Evaluation of Binding and Abrasion Properties of Grey Mangrove (Avicennia marina) Leaf Extract Against Escherichia coli K12 DNA

Background: Mangroves are globally known for their ecological importance and are found to be extensively used in traditional medicine. Avicennia marina, commonly known as grey mangroves exhibit strong antimicrobial properties and are also considered being a promising drug candidate in neutralizing pathogens. Objective: In our present study, the leaf extract from Avicennia marina was isolated using organic solvents of ascensive polarity to evaluate binding and abrasive properties in Escherichia coli K12 DNA. Methods: Samples of the pulverized leaves were used for sequential extraction using ethyl acetate, chloroform and acetone. The minimum inhibitory concentration of isolates from ethyl acetate, chloroform and acetone were quantified to be 0.125gL-1, 0.0625gL-1 and 0.125gL-1, respectively. These values were further utilized to calculate the binding constant between Escherichia coli DNA and isolates. In addition, mutagenicity of the isolates was assessed using Ames test in which the Escherichia coli K12 (strain AB1157) bacteria was cultured in minimal glucose media supplemented with isolates for assessing their DNA modifying ability. Further, DNA abrasion potential was assessed for all the isolates using Comet assay. Results: Results of Ames test showed that the isolates have DNA modifying ability, whereas the Comet assay demonstrated that isolates do not exhibit DNA degrading potential. Conclusion: In conclusion, the mechanism by which the isolates degrade the bacterial cell must be contrary to its DNA degrading potential. Experiments paved the way for further quantification and examination using bioinformatics tools to find the best drug candidate and to run clinical trials

Synthesis, Antitumor and Antibacterial Studies of New Shortened Analogues of (KLAKLAK)2-NH2 and Their Conjugates Containing Unnatural Amino Acids

(1) Background: (KLAKLAK)2 is a representative of the antimicrobial peptide group which also shows good anticancer properties. (2) Methods: Herein, we report synthesis using SPPS and characterization by HPLC/MS of a series of shortened analogues of (KLAKLAK)2. They contain single sequence KLAKLAK as C-terminal amides. In addition, substitution of some natural amino acids with unnatural β-Ala and nor-Leu is realized. In addition, these structures are conjugated with second pharmacophore with well proven anticancer properties 1,8-naphthalimide or caffeic acid. Cytotoxicity, antiproliferative effect and antimicrobial activity of newly synthesized structures were studied. (3) Results: The obtained experimental results reveal significant selective index for substances with common chemical structure KLβAKLβAK-NH2. The antibacterial properties of newly synthesized analogues at two different concentrations 10 μM and 20 μM, were tested against Gram-negative microorganisms Escherichia coli K12 407. Only two of the studied compounds KLAKLAK-NH2 and the one conjugated with second pharmacophore 1,8-naphthalimide and unnatural amino acid nor-Leu showed moderate activity against tested strains at concentration of 20 μM. (4) Conclusions: The obtained results reveal that the introducing of 1,8-naphthalimideGly- and Caf- increase the cytotoxicity and antiproliferative activity of the peptides but not their selectivity. Only two compounds KLAKLAK-NH2 and 1,8-naphthalimideGKnLAKnLAK-NH2 show moderate activity against Escherichia coli K12 at low concentration of 20 μM.