Heme iron from meat and risk of colorectal cancer: a meta-analysis and a review of the mechanisms involved

Red meat and processed meat intake is associated with a risk of colorectal cancer, a major cause of death in affluent countries. Epidemiological and experimental evidence supports the hypothesis that heme iron present in meat promotes colorectal cancer. This meta-analysis of prospective cohort studies of colon cancer reporting heme intake included 566,607 individuals and 4,734 cases of colon cancer. The summary relative risk of colon cancer was 1.18 [95%C.I.: 1.06-1.32] for subjects in the highest category of heme iron intake compared with those in the lowest category. Epidemiological data thus show a suggestive association between dietary heme and risk of colon cancer. The analysis of experimental studies in rats with chemically-induced colon cancer showed that dietary hemoglobin and red meat consistently promote aberrant crypt foci, a putative pre-cancer lesion. The mechanism is not known, but heme iron has a catalytic effect on (i) the endogenous formation of carcinogenic N-nitroso compounds and (ii) the formation of cytotoxic and genotoxic aldehydes by lipoperoxidation. A review of evidence supporting these hypotheses suggests that both pathways are involved in heme iron toxicit

La pollution par les composés fluorés et ses effets sur les arbres fruitiers du Valais

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Noniterative approach to the total asymmetric synthesis of 15-carbon polyketides and analogs with high stereodiversity

Starting from inexpensive furan and furfuryl alcohol, a noniterative approach to the synthesis of pentadeca-1,3,5,7,9,11,13,15-octols and their derivatives has been developed. The method relies upon the double [4+3]-cycloaddition of 1,1,3-trichloro-2-oxylallyl cation with 2,2'-methylenedifuran and conversion of the adducts into meso and (±)-threo-1,1'-methylenebis (cis- and trans-4,6-dihydroxycyclohept-1-ene) derivatives. The latter undergo oxidative cleavage of their alkene moieties, generating 5-hydroxy-7-oxoaldehydes that are reduced diastereoselectively into either syn or anti-5,7-diols. Asymmetry is realized using either chiral desymmetrization with Sharpless asymmetric dihydroxylation or by kinetic resolution of polyols using lipase-catalyzed acetylations. All of the possible stereomeric pentadeca-1,3,5,7,9,11,13,15-octols and derivatives can be obtained with high stereoselectivity applying simple operations, thus demonstrating the high stereodiversity of this new, noniterative approach to the asymmetric synthesis of long-chain polyketide

A novel approach to the synthesis of N-substituted 1-C-aminomethyl glycofuranosides

Reductive amination of formyl C-glycofuranosides, easily available from hexose-derived equatorial-2-OH-glycopyranosides by DAST-promoted ring contraction, afforded N-substituted 1-C-aminomethyl glycofuranosides in most cases in high yield.European Commission, Directorate General for Science and Development FP6-508430Junta de Andalucía FQM14

Accuracy Evaluation of an Optical Lattice Clock with Bosonic Atoms

We report the first accuracy evaluation of an optical lattice clock based on the 1S0 - 3P0 transition of an alkaline earth boson, namely 88Sr atoms. This transition has been enabled using a static coupling magnetic field. The clock frequency is determined to be 429 228 066 418 009(32) Hz. The isotopic shift between 87Sr and 88Sr is 62 188 135 Hz with fractional uncertainty 5.10^{-7}. We discuss the conditions necessary to reach a clock accuracy of 10^{-17} or less using this scheme.Comment: 3 pages, 4 figures, uses ol.sty fil

Research Topics

Quantum-mechanical calculations have been applied to predict thermodynamic and reactivity properties of unknown organic molecules, being stable compounds or reactive intermediates. Through synthesis some of the theoretical systems become real compounds that can be synthons (synthetic intermediates) or chirons (optically pure synthetic intermediates) useful in the preparation of natural products and analogues of biological interest (anti-cancer, anti-virus, antibiotic, anti-diabetes agents). Our interests concentrate on remote substituent effects as we want to play with them together with polyfunctional systems and reactions that constitute new synthetic approaches. These have to be convergent, highly stereoselective, and versatile (applicable to a large variety of derivatives: molecular diversity). We often rely on tandem reactions or/and reaction cascades. Sometimes the new compounds and their new reactions send us back to the theory and to mechanistic studies