Improved electrochemical epoxidation of cholesterol and avarol dimethyl ether

Electrochemical epoxidation of cholesterol and avarol dimethyl ether with bromide as heteromediator was performed, and its mechanism discussed. The influence of the solvent, the mediator concentration, and different electrolytic techniques on yield of the products was examined. Under optimal conditions, the yield of the cholesterol epoxides (5α,6α and 5β, 6β) was 88%, and of the corresponding epoxides of the avarol dimethyl ether 72%

Improved electrochemical epoxidation of cholesterol and avarol dimethyl ether

Electrochemical epoxidation of cholesterol and avarol dimethyl ether with bromide as heteromediator was performed, and its mechanism discussed. The influence of the solvent, the mediator concentration, and different electrolytic techniques on yield of the products was examined. Under optimal conditions, the yield of the cholesterol epoxides (5α,6α and 5β, 6β) was 88%, and of the corresponding epoxides of the avarol dimethyl ether 72%

Electrochemical reactivity of biologically active quinone/hydroquinone sesquiterpenoids on glassy carbon electrodes

The redox reactivity of avarone and avarol, a quinone/hydroquinone couple isolated from the marine sponge Dysidea avara, was investigated by cyclic voltammetry, using a glassy carbon electrode. Both oxidation of avarol and reduction of avarone in aqueous ethanol (1:1 V/V) take place by a 2 e- process at a wide range of pH values; in acetonitrile, however, the reduction of avarone occurs as a stepwise electron transfer process. The mechanisms, as well as the scope and limitations of the method are discussed with reference to the biological activity of the two sesquiterpenoids. © 1987

Isolation and partial characterization of a lectin from the marine sponge Crambe crambe

A lectin was isolated from the marine sponge Crambe crambe. The lectin is a monomeric glycoprotein with relative molecular mass of 14000. It agglutinates sheep and human red blood cells. The agglutination was found to be inhibited weakly only by L-fucose. The lectin has mitogenic properties, stimulating T-lymphocytes

Biological activities of avarol derivatives, 1. Amino derivatives

Nine amino derivatives, compounds 3-11. of avarone were synthesized. Their antibacterial and cytotoxic activities are evaluated, and the results of a prescreen for antitumor effects are reported

Structure and reactivity of steroidal quinones

The preparation of substituted steroidal A-ring 1,4-quinones by nucleophilic addition results in pronounced regioselectivity at C(2), as confirmed by the X-ray analysis of 2-methoxy-2,5(10)-diene-1,4,17-trione. Conformational analysis (PM3, AM1, MNDO) of the suggested protonated intermediates and the difference in the relative energies of the transition states are considered. The results of cytotoxicity tests of selected quinones are also presented

Structure and reactivity of steroidal quinones

The preparation of substituted steroidal A-ring 1,4-quinones by nucleophilic addition results in pronounced regioselectivity at C(2), as confirmed by the X-ray analysis of 2-methoxy-2,5(10)-diene-1,4,17-trione. Conformational analysis (PM3, AM1, MNDO) of the suggested protonated intermediates and the difference in the relative energies of the transition states are considered. The results of cytotoxicity tests of selected quinones are also presented

Evaluation of the activity of the sponge metabolites avarol and avarone and their synthetic derivatives against fouling micro- and macroorganisms

The sesquiterpene hydroquinone avarol (1) was isolated from the marine sponge Dysidea avara, whereas the corresponding quinone, avarone (2), was obtained by oxidation of avarol, and the significantly more lipophilic compounds [3′-(p-chlorophenyl) avarone (3), 3′,4′-ethylenedithioavarone (4), 4′-isopropylthioavarone (5), 4′-tert-butylthioavarone (6), 4′-propylthioavarone (7), 4′-octylthioavarone (8)] were obtained by nucleophilic addition of thiols or p-chloroaniline to avarone. All these compounds were tested, at concentrations ranging from 0.5 to 50 μg/mL, for their effect on the settlement of the cyprid stage of Balanus amphitrite, for toxicity to both nauplii and cyprids and for their growth inhibitory activity on marine bacteria (Cobetia marina, Marinobacterium stanieri, Vibrio fischeri and Pseudoalteromonas haloplanktis) and marine fungi (Halosphaeriopsis mediosetigera, Asteromyces cruciatus, Lulworthia uniseptata and Monodictys pelagica). © 2007 by MDPI