The kinetics of the reduction of the lipophilic quinone avarone by n-alkyl-1,4-dihydronicotinamides of various lipophilicities

Several NADH model compounds, N-alkyl-1,4-dihydronicotinamides, some of them possessing amphiphilic properties, have been synthesized, and the kinetics of their reaction with a biologically active liphophilic quinone, avarone, has been studied in a protic solvent both in the presence and absence of cationic, anionic or non-ionic surfactants. In the absence of micellar agents, the medium- and long-chain N-dodecyl (3) and N-heptadecyl (4) derivatives show a significant increase in the reaction rates compared to other model compounds, due to the stabilization of the semiquinone intermediate. Anionic surfactants retard the reaction, non-ionic surfactants slightly accelerate the reaction with the short-chain derivatives, and retard the reaction with the medium- and long-chain derivatives, and the cationic surfactants increase the reaction rate with all derivatives except the long-chain 4. The results support the e-p-e mechanism of the reduction of lipophilic quinones by NADH models in protic medium

Reactivity and biological activity of the marine sesquiterpene hydroquinone avarol and related compounds from sponges of the order Dictyoceratida

A review of results of bioactivity and reactivity examinations of marine sesquiterpene (hydro)quinones is presented. The article is focused mostly on friedo-rearranged drimane structural types, isolated from sponges of the order Dictyoceratida. Examples of structural correlations are outlined. Available results on the mechanism of redox processes and examinations of chemo- and regioselectivity in addition reactions are presented and, where possible, analyzed in relation to established bioactivities. Most of the bioactivity examinations are concerned with antitumor activities and the mechanism thereof, such as DNA damage, arylation of nucleophiles, tubulin assembly inhibition, protein kinase inhibition, inhibition of the arachidonic cascade, etc. Perspectives on marine drug development are discussed with respect to biotechnological methods and synthesis. Examples of the recognition of validated core structures and synthesis of structurally simplified compounds retaining modes of activity are analyzed

The Avarol-Avarone Redox Behaviour in Acetonitrile

The oxidation of avarol and the reduction of avarone were studied at a Pt electrode in acetonitrile-tetraethyl-ammonium perchlorate media. The oxidation of avarol in acetonitrile takes place by formation of a two electron oxidation product, presumably the »protonated avarone«. The reduction of avarone takes place in two steps by formation of the stable radical anion which is reduced to the dianion at amore negative potential

Takmičenja iz hemije u periodu od 1984. do 2004. godine - II deo

Development of chemistry competitions for the higher grades of elementary, and for the secondary scholars in former Yugoslavia, and particularly Serbia, within the action 'Science to the Young' in the period 1964-1984 (part I) were described in the Chemical Review 45/3 (2004). In the present text (part II) the development of chemistry competitions for the elementary and secondary scholars in the period 1984-2004 was presented.U Hemijskom pregledu br. 3 (2004) prikazan je razvoj takmičenja iz hemije u okviru Pokreta 'Nauku mladima' u periodu od 1964. do 1984. godine (deo I). U ovom članku prikazan je razvoj i propozicije takmičenja iz hemije u periodu od 1984. do 2004. godine (II deo)

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%

Synthesis and investigation of biological activity of arylthio and aralkylthio derivatives of 2-tert-butyl-1.4-benzoquinone

Sintetisana su dva ariltio i dva aralkiltio derivata 2-terc-butil-1,4-benzohinona reakcijom Michael-ove adicije tiola na hinonsko jezgro u etanolu. Dobijenim derivatima je ispitana antimikrobna i antioksidativna aktivnost, kao i toksinost na raie Artemia salina. Najjau antimikrobnu aktivnost je pokazao derivat 4, najveu antioksidativnu aktivnost je imao derivat 2 (IC50=0,0526 mM), dok je toksinost prema raiima ispoljio samo derivat 4 (LC50=0,032 mM).Two arylthio and aralkylthio derivatives of 2-tert-butyl-1.4-benzoquinone were synthesized by Michael addition of thiols on quionone moiety in ethanol. For all compounds antimicrobial and antioxidant activity was investigated, as well as toxicity towards nauplii of Artemia salina. Derivative 4 showed the strongest antimicrobial activity, derivative 2 showed the most intense antioxidant activity (IC50=0.0526 mM), while only derivative 4 showed toxicity against nauplii of A. salina (LC50=0.032 mM)

Interakcije antitumorskog seskviterpenskog hidrohinona avarola sa DNA in vitro

Changes in electrophoresis pattern after interaction of supercoiled plasmid pBR322 DNA with avarol was studied at a micromolar concentration of reactants under mild reaction conditions. Interactions of avarol with linear high-molecular CT-DNA at millimolar concentrations were analyzed by electrophoresis and UV spectrophotometry. It was observed that avarol is capable of quenching ethidium bromide fluorescence in DNA bands. An increase in the absorbance of DNA was detected. The results indicate the binding of avarol to DNA and/or modification of nucleotide bases.Proučavane su promene elektroforetskog ponašanja DNA posle interakcija superhelikoidalnog plazmida pBR322 s avarolom pri mikromolarnim koncentracijama reaktanata pod blagim reakcionim uslovima. Interakcije avarola sa linearnom visokomolekulskom CT-DNA pri milimolarnim koncentracijama analizirane su elektroforezom i UV spektrofotometrijom. Uočeno je da je avarol u stanju da gasi fluorescenciju etidijum-bromida u trakama koje potiču od DNA. Detektovan je porast apsorbancije DNA. Rezultati ukazuju na vezivanje avarona za DNA i/ili modifikaciju nukleotidnih baza

Kinetika redukcije lipofilnog hinona avarona n-alkyl-1,4-di -hidronikotinamidima različite lipofilnosti

Several NADH model compounds, N-alkyl-1,4-dihydronicotinamides, some of them possessing amphiphilic properties, have been synthesized, and the kinetics of their reaction with a biologically active liphophilic quinone, avarone, has been studied in a protic solvent both in the presence and absence of cationic, anionic or non-ionic surfactants. In the absence of micellar agents, the medium-and long-chain N-dodecyl (3) and N-heptadecyl (4) derivatives show a significant increase in the reaction rates compared to other model compounds, due to the stabilization of the semiquinone intermediate. Anionic surfactants retard the reaction, non-ionic surfactants slightly accelerate the reaction with the short-chain derivatives, and retard the reaction with the medium-and long-chain derivatives, and the cationic surfactants increase the reaction rate with all derivatives except the long-chain 4. The results support the e-p-e mechanism of the reduction of lipophilic quinones by NADH models in protic medium.Sintetisano je nekoliko N-alkil-1,4-dihidronikotinamida, model-jedinjenja NADH, od kojih neki imaju amfifilne osobine, i proučavana je kinetika njihove reakcije sa biološkim aktivnim, lipofilnim hinonom avaronom u protinom rastvaraču u prisustvu katjonskih, anjonskih ili nejonskih površinski aktivnih supstanci i bez njh.Bez dodatih micelarnih agenasa, N-dodecil-derivat 3 (derivat srednje dužine niza) i dugolančani N-heptadecil-derivat 4 pokazuju značajno povećanje brzine reakcije u poređenju sa drugim model-jedinjenjima, usled stabilizacije semihinonskih intermedijera. Anjonski površinski aktivni agensi usporavaju reakciju, nejonski agensi dovode do slabog ubrzanja sa derivatima kratkog alkilniza, a usporavaju reak ciju sa derivatima srednjeg i dugog niza, dok katjonski agensi ubrzavaju reakciju sa svim derivatima, sem sa dugolančanim 4. Rezultati ukazuju na mehanizam e-p-e redukcije lipofilnih hinona modelima NADH u protičnom medijumu

Sastav sterolne smese algi jadranskog mora Ulva lactuca, Codium dichotomum, Cystoseira adriatica i Fucus virsoides

The sterol composition of two green algae and two brown algae from the South Adriatic was determined. In the green alga Ulva lactuca, the principal sterols, were cholesterol and isofucosterol. In the brown alga Cystoseira adriatica, the main sterols were cholesterol and stigmast-5-en-3 beta-ol, while the characteristic sterol of the brown algae, fucosterol, was found only in low concentration. The sterol fractions of the green alga Codium dichotomum and the brown alga Fucus virsoides contained practically only one sterol each, comprising more than 90 % of the total sterols (clerosterol in the former and fucoserol in the latter).Određen je sastav sterolne smese dve zelene i dve mrke alge iz južnog Jadrana. U zelenoj algi Ulva lactuca glavni steroli su holesterol i izofukosterol. U mrkoj algi Cystoseira adriatica glavni steroli su holesterol i stigmast-5-en-3ß-ol, dok je fukosterol, sterol karakterističan za mrke alge, nađen samo u maloj količini. Sterolne smese zelene alge Codium dichotomum i mrke alge Fucus virsoides sastoje se praktično samo od po jednog sterola, klerosterola u prvoj i fukosterola u drugoj, koji sačinjavaju više od 90 % sterolnih frakcija