https://hdl.handle.net/20.500.12809/31 2026-04-20T03:37:27Z 2026-04-20T03:37:27Z Talla, Rostan Mangoua Tamfu, Alfred Ngenge Wakeu, Brussine Nadège Kweka Ceylan, Özgür https://hdl.handle.net/20.500.12809/10923 2023-08-28T13:22:38Z 2023-01-01T00:00:00Z

Evaluation of anti-quorum sensing and antibiofilm effects of secondary metabolites from Gambeya lacourtiana (De Wild) Aubr. & Pellegr against selected pathogens Talla, Rostan Mangoua; Tamfu, Alfred Ngenge; Wakeu, Brussine Nadège Kweka; Ceylan, Özgür Background: Microbial infections cause serious health problems especially with the rising antibiotic resistance which accounts for about 700,000 human deaths annually. Antibiotics which target bacterial death encounter microbial resistance with time, hence, there is an urgent need for the search of antimicrobial substances which target disruption of virulence factors such as biofilm and quorum sensing (QS) with selective pressure on the pathogens so as to avoid resistance. Methods: Natural products are suitable leads for antimicrobial drugs that can inhibit bacterial biofilms and QS. Twenty compounds isolated from the medicinal plant Gambeya lacourtiana were evaluated for their antibiofilm and anti-quorum sensing effects against selected pathogenic bacteria. Results: Most of the compounds inhibited violacein production in Chromobacterium violaceum CV12472 and the most active compound, Epicatechin had 100% inhibition at MIC (Minimal Inhibitory Concentration) and was the only compound to inhibit violacein production at MIC/8 with percentage inhibition of 17.2 ± 0.9%. Since the bacteria C. violaceum produces violacein while growing, the inhibition of the production of this pigment reflects the inhibition of signal production. Equally, some compounds inhibited violacein production by C. violaceum CV026 in the midst of an externally supplied acylhomoserine lactone, indicating that they disrupted signal molecule reception. Most of the compounds exhibited biofilm inhibition on Staphyloccocus aureus, Escherichia coli and Candida albicans and it was observed that the Gram-positive bacteria biofilm was most susceptible. The triterpenoids bearing carboxylic acid group, the ceramide and epicatechin were the most active compounds compared to others. Conclusion: Since some of the compounds disrupted QS mediated processes in bacteria, it indicates that this plant is a source of antibiotics drugs that can reduce microbial resistance.

2023-01-01T00:00:00Z Ceylan, Özgür Tamfu, AlfredNgenge Küçükaydın, Selçuk Koudoro, Alain Yaya https://hdl.handle.net/20.500.12809/10878 2024-04-04T08:31:46Z 2023-01-01T00:00:00Z

Phenolic Composition, Anti-Biofilm, Anti-Quorum Sensing, Antioxidant and Enzyme Inhibitory Activities of Pteleopsis Suberosa (Combretaceae) Leaves Ceylan, Özgür; Tamfu, AlfredNgenge; Küçükaydın, Selçuk; Koudoro, Alain Yaya P. suberosa is a multipurpose medicinal plant in West and Central Africa. Fourteen phenolic compounds were identified in the P. suberosa leaves extract using HPLC-DAD and gallic acid (175.10 & PLUSMN;0.42 & mu;g/g) was the most abundant. The total phenolic content was 112.16 & PLUSMN; 0.33 mg GAE/g DW while the total flavonoid content was 36.10 & PLUSMN;0.58 mg QE/g DW. Minimal inhibitory concentration (MIC) values for antimicrobial activity were 0.3125 mg/mL and 1.25 mg/mL on S. aureus and E. faecalis respectively and 2.5 mg/mL and 0.3125 mg/mL on E. coli and S. typhi respectively. Biofilm inhibition evaluated at sub-MIC concentrations revealed that gram-negative biofilms were more susceptible to P. suberosa extract than gram-positive ones and E. coli biofilms were the most susceptible. The extract inhibited violacein production and quorum sensing with inhibition zones varying from 17.0 & PLUSMN;0.5 mm at MIC to 12.0 & PLUSMN;0.1 mm at MIC/4. The extract showed good antioxidant capacity and was more active in the DPPH & BULL; assay than the two standards & alpha;- tocopherol and BHA used. In the ABTS & BULL;+ and CUPRAC assays, the activity of the extract was greater than that of & alpha;-Tocopherol and very close to that of BHA. The extract showed potential to alleviate Alzheimer's disease by inhibiting acetylcholinesterase and butyrylcholinesterase as well as antidiabetic activity by inhibiting & alpha;-amylase and & alpha;-glucosidase. This is an open-access article distributed under the terms of the Creative Commons Attribution -Non Commercial-Share Alike 4.0 License, which allows others to remix, tweak, and build upon the work non commercially, as long as the author is credited and the new creations are licensed under the identical terms.

2023-01-01T00:00:00Z Boudiba, Sameh Tamfu, Alfred Ngenge Hanini, Karima Selatnia, Ilhem https://hdl.handle.net/20.500.12809/10853 2023-08-07T08:15:11Z 2023-01-01T00:00:00Z

Synthesis of a new diarylhydrazone derivative and an evaluation of its in vitro biofilm inhibition and quorum sensing disruption along with a molecular docking study Boudiba, Sameh; Tamfu, Alfred Ngenge; Hanini, Karima; Selatnia, Ilhem Molecules that target quorum sensing and biofilm inhibition are useful antimicrobials. In this regard, a new diarylhydrazone was synthesized and characterized using infrared, high-resolution mass spectrometry and nuclear magnetic resonance experiments as N-[(E)-4-bromo-2,5-diheptyloxybenzylideneamino]-2,4-dinitroaniline (BHBANA). Minimal inhibitory concentrations (MICs) vary from 0.625 to 2.5 mg mL−1. This compound was screened in vitro for its inhibition of quorum sensing–mediated violacein production by Chromobacterium violaceum CV12472 at MIC and sub-MIC and showed percentage inhibition varying from 100% at MIC to 5.7% ± 0.2% at MIC/32. Against Chromobacterium violaceum CV026, BHBANA exhibited anti-quorum-sensing zone diameters of 10.5 ± 0.3 mm and 7.0 ± 0.1 mm at MIC and MIC/2, respectively. BHBANA shows concentration-dependent inhibition of swarming motility on flagellated Pseudomonas aeruginosa PA01 with the highest % inhibition of 28.30% ± 0.50% μg mL−1 at MIC. The product inhibits biofilm formation, with the best biofilm inhibition being observed against Staphylococcus aureus varying from 72.24% ± 0.86% (MIC) to 09.82% ± 0.10% (MIC/8). Molecular docking studies carried out utilizing the Schrodinger software identified interactions between BHBANA and different receptor compartments of Chromobacterium violaceum, which can block pathogenic gene expression. The results suggest the potential of BHBANA in reducing microbial virulence.

2023-01-01T00:00:00Z Altıkulaç, Aydan Turhan, Şeref https://hdl.handle.net/20.500.12809/10823 2023-08-01T10:32:09Z 2023-01-01T00:00:00Z

Assessment of the Levels of Potentially Toxic Elements Contained in Natural Bentonites Collected from Quarries in Turkey Altıkulaç, Aydan; Turhan, Şeref Potentially toxic elements (PTEs) are an important type of pollutant, causing constant and far-reaching concerns around the world due to their increase in the mining process. Bentonite formed by the alteration of glass-rich volcanic rocks is a smectite clay consisting mostly of montmorillonite. Bentonite is an important mineral used in a wide range of applications in many fields such as oil and gas, agriculture, food, pharmacological, cosmetic, and construction industries due to its unique qualities. Given the widespread distribution of bentonite in nature and its use in a wide variety of consumer products, it is inevitable that the general population will be exposed to PTEs contained in bentonites. In this study, concentrations of PTEs in 69 bentonite samples collected from quarries located in different geographical regions of Turkey were analyzed by an energy-dispersive X-ray fluorescence spectrometric method. The average concentrations of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Zr, and Pb in bentonite samples were found to be 3510, 95, 129, 741, 30,569, 67, 168, 25, 62, 9, 173, and 28 mg/kg dry weight, respectively. Results of the enrichment factor relating to Earth’s crust average indicated moderate enrichment with Cr, Ni, and Pb and significant enrichment with Co and As.

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