Green synthesis of silver nanoparticles using aqueous seed extract of Cuminum cyminum L. and evaluation of their biological activities

There are many reports on the application of medicinal plants in traditional medicine, as well as numerous applications of metallic nanoparticles in different biomedical fields. Plant extract mediated green synthesis of nanoparticles and investigations on their therapeutic effects are new concepts. The medicinal plant of Cuminum cyminum L. includes a wide range of secondary metabolites with a high reducing power, which can be used for green biosynthesis of silver nanoparticles. The main aims of this study were phytochemical analysis of seed aqueous extract of Cuminum cyminum, biosynthesis of silver nanoparticles using this extract, the achievement of optimization condition for the synthesis of silver nanoparticles, and assessment of biological activaties of both the extract and the synthesized nanoparticles.

Total phenol and flavonoid, reducing sugar, starch, and ascorbic acid contents were measured by Folin-Ciocalteo, aluminum chloride, dinitrosalicylic acid, anthrone, and dinitrophenyl hydrazine reagents, respectively. The Ag+ ions reduction and characterization of silver nanoparticles were assessed by UV-Visible spectrophotometry, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Antioxidant activity of the samples was screened by DPPH free radical scavenging. Antibacterial activity of the samples was also evaluated against four gram-positive and -negative bacteria namely, Bacillus cereus (PTCC 1247), Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 35218), and Pseudomonas aeruginosa (ATCC 27853) by disc diffusion method. In addition, antifungal activity was assessed against Fusarium oxysporum.

The indings indicated that the seed extract contained the high amounts of total phenolic and flavonoidic compositions, as well as sugar, starch, and ascorbic acid. Different analyses showed that the mean size of the synthesized nanoparticles was 5-45 nm in the optimal condition. The samples had proper antioxidant potential (IC50=1.35-1.67 mg/ml) and the extract in combination with silver nanoparticles represented synergistic effect in DPPH free radical scavenging (IC50=1.35 mg/ml). In addition, the investiogated samples had a good antibacterial activity against some of tested bacteria and also antifungal activity against Fusarium oxysporum.

Discussion & It seems that the secondary metabolites of Cuminum cyminum have good potential for the reduction and stabilization of the synthesized Ag nanoparticles. Both the seed extract and synthesized nanoparticles using this extract have considerable biological activities and may be used in antioxidant nutrient production or medicinal supplements in future.