Evaluation of antioxidant and antimicrobial properties of the Angolan Cymbopogon Citratus essential oil with a view to its utilization as food biopreservative

It was studied the chemical composition, antioxidant, antibacterial and antifungal properties of the essential oil obtained from the Cymbopogon citratus of Angolan origin. Its major constituents analyzed by GC-MS were α-citral (40.55%), β-citral (28.26%), myrcene (10.50%) and geraniol (3.37%). The essential oil antioxidant capacity was statistically identical to that of synthetic antioxidants (DPPH IC50 of 41.7 μg/ml) and superior to that of extracts obtained from fresh leaves of the plant (DPPH IC50 of 55.7 μg/ml). The oil also demonstrated to possess high antibacterial activity even against multidrug resistant strains of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Klebsiella pneumoniae and antifungal activity against Candida albicans and Non-Candida albicans, Candida parapsilosis and Candida tropicalis. The results of this study, in conjunction with already published data on the properties of other Cymbopogon citratus oils, provide evidence that it could have a potential application as food preservative.info:eu-repo/semantics/publishedVersio

Laccase–Prussian blue film–graphene doped carbon paste modified electrode for carbamate pesticides quantification

A novel enzymatic biosensor for carbamate pesticides detection was developed through the direct immobilization of Trametes versicolor laccase on graphene doped carbon paste electrode functionalized with Prussianblue films (LACC/PB/GPE). Graphene was prepared by graphite sonication-assisted exfoliation and characterized by transmission electron microscopy and X-ray photoelectron spectro- scopy. The Prussian blue film electrodeposited onto graphene doped carbon paste electrode allowed considerable reduction of the charge transfer resistance and of the capacitance of the device.The combined effects of pH, enzyme concentration and incubation time on biosensor response were optimized using a 23 full-factorial statistical design and response surface methodology. Based on the inhibition of laccase activity and using 4-aminophenol as redox mediator at pH 5.0,LACC/PB/GPE exhibited suitable characteristics in terms of sensitivity, intra-and inter-day repeatability (1.8–3.8% RSD), reproducibility (4.1 and 6.3%RSD),selectivity(13.2% bias at the higher interference: substrate ratios tested),accuracy and stability(ca. twenty days)for quantification of five carbamates widely applied on tomato and potato crops.The attained detection limits ranged between 5.2×10−9 mol L−1(0.002 mg kg−1 w/w for ziram)and 1.0×10−7 mol L−1 (0.022 mg kg−1 w/w for carbofuran).Recovery values for the two tested spiking levels ranged from 90.2±0.1%(carbofuran)to 101.1±0.3% (ziram) for tomato and from 91.0±0.1%(formetanate)to 100.8±0.1%(ziram)for potato samples.The proposed methodology is appropriate to enable testing pesticide levels in food samples to fit with regulations and food inspections