The new reference values for the xar thurenic acid excretion under these conditions are 68.8 +/- 19.0 mumols/24 h.

Aging↗
PubMed1989

Monoamineoxidase activity in certain brain regions associated with xanthurenic acid excretion in rats on oral contraceptive steroids.

Monoamineoxidase (MAO) activity in some regions of brain and urinary xanthurenic acid were investigated in female rats administered with oral contraceptive (OC) steroids-ethynyl estradiol (Ees), lynestrenol (Ly) and both in combination (Cm) for 75 days. The MAO activity was reduced significantly in most regions specially in cortex-the extent of reduction being 65 per cent with Ees, 51 per cent with Ly and 69 per cent with Cm treatments. In the hypothalamus, the activity was decreased by 50 per cent with Ees, 38 per cent with Ly and by 40 per cent with Cm treatments. In the corpus striatum the activity was reduced by 14 per cent with Ly treatment, 25 per cent with Cm treatment and in the midbrain by 59 per cent with Ees treatment only. The concentration of xanthurenic acid in urine was higher by 55 per cent with Ees, 109 per cent with Ly and by 120 per cent with Cm treatments. These changes in MAO activity and level of xanthurenic acid excretion indicate the possible alteration in the metabolism of neurotransmitter, associated with prolonged use of OC.

Animals↗
PubMed1976

Effect of varying vitamin B6 intake of early-weaned piglets on urinary xanthurenic and kynurenic acid excretion, serum transaminase activity and urea concentration.

In a bipartite rearing experiment (day 1-24 and 24-45) 72 early-weaned piglets were used to study the effect of varying dietary vitamin B6 contents on renal excretion of xanthurenic and kynurenic acid after a tryptophan load, on urea concentration and activities of two transaminases in serum at the end of each period. The animals, divided into 6 groups, were fed ad libitum a prestarter and a starter in period I and II, respectively, each containing 0.5, 1.2, 2.0, 2.8, 3.5 or 6.6 mg vitamin B6 per kg dry matter. The urinary xanthurenic acid excretion was elevated especially at the vitamin B6 supply of 0.5 ppm and rose severalfold with increasing depletion time (period II). In both periods, the smallest amount was excreted by piglets supplemented with 2.8 ppm. In comparison to groups B (1.2 ppm) and C (2.0 ppm), their average excretion rate was reduced by 29% and 15%, respectively, in period I and by 50% and 22%, respectively, in period II. Analogously to xanthurenic acid, the smallest amount of kynurenic acid was excreted by group D (2.8 ppm). Starting from the lowest vitamin B6 supply, the activity of SGPT showed an almost linear increase in both experimental periods. In contrast, SGOT already reached an upper activity level with the dietary vitamin B6 content of 3.5 and 2.8 ppm at the end of period I and II, respectively. The concentration of serum urea was influenced only by the lowest vitamin B6 supply of 0.5 ppm.

Alanine Transaminase↗
PubMedDate not supplied

[Renal excretion of xanthurenic acid as an index of vitamin B6 allowance in infants].

Renal excretion of xanthurenic acid without any tryptophan load, passage of 4-pyridoxic acid with diurnal urine and its excretion with urine collected during 1 hour in the morning on an empty stomach were investigated in 86 practically healthy infants and in 77 others with acute respiratory viral infections aged from two weeks to one year. Investigations of the tryptophan tolerance in infants yielded negative results, viz. on administering to them of D,L-tryptophan in a load dose the infants started vomiting. Practically healthy infants did not excrete xanthurenic acid, while the renal excretion of 4-pyridoxic acid remained within normal limits. In patients at the height of the disease the passage of 4-pyridoxic acid steeply increased. In 9 of them xanthurenic acid appeared in the diurnal urine. In the quiscent stage of the affection in two infants xanthurenuria continued against the general background of diminished excretion of 4-pyridoxic acid. There is no reason to relate the disclosed xanthurenuria in sick infants with the state of hypovitaminosis in them.

Age Factors↗
PubMed1994

Determination of 8-methyl ether of xanthurenic acid in human urine by high-performance liquid chromatography.

We developed a simple and sensitive assay for the urinary 8-methyl ether of xanthurenic acid (XA-OMe) by high-performance liquid chromatography with fluorescence detection (excitation at 340 nm; emission at 450 nm). Urine samples were diluted with 0.03 M potassium phosphate buffer (pH 6.0) and applied to an octadecylsilane-bonded column (Nucleosil 5C18, 150 x 4 mm I.D.). The mobile phase used was a mixture of this same buffer and acetonitrile (1000:140, v/v). Both direct injection of urine and solvent extraction prior to HPLC were tested and showed a good correlation and sensitivity, although the peak of XA-OMe was occasionally less distinguishable from close peaks in urine from normal controls by the direct injection method. The quantification limit was 5 x 10(-14) mol which was sensitive enough to detect XA-OMe in urine from normal subjects. The method was applied to samples from patients with a deficiency in tryptophan catabolism, xanthurenic acid/3-hydroxykynurenine-uria and showed a striking elevation in urinary XA-OMe excretion.

Child, Preschool↗
PubMed2002

Formation of kynurenic and xanthurenic acids from kynurenine and 3-hydroxykynurenine in the dinoflagellate Lingulodinium polyedrum: role of a novel, oxidative pathway.

The dinoflagellate Lingulodinium polyedrum (syn. Gonyaulax polyedra) was used as a model organism for studying the effects of high and low physiological oxidative stress on the formation of kynurenic and xanthurenic acids from kynurenine and 3-hydroxykynurenine. Cell were incubated with the precursors and exposed to light (high physiological stress due to photosynthetically formed oxidants) or kept in darkness (low stress). In cultures of less than 0.5 ml cell volume/l of medium, cells took up approximately one half of 0.1 mM extracellular kynurenine within 18 h. The amino acid was partially converted to kynurenic acid, most of which was released to the medium; however, intracellular concentrations of the product were by approximately 10-fold higher than extracellular levels. Rates of kynurenic acid release exceeded by far those explained by kynurenine and tryptophan aminotransferase activities, the latter representing an additional source of kynurenic acid formation via indole-3-pyruvic acid. Light enhanced the release of kynurenic acid by approximately 4-fold; these rates were further increased by exposure to continuous light. Diurnal rhythmicity of kynurenic acid release was clearly exogenous and did not match with the circadian pattern of kynurenine or tryptophan aminotransferase activities; no rhythm was detected in constant darkness. Similar findings were obtained on turnover of 3-hydroxykynurenine to xanthurenic acid and release of the product to the medium. However, light/dark differences were relatively smaller, and additional products were formed, according to HPLC data obtained with electrochemical detection. Results are most easily explained on the basis of a recently discovered pathway of kynurenic acid formation from kynurenine, involving either non-enzymatic oxidation by H(2)O(2) or, at higher rates, enzymatic catalysis by hemoperoxidase. A corresponding mechanism may exist for the hydroxylated analogue.

Animals↗
PubMed2003

Melatonin, xanthurenic acid, resveratrol, EGCG, vitamin C and alpha-lipoic acid differentially reduce oxidative DNA damage induced by Fenton reagents: a study of their individual and synergistic actions.

DNA damage generated by oxygen-derived free radicals is related to mutagenesis, carcinogenesis and aging. In the last several years, hundreds of publications have confirmed that melatonin is a potent endogenous free radical scavenger. In the present in vitro study, we have examined the efficacy of three polyphenolic antioxidants, i.e. xanthurenic acid, resveratrol (3,4',5-trihydroxy-trans-stilbene) and (-)-epigallocatechin-3-gallate (EGCG) and two classical non-polyphenolic antioxidants, i.e. vitamin C (ascorbic acid) and alpha-lipoic acid (LA, 1,2-dithiolane-3-pentanoic acid) in inhibiting *OH-induced oxidative DNA damage. We compared the efficacy of these five antioxidants with the effectiveness of melatonin (N-acetyl-5-methoxytryptamine) and we also investigated the possible synergistic effects of melatonin with the other five molecules. Using high performance liquid chromatography (HPLC), the formation of 8-hydroxy-2-deoxyguanosine (8-OH-dG) in purified calf thymus DNA treated with the Fenton reagents, chromium(III) (as CrCl3) plus hydrogen peroxide (H2O2) (Cr(III)/H2O2), was measured in the presence or absence of the antioxidants alone or in combination with melatonin. 8-OH-dG is considered a biomarker of oxidative DNA damage. Among the antioxidants tested, melatonin was the most effective of these with an IC50 = 3.6 +/- 0.1 micro m. For the other antioxidants the IC50 values were as follows: xanthurenic acid (IC50 = 7.9 +/- 0.3), resveratrol (IC50 = 10.9 +/- 0.3), EGCG (IC50 = 5.7 +/- 0.3), vitamin C (IC50 = 16.9 +/- 0.5) and LA (IC50 = 38.8 +/- 0.7). These values differ from that of melatonin with a P < 0.01. Melatonin (1 micro M) reversed the pro-oxidant effect of resveratrol (0.5 micro M) and vitamin C (0.5 micro M), had an antagonistic effect when used in combination with EGCG (1 micro M) and it exhibited synergism in combination with vitamin C (0.5 micro M) and with LA (5 micro M).

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1977

Interaction between xanthurenic acid-insulin complex and zinc ions.

An equimolar mixture of a xanthurenic acid-insulin complex and ZnSO4 was separated into an insulin peak and a peak containing xanthurenic acid (XA) and Zn by Sephadex G-75 column chromatograpy. XA and di-[L-histidino]-zinc (II) readily combined to produce di-[L-histidino]-di-xanthurenato zinc (II) (His2-Zn2+-XA2). By increase in the concentration of Zn2+ ions, XA was removed from di-[L-histidino]-di-xanthurenato zinc (II) (His2-Zn2+-XA2) as XA-Zn2+. The XA-insulin complex showed dcreased relative intensity of fluorescence compared with the Zn-insulin when excited at a wavelength of 284 nm. The difference spectrum between native Zn-insulin and XA-insulin complexes showed a slight red shift. A diffference in the CD spectrum between native Zn-insulin and XA-insulin complexes was observed.

Binding Sites↗
PubMed2004

The Pseudomonas siderophore quinolobactin is synthesized from xanthurenic acid, an intermediate of the kynurenine pathway.

To cope with iron deficiency fluorescent pseudomonads produce pyoverdines which are complex peptidic siderophores that very efficiently scavenge iron. In addition to pyoverdine some species also produce other siderophores. Recently, it was shown that Pseudomonas fluorescens ATCC 17400 produces the siderophore quinolobactin, an 8-hydroxy-4-methoxy-2-quinoline carboxylic acid (Mossialos, D., Meyer, J.M., Budzikiewicz, H., Wolff, U., Koedam, N., Baysse, C., Anjaiah, V., and Cornelis, P. (2000) Appl Environ Microbiol 66: 487-492). The entire quinolobactin biosynthetic, transport and uptake gene cluster, consisting out of two operons comprising 12 open reading frames, was cloned and sequenced. Based on the genes present and physiological complementation assays a biosynthetic pathway for quinolobactin is proposed. Surprisingly, this pathway turned out to combine genes derived from the eukaryotic tryptophan-xanthurenic acid branch of the kynurenine pathway and from the pathway for the biosynthesis of pyridine-2,6-bis(thiocarboxylic acid) from P. stutzeri, PDTC. These results clearly show the involvement of the tryptophan-kynurenine-xanthurenic acid pathway in the synthesis of an authentic quinoline siderophore.

Cloning, Molecular↗
PubMed1975

Development of analytical methods for the detection and determination of kynurenic and xanthurenic acids.

A survey was carried out on the techniques developed by numerous research workers in this important field since Liebig discovered the presence of kynurenic acid in the urine of dogs fed on meat and Musajo that of xanthurenic acid in the urine of rats on a fibrin diet. The survey starts with the old methods of assay by precipitation of kynurenic acid and goes on to include the more recent ones of colorimetric assay of xanthurenic acid with ferrous sulphate or ferric chloride and of kynurenic acid by means of transformation into a chloro-derivative of the type of Besthorn dyes. Chromatographic techniques including paper chromatography, thin-layer chromatography, column chromatography nad gas chromatography, enabled researchers to detect the slightest traces of the two quinolincarbonic acids in the biological fluids together with the other metabolites of tryptophan. Among the techniques adopted for this purpose electrophoresis, automatic analyzers, polarography and, finally, the use of labelled substances, in particular L-tryptophan-3-C14, are included.

Animals↗