Search

In this study, we report the green synthesis of gold nanoparticles (AuNPs) with the use of easily available, safe to handle juniper extract (Juniperus communis L.) as a reducing and stabilizer agent. The AuNPs were characterized by UV–Vis absorption spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM). Their growth was examined by UV–Vis spectroscopy over 24 h during storage at room temperature. Absorption measurements showed that the plasmon resonance wavelength appears around 530 and 700 nm. Electron-dispersive X-ray analysis (EDX) and selected area electron diffraction (SAED) of AuNPs evidenced the presence of Au (fcc) phases. TEM analysis showed spherical AuNPs and gold triangular nanoprisms. Differences in size and shape of the AuNPs were observed. ATR–FTIR confirmed the typical functional groups of polyphenols and their oxidation products on the AuNPs’ surface.

In the present study, in vitro hydroxyl radical scavenging activities, total phenols and terpene contents in 70% ethanol extracts were evaluated. Samples of crushed (CB) and non-crushed ripe juniper berries (NCB) collected at five localities in North-East Slovakia during the years 2012&ndash, 2014 were compared. Standard or modified methods for determining phytochemical and antioxidant activity were used together with a novel method for the evaluation of the results after the correction of the measured values per gram of dry matter (DM). Statistically significantly higher DM contents (average values for three years) were found in the CB extracts (ranging from 18.86 to 21.91 mg/mL) in comparison to those for NCB (ranging from 2.59 to 9.90 mg/mL). Depending on the localities and years, the hydroxyl radical scavenging activity ranged from 15.52 to 32.85% for NCB and from 65.59 to 88.12% for CB, respectively. The contents of total phenols ranged from 43.75 to 246.75 mg gallic acid equivalents (GAE)/L (NCB) and from 151.84 to 278.19 mg GAE/L (CB), respectively. However, the higher content of total phenols per gram of DM was found in the NCB extracts (8.49&ndash, 42.23 mg GAE/g DM) and then in CB (6.87&ndash, 18.77 GAE/g DM). The results obtained in this study showed a higher efficiency for extraction from juniper berries in 70% ethanol if the pericarp was disrupted in comparison to that achieved with the maceration of intact berries.

The aim of the present study was the achievement of sterile shoot cultures from peppermint (Mentha × piperita L. cv. ʻKristinkaʼ), their multiplication and the evaluation of the production of essential oils in in vitro conditions. The study was carried out by culturing the nodal segments both on basal or on media supplemented with different concentrations of growth regulators (2,4-D, kinetin, BAP, ZEA) or elicitors (CoCl2). The growth of nodal segments did not showed differences after subculturing, neither when cultivated on media supplemented with 2,4-D or CoCl2. The supplementation of 0.5 mg L−1 BAP caused an increase in the number of de novo formed shoots. The composition of the essential oils showed remarkable differences, with an enhancement of the percentage of menthofuran after the supplementation of 2,4-D and CoCl2 or of pulegone after application of BAP and ZEA.

Solidago canadensis L. (SC) (Canadian goldenrod) is a dangerous plant invader in Europe, which suppress the indigenous flora. Essential oils (EOs) are considered biological control agents. GC-MS analysis for identification of main components was conducted and the potential phytotoxicity of six EOs were also evaluated. Limonene and β-thujone were dominant components in Salvia officinalis L., menthone and menthol in Mentha × piperita L., carvacrol in Origanum vulgare L., estragole/anisole and anethole in Foeniculum vulgare Mill., limonene and carvone in Anethum graveolens L., and anethole in Pimpinella anisum L. Along with EOs, anethole, anisole, camphor, carvone, estragole, limonene, menthol, menthone, thujone and thymol were used independently to evaluate phytotoxic effect against Canadian goldenrod seed germination. A significant inhibitory effect was registered for origanum (1.250 µg.ml−1). The influence of single components was significant. The highest phytotoxic activity was registered with anethole and estragole. Phenolic compounds were the inhibitoriest, followed by oxygenated and hydrocarbon monoterpenes.

The present study evaluated the influence of some environmental factors on the quantity and composition of essential oil (EO) in ripe berry cones of Juniperus communis L. The berry cones were collected from juniper shrubs growing wild at five localities of north-east Slovakia during the years 2012–2014. The EO yield ranged from 0.4 to 1.9%, depending on the locality and year. In the EO, eight monoterpenes (α-pinene, β-pinene, β-myrcene, sabinene, limonene, terpinene-4-ol, borneol, bornylacetate) and one sesquiterpene (β-caryophyllene) were identified. The dominant component was the monoterpene α-pinene, ranging from 31.0 to 49.0%. The amount and composition of the EO was affected by soil composition (content of humus and pH) and topographic environmental factors, including air temperature and precipitation. According to the composition of the EO, the studied juniper shrubs belong to the α-pinene chemotype.

A new menthol cultivar of Mentha x piperita L. bred in East Slovakia was evaluated for the biological activity of its essential oils (EOs). The content and composition of the EO components changed during plant development and the different effects of samples collected each month (April - September) within the growing season were noted. EOs are considered to be an important source of potential allelochemicals. Changes in EO composition influenced phytotoxic activity. Stimulation and inhibition of seed germination and root elongation occurred with different EO concentrations. The four tested bacterial strains presented different resistance to the samples collected in different growing periods.