Seasonal variation of volatile oil composition and antioxidant property of aerial parts of Syzygium paniculatum Gaertn. grown in the Eastern Cape,South Africa

Syzygium paniculatum Gaertn of the family Myrtaceae is a medicinal and aromatic plant. The hydrodistilled volatile oil (VO) from the aerial parts was characterised by GC-MS and Kovat’s index, while the antioxidant property was investigated using spectrophotometric techniques. Antioxidant capacities of the aerial parts VOs range from 0.12 to 0.93?mg/mL in scavenging 2, 2-diphenyl-1-picrylhydrazyl radicals (DPPH^?). Overall, 75 and 67 compounds were identified from the summer and winter VOs, respectively. The main compounds were α-pinene (33.13%), n-hexadecanoic acid (19.14%), limonene (14.26%), farnesol (14.21%), β-ocimene (13.04%), citronellol (12.67%), linoleic acid (11.50%), octahydro-1,4-dimethyl azulene (11.57%), citral (9.91%), phytol (5.07%), linolenic acid (4.85%) and thymol (2.23%). The bioavailability of citronellol, thymol, β-ocimene and linoleic acid, used as bactericidal, fungicidal and antioxidant agents in cosmetics and perfumery, suggests S. paniculatum potential as a natural food flavouring and source of antibiotics in this era of emerging multi-drug-resistant pathogens.     

Electrochemical Peptide-Based Sensors for Foodborne Pathogens Detection

Food safety and quality control pose serious issues to food industry and public health domains, in general, with direct effects on consumers. Any physical, chemical, or biological unexpected or unidentified food constituent may exhibit harmful effects on people and animals from mild to severe reactions. According to the World Health Organization (WHO), unsafe foodstuffs are especially dangerous for infants, young children, elderly, and chronic patients. It is imperative to continuously develop new technologies to detect foodborne pathogens and contaminants in order to aid the strengthening of healthcare and economic systems. In recent years, peptide-based sensors gained much attention in the field of food research as an alternative to immuno-, apta-, or DNA-based sensors. This review presents an overview of the electrochemical biosensors using peptides as molecular bio-recognition elements published mainly in the last decade, highlighting their possible application for rapid, non-destructive, and in situ analysis of food samples. Comparison with peptide-based optical and piezoelectrical sensors in terms of analytical performance is presented. Methods of foodstuffs pretreatment are also discussed.     

Evaluation of various biological activities of natural compounds by TLC/HPTLC

Abstract

Over the last years, thin layer chromatography (TLC) has become an increasingly important tool in the analysis of natural compounds, being used not only as a simple method of separation, identification, and quantitative determination of natural constituents, but also as a method for evaluating the potential applications of the separated compounds, different bioassays being compatible with TLC. This is due to the TLC advantages, of which could be mentioned: the possibility to simply, quickly, and flexibly analyze many samples in parallel, without the need for special steps of sample purification, obtaining visual results, and the possibility of multiple detections, all of these being achieved at very low costs. Considering these, the aim of this study is to give an overview on the application of TLC in evaluation of different biological activities of natural compounds, focusing on antioxidant, enzymatic, antimicrobial, and hormonal activities.     

Simultaneous determination of methylxanthines in different types of tea by a newly developed and validated TLC method

The aim of this paper is to develop a new simple, fast and economical method for simultaneous quantitative determination of methylxanthine compounds based on TLC combined with image analysis. To obtain certain results, both extraction and chromatographic separation were optimized. The optimum extraction conditions were maceration in ethanol-water 8:2, v/v. The chromatographic separations were done on the silica gel F(254) TLC plates developed with chloroform-dichloromethane-isopropanol, 4:2:1 v/v/v. Detection was performed under UV lamp at 254?nm and the evaluation of the chromatographic plate was based on digital processing of chromatographic images. The developed TLC method was validated for parameters such as specificity, linearity and range, LOD and LOQ, precision, robustness and accuracy. This method was then applied for determination of caffeine, theobromine and theophylline in different types of tea, commercially available. Moreover, the content of methylxanthines detected and determined in commercial tea samples can be used as chemical marker in quality control.     

Ikirydinium A: a new indole alkaloid from the seeds of Hunteria umbellata (K. Schum)

Chemical investigations into samples of Hunteria umbellata (K. Schum) collected in Osun State, Nigeria, led to the discovery of a new indole alkaloid, ikirydinium A, featuring an unprecedented 3-alkylpyridinium-indole-2-carboxylate scaffold. Ikirydinium A was found to exhibit antimicrobial activity (IC₅₀ 0.6 μM) against Bacillus subtilis ATCC 6051. The involvement of a common intermediate in the biosynthesis of ikirydinium A and vinblastine is hypothesized.     

Modeling of Thin-Layer Chromatographic Separation of Androstane Isomers

JPC – Journal of Planar Chromatography – Modern TLC - Modeling of thin-layer chromatographic separation of androstane isomers to find the optimum mobile phase is described in this...     

Re-Analysis of Abdominal Gland Volatilome Secretions of the African Weaver Ant,Oecophylla longinoda (Hymenoptera: Formicidae)

The African weaver ant, Oecophylla longinoda, is used as a biological control agent for the management of pests. The ant has several exocrine glands in the abdomen, including Dufour’s, poison, rectal, and sternal glands, which are associated with pheromone secretions for intra-specific communication. Previous studies have analyzed the gland secretions of Dufour’s and poison glands. The chemistry of the rectal and sternal glands is unknown. We re-analyzed the secretions from Dufour’s and poison glands plus the rectal and sternal glands to compare their chemistries and identify additional components. We used the solid-phase microextraction (SPME) technique to collect gland headspace volatiles and solvent extraction for the secretions. Coupled gas chromatography–mass spectrometry (GC-MS) analysis detected a total of 78 components, of which 62 were being reported for the first time. These additional components included 32 hydrocarbons, 12 carboxylic acids, 5 aldehydes, 3 alcohols, 2 ketones, 4 terpenes, 3 sterols, and 1 benzenoid. The chemistry of Dufour’s and poison glands showed a strong overlap and was distinct from that of the rectal and sternal glands. The different gland mixtures may contribute to the different physiological and behavioral functions in this ant species.