The Scent of Antifungal Propolis.

Propolis contains many effective antifungal compounds that have not yet been identified and evaluated. In addition, distinguishing samples of propolis with high antifungal activity from less active ones would be beneficial for effective therapy. Propolis samples were collected from four different geographical regions in Hungary and used to prepare ethanol extracts for analysis. First, an antifungal susceptibility test was performed on Candida albicans. Then, gas chromatography-mass spectrometry (GC-MS) and an opto-electronic nose were applied for the classification of propolis samples. In three propolis samples, the IC50 was measured between 72 and 134 µg/mL, but it was not calculable in the fourth sample. GC-MS analysis of the four propolis samples identified several compounds belonging to the various chemical classes. In the antifungal samples, the relative concentration of 11,14-eicosadienoic acid was the highest. Based on the opto-electronic electronic nose measurements, 98.4% of the original grouped antifungal/non-antifungal cases were classified correctly. We identified several molecules from propolis with potential antifungal properties. In addition, this is the first report to demonstrate the usefulness of a portable opto-electronic nose to identify propolis samples with high antifungal activity. These results may contribute to the rapid and efficient selection of new fungicide-candidate molecules and effective propolis samples for treatment.

Voltammetric determination of the herbicide Linuron using a tricresyl phosphate-based carbon paste electrode.

This paper summarises the results of voltammetric studies on the herbicide 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (Linuron), using a carbon paste electrode containing tricresyl phosphate (TCP-CPE) as liquid binder. The principal experimental conditions, such as the pH effect, investigated in Britton-Robinson buffer solutions (pH 2.0-7.0), the peak characteristics for the analyte of interest, or instrumental parameters for the differential pulse voltammetric mode were optimized for the method. As found out, the best electroanalytical performance of the TCP-CPE was achieved at pH 2.0, whereby the oxidation peak of Linuron appeared at ca. +1.3 V vs. SCE. The analytical procedure developed offers good linearity in the concentration range of 1.25-44.20 µg mL(-1) (1.77 × 10(-4)-5.05 × 10(-6) mol L(-1)), showing-for the first time-the applicability of the TCP-CPE for anodic oxidations in direct voltammetry (without accumulation). The method was then verified by determining Linuron in a spiked river water sample and a commercial formulation and the results obtained agreed well with those obtained by the reference HPLC/UV determination.

Bismuth modified carbon-based electrodes for the determination of selected neonicotinoid insecticides.

Two types of bismuth modified electrodes, a bismuth-film modified glassy carbon (BiF-GCE) and a bismuth bulk modified carbon paste, were applied for the determination of selected nitroguanidine neonicotinoid insecticides. The method based on an ex situ prepared BiF-GCE operated in the differential pulse voltammetric (DPV) mode was applied to determine clothianidin in the concentration range from 2.5 to 23 µg cm⁻³ with a relative standard deviation (RSD) not exceeding 1.5%. The tricresyl phosphate-based carbon paste electrodes (TCP-CPEs), bulk modified with 5 and 20 w/w% of bismuth, showed a different analytical performance in the determination of imidacloprid, regarding the peak shape, potential window, and noise level. The TCP-CPE with 5% Bi was advantageous, and the developed DPV method based on it allowed the determination in the concentration range from 1.7 to 60 µg cm⁻³ with an RSD of 2.4%. To get a deeper insight into the morphology of the bismuth-based sensor surfaces, scanning electron microscopic measurements were performed of both the surface film and the bulk modified electrodes.