Chemical characterization, in vitro biological activity of essential oils and extracts of three Eryngium L. species and molecular docking of selected major compounds.

Many Eryngium species have been traditionally used as ornamental, edible or medicinal plants. The gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS) analyses have shown that the major compounds in the aerial parts were spathulenol (in E. campestre and E. palmatum oils) and germacrene D (in E. amethystinum oil). The main compounds in the root oil were nonanoic acid, 2,3,4-trimethylbenzaldehyde and octanoic acid for E. campestre, E. amethystinum and E. palmatum, respectively. All the oils expressed the highest potential against Gram-positive bacteria Staphylococcus aureus as well as Gram-negative Klebsiella pneumoniae and Proteus mirabilis. Molecular docking analysis was used for determining a potential antibacterial activity mechanism of compounds present in the essential oils. Molecular docking confirmed that the binding affinity of spathulenol to the active site of tyrosyl-tRNA synthetase was the highest among the tested dominant compounds. Regarding the total phenolic content (determined by the Folin-Ciocalteu assay) and flavonoid content (evaluated using aluminum nitrate nonahydrate), the highest amount was found in the ethyl acetate extract of E. palmatum. The results of DPPH and ABTS assay indicated that the highest antioxidant activity was present in the water extract of E. amethystinum. Extracts of the aerial parts presented as minimum inhibitory concentration (MIC) expressed the activity in the range 0.004-20.00 mg/mL, with the highest activity exhibited by the acetone and ethyl acetate extracts against Proteus mirabilis. The obtained results suggest that Eryngium species may be considered a beneficial native source of the compounds with antioxidant and antimicrobial properties.

Biological activity of Pinus nigra terpenes--evaluation of FtsZ inhibition by selected compounds as contribution to their antimicrobial activity.

In the current work, in vitro antioxidant, antibacterial, and antifungal activites of the needle terpenes of three taxa of Pinus nigra from Serbia (ssp. nigra, ssp. pallasiana, and var. banatica) were analyzed. The black pine essential oils showed generally weak antioxidative properties tested by two methods (DPPH and ABTS scavenging assays), where the highest activity was identified in P. nigra var. banatica (IC50=25.08 mg/mL and VitC=0.67 mg (vitamin C)/g when tested with the DPPH and ABTS reagents, respectively). In the antimicrobial assays, one fungal (Aspergilus niger) and two bacterial strains (Staphylococcus aureus and Bacillus cereus) showed sensitivity against essential oils of all three P. nigra taxa. The tested oils have been shown to possess inhibitory action in the range from 20.00 to 0.62 mg/mL, where var. banatica exhibited the highest and ssp. nigra the lowest antimicrobial action. In order to determine potential compounds that are responsible for alternative mode of action, molecular docking simulations inside FtsZ (a prokaryotic homolog of tubulin) were performed. Tested compounds were the most abundant terpenoid (germacrene D-4-ol) and its structurally similar terpene (germacrene D), both present in all three essential oils. It was determined that the oxygenated form of the molecule creates stable bonds with investigated enzyme FtsZ, and that this compound, through this mechanism of action participates in the antimicrobial activity.

Antioxidant properties of selected 4-phenyl hydroxycoumarins: Integrated in vitro and computational studies.

A study on the structure-activity relationship of three hydroxy 4-phenyl coumarins, carried out by employing a series of different chemical cell-free tests is presented. Different assays involving one redox reaction with the oxidant (DPPH, ABTS, FRAP and CUPRAC) were employed. Further, the measurement of inhibition of oxidative degradation, such as lipid peroxidation, was used to define compound antioxidant activity. Our results confirm the good antioxidant activity of the 7,8-dihydroxy-4-phenyl coumarin and moderate antioxidant activity of 5,7-dihydroxy-4-phenyl coumarin. In this work, quantum chemical calculations based on density functional theory have been employed at B3LYP/6-311++G(d,p) level of theory to study the influence of number and position of hydroxyl groups in coumarin molecules on antioxidant activity. Calculated values for HOMO and LUMO energies, energy gap, stabilization energies and spin density distribution confirmed experimental results and were used for SAR definition. For determination of reaction mechanism in gas phase and selected solvents bond dissociation enthalpy, adiabatic ionization potential, proton dissociation enthalpy, proton affinity, electron transfer enthalpy and gas phase acidity have been calculated. Hydrogen Atom Transfer mechanism in vacuum and Single-Electron Transfer followed by the Proton Transfer mechanism in other studied systems are most probable free radical scavenging pathways. On the basis of these findings, these hydroxy 4-phenyl coumarins may be considered as potential therapeutic candidates for pathological conditions characterized by free radical overproduction.