Benzylamine antioxidants: relationship between structure, peroxyl radical scavenging, lipid peroxidation inhibition, and cytoprotection

Neutral sphingomyelinase 2 inhibitors based on the 4-(1H-imidazol-2-yl)-2,6-dialkoxyphenol scaffold

Neutral sphingomyelinase 2 (nSMase2), a key enzyme in ceramide biosynthesis, is a new therapeutic target for the treatment of neurological disorders and cancer. Using 2,6-dimethoxy-4-[4-phenyl-5-(2-thienyl)-1H-imidazol-2-yl]phenol (DPTIP), our initial hit compound (IC₅₀ = 30 nM) from nSMase2 screening efforts, as a molecular template, a series of 4-(1H-imidazol-2-yl)-2,6-dialkoxyphenol derivatives were designed, synthesized, and evaluated. Systematic examination of various regions of DPTIP identified the key pharmacophore required for potent nSMase2 inhibition as well as a number of compounds with the 4-(1H-imidazol-2-yl)-2,6-dialkoxyphenol scaffold with similar or higher inhibitory potency against nSMase2 as compared to DPTIP. Among them, 4-(4,5-diisopropyl-1H-imidazol-2-yl)-2,6-dimethoxyphenol (25b) was found to be metabolically stable against P450 metabolism in liver microsomes and displayed higher plasma exposure following oral administration as compared to DPTIP. Analysis of plasma samples identified an O-glucuronide as the major metabolite. Blockade of the phase II metabolism should further facilitate our efforts to identify potent nSMase2 inhibitors with desirable ADME properties.

Synthesis and antioxidant activities of 3,5-dialkoxy-4-hydroxycinnamamides

A series of 3,5-dialkoxy-4-hydroxycinnamamides 6 and 7 was synthesized, and their antioxidant activity was assessed using the thiobarbituric acid reactive substance (TBARS) assay. Interestingly, cinnamamides with longer alkoxy groups on the C-3 and C-5 positions display enhanced inhibition, and most of the compounds in the series tested exhibit excellent lipid peroxidation inhibitory activities. Some cinamamides bearing hexyloxy or 2,6-di-tert-butyl-4-methyl phenol groups have submicromolar inhibitory activities.

Antioxidant properties of novel lipophilic ascorbic acid analogues

Structural modifications of ascorbic acid by the introduction of lipophilic moieties has led to derivatives with increased stability against thermal and oxidative degradation. Two series of new lipophilic ascorbic analogues were synthesized to obtain antioxidants devoid of autooxidant properties: 4-benzoyl-3-hydroxyfuran-2(5H)-ones (3a-j) and 4-acetyl-5-aryl-3,4-dihydrofuran-2(5H)ones (5a-f). These compounds were submitted to three different tests: reduction of the stable free radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH); superoxide-anion scavenging assay; and lipid-peroxidation assay. Most compounds interacted with DPPH: at a concentration of 5 x 10(-3) M, the reducing activity of 4-benzoyl derivatives, 3c and 3h, was more than 50%; under the same conditions, the rate of inhibition for 4-acetylbutanolides, 5a and 5f, reached 60.6% and 87.3%, respectively; 93.3% inhibition was observed with ascorbic acid. In the superoxide-anion scavenging assay, at a concentration of 1 mg mL(-1), 4-benzoyl derivatives, 3g and 3i, exhibited a good activity, with IC50 (dose resulting in 50% inhibition) values of 1.45 and 1.35 x 10(-3) M, respectively. 4-Acetylbutanolide, 5f, significantly inhibited the Fe2+/ADP/ascorbate-induced lipid peroxidation of rat liver microsomes with an IC50 of 4.9 x 10(-4) M. This study demonstrates that enol functions in the structure of ascorbic acid analogues are not absolutely essential to bring about antioxidant effects.

Synthesis of benzylideneacetophenones and their inhibition of lipid peroxidation

A series of benzylideneacetophenone derivatives have been synthesized and found to show potent inhibition of the lipid peroxidation (LPO) in rat liver microsomes. All 19 compounds prepared in this series are LPO inhibitors. The highest activity was found in para hydroxy derivatives with two meta tert-butyl substituents.

Relations between the selenium status and the low T3 syndrome after major trauma

OBJECTIVE

Thyroxine (T4) is deiodinated to triiodothyronine (T3) by the hepatic type I iodothyronine deiodinase, a selenoprotein that is sensitive to selenium (Se) deficiency. After severe injury, T4 deiodination is decreased, leading to the low T3 syndrome. Injury increases free radical production, which inactivates the iodothyronine deiodinase. The aims were to study the Se status after major trauma and to investigate its relation to the low T3 syndrome.

DESIGN

Preliminary prospective descriptive study.

SETTING

Intensive care unit at a university teaching hospital.

PATIENTS AND METHODS

11 patients aged 41 +/- 4 years (mean +/- SEM), with severe multiple injuries (Injury Severity Score 29 +/- 2 points). A balance study was performed from day 1 to day 7. Serum and urine samples were collected from the time of admission until day 7, then on days 10, 15, 20, 25 and 30. Non-parametric tests and Pearson's correlation coefficients were used for analysis.

RESULTS

Cumulated Se losses were 0.88 +/- 0.1 mumol/24h. Serum Se was decreased from admission to day 7. T3, free T3, and the T3/T4 ratio were low until day 5, being lowest on day 2; T4 and thyroid stimulating hormone were normal. Serum Se was correlated with T3 (r = 0.55, p = 0.0001), and with free T3 (r = 0.35).

CONCLUSION

Se status is altered after trauma, with decreased Se serum levels upon admission to the ICU but with no major Se losses. Se is probably redistributed to the tissues. The correlation between Se and T3, along with the parallel decrease in T4 deiodination, indicates that reduced deiodination might be related to the transient decrease in serum Se.

Effect of aminoethylpyrroles on carrageenan-induced inflammation and on lipid peroxidation in rats: some structural aspects

Nine 3-(2-aminoethyl)pyrrole derivatives were investigated as anti-inflammatory agents in the carrageenan-induced rat paw oedema model and as antioxidants in the non-enzymatic lipid peroxidation assay. It was found that the derivatives which were substituted with a p-toluenesulphonyl group exhibited considerable anti-inflammatory activity and some also showed antioxidant properties. However, the presence of a p-toluenesulphonyl group did not invariably lead to activity. A structural feature which was essential for both activities was the aminoethyl side chain. Although a relationship between the antiinflammatory and the antioxidant activities was not apparent, the combination of these properties could be useful.