Novel glucocorticoid antedrugs possessing a 17beta-(gamma-lactone) ring

The chemical synthesis and structure-activity relationships of a novel series of 17beta-glucocorticoid butyrolactones possessing either a 16alpha,17alpha-isopropylidene or -butylidene group are described. The sulfur-linked gamma-lactone group was incorporated onto the 17beta-position of the androstane nucleus via Barton ester decarboxylation and trapping the generated 17-radical with butyrolactone disulfides. The glucocorticoid butyrolactones were hydrolyzed in human plasma by the enzyme paraoxonase to the respective hydroxy acids, which were very weak glucocorticoid agonists. The rate of hydrolysis in plasma was very rapid (t1/2 = 4-5 min) in the case of lactones possessing a sulfur atom in the alpha-position of the butyrolactone group, whereas carbon-linked lactones were stable in plasma. 16alpha,17alpha-Butylidenes were more potent glucocorticoid agonists than the corresponding isopropylidene derivatives. Similarly, 1,4-dien-3-ones were more potent than the corresponding 4-en-3-ones. The butyrolactones linked to the steroidal nucleus via the beta-position were more potent glucocorticoid agonists than those linked through the alpha-position of the lactone. The most potent compounds were also shown to be stable in human lung S9 fraction, showed much lower systemic effects than budesonide in the thymus involution test, and possessed topical antiinflammatory activity in the rat ear edema model.

The squalestatins: inhibitors of squalene synthase. Enzyme inhibitory activities and in vivo evaluation of C3-modified analogues

Squalestatin analogues modified at C3 were prepared and evaluated for their ability to inhibit rat liver microsomal squalene synthase in vitro. While the 4,6-dimethyloctenoate ester group at C6 was maintained, a number of modifications to the C3 carboxylic acid were well tolerated. However, in the absence of the C6 ester group, similar modifications to the C3 carboxyl group caused loss of activity. Selected compounds were evaluated for their ability to inhibit cholesterol biosynthesis in vivo in rats 1 and 6 h postadministration. Analogues of squalestatin 1 (S1) modified at C3 were found to possess a shorter duration of effect in vivo which is reflected in their substantially reduced ability to lower serum cholesterol levels in marmosets. Significant cholesterol lowering (up to 62%) for the C3 hydroxymethyl analogue 1b was observed only when this compound was dosed three times a day for 3 days.

The squalestatins: decarboxy and 4-deoxy analogues as potent squalene synthase inhibitors

Squalestatins without either the hydroxy group at C-4 or the carboxylic acid at C-3 or C-4 were prepared and evaluated for their ability to inhibit rat liver microsomal squalene synthase (SQS) in vitro. These modifications were well tolerated for compounds with the 4,6-dimethyloctenoate ester at C-6 (S1 series). However in analogues without the C-6 ester (H1 series), removal of the C-4 hydroxy group gave compounds with reduced potency, whereas decarboxylation at C-3 resulted in a dramatic loss of SQS inhibitory activity. In comparison with S1 1, C-4 deoxyS1 3 and C-3 decarboxyS1 10 have shorter in vivo durations of action on the inhibition of hepatic cholesterol biosynthesis in rats. C-4 deoxyS1 3 retains good serum cholesterol-lowering ability in marmosets, while C-3 decarboxyS1 10 showed only a marginal effect even at high dose.

The squalestatins: novel inhibitors of squalene synthase. Enzyme inhibitory activities and in vivo evaluation of C1-modified analogues

Squalestatin analogues modified in the C1 side chain were prepared and evaluated for their ability to inhibit rat liver microsomal and Candida squalene synthase (SQS) in vitro. While maintaining the 4,6-dimethyloctenoate or 4,6-dimethyloctanoate ester groups at C6, a number of modifications to the C1 side chain were well tolerated. However, in the absence of the C6 ester group, similar modifications to the C1 side chain caused substantial loss of activity. Compounds were also evaluated for their ability to inhibit cholesterol biosynthesis in vivo in rats and to reduce serum cholesterol levels in marmosets. These studies revealed that compounds with similar SQS inhibitory activities can possess different in vivo durations of action and lipid-lowering abilities.

Cell wall and membrane changes associated with ethambutol resistance in Mycobacterium tuberculosis H37Ra

Biochemical variations accompanying the acquisition of ethambutol (EMB) resistance in a single-step mutant of Mycobacterium tuberculosis H37Ra were analyzed. Comparative analysis of phospholipids revealed a reduced content in the EMB-resistant strain, particularly in the cell membrane fraction. Significant alterations were observed in the individual phospholipid content and phospholipid fatty acyl group composition of whole cells and subcellular fractions. Quantitative changes were seen in the chemical constituents of the cell walls of resistant cultures in comparison with those of EMB-susceptible cultures of M. tuberculosis. Alterations in the binding of 1-anilinonaphthalene-8-sulfonate to whole cells of an EMB-resistant strain indicated structural changes on the cell surface. Structural changes in the cell wall may play an important role in the resistance of M. tuberculosis H37Ra to EMB.

Effect of ethambutol on the phospholipids of ethambutol susceptible and resistant strains of Mycobacterium smegmatis ATCC 607

Effect of ethambutol (EMB) on phospholipid composition and metabolism of EMB-susceptible and EMB-resistant strains of M. smegmatis ATCC 607 was studied. Treatment with ethambutol had different effect in both the strains resulting in decreased total phospholipid and cardiolipin content in EMB-susceptible strain and increased content in EMB-resistant strain, with no effect on fatty acyl group composition. These changes were further corroborated by the use of [1-14C]sodium acetate in these studies.