Irena Vedrina-Dragojević

The content of essential and toxic elements in Croatian propolis samples and their tinctures

Summary There is a general lack of scientific literature dealing with the mineral composition of propolis, despite the fact that the presence of minerals in plant tissues can significantly affect the pharmacotherapeutic properties of derived products. Raw propolis samples collected from different Croatian regions and their respective tinctures were therefore analysed for mineral composition by atomic emission/absorption spectrometry. Contents of macro- and trace elements (Ca, K, Mg, Na, Al, B, Ba, Cr, Cu, Fe, Mn, Ni, Sr and Zn) were determined. Levels of toxic elements (As, Cd, Hg, and Pb) were also analysed, since they are possible environmental contaminants that could be transferred into propolis products for human consumption. Following the European Pharmacopoeia requirements for quality control of herbal drugs, crude propolis samples were also analysed for total ash content. Significant correlation between the total mineral content and total ash of raw propolis (r = 0.9273) showed that total ash might serve as the first information that justifies the need for detailed mineral analysis of tested samples. Among analysed minerals, Ca, Mg, K, Al, Fe and Zn were found to be the most abundant in raw propolis, ranging from 12.06 (Mg) to 932.6 mg/100g (Zn). Mineral contents of all investigated tinctures were significantly lower compared to the respective raw propolis samples. Extractability was variable due to influence of the sample matrix and correlated with the mineral content of raw propolis only in the case of Fe, Mg, Sr and Zn. All samples met the World Health Organization (WHO) standards regarding the maximum permitted amounts of Hg, Pb, As and Cd except for two raw propolis samples with increased lead content indicating pollution of the collection areas.

Spectrofluorometric method for determination of the total mercury content in environmental samples — Waste waters

A highly selective spectrofluorometric method for the determination of total mercury (Hg) in waste waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, is the basis of this sensitive method. All forms of mercury, including organic compounds, are pre-oxidized to ionic mercury by acidic potassium permanganate. The final and complete oxidation is achieved by adding potassium persulphate and heating. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. The recoveries were done by adding 3.0 μg Hg/100 ml to each sample before the digestion. It was indicated that the recoveries for determining mercury in waste waters were 98.3%–102.7%. The method gives reliable results down to a concentration of 10 ng Hg/ml waste water.

Preliminary investigation of metal and metalloid contamination of homeopathic products marketed in Croatia

BACKGROUND Due to their popularity as a complementary therapy in many diseases, homeopathic products of animal, vegetable, mineral and chemical origin should be tested for the presence of contaminants to prevent eventual toxic effects. OBJECTIVE Thirty samples of homeopathic products were analyzed to estimate possible contamination with potentially toxic elements: Pb, Cd, As, Hg, Cr, Ni and Zn, and to assess human exposure to these metals/metalloid as a consequence of their consumption. METHODS Atomic absorption spectrometry was used to determine metal and metalloid concentrations. RESULTS Most tested products had very low metal/metalloid levels (below the limit of quantification of the method), but the metal/metalloid levels in the remaining products were in the following ranges (in microg g(-1)): Pb 0.33-1.29 (6 samples), Cd 2.78 (1 sample), As 0.22 (1 sample), Hg 0.02-0.12 (24 samples), Cr 0.40-10.27 (10 samples), Ni 0.43-55.00 (19 samples), and Zn 2.20-27.80 (11 samples). In the absence of regulatory standards for homeopathic products, the obtained results were compared to maximum allowable levels (MALs) as proposed by USP Ad Hoc Advisory Panel. Some analyzed preparations had metal levels above MALs (Pb: 2 samples; Cd: 1 sample; Ni: 2 samples). However, estimated cumulative daily intakes from tested homeopathic products were in all cases lower than permitted daily exposures for all dosage forms. CONCLUSION The risk of bioaccumulation of metals/metalloid from the homeopathic medicines seems to be rather low, due to small quantities of those products prescribed to be applied per day, as well as insignificant metal contamination of the majority of tested products. However, the fact that particular formulations were contaminated by metals above MALs indicates potential risk and points to the necessity of regular monitoring of homeopathic products for metal contamination, due to their frequent and mostly unsupervised use.

Changes in available methionine and tryptophan contents during cereal flake production

The changes in available methionine and tryptophan contents during industrial production of wheat, rye, barley and oat flakes have been investigated. The contents of available methionine and tryptophan were lowered significantly (p = 0.05) under conditions of technological processing. The total decrease in available methionine ranged from 13 to 26% and tryptophan from 10 to 20%. Hydrothermal treatment (120°C, 60min, 1.99 x 10 5 Pa) of whole cereal grain had a considerable impact on the damage to available methionine, but the highest decrease in tryptophan was determined after the flaking process (70°C, 0.3 mm gap). The total decrease in these amino acids correlates significantly (p =0.001) and positively with values for lipid oxidation products, expressed on a total lipid basis, in cereal flakes as well as in untreated cereal grains. Available methionine and tryptophan contents in proteins of cereal flakes equalled or exceeded requirements for adults recommended by the FAO 1985 reference pattern.

Dynamics of the accumulation of thiamine during maturation of soybean seeds

Summary The dynamics of the accumulation of thiamine were followed in developing seeds of four genotypes of soybean under defined climatic and constant topographical and agrotechnical conditions in the course of three consecutive vegetation years. Tests were carried out at weekly intervals until the seeds were completely mature and had a moisture content of about 14%. Thiamine content was determined fluorometrically by measuring the intensity of thiocrome fluorescence. It was found that the greatest accumulation of the dry matter took place during the seed development stages III and IV whereas thiamine accumulation is more or less linear during the development. Maximal concentrations of thiamine were found in mature seeds. Although the dynamics of accumulation, regardless of the year of investigation, were the same in all the genotypes, the analysis of the impact of climatic factors showed that higher precipitation during the period of seed development, along with moderate air temperature, affected thiamine accumulation of some soybean genotypes more than others.

Spectrofluorometric method for determination of the total mercury content in natural waters.

ZusammenfassungEs wurde eine einfache, schnelle und hochselektive spektrofluorometrische Methode zur quantitativen Bestimmung des Gehalts an Gesamtquecksilber in Wasser beschrieben. Diese empfindliche Methode begründet sich auf der Fluorescenzlöschung in Rodamin-B-Lösung mittels Hg(II) bei Anwesenheit von Jodid und nach einem Verfahren, das den Zweck einer Quecksilberanreicherung hat. In Wasserproben wurden die organischen als auch anorganischen Quecksilberverbindungen mit H2SO4 aufgeschlossen und mit KMnO4 oxydiert. Nach der Beseitigung des entstandenen MnO2-Niederschlags bzw. des überschüssigen Permanganats mit HONH3Cl wurde das Quecksilber mit SnCl2 reduziert. Dann wurde das flüchtige Quecksilber durch einen Luftstrom in wässerige Absorptionslösung mit H2SO4 und KMnO4 eingeleitet und damit angereichert. In dieser Meßlösung wurde die Fluorescenzlöschung des Rodamin-B bei der Anregungswellenlänge von 485 nm und Emissionswellenlänge von 586 nm ermittelt. Das entwickelte Untersuchungsverfahren ist für die Bestimmung des Gehalts an Gesamtquecksilber in Trinkwasser und Oberflächengewässern anwendbar. Die Nachweisgrenze liegt bei etwa 0,5 μg Quecksilber/L Wasser. Zusätze von Quecksilber zu untersuchten Wasserproben ergaben eine Wiederfindungsrate und Standardfehler von im Durchschnitt 97,3±2,39.AbstractA simple and highly selective spectrofluorometric method for the determination of the total mercury (Hg) in natural waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, has been made the basis of this sensitive method. Organic and inorganic Hg compounds in water samples were decomposed with sulphuric acid and potassium permanganate. Precipitated manganese dioxide and excess oxidants (permanganate) were destroyed with hydroxylammonium chloride. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. This method is suitable for the determination of total Hg in drinking and surface waters. The method gives reliable results down to a concentration of 0.5 μg Hg per litre of water. The water samples analysed by this method gave a mean recovery and standard error of 97.3±2.39 for added Hg.

Effect of frozen storage on the degree of vitamin B6 degradation in different foods

ZusammenfassungAus den Ergebnissen der Untersuchung des Gefriervorgangs und der fünfmonatigen Lagerung bei -18°C auf die Stabilität des Gesamtvitamin B6 bei Lebensmitteln verschiedener Herkunft kann geschlossen werden, daß die Verluste des Vitamins Bß von 18,92% bis 60,26% betragen und daß der Verlust bei den Lebensmitteln tierischer Herkunft (ca. 55,0%) bedeutsam höher ist. Es ist offensichtlich, daß die Biostruktur, beziehungsweise die chemische Zusammensetzung, einer der wesentlichen Gründe ist, die die Höhe des Verlustes des Vitamins B6 bei den Lebensmitteln, die bei -18 °C gelagert werden, beeinflussen. Wenn man aber den biologischen Wert des Lebensmittels betrachtet, auch bei einigen Lebensmitteln pflanzlicher Herkunft, ist der Verlust des biologischen Wertes schon nach fünf Monaten verhältnismäßig hoch, jedoch nach der Deklaration kann tiefgefrorenes Gemüse bis zu 12 bzw. 24 Monaten gelagert werden.AbstractInvestigation of the effect of freezing and storage at-18° C for 5 months on the stability of total vitamin B6 in foods of different origin leads to the conclusion that the decrease in vitamin B6 content ranged from 18.92% to 60.26% and that the loss is significantly greater in food of animal origin (an average of 55.0%). Obviously, biostructure, that is chemical composition, is one of the basic factors affecting the degradation degree of vitamin B6 in foods preserved by freezing. However, in relation of their biological value and with reference to the declaration allowing deep-frozen vegetables to be stored for 12–24 months, some foods of vegetable origin preserved by freezing exhibit a relatively high loss of biological value in terms of vitamin B6 as early as after 5 months of storage.

Fluorometric method for determination of vitamin B6 in soya bean

ZusammenfassungDie einfache fluorometrische Methode zur Bestimmung von zugegebenem Pyridoxin in angereicherten Lebensmitteln basiert auf der Oxidation des Pyridoxins mit Kaliumpermanganat zur 4-Pyridoxinsäure und wurde für die Bestimmung des gesamten Vitamin B6 in Soja modifiziert. Im Vergleich mit anderen fluorometrischen Methoden ist die vorgeschlagene, einfach, schnell und leicht durchzuführen. Diese Methode braucht nur wenig Zeit für die Oxidation und verwendet ungiftige Chemikalien (KMnO4 statt KCN). Die gute Wiederfindung, die geringe relative Standardabweichung und der geringe Gesamtfehler reiht das vorgeschlagene Verfahren in die Gruppe der ausgezeichneten Methoden ein.SummaryThe simple fluorometric method for determination of added pyridoxine-HCl in enriched food, based on oxidation of pyridoxine to 4-pyridoxic acid by means of KMnO4, has been modified for determination of total B6 in soya bean. In comparison to the other fluorometric procedures, the proposed method is the simplest one, rapid and easy to perform, demanding the least time for oxidation and not using hazardous chemicals (KMnO4 instead of KCN). Good recovery, low relative standard deviation and low total error allow the proposed procedure to be included into the group of excellent methods.

Modified lumiflavin procedure for determination of riboflavin in soyabean

ZusammenfassungDurch Prüfen der Anwendungsmöglichkeit verschiedener Methoden zur Bestimmung von Riboflavin wurde festgestellt, daß die Lumiflavin-methode von Hausheer u. Mitarb. [1] die geeigneste zur Bestimmung von Riboflavin in Stoffen komplexer Zusammensetzung wie Soja ist. Infolge der nicht angemessenen Vorbereitung der Blindprobe wird die Methode durch einen positiven Resultatfehler belastet. Durch die Modifizierung der Blindprobe und des Verfahrens wurden genauere Resultate, eine größere Geschwindigkeit und eine einfachere Methode erzielt. Die Soja-Muster, die nach diesem modifizierten Verfahren analysiert wurden, haben eine Wiederfindung des Riboflavins und einen Standardfehler von 102,9±2,1SummaryInvestigation of the application of different methods for riboflavin determination proved the lumiflavin method recommended by Hausheer et al. [1] to be the most suitable one for determining riboflavin in materials of complex composition, such as soyabean. However, due to inadequate preparation of the blank sample, the method is burdened by a positive error. By modifying the blank sample and certain modifications in the procedure, more precise results, greater speed and simplification of the method were achieved. The soyabean sample analysed by this modified procedure gave a mean recovery and standard error of 102.9±2.1 for added riboflavin, which is very satisfactory.