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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.

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.

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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.

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Cellulose nanocrystals (CNCs) or cellulose nanofibers (CNFs) with different morphologies, chemical, mechanical and physical properties can be obtained when microcrystalline cellulose is subjected to enzymatic, chemical or mechanical treatment. With the aim of utilizing cellulose nanofibrils (CNFs) from Oryza sativa, we isolated microcrystalline cellulose using the Kraft process, followed by successive fiber fibrillation using mechanical grinding, then (2,2,6,6-Tetrame thylpiperidin-1-yl)oxyl (TEMPO) mediated oxidation. Analysis of pulp fibers obtained after each treatment step revealed that fiber properties such as length, crystallinity and crystal size changed when the pulp was subjected to mechanical grinding, ultrasonication and TEMPO mediated oxidation. The degree of crystallinity of the fibers increased while crystal size and fiber length decreased after each treatment. TEMPO mediated oxidation led to a decrease in fiber length and an increase in degree of crystallinity of the fibers as compared to mechanical treatment and ultrasonication. It further introduced carboxyl functional groups (COOH) on the surface of the fibrils, which implies that the nanofibers obtained in this study could be further functionalized. Hence, TEMPO mediated oxidation offers the possibility of further chemical functionalization of cellulose nanofibers isolated from agricultural residues. 摘要 微晶纤维素经酶、化学或机械处理后，可以获得具有不同形貌、化学性 质、机械性质和物理性质的纤维素纳米晶体(CNCs)或纤维素纳米纤维 (CNFs). 为了利用来自水稻的纤维素纳米纤维(CNFs)，我们用牛皮纸法分 离微晶纤维素，然后用机械研磨法连续纤维纤颤，然后(2,2,6,6-四甲基哌 啶-1-基)氧化(TEMPO)介导氧化. 对每个处理步骤后得到的纸浆纤维进行分 析，发现当纸浆经过机械研磨、超声波处理和TEMPO介导氧化处理后， 纤维的长度、结晶度和晶体大小等特性发生了变化. 各处理后纤维结晶度 均有所提高，晶粒尺寸和纤维长度均有所减小. 与机械处理和超声处理相 比，TEMPO介导的氧化导致纤维长度缩短，纤维结晶度增加. 进一步在纤 维表面引入羧基官能团(COOH)，说明本研究得到的纳米纤维可以进一步 功能化. 因此，TEMPO介导氧化为进一步实现从农业残留物中分离的纤维 素纳米纤维的化学功能化提供了可能.