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The purpose of this study is to assess the repellent activity of lemongrass (Cymbopogon citratus) essential oil (EO), grown in Serbia under greenhouse conditions, against four prevalent stored product pests: Plodia interpunctella (larvae), Sitophilus oryzae, Acanthoscelides obtectus and Tribolium castaneum (adults). The lemongrass EO repellency was tested using filter paper in Petri dishes and a Y-tube olfactometer. According to the repellency index (RI), the lemongrass EO repellency was divided into 5 classes. Prior to biotesting, the chemical characterization of lemongrass EO was performed and the following main compounds were detected: myrcene (31.0%), geranial (30.0%), and neral (23.6%). The C. citratus EO considered was found to exhibit the Class III repellent activity against P. interpunctella larvae only at the highest concentration (namely 0.5%). This is the very first report on the C. citratus EO repellent activity against this pest. The lemongrass EO examined showed strong repellency (Class IV) against S. oryzae (0.2% and 0.5% of EO), A. obtectus (0.1% and 0.2%), and T. castaneum (0.05-0.1%). Moreover, higher lemongrass EO concentrations (0.5%) were found to exhibit extreme repellency (Class V) against A. obtectus and T. castaneum. The results obtained were confirmed in the bioassays performed, indicating the great potential of lemongrass EO as a bio-repellent when applied in higher concentrations to all the insects considered, regardless of the exposure period.

The application of high performance thin layer chromatography (HPTLC)-based non-targeted metabolomics as a holistic approach to compare fingerprints of metabolite changes during Artemisia annua development is described. Images of HPTLC chromatograms obtained after derivatization with anisaldehyde-sulphuric acid reagent were used as a dataset for multivariate analysis. Principal component analysis and orthogonal partial least squares discriminant analysis confirmed the differentiation of samples belonging to vegetative phase, flowering stage, and seed formation stage of the plant development. The obtained results showed that the HPTLC-based metabolomics approach can be a very reliable technique for the investigation of metabolic changes during plant development, complementary to gas chromatography-mass spectrometry and nuclear magnetic resonance-based metabolomics. [ABSTRACT FROM AUTHOR]

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The objective of this study was to test four-dimensional LC-ESI-MS//MS chromatography in analysis of complex mixture such as ethanol extracts of different propolis samples. In total more than 1200 picks were identified and only for 185 literature conformation was found. The given data represent the result of tentative identification, and summarized results are given in the text. Comparing the samples, from different altitudes, 96 components were detected as characteristic in high altitude samples and 18 in samples collected at low altitudes. Antimicrobial activity of ethanol extracts of propolis (EEP) and propylene glycol extracts of propolis (PGEP) were carried out on S. aureus, B. cereus, M. flavus, L. monocytogenes, P. aeruginosa, S. typhimurium, E. coli and E. cloacae bacterial strains and compared with broad-spectrum antibiotics, streptomycin and ampicillin. Anti-quorum sensing activity was performed on P. aeruginosa by testing the effect of representative propolis extracts on biofilm formation, twitching and motility activity and production of pyocyanin. We demonstrated that the majority of explored propolis extracts have greater or equal minimal inhibitory concentration and minimum bactericidal concentration values compared to antibiotics, independently of the solvent used for the extraction. The samples collected from the highest altitude emerged as least active antimicrobial agents but with the greatest potential as anti-quorum sensing agents. [ABSTRACT FROM AUTHOR]