Investigation of the Chemical Composition, Antimicrobial, and Antioxidant Activity of Endemic Onosma halophila Boiss. & Heldr.

The Onosma halophila Boiss. & Heldr. belongs to the Boraginaceae family and it is endemic species from Turkey that distributes in Salt Lake (Tuz Gölü) and the surrounding salty steppes. In this study, the chemical content, antimicrobial, and antioxidant activity of endemic O. halophila were determined for the first time. Thirty-one components were identified by GC-MS analysis in O. halophila. Antimicrobial activity was tested against a total of eight microorganisms, including three Gram-positive, three Gram-negative bacterial strains, and two fungal strains, using the Micro dilution technique. The obtained extracts showed strong antifungal and antibacterial activity. The MIC value of extracts samples against the tested strains ranged from 15.625 to 125 µg/mL. In addition, it was determined that the extracts had different levels of antioxidant activity. The IC50 values were determined 45.20-1760 µg/mL for DPPH radical scavenging assay, 3.125-1016 µg/mL for H2O2 radical scavenging assay, and 147.12-1837 µg/mL for superoxide radical scavenging assay, respectively. As a result, it has been determined that O. halophila has the potential to be used in complementary medicine and various ethnobotanical fields in future due to the important components it contains.

Synthesis of Graphene Quantum Dot Magnesium Hydroxide Nanocomposites and Investigation of Their Antioxidant and Antimicrobial Activities.

In this paper, we synthesized graphene quantum dots magnesium hydroxide nanocomposites (GQDs/Mg(OH)2). The synthesized nanocomposites were characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Malvern Zetasizer. The antimicrobial and antioxidant properties of the obtained GQDs/Mg(OH)2 nanocomposites were investigated. GQDs/Mg(OH)2 nanocomposites have MIC values of 15.625 µg/mL against fungi (C. metapsilosis and C. parapsilosis) and 62.5 µg/mL against Gram (+) (S. pneumonia and E. faecalis) and Gram (-) (E. coli). The synthesized GQDs/Mg(OH)2 nanocomposites showed moderate antioxidant activity. The results showed that at 100-µg/mL GQDs/Mg(OH)2 nanocomposite concentration, the H2O2 scavenging activity was 62.18%.

Green synthesis of silver nanoparticles using pollen extract: Characterization, assessment of their electrochemical and antioxidant activities.

In the present study, a simple, cheaply and environmental friendly method was evaluated for the synthesis of silver nanoparticle via Cupressus sempervirens L. (CSPE) pollen extract as reducing and stabilizing agent. Various parameters such as volume of CSPE, temperature and reaction time on AgNPs formation were investigated spectrophotometrically to optimize reaction conditions. The electrochemical behavior of the biosynthesized AgNPs were investigated by cyclic voltammetry and square wave voltammetry techniques. An electrosensor based on AgNPs modified glassy carbon electrode were constructed and tested on electro reduction of hydrogen peroxide in phosphate buffer medium. The prepared electrosensor could detect the H2O2 in the range of 5.0 µM - 2.5 mM with a detection limit of 0.23 µM. In addition, the antioxidant activity of biosynthesized AgNPs were evaluated against DPPH free radical. Results obtained from the antioxidant study suggested that CSPE mediated AgNPs exhibit a good antioxidant effect.