Document Type : Research Paper

Authors

• Shahab Ojani ¹
• Farid Gholamreza Fahimi ²
• Mohsen Mohammadi ³
• Meysam Pashaee ⁴

¹ Institute of Nano Science and Nano Technology, University of Kashan, Kashan, Iran.

² Department of Environment, Tonekabon Branch, Islamic Azad University, Tonekabon, Iran.

³ Department of Biology, Tonekabon Branch, Islamic Azad University, Tonekabon, Iran.

⁴ Young Researchers and Elite Club, Islamic Azad University, Karaj Branch. Karaj. Iran.

Abstract

Nanotechnology has seen significant advances in nanomaterials today, with the development and discovery of new methods, concerns about environmental pollution by nanoparticles through chemical and physical methods have increased. So the need for green chemistry methods that are non-toxic and environmentally friendly is felt. Hence, the aim of the present project is to synthesize silver nanoparticles in an environmentally friendly way using Laurencia caspica (L. caspica) hydroalcoholic extract and evaluation its antioxidant and antibacterial properties. To do this research, the red algae L. caspica was collected from the beaches of Tonekabon and used the microwave assisted extraction (MAE) method to make the extract. Then, in order to identify the bioactive compounds (secondary metabolites) in the extract based on Pharmacopoeia, available methods such as trease and evans were used. Next, the measurement of the total amount of phenolic and flavonoid compounds of the extract was determined by the folin-ciocalteu and aluminum chloride colorimetric methods respectively. An environmentally friendly phytosynthesis method was then used as a reducing agent for the center of silver nanoparticles and was characterized by UV-VIS, FT-IR, XRD and TEM synthesized nanoparticles. Next, the antioxidant properties were then calculated by DPPH⁰ and finally the diffusion disc method was used to evaluate antibacterial activity against bacteria Staphylococcus aureus and Escherichia coli. Phytochemical screening of L. caspica hydroalcoholic extract confirmed the presence of secondary metabolites such as flavonoids, phenols, tannins, quinones, terpenoids and saponins. The total amount of phenolic and flavonoid compounds of L. caspica hydroalcoholic extract was calculated at 95.61±4 and 69.23±2 mg­/­mL respectively. The images and patterns of the peaks obtained from the device­s showed that silver nanoparticles have a roughly spherical shape and with a nanoparticle size of 15 nanometers. The percentage of free radical inhibition related to L. caspica hydroalcoholic extract and silver nanoparticles synthesized 76.35±0.5 and 88.54±0.1 respectively, and their IC₅₀ value was also obtained 0.47 and 0.32 mg/ml respectively. The results of the antibacterial activity revealed that in each of the two strains of bacteria, the zone of inhibition (mm) in the sample related to silver nanoparticles increased significantly compared to pure extract, and this amount was higher in both samples in gram negative bacteria than in gram positive bacteria. Therefore, according to the results, the proposed phytosynthesis method, which is environmentally friendly and can be used in various fields as an antibacterial and antioxidant agent, taking into account the secondary metabolites present in L. caspica and its significant bioactivity by conducting supplementary studies.

Keywords

• Antioxidant properties
• Environment
• Escherichia coli
• Laurencia caspica
• Silver nanoparticles