Silver nanoparticles are one of the most extensively studied nanomaterials due to their high stability and low chemical reactivity in comparison to other metals. They are commonly synthesized using toxic chemical reducing agents which reduce metal ions into uncharged nanoparticles. However, in the last few decades, several efforts were made to develop green synthesis methods to avoid the use of hazardous materials. The natural biomolecules found in plants such as proteins/enzymes, amino acids, polysaccharides, alkaloids, alcoholic compounds, and vitamins are responsible for the formation of silver nanoparticles. The green synthesis of silver nanoparticles is an eco-friendly approach, which should be further explored for the potential of different plants to synthesize nanoparticles. In the present review we describe the green synthesis of nanoparticles using plants, bacteria, and fungi and the role of plant metabolites in the synthesis process. Moreover, the present review also describes some applications of silver nanoparticles in different aspects such as antimicrobial, biomedicine, mosquito control, environment and wastewater treatment, agricultural, food safety, and food packaging.

The antibacterial potency of garlic extract (Allium sativum) against gram positive and gram negative skin pathogenic bacteria including; Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, and Pseudomonas aeruginosa were studied using agar well diffusion and broth dilution assays.Agar well diffusion assay for aqueous garlic extract (AGE) was characterized with zones of inhibition ranging from 4.40 -3.80cm, 4.13 -3.57cm, 3.40 -2.67cm for S. aureus, S. epidermidis and Strep. pyogenes, respectively, however, Ps. aeruginosa had lesser zone of inhibition ranging from 2.32 -1.55cm. Studying the antibacterial potency of AGE against the selected isolates, revealed that it is affected by temperature of storage. Current results showed that storage of AGE at low temperature of -20 o C, does not affect its potency, however, its potency was slightly lost at high temperatures above 37 o C. The broth dilution test was performed to investigate the Minimum inhibitory concentration (MIC) andMinimum bactericidal concentration (MBC) of the AGE against the bacterial isolates at 37 o C.Investigating the activity of AGE loaded on Gel dressing revealed that it can have potency when applied on patients with Staphylococcal skin infections. Findings from this study encourage and support the use of AGE in treating bacterial skin infections especially in developing countries like Africa, as it is available, economic and have no side effects.

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Poverty and lack of access to health facilities had necessitated the less privileged to depend on herbal remedies to treat a number of diseases  including malaria. The successes recorded from the discovery of novel antimalarials from plant sources had paved the way for the search of  antimalarial compounds from traditional pharmacopeia. Phytochemical analysis as well as GC-MS analysis of crude leaves extract of Senna siamea was conducted, with a view to identifying compounds with biological activities. Further antimalarial assessment of the crude extracts was also performed in an in vitro assay. The phytochemicals; phenols, tannins, anthraquinones, alkaloid and flavonoids were detected from hexane and methanol extracts. GC-MS analysis revealed the presence of Saponins specifically, triterpenoids (Lupeol, α-amyrin), Sesquiterpene (Octadecane), Diterpenes (Eicosane), Esters of pthalic acids (Diethyl phthalate) Squalene, α-Tocopherol (a fat soluble Vitamin E) and hexadecanoic acid butyl ester. A dose dependent suppression of parasite growth was observed for all extracts, with methanolic extract showing less antimalarial potency (IC50= 3.74 μg/mL) when compared to the hexane extract (IC50=4.349 μg/mL). Extracts and compounds detected from the leaves of this plant could be used as novel lead compounds to develop new drugs. Keywords: Phytochemical analysis; GC-MS; antimalarial; Senna siamea; medicinal plants.

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