Biogenic synthesis of noble metal nanoparticles using Melissa officinalis L. and Salvia officinalis L. extracts and evaluation of their biosafety potential

In this study we targeted the noble metal nanoparticles (MNPs) biogenic synthesis capacity of two medicinal species with therapeutic potential, namely Melissa officinalis L. (lemon balm) and Salvia officinalis L. (sage), cultivated in Romania. Plant material was extracted by maceration, microwave assisted extraction (MAE) and ultrasound assisted extraction (UAE). Bright field scanning transmission electron microscopy and energy dispersive X-ray spectroscopy (BFSTEM-EDS) techniques were used in order to investigate particles shape, dispersion and chemical elemental analysis. The total polyphenol content for both simple extracts and nanostructured mixtures was determined using the Folin-Ciocalteu method and antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Identification and quantification of secondary metabolites of M. officinalis and S. officinalis were performed by ultra-high performance liquid chromatography (UHPLC). The Allium assay was used to evaluate the potential cytogenotoxic activity, for both simple and nanostructured phytochemical complexes, in the case of S. officinalis L. species being performed for the first time. Spherical shaped MNPs with diameters of about 20 nm were biosynthesised in lemon balm extracts. Larger AuNPs were phytosynthesized in sage extract obtained by UAE. Compared to the simple extracts, the antioxidant capacity as well as the amount of total polyphenols in the nanostructured extracts decreased, substantiating the involvement of bioorganic material in the reduction of metal ions. Low frequency of chromosomal aberrations corresponding to crude extracts and extracts supplemented with MNPs, suggest the cytoprotective, antigenotoxic, and safe use of these plant species as potential therapeutic forms in various diseases.