Ribes nigrum L. Extract-Mediated Green Synthesis and Antibacterial Action Mechanisms of Silver Nanoparticles.

Silver nanoparticles (Ag NPs) represent one of the most widely employed metal-based engineered nanomaterials with a broad range of applications in different areas of science. Plant extracts (PEs) serve as green reducing and coating agents and can be exploited for the generation of Ag NPs. In this study, the phytochemical composition of ethanolic extract of black currant (Ribes nigrum) leaves was determined. The main components of extract include quercetin rutinoside, quercetin hexoside, quercetin glucuronide, quercetin malonylglucoside and quercitrin. The extract was subsequently employed for the green synthesis of Ag NPs. Consequently, R. nigrum leaf extract and Ag NPs were evaluated for potential antibacterial activities against Gram-negative bacteria (Escherichia coli ATCC 25922 and kanamycin-resistant E. coli pARG-25 strains). Intriguingly, the plant extract did not show any antibacterial effect, whilst Ag NPs demonstrated significant activity against tested bacteria. Biogenic Ag NPs affect the ATPase activity and energy-dependent H+-fluxes in both strains of E. coli, even in the presence of N,N'-dicyclohexylcarbodiimide (DCCD). Thus, the antibacterial activity of the investigated Ag NPs can be explained by their impact on the membrane-associated properties of bacteria.

Artemisia dracunculus L. essential oil phytochemical components trigger the activity of cellular antioxidant enzymes.

Investigation of dietary biologically active phytochemicals is of interest due to the availability, low cost, and low rate of side effects of these substances. The main objective of this work was to investigate the influence of the essential oil (EO) extracted from the aerial parts of Artemisia dracunculus on the antioxidant capacity of cells as this plant is one of the most available and widely used as spice and in folk medicine. For this, BV-2 microglial wild type (WT) and acyl-CoA oxidase type 1 (ACOX1) deficient cells (Acox1-/- ) were used. Acox1-/- cells were applied as the model of cellular oxidative damage. The main component of EO of A. dracunculus was estragole, which was reaching 84.9% in plants cultivated at high altitude Armenian landscape. IC50 value of EO in 1,1-diphenyl-2-picrylhydrazyl assay was 94.2 µg/ml. Sub-cytotoxic concentration in the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test for both BV-2 WT and Acox1-/- cell lines was 5.10-1  µg/ml. Seventy-two-hours treatment with EO leads to the increased viability (up to 12% in WT and up to 14% -in BV-2 Acox1-/- cells). The 48-hr treatment increased the ACOX1 activity up to 70% in WT cells. Catalase and superoxide dismutase activities of both cell lines increased following the 24-48-hr treatment. These results indicate that A. dracunculus EO can be considered as a potential protective agent useful in preventive medicine.

Origanum vulgare L. extract-mediated synthesis of silver nanoparticles, their characterization and antibacterial activities.

Plant extracts serve as reducing and coating agents and are, therefore, commonly employed for the generation of silver (Ag) nanoparticles (NPs). Plant extract mediated synthesis of Ag NPs is a green, environmentally friendly and cost-effective technique which offers a new and potential alternative to chemically synthesized NPs, decreasing the utilization of hazardous and toxic chemicals and protecting the environment. Origanum vulgare L. extracts were evaluated for total flavonoid and phenol content. The free radical scavenging activity was determined employing 2,2-diphenyl-1-picrylhydrazyl assay. Ag NPs were produced exploiting ethanolic extracts of O. vulgare L. leaves. The generation of Ag NPs was carried out both in light and dark conditions. The biosynthesized Ag NPs were characterized employing microscopic and spectroscopic techniques. Antibacterial activities of Ag NPs were determined following appropriate methods. The results revealed that energy of photons was required to reduce Ag+ to Ag0. According to scanning electron microscopy reports, biologically formed Ag NPs ranged in size from 1 to 50 nmand were presented instability causing aggregation. They indicated that O. vulgare L. extracts were rich in flavonoids and phenols and exhibited strong antioxidant activity. Ag NPs exhibited good antibacterial activity immediately after production. Gram-positive strains showed higher sensitivity to Ag NPs compared to Gram-negative stains. Ag NPs can serve as an effective antibacterial agent against antibiotic-resistant strains. The kanamycin-resistant strain was more sensitive to Ag NPs than the ampicillin-resistant strain. Thus, Origanum extract-mediated synthesized Ag NPs can be recommended as alternative effective antibacterial agents, but their activity depended on bacterial species and strains.

The Caucasian flora: a still-to-be-discovered rich source of antioxidants.

Cellular redox homeostasis is a state of balance between the formation of Usually Reactive Oxygen and / or Nitrogen Species (ROS/RNS), endogenous antioxidant defence systems, and exogenous dietary antioxidants. The disturbance of redox homeostasis, by the overproduction of endogenous ROS/RNS, may increase the risk of development of so-called civilisation diseases. The solution seems to be either the increased production of endogenous or consumption of exogenous antioxidants. Plant-borne antioxidants act via different chemical and molecular mechanisms, such as decreasing the level of oxidative damage in cells directly by reacting with ROS/RNS or indirectly - by inhibition of the activity and expression of free radical generating enzymes or by enhancing the activity or expression of intracellular antioxidant defence enzymes. Despite the fact that the Caucasian flora is rich of health promoting edible/medicinal plants, recent studies concerning the biological activity of these plants are very scarce. This review is summarising the state-of-art on the health-promoting potential of plants representing the Caucasian flora, whose antioxidant capacity have been investigated in various in vitro models.

The Activity of Alkanna Species in vitro Culture and Intact Plant Extracts Against Antibiotic Resistant Bacteria.

Overcoming the antibiotic resistance is nowadays a challenge. There is still no clear strategy to combat this problem. Therefore, the urgent need to find new sources of antibacterial agents exists. According to some literature, substances of plant origin are able to overcome bacterial resistance against antibiotics. Alkanna species plants are among the valuable producers of these metabolites. But there is a problem of obtaining the standardized product. So, this review is focused on the discussion of the possibilities of biotechnological production of antimicrobial agents from Alkanna genus species against some microorganisms including antibiotic resistant bacterial strains.

Essential Oil and Ethanol Extract of Oregano (Origanum vulgare L.) from Armenian Flora as a Natural Source of Terpenes, Flavonoids and other Phytochemicals with Antiradical, Antioxidant, Metal Chelating, Tyrosinase Inhibitory and Antibacterial Activity.

BACKGROUND: Origanum vulgare is used in Armenian cuisine as well as in folk medicine. The aim of this investigation was to determine the peculiarities of the chemical composition of Armenian flora's oregano essential oil (EO) and ethanol extract (EE) and to characterize mainly antioxidant and antibacterial properties in vitro. METHODS: EO of plant aerial parts was extracted by the hydro-distillation method, and the composition was analyzed by gas-chromatography (GC). EE was prepared using ethanol as a solvent. Antioxidant, antibacterial and other biological activity of EO and EE was determined using appropriate methods. RESULTS: The terpenes were found to be the greatest part of oregano EO (ß-caryophyllene epoxide - 13.3 %; ß- caryophyllene -8.2 %; ο-cymene - 5.2 %). The flavonoid content of EE was 3.9±0.7 mg g-1 catechin equivalents. Antiradical activities of EO and EE expressed with half-maximum inhibitory concentrations were 1057 µg mL-1 and 19.97 µg mL-1. The antioxidant index in the case of using extract (1000 µg mL-1) was 77.3±1.5 %. The metal chelating activity of EE was 74.5±0.2 %. The tyrosinase inhibitory activities of EO, EE and arbutin were 26.5±0.3 %, 6.5±0.2 % and 50±0.1 %, respectively. Both EO and EE of oregano were able to suppress the growth of testmicroorganisms including clinical pathogen isolates, but have moderate antimicrobial activity. EO antibacterial activity against ampicillin-resistant Escherichia coli was similar to the activity against non-resistant strain. EE was not active against ampicillin-resistant E. coli in contrast to non-resistant one. CONCLUSION: The results indicate high antioxidant and moderate antibacterial as well as high antiradical, metal chelating, tyrosinase inhibitory activity of oregano EO and EE, which can be used as a natural source of terpenes, flavonoids and other phytochemicals in medicine, pharmaceutics, cosmetics and food industry. EO has antibacterial activity also against ampicillin-resistant E. coli.

Antimicrobial activity of some plant materials used in Armenian traditional medicine.

BACKGROUND: Antibiotic resistance has become one of the major problems facing humanity. The need for new antimicrobials has been increased dramatically. Plants are considered as one of the most promising sources for new antimicrobials discovery. Despite relatively small area, Armenia has large diversity of flora with many endemic species. In Armenian folk medicine plant materials have been used to treat various microbial diseases since ancient times. The goal of our research was to evaluate antimicrobial efficiency of different parts of five wild plants species which are commonly used in Armenian traditional medicine. METHODS: Plant crude extracts were obtained with maceration technique using five solvents separately: distilled water, methanol, chloroform, acetone, and hexane. Agar well diffusion assay was used for initial evaluation of antimicrobial properties of plant materials against five bacterial and two yeast strains. Minimum inhibitory concentrations of the most active plant parts were determined by broth microdilution method. RESULTS: Crude extracts of all five tested plants expressed antimicrobial activity against at least four test strains at 500 µg ml-1 concentration. Minimum inhibitory and bactericidal/fungicidal concentrations of selected plant parts were determined. Crude acetone and hexane extracts of Hypericum alpestre and acetone extract of Sanguisorba officinalis inhibited the growth of P. aeruginosa even at 64 µg ml-1 concentration. Chloroform and acetone extracts of Sanguisorba officinalis exhibited cidal activity against P. aeruginosa till 256 µg ml-1. Acetone was the most effective solvent for solubilizing antimicrobial compounds for almost all tested plant materials. CONCLUSIONS: Thus, antimicrobial activity of some medicinal plants used in Armenian traditional medicine was evaluated. Some of the plants had rather low minimum bacteriostatic/bactericidal concentrations and therefore they have prospective for further more inclusive studies.

Chemical composition and some biological activities of the essential oils from basil Ocimum different cultivars.

BACKGROUND: The plants belonging to the Ocimum genus of the Lamiaceae family are considered to be a rich source of essential oils which have expressed biological activity and use in different area of human activity. There is a great variety of chemotypes within the same basil species. Essential oils from three different cultivars of basil, O. basilicum var. purpureum, O. basilicum var. thyrsiflora, and O. citriodorum Vis. were the subjects of our investigations. METHODS: The oils were obtained by steam distillation in a Clevenger-type apparatus. The gas chromatography mass selective analysis was used to determine their chemical composition. The antioxidant activities of these essential oils were measured using 1,1-diphenyl-2-picrylhydrazyl assays; the tyrosinase inhibition abilities of the given group of oils were also assessed spectophotometrically, and the antimicrobial activity of the essential oils was determined by the agar diffusion method, minimal inhibitory concentrations were expressed. RESULTS: According to the results, the qualitative and quantitative composition of essential oils was quite different: O. basilicum var. purpureum essential oil contained 57.3% methyl-chavicol (estragol); O. basilicum var. thyrsiflora oil had 68.0% linalool. The main constituents of O. citriodorum oil were nerol (23.0%) and citral (20.7%). The highest antioxidant activity was demonstrated by O. basilicum var. thyrsiflora essential oil. This oil has also exhibited the highest tyrosinase inhibition level, whereas the oil from O. citriodorum cultivar demonstrated the highest antimicrobial activity. CONCLUSIONS: The results obtained indicate that these essential oils have antioxidant, antibacterial and antifungal activity and can be used as natural antioxidant and antimicrobial agents in medicine, food industry and cosmetics.