Discovering protein-ligand chalcogen bonding in the protein data bank using endocyclic sulfur-containing heterocycles as ligand search subsets.

The chalcogen bond, the noncovalent, electrostatic attraction between covalently bonded atoms in group 16 and Lewis bases, is present in protein-ligand interactions based on X-ray structures deposited in the Protein Data Bank (PDB). Discovering protein-ligand chalcogen bonding in the PDB employed a strategy that focused on searching the database for protein complexes of five-membered, heterocyclic ligands containing endocyclic sulfur with endo electron-withdrawing groups (isothiazoles; thiazoles; 1,2,3-, 1,2.4-, 1,2,5-, 1,3,4-thiadiazoles) and thiophenes with exo electron-withdrawing groups, e.g., 2-chloro, 2-bromo, 2-amino, 2-alkylthio. Out of 930 ligands investigated, 33 or 3.5% have protein-ligand S---O interactions of which 31 are chalcogen bonds and two appear to be S---HO hydrogen bonds. The bond angles for some of the chalcogen bonds found in the PDB are less than 90°, and an electrostatic model is proposed to explain this phenomenon.

Structural requirements for the antitubercular quaternized triflupromazine pharmacophore.

Quaternized triflupromazine derivatives (QTDs) must possess benzyl groups attached to the quaternary nitrogen in order to have significant antitubercular potency. Replacing the quaternary amine with a triazole abolishes antitubercular activity. A modest halogen substitution effect exists, with the 4-bromophenyl QTD 3 having the best selectivity index (>21). All N-benzyl QTDs 1-4 similarly inhibit non-replicating, persistent Mycobacterium tuberculosis with MIC<8 µM, and compounds 1-3 were all nontoxic to mammalian cells in vitro (IC(50)>128 µM).

Antiviral activity and synthesis of quaternized promazine derivatives against HSV-1.

N-(4-chlorobenzyl)triflupromazinium chloride, a known antitubercular agent, has been found to also be active against HSV-1. A preliminary structure-activity relation has been explored to determine which groups are crucial to viral inhibition. Antiviral assessments such as GFP reduction, plaque reduction, treatment timing and wash-out studies have also been probed to determine a mode of action for QPD-1. Based on this preliminary data, it appears that QPD-1 is a reversible inhibitor, suspected to inhibit early stages of viral replication of HSV-1 at 50 µM, equipotent to acyclovir.

In silico ligand-receptor docking of potentially selective butyrylcholinesterase inhibitors structurally related to the marine natural product debromoflustramine B.

Selective human butyrylcholinesterase (BChE) inhibitors such as cymserine have shown considerable promise for restoring cognition in Alzheimer's disease. Recently, (-)-debromoflustramine B, 1, a hexahydropyrrolo-[2,3-b]indole natural product isolated from the marine bryozoan Flustra foliacea, has demonstrated micromolar potency as a selective BChE inhibitor. Since (±)-demethyldebromoflustramine B, (±)-2, has an even lower IC(50), and the active enantiomer is (-)-2, derivatives of (-)-2 were constructed in silico and docked into the active site of BChE. Several compounds exhibited improved inhibitor potency and could be candidates for future synthesis and in vitro enzyme inhibition study.

Synthesis and antitubercular activity of quaternized promazine and promethazine derivatives.

Quaternized chlorpromazine, triflupromazine, and promethazine derivatives were synthesized and examined as antitubercular agents against both actively growing and non-replicating Mycobacterium tuberculosis H37Rv. Impressively, several compounds inhibited non-replicating M. tuberculosis at concentrations equal to or double their MICs against the actively growing strain. All active compounds were non-toxic toward Vero cells (IC50 > 128 microM). N-Allylchlorpromazinium bromide was only weakly antitubercular, but replacing allyl with benzyl or substituted benzyl improved potency. An electron-withdrawing substituent on the phenothiazine ring was also essential. Branching at the carbon chain decreased antitubercular activity. The optimum antitubercular structures possessed N-(4- or 3-chlorobenzyl) substitution on triflupromazine.

Antibacterial activity of (-)-deoxypseudophrynaminol versus its racemate and derivatives.

(-)-Deoxypseudophrynaminol 1 possesses 43-fold greater antibacterial potency than the racemate toward Staphylococcus aureus, indicating that the (-)-enantiomer is the biologically active isomer in this assay. Comparison of the percent growth inhibition by derivatives of 1 indicates that prenylation of N8 and replacement of N1-methyl by methyl carbamate are detrimental to antibacterial potency. (-)-1 is a promising lead structure for the development of the novel hexahydropyrrolo[2,3-b]indole class of antibacterial agents.

An image contrast agent selectively activated by prostate specific antigen.

A family of image contrast agent conjugates designed to undergo enzymatic activation has been synthesized. The agents underwent activation both with enzymatically active prostate specific antigen (PSA) and alpha-chymotrypsin, releasing free fluorophore via cleavage of a three-component system. A hexapeptide derivative showed exclusive activation by PSA and constitutes a method for tracking PSA activity in vitro.