Flow injection analysis coupled with carbon electrodes as the tool for analysis of naphthoquinones with respect to their content and functions in biological samples

Naphthoquinones are one of the groups of secondary metabolites widespread in nature, where they mostly appear as chromatic pigments. They embody broad-range of biological actions from phytotoxic to fungicidal. An anticancer effect of naphthoquinones stimulates an interest in determination and characterization of single derivatives of 1,2- and 1,4-quinones in biological samples. The main aim of this work was to suggest a technique suitable to determine lawsone, juglone and/or plumbagin in biological samples and to study of their influence on BY-2 tobacco cells. The BY-2 tobacco cells were cultivated in the presence of the naphthoquinones of interest ( 500 mu g.l(-1)) for 24 h and then the morphological changes were observed. We found out that naphthoquinones triggered the programmed cell death at BY-2 cells, which can be confirmed by the apoptotic bodies in nucleus. After that we suggested and optimized different electrochemical techniques such differential pulse voltammetry ( DPV) coupled with hanging mercury drop ( HMDE) and carbon paste electrode, micro flow device coupled with carbon screen printed electrodes and flow injection analysis coupled with Coulochem III detector to determine them. The detection limits of naphthoquinones of interest were expressed as 3S/N and varied from units to hundreds of ng per millilitres according to methods used. Moreover, we utilized DPV coupled with HMDE and micro flow device to determine content of juglone in leaves Persian walnut ( Juglans regia). We determined that the leaves contained juglone tenths of g per 100 g of fresh weight. The results obtained show the convincing possibilities of using of these methods in analysis of plant secondary metabolites

Palladium biosensor

In this paper we proposed a palladium(II) biosensor. The biosensor is based on determining of interactions between palladium(II) and metallothionein modified hanging mercury drop electrode by means of differential pulse voltammetry. We studied influence of two supporting electrolytes (potassium or sodium chloride) on the signals of the biosensor. Based on the results obtained we found potassium chloride (0.05 M) as the most suitable supporting electrolyte to determine palladium(II). The detection limit of the biosensor for palladium ions was evaluated as 100 nM with RSD about 10%. Moreover, we utilized the biosensor for measurement of the target molecule in the presence of human blood serum and human urine

Toxicological aspects of flavonoid interaction with biomacromolecules

OBJECTIVES: Flavonoids are widely accepted as health promoting phytochemicals, however, some flavonoids show ability of direct interaction with DNA and/or enhance carcinogen activation into DNA modifying agents. Thus, their potential harmful effect on the human body should be examined in detail. METHODS: Direct interaction of flavonoids (quercetin, rutin) with DNA was examined using square wave voltammetry on carbon paste electrode. Induction effect of selected flavonoids on content of cytochrome P450 1A1, carcinogens activating enzyme, in colon and liver microsomal samples of animals exposed to flavonoids was determined by Western blotting, using anti-cytochrome P450 lAl specific antibody. RESULTS: Of the natural flavonoids tested, induction of CYPIA1 was elicited by the typical citrus flavonoid naringenin in the colon, as well as by flavone in the liver. Moreover, synthetic (beta-naphthoflavone and naturally occurring chrysin, quercetin and diosmin induced CYP1A1 in both tissues. The oxidation signals of guanine and adenine in the DNA molecule were decreased in the presence of flavonoids. CONCLUSIONS: Although flavonoids are often considered to be safe because of their "plant origin"; ingestion of flavonoids should be taken with caution. Enhanced expression of CYPIA1 in colon tissue might be responsible for increasing incidence of colorectal carcinoma in humans. Electrochemistry can be used to study the interactions of flavonoids and DNA

Determination of isoflavones using liquid chromatography with electrochemical detection

Among the biologically important roles of isoflavones is also their effect on carcinogenesis. We used flow injection analysis and high performance liquid W with electrochemical detection to simultaneously determine certain isoflavones (biochanin A, formononetin, sissotrin, daidzin, daidzein, glycitin, glycitein and genistein). The most suitable chromatographic conditions were: mobile phase: 0.2 mol L-1 acetate buffer (pH 5.0); flow rate 2.0 mL min(-1); column and detector temperature: 26 degrees C; detection potential: 800 mV. Under the optimal conditions, the detection limits were in the range of several ng mL(-1). Their simultaneous determination takes 15 min

Utilizing of square wave voltammetry to detect flavonoids in the presence of human urine

About biological affecting of flavonoids on animal organisms is known less, thus we selected flavonoids, flavanones and flavones, and their glycosides, which were examined as potential inducers of cytochrome(s) P450 when administrated by gavages into experimental male rats. The study was focused on induction of CYP1A1, the major cytochrome P450 involved in carcinogen activation. The data obtained demonstrate the necessity of taking into account not only ability of flavonoids to bind to Ah receptor (induction factor) but also to concentrate on their distribution and metabolism (including colon microflora) in the body. After that we examined certain flavonoids as potential inducers of cytochrome P450, we wanted to suggest and optimize suitable electrochemical technique for determination of selected flavonoids (quercetin, quercitrin, rutin, chrysin and diosmin) in body liquids. For these purposes, we selected square wave voltannetry using carbon paste electrode. Primarily we aimed on investigation of their basic electrochemical behaviour. After that we have optimized frequency, step potential and supporting electrolyte. Based on the results obtained, we selected the most suitable conditions for determination of the flavonoids as follows: frequency 180 Hz, step potential 1.95 mV/s and phosphate buffer of pH 7 as supporting electrolyte. Detection limits (3 S/N) of the flavonoids were from units to tens of nM except diosmin, where the limit were higher than M. In addition, we attempted to suggest a sensor for analysis of flavonoids in urine. It clearly follows from the results obtained that flavonoids can be analysed in the presence of animal urine, because urine did not influence much the signals of flavonoids (recoveries of the signals were about 90 %)

Bio-Assessing of Environmental Pollution via Monitoring of Metallothionein Level Using Electrochemical Detection

In this paper, we report on an investigation of affecting guppy fishes (Poecilia reticulata) by silver ions (0, 0.3, 0.6, 1.2, 2.5, and 5 mu M) for seven days under well-controlled experimental conditions. To observe the physiological changes, we attempted to determine metallothionein (MT) as a biomarker of heavy metal stress. For this purpose, we proposed a sensor utilizing a carbon electrode coupled with flow injection analysis. The experimental conditions, which have been optimized, were as follows-applied potential: 750 mV, mobile phase: Britton-Robinson buffer (pH 1.9) with How rate of 0.6 ml/min, time filter: 2.5 s, "current R": 1 mu A. Under these conditions, the detection limit of MT was estimated as 100 pM. After the optimizing step, the fish tissues were measured. Based on the results obtained, MT content increased with increasing dose of silver ions and time of the treatment. The results obtained were in good correlation with those obtained by adsorptive transfer stripping technique coupled with differential pulse voltammetry Brdicka reaction, which was used as the reference technique