Antinociceptive and Cytotoxic Activity of Opioid Peptides with Hydrazone and Hydrazide Moieties at the C-Terminus

In the present contribution, we analyze the influence that C-terminal extension of short opioid peptide sequences by organic fragments has on receptor affinity, in vivo analgesic activity, and antimelanoma properties. The considered fragments were based on either N-acylhydrazone (NAH) or N'-acylhydrazide motifs combined with the 3,5-bis(trifluoromethyl)phenyl moiety. Eleven novel compounds were synthesized and subject to biological evaluation. The analyzed compounds exhibit a diversified range of affinities for the µ opioid receptor (MOR), rather low δ opioid receptor (DOR) affinities, and no appreciable neurokinin-1 receptor binding. In three out of four pairs, N-acylhydrazone-based derivatives bind MOR better than their N'-acylhydrazide counterparts. The best of the novel derivatives have similar low nanomolar MOR binding affinity as the reference opioids, such as morphine and biphalin. The obtained order of MOR affinities was compared to the results of molecular docking. In vivo, four tested compounds turned out to be relatively strong analgesics. Finally, the NAH-based analogues reduce the number of melanoma cells in cell culture, while their N'-acylhydrazide counterparts do not. The antimelanoma properties are roughly correlated to the lipophilicity of the compounds.

Molecular Antioxidant Properties and In Vitro Cell Toxicity of the p-Aminobenzoic Acid (PABA) Functionalized Peptide Dendrimers

BACKGROUND

Exposure to ozone level and ultraviolet (UV) radiation is one of the major concerns in the context of public health. Numerous studies confirmed that abundant free radicals initiate undesired processes, e.g. carcinogenesis, cells degeneration, etc. Therefore, the design of redox-active molecules with novel structures, containing radical quenchers molecules with novel structures, and understanding their chemistry and biology, might be one of the prospective solutions. Methods: We designed a group of peptide dendrimers carrying multiple copies of p-aminobenzoic acid (PABA) and evaluated their molecular antioxidant properties in 1,1'-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) tests. Cytotoxicity against human melanoma and fibroblast cells as well as against primary cerebral granule cells (CGC) alone and challenged by neurotoxic sodium glutamate and production of reactive oxygen species (ROS) in presence of dendrimers were measured. Results: PABA-terminated dendrimers express enhanced radical and radical cation scavenging properties in relation to PABA alone. In cellular tests, the dendrimers at 100 M fully suppress and between 20⁻100 M reduce proliferation of the human melanoma cell line. In concentration 20 M dendrimers generate small amount of the reactive oxygen species (<25%) but even in their presence human fibroblast and mouse cerebellar granule cells remain intact Moreover, dendrimers at 0.2⁻20 µM concentration (except one) increased the percentage of viable fibroblasts and CGC cells treated with 100 M glutamate. Conclusions: Designed PABA-functionalized peptide dendrimers might be a potential source of new antioxidants with cationic and neutral radicals scavenging potency and/or new compounds with marked selectivity against human melanoma cell or glutamate-stressed CGC neurons. The scavenging level of dendrimers depends strongly on the chemical structure of dendrimer and the presence of other groups that may be prompted into radical form. The present studies found different biological properties for dendrimers constructed from the same chemical fragments but the differing structure of the dendrimer tree provides once again evidence that the structure of dendrimer can have a significant impact on drug⁻target interactions.

Hydrazone Linker as a Useful Tool for Preparing Chimeric Peptide/Nonpeptide Bifunctional Compounds

The area of multitarget compounds, joining two pharmacophores within one molecule, is a vivid field of research in medicinal chemistry. Not only pharmacophoric elements are essential for the design and activity of such compounds, but the type and length of linkers used to connect them are also crucial. In the present contribution, we describe compound 1 in which a typical opioid peptide sequence is combined with a fragment characteristic for neurokinin-1 receptor (NK1R) antagonists through a hydrazone bridge. The compound has a high affinity for μ- and δ-opioid receptors (IC₅₀= 12.7 and 74.0 nM, respectively) and a weak affinity for the NK1R. Molecular modeling and structural considerations explain the observed activities. In in vivo test, intrathecal and intravenous administrations of 1 exhibited a strong analgesic effect, which indicates potential BBB penetration. This letter brings an exemplary application of the hydrazone linker for fast, facile, and successful preparation of chimeric compounds.