Sorin Marius Avramescu

Phyto-mediated metallic nano-architectures via Melissa officinalis L. : synthesis, characterization and biological properties

The development of methods for obtaining new materials with antimicrobial properties, based on green chemistry principles has been a target of research over the past few years. The present paper describes the phyto-mediated synthesis of metallic nano-architectures (gold and silver) via an ethanolic extract of Melissa officinalis L. (obtained by accelerated solvent extraction). Different analytic methods were applied for the evaluation of the extract composition, as well as for the characterization of the phyto-synthesized materials. The cytogenotoxicity of the synthesized materials was evaluated by Allium cepa assay, while the antimicrobial activity was examined by applying both qualitative and quantitative methods. The results demonstrate the synthesis of silver nanoparticles (average diameter 13 nm) and gold nanoparticles (diameter of ca. 10 nm); the bi-metallic nanoparticles proved to have a core-shell flower-like structure, composed of smaller particles (ca. 8 nm). The Ag nanoparticles were found not active on nuclear DNA damage. The Au nanoparticles appeared nucleoprotective, but were aggressive in generating clastogenic aberrations in A. cepa root meristematic cells. Results of the antimicrobial assays show that silver nanoparticles were active against most of the tested strains, as the lowest MIC value being obtained against B. cereus (approx. 0.0015 mM).

Thermal and spectroscopic investigation of Romanian historical documents from the nineteenth and twentieth century

Abstract In 1958, at the end of the restoration and at re-consecration of St. Elijah Church in Pitesti (Romania), in an improvised archive, were discovered some historical documents (testaments, petitions, notices, etc.) going back to 1841. With the occasion of the re-consecration, another document was signed by the priests involved. All these documents were gathered together and transmitted from one priest to another, as the documents were considered valuable, presenting the habits of past generations and events of local historical importance. The present paper describes the characterization of eight paper documents selected from this collection, performed by thermal analysis, together with optical microscopy, Fourier transform infrared spectroscopy, inductively coupled plasma-atomic emission spectrometry, energy-dispersive X-ray fluorescence, X-ray diffraction as well as by the evaluation of the degree of polymerization and the colour change. The results revealed the type of fillers used (different from one sample to another); also, one of the samples presents a much higher content of lignin and hemicelluloses than the other samples. Thus, the conclusion that could be reached is that although all the documents originated from the same geographical area, the papers on which they are written have very different origin, in terms of composition and fillers used.

Phytosynthesis of gold and silver nanoparticles enhance in vitro antioxidant and mitostimulatory activity of Aconitum toxicum Reichenb. rhizomes alcoholic extracts

Extracts obtained from different plant species proved to be a valuable tool in various biomedical applications. In the same time, the phytosynthesis of noble metal nanoparticles represents an already well-established route for obtaining nanoparticles with biological activity. The present paper studies the antioxidant activity and the cytogenetic effects of the alcoholic extracts from rhizomes of Aconitum toxicum Rchb., before and after the phytosynthesis of gold and silver nanoparticles, on the meristematic root cells of Allium cepa L., and on the general mitotic index and the progression rate through the mitotic phases, respectively, as well as on the genetic material organized in chromosomes. The extracts were characterized in terms of total polyphenolics content (1.49% and, respectively, 2.29%) and aconitine content (by HPLC - 4.891 mg/L and, respectively, 18.211 mg/L), while the phytosynthesis of metallic nanoparticles was monitored by UV-Vis spectrometry, X-ray diffraction, X-ray fluorescence and electron microscopy. Both the extracts and the obtained nanoparticles were evaluated for antioxidant potential (the antioxidant activity ranging between 78% and 84.32%) and cytogenetic effects. The obtained results prove the phytosynthesis of AgNPs and AuNPs with dimensions ranging from 9 nm to 15 nm for AuNPs, respectively from 53 nm to 67 nm for AgNPs. The extracts obtained from rhizomes of A. toxicum Rchb. induced mitotic stress, as well as a series of nuclear and mitotic aberrations. The biosynthesis of AgNPs and AuNPs intensified the antioxidant and mitostimulatory activity of the extracts.