Background: Plants are new sources of antibacterial agents, hence the need to determine and evaluate the antibacterial properties, antioxidant activity and gas chromatography – mass spectrometer (GC-MS) profile of medicinal plants. Methodology: In this study, sequential extraction of Prunus africana and Harrisonia abyssinica was used to obtain ethyl acetate and methanol extracts. Antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), whereas the total phenolic and total flavonoid contents were estimated using Folin-Ciocalteu and aluminium chloride, respectively. Antibacterial properties of the extracts against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coliand Candida albicans were estimated using the disc diffusion method and compared against streptomycin. Results: Screening of crude methanolic extracts revealed the presence of secondary metabolites which was further confirmed by Fourier transform infrared (FT-IR) characterisation that revealed the presence of H-bonded OH functional groups. The extracts revealed that P. africana had a higher total phenolic and total flavonoid contents compared to H. abyssinica. Methanolic extracts of both plants had moderate activity against selected microorganisms and both inhibited DPPH radical scavenging activity. GC-MS analysis of P. africana and H. abyssinica extracts revealed the presence of several phytochemicals that have been reported to have medicinal uses. Total phenolic and flavonoid contents showed positive correlations with the DPPH radical scavenging activity and negative correlations with EC50. Conclusion: Prunus africana and H. abyssinica extracts had moderate antimicrobial properties against the selected microorganisms because of the presence of secondary metabolites.

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Metallic nanoparticles synthesized using aqueous plant extracts are environment-friendly, biocompatible, and highly stable. The aim of this study was to synthesize iron nanoparticles using aqueous Ageratum conyzoides extracts and evaluating their antimicrobial and photocatalytic properties. The particles were analysed using UV-Vis spectrophotometer, FT-IR Spectrophotometer, X-ray diffractometer and Scanning electron microscope. GC-MS profile of the extracts revealed presence of secondary metabolites which were further quantified to determine the total phenolic and total flavonoids content of the extracts. The antibacterial activity of the plant extract and the synthesized iron oxide nanoparticles was evaluated against five microorganisms using agar well diffusion method. Iron nanoparticles synthesized in a one step process observed using visible spectra and the functional groups present such as C=O were identified from IR spectrum. SEM-EDX profile identified presence of iron, oxygen, chlorine, calcium in the particles while XRD data revealed the particles synthesized were composed oxides of iron which had moderate activity against the selected microorganisms as compared to the antibiotic ciprofloxacin. The particles were able to photocatalytic degrade methylene blue with a degradation efficiency of 92%. The results obtained in this study confirms that Ageratum conyzoides can play an important role in the bioreduction of Fe ions to FeNPs which have moderate activity against microorganisms and can act as photocatalyst to degrade methylene blue.

Anaerobic microorganisms of the Geobacter genus are effective electron sources for the synthesis of nanoparticles, for bioremediation of polluted water, and for the production of electricity in fuel cells. In multistep reactions, electrons are transferred via iron/heme cofactors of c‐type cytochromes from the inner cell membrane to extracellular metal ions, which are bound to outer membrane cytochromes. We measured electron production and electron flux rates to 5×105 e s−1 per G. sulfurreducens. Remarkably, these rates are independent of the oxidants, and follow zero order kinetics. It turned out that the microorganisms regulate electron flux rates by increasing their Fe2+/Fe3+ ratios in the multiheme cytochromes whenever the activity of the extracellular metal oxidants is diminished. By this mechanism the respiration remains constant even when oxidizing conditions are changing. This homeostasis is a vital condition for living systems, and makes G. sulfurreducens a versatile electron source.

Cellulose is an inexpensive, renewable, bio-based and an abundant raw material suitable for the development of filter membranes for water purification. This is because it has numerous functional groups that afford ease of modification to create active surfaces upon chemical modification. In this study, cellulose was isolated from two abundant biomasses, namely, Eichhornia crassipes and Cyperus papyrus using the soda process followed by bleaching with peracetic acid. The percent yield of cellulose nanofibrils (CNF) obtained from E. crassipes and C. papyrus was found to be 31.64 ± 1.46% and 29.55 ± 0.64% respectively. The degree of crystallinity and crystal sizes were calculated to be 71.42% and 0.059 nm for E. crassipes and 46.15% and 0.068 nm for C. papyrus respectively. The FT-IR absorption of the carbonyl functional group of an ester indicated that effective esterification of cellulose using citric acid was obtained when cellulose nanofibrils to citric Original Research Articleacid ratio was 1:1. From batch adsorption studies, the capacity for citric acid modified cellulose to remove heavy metals was determined to be 8.36 mg/g Zn 2+ , 18.06 mg/g Cu 2+ , 42.69 mg/g Cd 2+ and 21.64 mg/g Pb 2+ . In comparison to the % adsorption using unmodified cellulose of less than 5%, the heavy metals adsorption using modified nanocellulose materials were 86.47% Pb 2+ , 85.20% Cd 2+ , 77.40% Cu 2+ , and 70.04% Zn 2+ . From these results, it was concluded that modified cellulose could be used as a low cost adsorbent for removal of heavy metals and that development of household water filtration units using modified cellulose could be exploited.