Lothar Heinisch

Madurahydroxylactone Derivatives as Dual Inhibitors of Human Immunodeficiency Virus Type 1 Integrase and RNase H

ABSTRACT A series of 29 madurahydroxylactone derivatives was evaluated for dual inhibition of human immunodeficiency virus type 1 (HIV-1) integrase and RNase H. While most of the compounds exhibited similar potencies for both enzymes, two of the derivatives showed 10- to 100-fold-higher selectivity for each enzyme, suggesting that distinct pharmacophore models could be generated. This study exemplifies the common and divergent structural requirements for the inhibition of two structurally related HIV-1 enzymes and demonstrates the importance of systematically screening for both integrase and RNase H when developing novel inhibitors.

A novel type of nonsteroidal estrone sulfatase inhibitors

Madurahydroxylactone (MHL) is a secondary metabolite produced by the soil bacterium Nonomuria rubra and belongs to the family of benzo[a]naphthacenequinones. We report the initial results and structure-activity relationships of our study into a series of thiosemicarbazone derivatives of madurahydroxylactone as potential nonsteroidal inhibitors of the enzyme estrone sulfatase. The most active compound, the cyclohexylthiosemicarbazone, was shown to be a non-competitive inhibitor with a K(i) of 0.35microM. This compound is devoid of estrogenic properties and showed low acute toxicity in the hens fertile egg screening test.

Growth promotion of synthetic catecholate derivatives on Gram-negative bacteria.

Derivatives of benzoic acid, glyoxylic acid benzhydrazone, oxanilic acid and N-dihydroxybenzylidene-2,4,6-trimethylaminobenzene were investigated as catecholic iron chelators under iron-depleted conditions. Some of the compounds showed strong positive reactions in the universal chemical siderophore assay (CAS): 3,4-dihydroxybenzoic acid, glyoxylic acid 2,3-dihydroxybenzhydrazone, N-3,4-dihydroxybenzylidene-2,4,6-trimethylaminobenzene. In particular these compounds also enabled removal of iron from iron-saturated transferrin. Using various siderophore indicator strains (enterobacteriacecae, Pseudomonas aeruginosa and Aeromonas hydrophila mutants) in bioassays the following growth promotion could be detected: vicinal substituents (e.g. 2,3- or 3,4-) were essential, the carboxyamido group seen in benzoic acids and glyoxylic acid benzhydrazones contributed to a positive reaction as well as the azomethin group (in N-3,4-dihydroxybenzylidene-2,4,6-trimethylaminobenzene). 2,3-Dihydroxybenzoic acid and the 2,3-diacetoxy substitute preferably promoted growth of enterobacteriaceae mutants. In contrast, the 3,4- positioned compounds preferably promoted growth of P. aeruginosa mutants and A. hydrophila SB 22. Glyoxylic acid di(methoxycarbonyloxy)-benzhydrazones (2,3- and 3,4- positioned) including the 2,3-dihydroxy compound preferably enabled growth of the non-fermenters. N-3,4-dihydroxybenzylidene-2,4,6-trimethylaminobenzene supplied all mutants of Salmonella, Escherichia coli, Klebsiella, Morganella, P. aeruginosa and A. hydrophila with iron. Transport of glyoxylic acid 2,3-dihydroxybenzhydrazone depended on tonB, and required the involvement of the iron-regulated outer membrane proteins (IROMPs) FepA, Cir and Fiu.

New synthetic catecholate-type siderophores based on amino acids and dipeptides.

New analogs of bacterial siderophores with one, two or three catecholate moieties were synthesized using various mono- and diamino acid and dipetide scaffolds, respectively. In addition to 2,3-dihydroxybenzoyl siderophore analogs and their acylated derivatives, 3,4-dihydroxybenzoyl derivatives were prepared. Furthermore, the synthesis of a new triscatecholate serving as an intimate model for enterobactin is reported. Most of the new compounds gave a positive CAS-test and were active as siderophores tested by growth promotion assays with a set of siderophore indicator mutants under iron limitation. Structure-activity-correlations have also been studied.

Effects of Synthetic Siderophores on Proliferation of Plasmodium falciparum in Infected Human Erythrocytes

ABSTRACT Because iron is essential for Plasmodium falciparum, we investigated the in vitro potential of various synthetic siderophores to kill P. falciparum in infected human erythrocytes. The substances with the most promising profile, i.e., low 50% lethal doses for plasmodia and minimum toxicity towards mammalian cells, were siderophores with an acylated monocatecholate or a triscatecholate as substituent.

New synthetic catecholate-type siderophores with triamine backbone

New analogues of triscatecholate siderophores based on linear or tripodal triamines with or without spacer groups or lipophilic and hydrophilic substituents were synthesized. The catecholate moieties were prepared in OH-forms, as acetylated compounds or masked as 8-methoxycarbonyloxy-2,4-dioxo-1,3-benzoxazine derivatives. Some of the new compounds were active as siderophores tested by growth promotion assays using various Gram-negative bacteria and mycobacteria under iron limitation and by CAS-assay. Structure-activity-correlations have been studied.

Catecholates and mixed catecholate hydroxamates as artificial siderophores for mycobacteria

Different mono-, bis- or triscatecholates and mixed mono- or biscatecholate hydroxamates were synthesized as potential siderophores for mycobacteria. Siderophore activity was tested by growth promotion assays using wild type strains and iron transport mutants of mycobacteria as well as Gram-negative bacteria. Some triscatecholates and biscatecholate hydroxamates were active in mutants of Mycobacterium smegmatis deficient in mycobactin and exochelin biosynthesis or exochelin permease, respectively, indicating an uptake route independent of the exochelin/mycobactin pathway. Structure activity relationships were studied. Ampicillin conjugates of some of these compounds were inactive against mycobacteria but active against Gram-negative bacteria.

New artificial siderophores based on a monosaccharide scaffold.

New artificial catecholate siderophores with methyl α-d-glucopyranoside as scaffold were synthesized. The dihydroxy- or di(acetoxy)benzoyl moieties were attached either directly or via aminopropyl spacer groups, to the carbohydrate scaffold. The siderophore activity of the prepared siderophore analogs was examined by a growth promotion assay using various Gram-negative bacteria and mycobacteria and by the CAS-assay.

Novel catecholate-type siderophore analogs based on a myo-inositol scaffold

A novel 1,3,5-triamino-myo-inositol derivative ispresented as a readily available scaffold for the design oftripodal siderophore mimetics.Based on this scaffold, various hexadentate catecholate-type siderophoreanalogs weresynthesized by attaching the catechols to the inositol scaffold via spacer units of differentstruc-tureand length. The potential to tune the polarity of the inositol containing siderophoreanalogs has also beendemonstrated by varying the protection group strategy. The siderophoreactivity of the prepared siderophoreanalogs was examined by cross-feeding tests withvarious Gram-negative bacteria and mycobacteria.