EastWest Chemistry Conference (EWCC), Lviv, Ukraine, 10 - 12 October 2018, pp.184
Rheum ribes (RR) is locally named as‘‘ışkın’’ in daily languages. RR is the only Rheum species geographically adapting in Turkey. Literature studies show that ethanol extract of RR stems has the potential to be a basis for anticancer, antimicrobial and antioxidant agents.With increasing global competitions there is a growing need to develop environmentally benevolent nanoparticles without the use of toxic chemicals. Green synthesis of silver nanoparticles(Ag-NPs) using plant extracts provides advancement over chemical and physical method as it is cost effective, no need to use high energy, environment friendly, and no toxic chemicals. In this study, an environmental friendly synthesis of Ag-NPs were rapidly biosynthesized using aqueous extract of R. ribes plant stems. Formation of Ag-NPs was confirmed by changing the medium color from yellow to dark brown due to surface plasmon resonance(SPR) phenomenon. The effect of temperature and pH on synthesized Ag-NPs size was also investigated and obtained different size of nanoparticles. The best conditions for efficient synthesis of Ag-NPs were found at 20g fresh stem /200 mL distilled water,10 mM AgNO3 solution, volume ratio of RR exract to AgNO3 solution: 0.3/9.7(v/v), at pH 8 for 1h reaction time and temperature
at 80◦C. Formation of Ag-NPs was confirmed from the SPR peaks centered between 420-460 nm and to identify the
compounds responsible for reduction of Ag+ ions were investigated by FTIR. SEM analysis showed that the Ag-NPs were mostly spherical in shapes. In addition, reducing power, total phenolic content, radical scavenging activity of RR extracts were examined. Antioxidant activity of methanol and aqueous extracts of RR stems was determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH●). IC50 values were calculated and compared with BHA and BHT. The phenolic compounds of extracts were determined according to the Folin–Ciocalteu method and expressed as gallic acid equivalents per 1000 μg extract.