https://hdl.handle.net/20.500.12809/8881 2026-04-20T04:45:54Z https://hdl.handle.net/20.500.12809/10923 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 https://hdl.handle.net/20.500.12809/10878 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 https://hdl.handle.net/20.500.12809/10853 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 https://hdl.handle.net/20.500.12809/10631 HPLC-DAD Phenolic Composition, Antioxidant, Anticholinesterase, Antidiabetic and Anti-quorum Sensing Properties of Bitter Kola (Garcinia kola) and Kolanut (Cola acuminata) Boudiba, Sameh; Küçükaudın, Selçuk; Tamfu, Alfred Ngenge; Blaise, Kom; Munvera, Aristide Mfifen; Ceylan, Özgür Background: Eating Cola acuminata and Garcinia cola nuts in African societies symbolizes in socio-cultural hospitality. They stimulate the nervous system, reduce fatigue and sleep. Objectives:To determine the phenolic composition and bioactivities of G. kola and C. acuminata. Materials and Methods: Hydro-ethanol extracts of the nuts were prepared and their phenolic profiles determined using HPLC-DAD. Antioxidant, anticholinesterase, antidiabetic, antimicrobial, antibiofilm and anti-quorum sensing properties were determined. Results:The most abundant phenolic compound was caffeic acid (105.4 +/- 0.75 mg/g) in C. acuminata and myricetin (277.2 +/- 0.90 mg/g) in G. kola. The extracts showed good antioxidant activity in five complementary assays and G. kola was more active than both alpha-tocopherol and BHA standards in the DPPH center dot, CUPRAC and ABTS center dot+ assays while C. acuminata was more active than only the alpha-tocopherol standard in the same assays. Activities were close to those of standards in the beta-Carotene-linoleic acid and metal chelation assays. Both extracts had good inhibition of Butyrylcholinesterase (BChE) and Acetylcholinesterase (AChE) with IC50 values 63.27 +/- 0.98 mg/mL and 94.15 +/- 1.05 mg/mL for C. acuminata and G. kola respectively compared to 5.50 +/- 0.25 mg/mL for galantamine in the AChE assay. In the BChE assay, the inhibitory activity was higher for G. kola (IC50 = 38.66 +/- 0.80 mg/ mL) that the standard galantamine (IC50 = 42.20 +/- 0.48 mg/mL) while that for C. acuminata (IC50 = 87.31 +/- 0.77 mg/mL) was moderate. The extracts inhibited alpha-amylase and alpha-glucosidase with G. kola (IC50=18.43 +/- 0.74 mg/mL) being more active than standard acarbose (IC50=20.52 +/- 0.84 mg/mL in the alpha-glucosidase assay. The nuts could inhibit expression of virulence factors in Chomobacterium violaceum CV12472 by disrupting violacein production and flagellated Pseudomonas aeruginosa PA01 by disrupting swarming motility. Conclusion:The results indicate good nutraceutical potential of both nuts. 2023-01-01T00:00:00Z