Abstract
This study aimed for green synthesis of silver nanoparticles (Ag-NPs) from the antimicrobial crude extracted in chloroform: methanol(1:1 v/v) from the two brown seaweeds Spatoglossum asperum and Hedophyllum sessile active against two pathogenic bacteria (Xanthomonas axonopodis pv. citri and X. oryzae pv. oryzae) and a fungus Ustilaginoidea virens cause diseases in plants under in vitro assay. Crude extracts exhibit high antibacterial activity and low antifungal activity. Green synthesized Ag-NPs showed very high antimicrobial properties on comparing its crude extracts. Among the crudes, extract of Spatoglossum asperum exhibits higher bioactivity than the extract of Hedophyllum sessile but Ag-NPs prepared from the extract of H. sessile possess very strong bioactivity over Ag-NPs of Spatoglossum asperum. Reduction of Ag-NPs was confirmed by UV spectra. FTIR data indicate that active groups related to terpenoids and phenols found in the crude extracts were responsible for the reduction of Ag-NPs. The XRD data showed that the pure three types of crystal silver structure at 2θ values 32.51, 46.50 and 74.62 corresponding to 111, 200 and 220 planes for silver, respectively. This study concludes that chloroform: methanol (1:1 v/v) extracts of Hedophyllum sessile and Spatoglossum asperum containing active groups related to terpenoids and phenols and they are acting as reducing agents for green synthesis of silver nanoparticles which are potential source for controlling the plant pathogens studied.
Highlights
Nanotechnology is emerging as a rapidly growing field with its application in Science and Technology for the purpose of manufacturing new materials at the nanoscale level (Prabhu et al, 2010)
Crude extracts obtained in chloroform: methanol (1:1 v/v) of two brown seaweeds Hedophyllum sessile and Spatoglossum asperum exhibit antimicrobial activities which was increased with increasing concentration of extracts (Fig. 1)
This study found that antibacterial activity of the crude extracts was higher than antifungal activity and crude extracts of Spatoglossum asperum exhibits more bioactivity (Fig. 1 and 2) than the extract of Hedophyllum sessile (Fig. 1 and 3)
Summary
Nanotechnology is emerging as a rapidly growing field with its application in Science and Technology for the purpose of manufacturing new materials at the nanoscale level (Prabhu et al, 2010). The current chemical methods for synthesizing nanoparticles are energy intensive; employ toxic chemicals which produce hazardous wastes that preclude them for any biomedical application. There is a growing need for the uses of bio-compatible, non-toxic, cost-effective and eco-friendly methods for production of silver nanoparticles (Jae et al, 2009). Biological methods are considered safe and ecologically sound for the nanomaterial fabrication and alternative to conventional physical and chemical methods. Biological systems such as yeast, fungi, bacteria, plants etc., considered as biomimetics for the synthesis of nanostructures of biocompatible metal and semiconductors. The marine organisms are greatly deserved for the syntheses of different nanoparticles (Klaus et al, 1999; Nair and Pradeep, 2002; Konishi and Uruga, 2007) because of their diversity richness and high tolerance under ambient
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