Green Synthesis of Metal Nanoparticles from Plant 2 Extracts, and Their Possible Application as 3 Antimicrobial Agents in the Agricultural Area 4

: Currently, metal nanoparticles have varied uses for different medical, pharmaceutical, 12 and agricultural applications. Nano-biotechnology combined with green chemistry has great 13 potential for the development of novel and necessary products that benefit human activities, while 14 encourages the reduction of hazardous reagents for nanoparticle production. Green chemistry has 15 an important role due to its contribution to unconventional synthesis methods of gold and silver 16 nanoparticles from plant extracts, which have exhibited antimicrobial potential among other 17 outstanding properties. Biodiversity-rich countries need to collect and convert knowledge from biological resources into processes, compounds, methods, and tools, which need to be achieved along with sustainable use and exploitation of biological diversity. Therefore, this review focuses 20 on the importance of metal nanoparticles, the use of plant extract for their synthesis as well as other available methods, and the relevant antimicrobial activity that can be exploited in a sustainable model of agricultural management through a modern nanotechnological approach.


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Currently, Green chemistry has been developed as an alternative to the use of environmentally 28 harmful processes and products, due to the serious consequences that the world is facing, and the

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Chen et al. state that circular economies should always aim to balance economic growth, 33 resource sustainability, and environmental protection [5]. The challenge for biodiversity-rich

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Chemical reduction synthesis mechanisms of AuNPs and AgNPs have been extensively used 129 through different methods such as the Turkevich, synthesis with sodium borohydride (NaBH4) with 4 of 25 or without citrate, seeding-growth, synthesis by ascorbic acid, and Brust-Schiffrin [51]. Nevertheless, 131 a major concern arises due to the use of reagents such as NaBH4, sodium citrate, ascorbate, elemental 132 hydrogen, Tollen reagent, N, N-dimethylformamide (DMF) and block copolymers of poly (ethylene 133 glycol) for reduction of compounds. The mentioned substances can lead to toxic by-products and 134 damage the environment. For this reason, the use of a green pathway for the design and synthesis of 135 NPs is currently being explored, since in this approach reducing agents are provided by plants'

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Although chemical methods are the most widely used and well-reported for high-quality 138 synthesis, these may lead to NPs with a narrow size distribution, and involve the use of hazardous 139 chemical agents (e.g. toxic organic solvents), which limit NPs applications [53]. On the other hand, 140 physical methods include simple one-step procedures and provide large-scale production in a short 141 time, but it is common that the resulting NPs exhibit size, shape, and size distribution defects [54].         This method employs microwave energy for the partition of analytes from the sample into the 199 solvent by rapid heating, which allows materials to reach the necessary level of energy associated 200 with the dielectric susceptibility of both, solvent and plant raw material [68,73]. Through its 201 implementation; extraction time and solvent volume are reduced compared to other methods [74].

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The aforementioned explains why it is recognized as a green technology [75]. Aside from that, 203 studies have shown improved recovery of analytes and reproducibility when executing the 204 extraction by this method. However, it is necessary to take into consideration two important aspects.

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In first place, special concerns have to be foresee for preventing the thermal degradation of the 206 samples, and second, research groups need to be aware that this method is limited to small-molecule 207 phenolic compounds [76].

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This method is quite diverse from others since extracts can be obtained from multiple parts of 225 the plant or its derivate products that have demonstrated their aptitude to be considered a metal NP 226 natural source, such as leaves, bark, stem, shoots, seeds, latex, secondary metabolites, roots, twigs, 227 peels, fruits, seedlings, essential oils, and tissues. The extracts usually contain a large number of

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In the case of metal NPs, it is well known that they can be used as antioxidants, biosensors, and

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Meier et al. presented the concern that anthropogenic activities can disrupt soil ecosystems, 425 resulting in the reduction of its microbial health. In order to evaluate the previous, they exposed