ABSTRACT
Phakellistatin peptides from marine organisms are the sources of proline-rich cyclic peptides with reported significant antitumor activities. Phakellistatin 18 (1), reported from marine sponge Phakellia fusca, contains three proline-peptide linkages in cis form. We attempted the total synthesis of natural product 1 through solution-phase macrocyclization approach, as a result, the synthetic cyclic peptide 2 was obtained as a rotamer of natural product having all three proline residues in trans-conformation. Here, we describe the synthesis, structural, and cytotoxicity studies of trans-Phakellistatin 18 (2), and its analog [Ala1,3,6]-Phakellistatin 18 (3). Detailed NMR studies were carried out to characterize the synthesized peptides, and anti-cancer screening was performed by using MTT assay. The synthetic trans-Phakellistatin 18 (2) (IC50=67.5 ± 2.938 µM) showed comparable cytotoxicity against HepG2 cancer cell line with standard drug doxorubicin (IC50=63.88 ± 6.48 µM). Here, the first synthetic and structural studies on trans-Phakellistatin 18 (2), and its anticancer screening against HepG2 cell line was reported.
Subject(s)
Porifera , Animals , Porifera/chemistry , Aquatic Organisms , Molecular Conformation , Peptides, Cyclic/chemistry , Proline/chemistryABSTRACT
Cervical cancer is among the leading causes of death in women. Chemotherapy options available for cervical cancer include highly cytotoxic drugs such as taxol, cisplatin, 5-florouracil, and doxorubicin, which are not specific. In the current study, we have identified a new peptide conjugate (Fur4-2-Nal3-Ala2-Phe1-CONH2) (conjugate 4), from screening of a small library of tripeptide-conjugates of furan, as highly potent anticancer compound against human cervical cancer cells (HeLa cells) (IC50 = 0.15 ± 0.05 µg/mL or 0.28 +/- 0.09 µM). Peptides were constructed on Rink amide resin from C- to N-terminus followed by capping by α-furoic acid moiety. The synthesized peptides were purified by recycling RP-HPLC, and structures of all the peptides were confirmed by using FABMS/ESIMS, 1H- NMR, 13C-NMR, and HR-FABMS. Conjugate 4 was furthermore found to be specifically active against human cervical cancer cells since it did not inhibit the proliferation of other human normal cells (HUVEC (human umbilical vein endothelial cells) and IMR-90 (normal human fibroblasts)), and cancer cells tested (HUVEC, MCF-7, and MDA-MB-231 cells), as well as in mice 3T3 cells (normal fibroblasts). This study revealed a good structure activity relationship of various peptide conjugates. Conjugate 4 in branched forms (4a and 4b) were also synthesized and evaluated against HeLa cells, and results revealed that both were inactive. Atomic force microscopy (AFM) studies and staining with rhodamine 123 and propidium iodide (PI) revealed that conjugate 4 possesses a membranolytic effect and causes the loss of mitochondrial membrane potential.
Subject(s)
Antineoplastic Agents/chemistry , Furans/chemistry , Peptides/chemistry , Uterine Cervical Neoplasms/drug therapy , 3T3 Cells , Amides , Animals , Apoptosis/drug effects , Cell Line, Tumor , Cell Proliferation , Cell Survival/drug effects , Doxorubicin/pharmacology , Drug Screening Assays, Antitumor , Endothelial Cells/drug effects , Female , HeLa Cells , Human Umbilical Vein Endothelial Cells , Humans , Inhibitory Concentration 50 , MCF-7 Cells , Magnetic Resonance Spectroscopy , Mice , Microscopy, Atomic Force , Protein DomainsABSTRACT
Helicobacterpylori is one of the most prevalent pathogens colonizing 50% of the world's population and causing gastritis and gastric cancer. Even with triple and quadruple antibiotic therapies, H. pylori shows increased prevalence of resistance to conventional antibiotics and treatment failure. Due to their pore-forming activity, antimicrobial peptides (AMP) are considered as a good alternative to conventional antibiotics, particularly in the case of resistant bacteria. In this study, temporin-SHa (a frog AMP) and its analogs obtained by Gly to Ala substitutions were tested against H. pylori. Results showed differences in the antibacterial activity and toxicity of the peptides in relation to the number and position of D-Ala substitution. Temporin-SHa and its analog NST1 were identified as the best molecules, both peptides being active on clinical resistant strains, killing 90-100% of bacteria in less than 1 h and showing low to no toxicity against human gastric cells and tissue. Importantly, the presence of gastric mucins did not prevent the antibacterial effect of temporin-SHa and NST1, NST1 being in addition resistant to pepsin. Taken together, our results demonstrated that temporin-SHa and its analog NST1 could be considered as potential candidates to treat H. pylori, particularly in the case of resistant strains.
