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

Abstract

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.