The influence of L-ascorbic acid on the antibacterial-toxic activity of aflatoxins on adsorbent layer.

AIMS: To substantiate the role of formaldehyde (HCHO) and its reaction products in the mechanism of the antibacterial-toxic effect of aflatoxins B1 (AFB1), B2, G1 and G2. MATERIALS AND RESULTS: Toxins were separated by overpressured layer chromatography, which was followed by biological evaluation directly on the adsorbent layer (BioArena system with Pseudomonas savastanoi pv. phaseolicola indicator bacteria). HCHO formed in this system was eliminated with exogenously added capturer molecule dimedone and L-ascorbic acid (AA) and measured as the adduct of dimedone and HCHO. The amount of HCHO was higher in the toxin-containing spots, particularly in the most toxic AFB1 spot, compared to a toxinless background. 0.1 mg ml(-1)AA augmented, 0.2 mg ml(-1) dimedone or 0.5 and 1 mg ml(-1) AA reduced the antibacterial effect of all four aflatoxins. CONCLUSION: The antibacterial-toxic effect of aflatoxins may be mediated by HCHO (and/or its reaction products) generated from bound HCHO forms in the bacterial cells. Basis of antibacterial-toxic activity of the four aflatoxins appears the same. SIGNIFICANCE AND IMPACT OF THE STUDY: Involvement of HCHO as a key molecule in the effect of aflatoxins indicates a totally new mechanism of action of these dangerous molecules. The BioArena system is useful to dissect the mode of action of antimicrobial compounds from different biological matrices.

Opposite effect of Cu(II) and Se(IV) ions on the antibacterial-toxic action of mycotoxins.

The effect of Se(IV) and Cu(II) ions on the antibacterial activity of aflatoxins and ochratoxin A (mycotoxins) was studied in BioArena as a complex bioautographic system. In the presence of 0.23 and 0.46 mg/100 mL Se(IV) the inhibition zones of mycotoxins were decreased, however, lower concentration (0.046 mg/100 mL) increased the antibacterial effect of aflatoxin B1. Cu(II) (1.53 mg/100 mL) enhanced the toxicity of mycotoxins. The results supported the possible role of formaldehyde and its reaction products (e.g. 1O2, O3) in the antibacterial-toxic action of mycotoxins. Cu(II) can probably generate and mobilise the formaldehyde molecules and so it could increase the toxicity with its potential reaction products. It is possible that the enzymatic or spontaneous methylation of Se(IV) takes place through formaldehyde, which may cause partial formaldehyde depletion in the system. The enhanced antibacterial effect at low concentration Se(IV) is overlapping with the often experienced prooxidant effect in cases of natural antioxidants.

Formaldehyde and some fully n-methylated substances in boar seminal fluids. Short communication.

On the basis of recent observations it is supposed that seminal fluids may contain--mainly in hydroxymethyl groups--formaldehyde (HCHO) and quaternary ammonium compounds as potential HCHO generators, therefore, preliminary investigations were carried out for the identification of these compounds in pig seminal fluids using OPLC, HPLC and MALDI MS techniques. The fresh pig seminal fluid was frozen in liquid nitrogen, powdered and aliquots (0.25 g) were treated with 0.7 ml ethanolic dimedone solution. The suspension was centrifuged and the clear supernatant was used for analysis by OPLC or after dilution with HPLC or MALDI MS technique. After OPLC separation of formaldemethone the fully N-methylated compounds which are stayed on the start point were separated by OPLC using an other eluent system. It has been established that the HCHO is really a normal component of the pig seminal fluid, as well. It can be isolated and identified in dimedone adduct form. The measurable amount of HCHO depended on the concentration applied of dimedone. According to OPLC and MALDI MS investigations L-carnitine is the main quaternary ammonium compound in pig seminal fluid which can generate a protection of the sperm cells against environmental and other influences. Considerable differences have been found among individuals concerning concentrations of quaternary ammonium compounds in the seminal fluid of pigs.

Formaldehyde promotes and inhibits the proliferation of cultured tumour and endothelial cells.

Formaldehyde was applied in various doses (0.1-10.0 mM) to HT-29 human colon carcinoma and HUV-EC-C human endothelial cell cultures. Cell number, apoptotic and mitotic index as well as proportion of cells in S-phase was investigated by morphological methods and flow cytometry. Ten mM of formaldehyde caused high degree of cell damage and practically eradicated the cell cultures. One mM of formaldehyde enhanced apoptosis and reduced mitosis in both types of cell cultures, in a moderate manner. The low dose (0.1 mM) enhanced cell proliferation and decreased apoptotic activity of the cultured cells, the tumour cells appeared to be more sensitive. The possible role of this dose-dependent effect of formaldehyde in various pathological conditions, such as carcinogenesis and atherogenesis is discussed with emphasis on the eventual interaction between formaldehyde and hydrogen peroxide.

Dose-dependent effect of resveratrol on proliferation and apoptosis in endothelial and tumor cell cultures.

Experimental data suggest that Resveratrol, a compound found in grapes and other fruits may influence cell proliferation and apoptosis. The aim of our experiments was to study the effect of Resveratrol on tumor cell cultures and an endothelial cell culture in order to examine the effect of various doses of this compound on active cell death and cell proliferation. Human tumor (HT-29, SW-620, HT-1080) and endothelial (HUV-EC-C) cells were treated with various doses of (0.1 to 100.0 microg/ml) Resveratrol in vitro. Cell number, apoptotic and mitotic index was measured 24, 48 and 72 h after treatment. Low doses (0.1-1.0 microg/ml) of Resveratrol enhance cell proliferation, higher doses (10.0-100.0 microg/ml) induce apoptosis and decrease mitotic activity, which is reflected in changes of cell number. Resveratrol influences dose dependently the proliferative and apoptotic activity of human tumor and endothelial cells. The possible role of formaldehyde in the mechanism of action of Resveratrol is discussed.

HPLC-OPLC-MS investigation of change of formaldehyde and its generators in human teeth of different physiological stage.

Taking into consideration the unquestionable intracellular occurrence of formaldehyde (HCHO) and its generators in cells of plant, animal and human organisms as well as in body fluids it was resolved to determine their levels in hard tissues of physiologically and pathologically changed teeth. The aim of the work was to determine the relationship between the level of HCHO and the levels of its generators in pathologically changed teeth, mainly carietic teeth as tooth caries is still a serious and commonly occurring problem. The occurrence of HCHO (captured as its dimedone adduct) and some of its potential generators was demonstrated in the hard tissues of healthy and pathological human teeth by means of OPLC, HPLC and MS analyses. It was established that the measurable level of HCHO was increased in the carietic teeth in comparison with healthy ones. In the case of paradontic tooth sample, a dramatic increase of HCHO was observed and at the same time the level of betaines was decreased considerably. The obtained results give a new insight into the pathology of hard tissues of teeth in strong correlation with the phases of stress syndrome.

Measurement of formaldehyde as dimedone adduct and potential formaldehyde precursors in hard tissues of human teeth by overpressured layer chromatography.

Simple, automatic overpressured layer chromatographic methods for the parallel determination of endogenous formaldehyde in the form of dimedone adduct and potential formaldehyde generators (betaines) in hard tissues of human teeth are described together with an efficient densitometric evaluation. These simple procedures involve the special preparation of teeth and extraction of formaldehyde, of different binding force in teeth, with methanol containing dimedone, and the isolation of betaines with an aqueous solution of methanol.

Formaldehyde cycle and the natural formaldehyde generators and capturers.

S-adenosyl-L-methionine serves as a methyl donor in virtually all of the vast number of enzymatic transmethylation reactions including DNA methylation. On the basis of our former experiences we questioned the formation of a methyl cation or methyl radical in the enzymatic transmethylation reactions. The formation of formaldehyde from the methyl moiety of S-adenosyl-L-methionine has been demonstrated. It became increasingly evident that there is a formaldehyde cycle in biological systems in which the formation of the methyl group of L-methionine takes place through formaldehyde and the formation of formaldehyde from S-adenosyl-L-methionine is linked to different enzymatic transmethylation reactions. It is also known that during demethylation processes both formaldehyde and demethylated compound can be formed. The abnormalities of the originally controlled formaldehyde cycle and the uncontrolled enzymatic production of formaldehyde from endogenous and/or exogenous substrates may be potential risk factors in pathogenesis of different disorders. The formaldehyde generator and capturer molecules may potentially normalise these abnormal processes. Trans-resveratrol (trans-3,5,4'-trihydroxystilbene), which is as phytoalexin, occurs naturally in grapes and a variety of medicinal plants. According to our present observations it is a natural concentration-dependent formaldehyde capture molecule. It would seem that elimination of the uncontrolled formaldehyde with resveratrol may exert a double effect in biological systems. The elimination of formaldehyde with resveratrol (first step) may cause a cardioprotective effect and the reaction products between resveratrol and formaldehyde (second step) may act as a chemopreventive factor against cancer.

Formaldehyde in the plant kingdom.

Formaldehyde, at its dimedone adduct, formaldemethone, has been detected by thin-layer and high-performance liquid chromatography in extracts of all species tested of marine algae, macrofungi, lichens, bryophytes, pteridophytes, gymnosperms and angiosperms. The yields of formaldehyde recorded in this study varied from 30 microg/g to 4060 microg/g, fresh weight.

Induction of resistance of wheat plants to pathogens by pretreatment with N-methylated substances.

It has been established that the application of N-methylated compounds as N, N-dimethyl-L-tyrosine and glycine-betaine can induce resistance to biotrophic fungi (Erysiphe graminis, Puccinia recondita) in wheat (Yubileynaya) at two different pretreatment concentrations. This dose-dependent "double immune response" of plants is the basic phenomenon of the biochemical immunization. These N-methylated compounds are potential formaldehyde generators and the formaldehyde formed can take part in the induction of resistance of wheat plants. It seems that the dose-dependent "double immune response" of plants is in correlation with the biotransformation steps of formaldehyde cycle as a fundamental biochemical pathway.

Identification and measurement of resveratrol and formaldehyde in parts of white and blue grape berries.

The phytoalexin resveratrol (3,5,4'-trihydroxy-trans-stilbene) and formaldehyde (as its dimedone adduct, formaldemethone) have been identified and measured in the extracts of parts of white and blue grapes as well as in white and red wines by overpressured layer chromatography (OPLC), high performance liquid chromatography (HPLC) and from matrix assisted laser desorption/ionization mass spectrometric data. It has been established that the level of resveratrol was very high in skin and in some cases in the stem. Blue grape varieties and red wines always contained a considerably higher amount of resveratrol than white grapes and wines. The measurable level of formaldehyde as well as the resveratrol content was always parallelly high in the same parts of the berries, however, the formaldehyde level was higher in white grapes than in blue ones. The simultaneous occurrence of resveratrol and formaldehyde gives a possibility for interaction between these two special molecules, consequently, hydroxymethyl derivatives of resveratrol can be formed. These resveratrol derivatives may be responsible for special biological activities of resveratrol in grapes and dietetically (cardioprotective effect and chemopreventive effect against cancer) in the human organism.

Relationship between dimedone concentration and formaldehyde captured in plant tissues.

In different parts of water-melon plants (Citrullus vulgaris L.) formaldehyde (HCHO), in dimedone adduct form (formaldemethone), and fully N-methylated substances were identified and determined by OPLC as well as HPLC, capillary GC and GC-MS methods using authentic substances. The HCHO captured originates from dynamic methylation and demethylation processes in which this simplest aliphatic aldehyde is bound in the form of highly reactive hydroxymethyl groups. Dimedone will react with the small quantity of HCHO in equilibrium with the hydroxymethyl groups and it follows from this that the rate of HCHO captured as the dimedone adduct will increase parallel to the increasing concentration of dimedone applied, as a methanolic solution, until a plateau is reached. The level of HCHO was very high in the roots of water-melon seedlings.

The use of HPLC for the detection and quantification of formaldehyde in the pteridophyta.

Formaldehyde, as its dimedone adduct, formaldemethone, has been detected and quantified in all species of Pteridophyta examined. The procedure involved the use of an Hypersil C-18 column, methanol-water (60 : 40 v/v) as the mobile phase and an UV detector set at 258 nm. Quantification was based on peak height. Yields varied from 30 microg/g fresh weight for Polystichum setiferum to 5370 microg/g fresh weight for Selaginella viticulosa.

Formaldehyde generators and capturers as influencing factors of mitotic and apoptotic processes.

There is a growing amount of evidence pointing to the fact that several endogenous and exogenous methylated compounds are potential formaldehyde generators in their biological reactions. N(G)-methylated lysines, N(G)-methylated as well as hydroxymethylated arginines, and 1'-methyl-ascorbigen have been examined in this respect. The apoptosis-inducing effect of formaldehyde molecules formed from methyl groups was earlier first published by our group. Dimedone, an artificial capturer molecule for formaldehyde, has been found to prevent the apoptosis-inducing effect of 1'-methyl-ascorbigen as well as N(G)-hydroxymethylated arginines. More recently resveratrol, present in grapes and wines, has been shown to have cardioprotective and cancer chemopreventive effect. Our group has been successful in demonstrating that this natural formaldehyde capturer molecule can also influence cell proliferation and apoptosis. The apoptosis-inducing or -preventing effect of formaldehyde generators and capturers seems to be dose-dependent and may be utilized in various disturbances of cell proliferation and active cell death.

Reduction of apoptosis of in vitro cultured lymphocytes of HIV-positive persons by N(G)-hydroxy-methylated-L-arginine and 1'-methyl-ascorbigen.

Some formaldehyde generating chemicals due to reduction of apoptosis in lymphocytes may slow down the progress of immune decline of HIV-infected individuals. N(G)-hydroxy-methylated-L-arginine (MAX) and 1'-methyl-ascorbigen (MeAsc) could enter this way the biochemical pathway of cells and affect the apoptotic process. Separated peripheral blood lymphocytes of five asymptomatic HIV-positive persons were cultured. Unstimulated, IL-2 stimulated and IL-2 stimulated plus 0.1, 1.0, 10.0 microg/ml MAX or MeAsc treated lymphocytes were investigated for apoptosis morphologically (HE) and by flow cytometrical DNA fragmentation method. IL-2 stimulation lowered the apoptotic rate in lymphocytes of HIV-positive persons related to unstimulated ones. MAX and MeAsc reduced the apoptotic activity of stimulated lymphocytes in the least or the middle doses while in the higher dose did not. MAX and MeAsc reduced the apoptotic activity of stimulated lymphocytes originated from HIV-positive patients in vitro. This compounds may have the same effect in vivo and may prolong the symptomless period of HIV-infected patients. The role of methylation and production of formaldehyde in this process is discussed.

Formaldehyde generation by N-demethylation.

Microsomal oxidation of exogenic compounds yields efferent metabolites with small molecular size. N-demethylation results in formaldehyde generation in addition to the nor-compound. Interesting changes in the level of formaldehyde elimination were observed after a single dose of either ( )-deprenyl or (+)-deprenyl. Urine elimination of the generated formaldehyde was determined using thin-layer chromatography after derivatization with dimedone.

Change of biotransformation steps of formaldehyde cycle in water-melon plants after infection with Fusarium oxysporum.

Recent experiments indicate that the measurable formaldehyde (HCHO) level is considerably elevated in the parts of water-melon plants immediately after a nonlethal infection with Fusarium oxysporum f. sp. niveum. At the same time the level of some quaternary ammonium compounds (N(epsilon)-trimethyl-L-lysine, choline) as potential HCHO generators (gene products) is considerably decreased. That is probably due to the fact that the alarm reaction phase of this biotic stress syndrome includes an intensive demethylation process. It has been proved that HCHO may play a role in dynamic methylation-demethylation processes that also may include the methylation of biotic stress proteins. In this paper we report on qualitative and quantitative changes in the biotransformation steps of the formaldehyde cycle in different parts of the water-melon plant after nonlethal infection (biotic stress) with Fusarium. In consequence of the infection identical quantitative changes, but to a different degree, of the compounds examined are observable in both varieties. The connections resulting from the depiction of the time-dependent quantitative changes of the measured methylated compounds due to infection show a picture similar to that of Selye's stress syndrome model.

Effect of 1-methylascorbigen on the resistance potential of plants to pathogens.

We have studied the effect of 1'-methylascorbigen, an immunostimulating substance in animal systems on the resistance potential of barley, bean and wheat plants to the fungal pathogens Erysiphe graminis, Uromyces phaseoli and Puccinia recondita, respectively. The effectiveness of protection depends - as in the case of other endogenous, N-methylated compounds - on the dosage of applied 1'-methylascorbigen and on the time interval between the chemical pretreatment and inoculation. The time- and dose-dependent double immune response was clearly demonstrated in case of the barley - Erysiphe graminis and bean - Uromyces phaseoli host-parasite relationships while in case of the wheat -Puccinia recondita relationship the relatively long-time interval between pretreatment and inoculation allowed manifestation of only a single immune response.

Structure determination and synthesis of lysine isopeptides influencing on cell proliferation.

The clavicepamines are lysine-rich basic proteins isolated from saprophytic culture of ergot (Claviceps purpurea), having human pharmacological importance. Based on structure determinations, it was demonstrated that the epsilon-lysine (poly)peptides are the fundamental structural units of clavicepamines. To study the relationship between chemical structure and biological effect, solution and solid-phase synthesis of lysine isopeptides were performed. Poly-epsilon-lysines were synthesized with polycondensation via application of p-nitrophenylester temporarily protecting groups together with simultaneous activation. The biological investigations of poly-epsilon-lysines showed a cell-proliferation retarding effect, so they inhibit growth of some animal tumors, practically without toxic side effects.

Simple determination of formaldehyde in dimedone adduct form in biological samples by high performance liquid chromatography.

A high performance liquid chromatographic method for the determination of endogenous formaldehyde in dimedone adduct form in biological samples is described. The simple procedure involves extraction of the formaldehyde of different binding force in biological samples with methanol containing dimedone as the capture molecule and separation on a C18 reversed phase column with methanol as eluent.