Synthesis, characterization and antioxidant activity of silver nanoparticles stabilized by aqueous extracts of wild blackberry (Rubus spp.) and raspberry (Rubus idaeus L.) leaves

Abstract

The green methods of silver nanoparticles (AgNPs) synthesis and their stabilization by biomolecules from aqueous extracts of wild blackberry (Rubus spp.) and raspberry (Rubus idaeus L.) leaves are described. The extracts, obtained from both plants by maceration and reflux extraction were used in nanoparticles synthesis at two different temperatures (room and boiling). Structural characterization of silver nanoparticles synthesized from obtained extracts (AgNPs-E) was performed by UV-Vis and FTIR spectroscopy. The size and high stability of synthesized nanoparticles at room temperature in the dark were proven by the position and monitoring of the surface plasmon resonance (SPR) band in the UV-Vis spectra. A chemical composition of pure extracts and supernatants, obtained by centrifugation of AgNPs-E suspensions, was investigated by LC-MS analysis. Most of the identified compounds belong to phenolic acids and flavonoids derivatives. A comparative LC-MS analysis of the extracts and AgNPs-E supernatants showed that some compounds from the extracts were involved in a higher extent in Ag + ions reduction and formed particles stabilization, suggesting the existence of a structure-activity relationship. The synthesized AgNPs-E showed a comparatively high antioxidant activity estimated by the DPPH test suggesting that they should be taken into account in a further design of skin-protective preparations.