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A study to describe the spectroscopic properties of a novel paramagnetic [2] rotaxane and its synthesis is conducted. The results prove that the proposed procedure for the construction of mechanical interlocked organic free radicals represent a promising route for the preparation of more complex paramagnetic supermolecular architectures whose properties could be exploited in many technDological applications.

The phenolic co-antioxidants in homogeneous hydrocarbon solution, is used for the study of the regeneration of alpha tocopherol (vitamin E). A model based on the knowledge of kinetic and thermochemical data concerning the various reactants, predicts the behavior of some relevant phenols.

Abstract: Irradiation of N-triphenylmethyloxy- or N-diphenylmethyloxy phthalimide is reported to result in the formation of phthalimide N-oxyl radical (PINO), which is able to initiate and propagate oxidative radical chain reactions of hydrocarbons. [Copyright &y& Elsevier]

A systematic investigation is reported on the regeneration of α-tocopherol (α-TOH) in homogeneous solution by coantioxidants in order to better understand the mechanism and the factors responsible for the effectiveness of this process. The current availability of thermochemical data concerning the reactants involved in the regeneration reactions, as well as a large number of the kinetic constants for the various reactions involved, allowed us to rationalize the experimental observations collected so far. Three limiting cases have been considered. The first case is that of a coantioxidant irreversibly regenerating α-TOH, where the effectiveness of the recycling process depends on the magnitude of the rate constant k[sub r]. The second case is that of a coantioxidant reversibly recycling α-TOH, where regeneration can only be observed if the bond dissociation enthalpy value of the coantioxidant is lower or at least close to that of the O-H bond of α-tocopherol. The third case is that of a catechol derivative (chosen as a model compound for polyphenolic antioxidants), where recycling of α-TOH is feasible even though the BDE value is significantly higher than that of vitamin E. In this case, the driving force for the recycling process is the removal of the semiquinone radical from the catechol derivative by the α-tocopheroxyl radical, which makes the regeneration of α-TOH practically irreversible. [ABSTRACT FROM AUTHOR]

Axially chiral, 3,5-dihydro-4H-dinaphtho[2,1-c:1',2'-e]azepine (dinaphthazepine) and 1,1'-binaphthyl-2,2'-disulfonimide (dinaphthosulfonimide) moieties were rigidly connected via N-p-phenylene linkers to photochemically (E)/(Z)-isomerisable 1,2-diethynylethene scaffolds. The chemical stability of the resulting systems was found to be critically related to the other substituents on the central π-conjugated scaffold. High helical twisting power (HTP), up to 315 μm(-1), for the induction of a cholesteric liquid-crystalline phase through doping of a nematic phase was measured, resulting from the introduction of the chiral, mesogenic 1,1'-binaphthyl motifs. Single crystal X-ray analysis revealed that the phenylene spacer is in π-conjugation with the N-atom of the dinaphthazepine but not with the N-atom of the dinaphthosulfonimide moiety. This difference in orientation results in visible-transparency in the electronic absorption spectrum and higher (E)/(Z)-photoisomerisation quantum yields of the dinaphthosulfonimide-derived chiral dopants, as compared to the dinaphthazepine systems, which feature intramolecular charge-transfer absorption in the visible region.

Axially chiral, N-arylated 3,5-dihydro-4H-dinaphtho[2,1-c:1',2'-e]azepines have been prepared by short synthetic protocols from enantiopure 1,1'-bi(2,2'-naphthol) (BINOL) and anilines. Alkynes substituted with two N-phenyldinaphthazepine donors readily undergo a formal [2+2] cycloaddition, followed by retro-electrocyclization, with tetracyanoethene (TCNE) to yield donor-substituted 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) featuring intense intramolecular charge-transfer (CT) interactions. A dicyanovinyl derivative substituted with one N-phenyldinaphthazepine donor was obtained by a "one-pot" oxidation/Knoevenagel condensation from the corresponding propargylic alcohol. Comparative electrochemical, X-ray crystallographic, and UV/Vis studies show that the electron-donor qualities of N-phenyldinaphthazepine are similar to those of N,N-dimethylanilino residues. The circular dichroism (CD) spectrum of a push-pull chromophore incorporating the chiral donor moiety features Cotton effects of exceptional intensity. With their elongated shape and the rigidity of the chiral N-aryldinaphthazepine donors, these chromophores are effective inducers of twist distortion in nematic liquid crystals (LCs). Thus, a series of the dinaphthazepine derivatives was used as dopants in the nematic LC E7 (Merck) and high helical twisting powers (beta) of the order of hundreds of microm(-1) were measured. Theoretical calculations were employed to elucidate the relation between the structure of the dopants and their helical twisting power. For the derivatives with two dinaphthazepine moieties, a strong dependence of the beta-values on the structure and conformation of the linker between them was found.

There is high current interest in the chemopreventive potential of Brassica vegetables (cruciferae), particularly due to their content in glucosinolates (GL), which upon myrosinase hydrolysis release the corresponding isythiocyanates (ITC). Some ITCs, such as sulforaphane (SFN) from broccoli ( Brassica oleacea italica), have been found to possess anticancer activity through induction of apoptosis in selected cell lines, as well as indirect antioxidant activity through induction of phase II detoxifying enzymes. Japanese daikon ( Raphanus sativus L.) is possibly the vegetable with the highest per capita consumption within the Brassicaceae family. Thanks to a recently improved gram scale production process, it was possible to prepare sufficient amounts of the GL glucoraphasatin (GRH) as well as the corresponding ITC 4-methylthio-3-butenyl isothiocyanate (GRH-ITC) from its sprouts. This paper reports a study on the cytotoxic and apoptotic activities of GRH-ITC compared with the oxidized counterpart 4-methylsulfinyl-3-butenyl isothiocyanate (GRE-ITC) on three human colon carcinoma cell lines (LoVo, HCT-116, and HT-29) together with a detailed kinetic investigation of the direct antioxidant/radical scavenging ability of GRH and GRH-ITC. Both GRH-ITC and GRE-ITC reduced cell proliferation in a dose-dependent manner and induced apoptosis in the three cancer cell lines. The compounds significantly ( p < 0.05) increased Bax and decreased Bcl2 protein expression, as well as producing caspase-9 and PARP-1 cleavage after 3 days of exposure in the three cancer cell lines. GRH-ITC treatment was shown to have no toxicity with regard to normal human lymphocytes (-15 +/- 5%) in comparison with SFN (complete growth inhibition). GRH and GRH-ITC were able to quench the 2,2-diphenyl-1-picrylhydrazyl radical, with second-order rate constants of 14.0 +/- 2.8 and 43.1 +/- 9.5 M(-1) s(-1), respectively (at 298 K in methanol), whereas the corresponding value measured here for the reference antioxidant alpha-tocopherol was 425 +/- 40 M (-1) s (-1). GRH reacted with H2O2 and tert-butyl hydroperoxide in water (pH 7.4) at 37 degrees C, with rate constants of 1.9 +/- 0.3 x 10(-2) and 9.5 +/- 0.3 x 10(-4) M(-1) s (-1) (paralleling recently developed synthetic antioxidants) being quantitatively (>97%) converted to GRE. It is demonstrated that GRH-ITC has interesting antioxidant/radical scavenging properties, associated with a selective cytotoxic/apoptotic activity toward three human colon carcinoma cell lines, and very limited toxicity on normal human T-lymphocytes.

Rocket (Eruca sativa Mill. or Eruca vesicaria L.) is widely distributed all over the world and is usually consumed fresh (leafs or sprouts) for its typical spicy taste. Nevertheless, it is mentioned in traditional pharmacopoeia and ancient literature for several therapeutic properties, and it does contain a number of health promoting agents including carotenoids, vitamin C, fibers, flavonoids, and glucosinolates (GLs). The latter phytochemicals have recently gained attention as being the precursors of isothiocyanates (ITCs), which are released by myrosinase hydrolysis during cutting, chewing, or processing of the vegetable. ITCs are recognized as potent inducers of phase II enzymes (e.g., glutathione transferases, NAD(P)H:quinone reductase, epoxide hydrolase, etc.), which are important in the detoxification of electrophiles and protection against oxidative stress. The major GL found in rocket seeds is glucoerucin, GER (108 +/- 5 micromol g(-)(1) d.w.) that represents 95% of total GLs. The content is largely conserved in sprouts (79% of total GLs), and GER is still present to some extent in adult leaves. Unlike other GLs (e.g., glucoraphanin, the bio-precursor of sulforaphane), GER possesses good direct as well as indirect antioxidant activity. GER (and its metabolite erucin, ERN) effectively decomposes hydrogen peroxide and alkyl hydroperoxides with second-order rate constants of k(2) = 6.9 +/- 0.1 x 10(-)(2) M(-)(1) s(-)(1) and 4.5 +/- 0.2 x 10(-)(3) M(-)(1) s(-) , respectively, in water at 37 degrees C, thereby acting as a peroxide-scavenging preventive antioxidant. Interestingly, upon removal of H(2)O(2) or hydroperoxides, ERN is converted into sulforaphane, the most effective inducer of phase II enzymes among ITCs. On the other hand, ERN (and conceivably GER), like other ITCs, does not possess any chain-breaking antioxidant activity, being unable to protect styrene from its thermally (37 degrees C) initiated autoxidation in the presence of AMVN. The mechanism and relevance of the antioxidant activity of GER and ERN are discussed.