The relationship of selenium tolerance and speciation in Lecythidaceae species.

Comparative study of selenium (Se) speciation in hyperaccumulator plants offers an interesting challenge from the analytical point of view. In our study the application of a sophisticated sample clean-up procedure and the combination of elemental and molecular mass spectrometric methods led to the identification of several new selenocompounds. The difference between the Se speciation of the primary accumulator Lecythis minor and the secondary accumulator Bertholletia excelsa confirmed the current opinion that the speciation pattern in hyperaccumulator plants is principally related to the mechanism of accumulation and not to taxonomy. The most abundant new selenocompounds were found to be the derivatives of selenohomocysteine (SeHCy) and selenomethionine (SeMet), including fatty acid metabolism related compounds. A series of SeHCy derived species containing multiple Se atoms (>2) was also detected and their structures were validated by the synthesis of their S-Se analogues.

Application of high-performance anion-exchange chromatography with pulsed amperometric detection to compare the kinetic properties of ß-glucosidase on oligosaccharides from lichenase digested barley ß-glucan.

A chromatographic method using HPAEC-PAD was developed to accurately quantify the major oligosaccharides derived from lichenase degradation of barley ß-glucan. This method was further used to follow ß-glucosidase degradation and product formation as progress curves. This approach allowed us to compare the kinetic characteristics of ß-glucosidase on each exclusive oligosaccharide substrate and their mixtures. Our results show that when determining the kinetic parameters of exohydrolases on oligosaccharides following the progress curve for the substrates is necessary since calculations based only on released monosaccharide products may lead to an error. The catalytic activity of almond ß-glucosidase on laminaribiose (G3G) was approximately half that measured against cellobiose (3.15 S(-1)). The enzyme had 12 times and 560 times less catalytic activity on 3-O-ß-cellobiosyl-D-glucose (G4G3G) and on 3-O-ß-cellotriosyl-d-glucose (G4G4G3G) respectively than on G3G. Our approach offers a useful tool for the determination of the kinetics of enzymatic or chemical modification of various carbohydrate substrates.

[Laboratory studies of the antioxidant effect and free radical elimination of CoD tea]. / A CoD tea antioxidáns és gyökelimináló hatásainak laboratóriumi vizsgálata.

Free radical elimination properties of anticarcinogenic CoD tea were studied in vitro in our laboratory. Therefore its antioxidant effect, lipid-hydroperoxide elimination property and reductive capacity were measured. The isoenzyme composition of CoD tea lipoxygenases was deduced from pH dependence of its lipoxygenase activity. It was found that the antioxidant effect and lipid-hydroperoxide elimination property of CoD tea were comparable with those of ascorbic acid and the reductive capacity of a cup of CoD tea and 11-13 mg ascorbic acid were the same. In spite of the heat sensibility of lipoxygenases, a strong lipoxygenase activity (1102 U/g) of CoD tea was detected in acidic medium (pH 4.5). It is supposed that these free radical elimination properties support anticarcinogenic effect of CoD tea.