The study was conducted to assess the antibacterial activity of Phyllanthus amarus (Schum and Thonn) extract against Salmonella typhi causative agent of typhoid fever at the laboratories of the Departments of Chemistry and Theoretical and Applied Biology of the College of Science, Kwame Nkrumah University of Science and Technology, Kumasi. The objectives were to determine the highest yield of crude extract of P. amarus using different proportions of water to ethanol and to determine the sensitivity of Salmonella typhi to these. Three different extraction procedures were carried out. In the first procedure, seven extraction setups each containing different proportions of the two extract (water and ethanol) were used with 10g of the plant sample. In the second procedure, eight setups were used for the two solvents. Ten grams of both fresh and dry plant sample were extracted in two different 200ml of water and in another two different 200ml of water; 20g of both fresh and dry plant sample were again extracted. The same procedure was repeated using ethanol as the solvent. In the third procedure, 10g each of fresh plant sample were boiled in 100ml and 200ml of water for 30 minutes. A sensitivity test to determine the zones of inhibition for the various plant extracts was done on Salmonella typhi isolated from human. Results from the crude yield of P. amarus using water only had the highest crude yield of 2.57g, followed by ethanol only which was 2.52g. The sensitivity studies conducted on the fresh P. amarus indicated that aqueous extract of P. amarus inhibited S. typhi to a zone of 5.00mm in 10g/200ml and 7.17mm in 20g/200ml. Ethanol extract also recorded an inhibition zone of 2.67mm and 5.33mm in 10g/200ml and 20g/200ml respectively. Again, sensitivity studies using dry P. amarus samples showed that the aqueous extracts recorded a zone of inhibition of 7.33mm in 10g/200ml and 13.50mm in 20g/200ml. Also ethanol extracts also recorded an inhibition zone of 6.83mm in 10g/200ml and 10.50mm in 20g/200ml. Significant differences were observed among the extracts and the control in both 10g/200ml and 20g/200ml concentrations (P<0.05). Aqueous and ethanol extracts of P. amarus proved inhibitory to S. typhi.

Chemical solvents are commonly used to prevent microbial growth; dangerous to human health and have limited antibacterial properties. On the other hand, Nanoparticles made of metallic elements (such as copper, silver, and gold) have several uses in the field of biotechnology. Silver nanoparticles are more efficient in their antimicrobial, antibacterial, anti-inflammatory and anti-cancer properties. The current study aimed to determine the green synthesis of silver nanoparticles and their antibacterial activity from the aqueous extracts of leaves of Couroupita guianensis, Punica granatum, Vitex negundo, Cirtrus maxima. AgNPs of plant extracts were prepared using silver nitrate with the respective plant extract. Then they were characterized by FTIR analysis. The respective functional groups in the synthesized silver nanoparticles were confirmed with FTIR Spectra. The antibacterial activities of the synthesized nanoparticle extract were observed by zone of inhibition. From the results, the nanoparticles synthesized from the plants extract could pave a way to formulate a drug to treat microbial infection.

In this Research work, Silver Nanoparticles were green synthesized from Psidium guajava leaves and different Characterization techniques including UV-Visible, FT-IR, SEM and XRD were all employed to ascertain the absorption peaks, functional group, surface morphology and crystalline size of the nanoparticles respectively. These nanoparticles green synthesized were applied against four different pathogens namely, S. aureus (gram- positive bacteria), E. coli (gram- negative bacteria), C. albicans (gram- positive fungus) and Aspergillus niger and the investigation showed that the Silver nanoparticles synthesized were potent against the selected pathogens. From the UV-Vis spectral analysis, it was observed that highest absorption peaks appeared at 400nm and 500nm reflecting the surface plasmon resonance of silver Nanoparticles from guava leaves which is characteristic of Silver Nanoparticles. From the FT-IR spectrum of the sample under studied, the peaks 3416.85 cm^-1, 2923.51 cm^-1, 1618.95 cm^-1, 1384.49 cm^-1 and 1033.63 cm^-1 were observed where the absorption band at 3416.85 cm^-1 corresponds to the stretching due to N-H, while the band at 2923.51 cm^-1 is associated with C-H stretch of alkane and O-H stretching. The peak at 1618.95 cm^-1 shows C=C stretching, 1384.49 cm^-1 reveals the existence of C-H bending and 1033.63 cm^-1 depicted C-O stretching. The SEM analysis revealed the shape of the nanoparticles as being spherical while XRD result admits that the average size of the green synthesized Ag NPs was 45.5 nm using the Scherer’s formula. Augmentin was used as control at concentration of 300μg/L throughout antimicrobial studies. Different concentrations of 100, 200, 300, 400 and 500μg/L of Silver Nanoparticles were tested against each pathogen. It was discovered that with increase in concentrations of Silver Nanoparticles of all the pathogens, there generally appeared to be increase in inhibition zone. At higher concentration of 500μg/L, the zones of inhibition were in the following order; 22.50 mm, 17.00mm, 15.44mm, and 13.23mm for E. Coli, S. aureus, C. albicans and Aspergillus niger respectively. For each concentration investigated, E. coli, demonstrated higher zone of inhibition as opposed to all other pathogens investigated in this research.