Plants are widely used for food and beverage preparation, most often in the form of complex mixtures of dried and ground parts, such as teas, spices or herbal medicines. Quality control of such products is important due to the potential health risks from the presence of unlabelled components or absence of claimed ones. A promising approach to analyse such products is DNA metabarcoding due to its high resolution and sensitivity. However, this method’s application in food analysis requires several methodology optimizations in DNA extraction, amplification and library preparation. In this study, we present such optimizations. The most important methodological outcomes are the following: 1) the DNA extraction method greatly influences amplification success; 2) the main problem for the application of metabarcoding is DNA purity, not integrity or quantity; and 3) the “non-amplifiable” samples can be amplified with polymerases resistant to inhibitors. Using this optimized workflow, we analysed a broad set of plant products (teas, spices and herbal remedies) using two NGS platforms. The analysis revealed the problem of both the presence of extraneous components and the absence of labelled ones. Notably, for teas, no correlation was found between the price and either the absence of labelled components or presence of unlabelled ones; for spices, a negative correlation was found between the price and presence of unlabelled components.

Bacteria and fungi emit a huge variety of volatile organic compounds (VOCs) that can provide a valuable arsenal for practical use. However, the biological activities and functions of the VOCs are poorly understood. This work aimed to study the action of individual VOCs on the bacteria Agrobacterium tumefaciens, Arabidopsis thaliana plants, and fruit flies Drosophila melanogaster. VOCs used in the work included ketones, alcohols, and terpenes. The potent inhibitory effect on the growth of A. tumefaciens was shown for 2-octanone and isoamyl alcohol. Terpenes (−)-limonene and (+)-α-pinene practically did not act on bacteria, even at high doses (up to 400 µmol). 2-Butanone and 2-pentanone increased the biomass of A. thaliana at doses of 200–400 μmol by 1.5–2 times; 2-octanone had the same effect at 10 μmol and decreased plant biomass at higher doses. Isoamyl alcohol and 2-phenylethanol suppressed plant biomass several times at doses of 50–100 μmol. Plant seed germination was most strongly suppressed by isoamyl alcohol and 2-phenylethanol. The substantial killing effect (at low doses) on D. melanogaster was exerted by the terpenes and the ketones 2-octanone and 2-pentanone. The obtained data showed new information about the biological activities of VOCs in relation to organisms belonging to different kingdoms.

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