Synthesis and characterization of piperic acid conjugates with homochiral and heterochiral dipeptides containing phenylalanine and their application in skin cancer.

The current work demonstrates the synthesis and characterization of piperic acid conjugates with homochiral/heterochiral dipeptides containing phenylalanine as anti-skin cancer agents. The conjugates PA-DPhe-LPhe-OH, FC-1; PA-LPhe-DPhe-OH, FC-2; PA-DPhe-DPhe-OH, FC-3; and PA-DPhe-DPhe-OH, FC-4 were synthesized, characterized and assessed for cytotoxicity against melanoma cell lines of human and murine origin. Among all, PA-DPhe-DPhe-OH (FC-3) conjugate was identified as a potential cytotoxic lead against melanoma cells by delineating the anti-proliferative and anti-migratory potential together with its anti-inflammatory potential against pro-inflammatory interleukins (IL-1ß, IL-6, and IL-8). Evidences from western blotting, fractionation, and immunocytochemistry experiments suggest that Stat-3 is a critical signaling molecule involved in the FC-3 mechanism of action. The results denote that FC-3 profoundly ablates Stat-3 expression, phosphorylation, and nuclear translocation. Stat-3 mRNA analysis revealed that FC-3 did not alter the transcription of Stat-3. However, in cells where proteasome mediated degradation was inhibited, FC-3 failed to check the Stat-3 expression implying that FC-3 augments the proteasomal degradation of Stat-3. Of note, FC-3 failed to reverse the IL-6 mediated hyperactivation of Stat-3 in A375 cells. Critically, in Stat-3 deficient cancer cells, the anti-clonogenic and anti-migratory potential of FC-3 was significantly subdued. Further, the in vivo efficacy of FC-3 was validated in the two-step (DMBA/TPA) chemically induced mouse skin cancer model. The FC-3-treated cohorts of mice unveiled a significant decrease in the cumulative number of tumors besides attenuation of tumor growth with respect to the vehicle-treated mice. Lastly, in corroboration with our in vitro findings, serum collected from mice groups at various intervals during the treatment regimen demonstrated decrement in IL-1ß and IL-6 levels in FC-3 treated groups compared to the vehicle-treated group.

Synthesis, Characterization, and Antimicrobial Activity of Ultra-Short Cationic ß-Peptides.

The development of new antibiotics is urgently required because of the rapidly growing resistance against conventional antibiotics. The antimicrobial peptides show potential as small antibiotic molecules. The stability of peptides is a primary concern for the use of peptides as drugs. Introducing ß-amino acids into peptide sequences can be useful in preventing biological degradation by proteolytic enzymes. Herein, we describe the synthesis, characterization, and antimicrobial activity of ultra-short cationic ß-peptides, LA-ß3,3-Pip-ß2,2-Ac6c-PEA, P1; LA-ß3,3-Pip(G)-ß2,2-Ac6c-PEA, P2; LAU-ß3,3-Pip-ß2,2-Ac6c-PEA, P3, and LAU-ß3,3-Pip(G)-ß2,2-Ac6c-PEA, P4. Peptides P1-P4 were evaluated against Gram-negative, Gram-positive, MRSA, and multi-drug resistant E. coli (MDR-E. coli). P3 exhibited the most potent antimicrobial activity against E. coli, S. epidermidis, S. aureus, K. pneumoniae, S. mutans, and E. faecalis, with MIC values 0.5, 2, 0.5, 1, 2, and 1 µg/mL, respectively. P3 exhibited time- and concentration-dependent bactericidal activities against E. coli, S. aureus, and E. faecalis with a killing rate of 1.6 logs/h. The treatment of E. coli with peptide P3 showed membrane disruption. In addition, P3 exhibited the inhibition of biofilm produced by E. coli, synergism with antibiotics (ciprofloxacin, streptomycin, and ampicillin), 100% cell viability against AML12, RAW 264.7, and HEK-293 cell lines at 1, and 10 µg/mL concentrations.

Synthesis, characterization, and wound healing properties of α/γ hybrid peptides.

The present work describes the synthesis, characterization, and wound healing properties of α/γ hybrid peptides: Boc-Phe-γ4 -Phe-Val-OMe (S1), Boc-D Phe-γ4 -Phe-Val-OMe (S2), Boc-Ala-γ4 -Phe-Val-OMe (S3), Boc-D Ala-γ4 -Phe-Val-OMe (S4), Boc-Leu-γ4 -Phe-Val-OMe (S5), and Boc-D Leu-γ4 -Phe-Val-OMe (S6). Peptides S1-S6 were screened against human keratinocytes (HaCaT) and RAW 264.7 cells. Among all, S1- and S2-treated cells exhibited high cell viability; S1 and S2 induced keratinocyte migration and inhibited the production of the cytokines IL-6 and TNF-α. In vivo results demonstrated that the hybrid peptides S1 and S2 accelerate wound healing in Wistar rats with 83% and 88% at 50 µg/ml, and 74% and 76% at 25 µg/ml, respectively.

Synthesis, conformation and cytotoxic activity of short hybrid peptides containing conformationally constrained 1-(aminomethyl)cyclohexanecarboxylic acid and gabapentin.

The present work describes the synthesis,conformation and cytotoxic activities of short ß/γ hybrid peptides, Boc-ß2,2-Ac6c-Gpn-NHMe, BG1; Boc-(ß2,2-Ac6c-Gpn)2-OMe, BG2; Boc-(ß2,2-Ac6c-Gpn)3-OMe, BG3; H-ß2,2-Ac6c-Gpn-NHMe, BG4; H-(ß2,2-Ac6c-Gpn)2-OMe, BG5; H-(ß2,2-Ac6c-Gpn)3-OMe, BG6, Boc-ß2,2-Ac6c-Gpn-OMe, BG7 and H-ß2,2-Ac6c-Gpn-OMe, BG8. Mixed C6/C7 conformations were observed for ß/γ hybrid peptides. Further, BG1-BG8 were screened against MCF-7 (Breast cancer), A549 (Lung Cancer), PC-3 (Prostate cancer), HCT-116 (Colon cancer), and MDA-MB-231 (Breast cancer) cell lines. Among all, BG6 exhibited potent cytotoxicity against all cancer cell lines with IC50 ranging from 1.6 µM to 6.3 µM with relatively low cytotoxicity against normal epithelial breast cell line fR-2 and human embryonic kidney cell line HEK-293. Minimal hemolytic activity was observed for BG6 against human erythrocytes. Peptide BG6 displayed anti-migratory and anti-invasive potentials showing strong interactions with intrinsic apoptotic markers Bcl-2, Bax, and cleaved-PARP, as well as the induction of the mitochondria maladjustment mediated apoptosis.

Tetrahydropiperic acid (THPA) conjugated cationic hybrid dipeptides as antimicrobial agents.

The present work describes the synthesis of hybrid dipeptides H-Lys-Gpn-PEA, C1; H-Lys-ß3,3AC6C-PEA, C2, and THPA conjugated dipeptides, THPA-Lys-Gpn-PEA, C3, and THPA-Lys-ß3,3AC6C-PEA, C4. All the peptides were evaluated against both Gram-negative and Gram-positive bacterial strains. Among all, peptide C4 exhibited the most potent activity with MIC 1.56 µM against P. aeruginosa (MTCC 424) and S. aureus (MTCC 737). Further, time-kill kinetics, fluorescence assays, and scanning electron microscopy (SEM) studies were performed in order to understand the mechanism of action and efficacy of peptide C4, The fluorescence assays and SEM images demonstrated the bacterial killing through membrane disruption. The peptide C4 exhibited very low hemolytic activity with negligible cytotoxicity against normal human breast cell line FR2.