Inhibitory effect of diet related sulphydryl compounds on the formation of carcinogenic nitrosamines.

N-Nitroso compounds (NOCs) are known to be strong carcinogens in various animals including primates (Preussman and Stewart, (1984) N-Nitroso Compounds). Human exposure to these compounds can be by ingestion or inhalation of preformed NOCs or by endogenous nitrosation from naturally occurring precursors (Bartsch and Montesano, Carcinogenesis, 5 (1984) 1381-1393; Tannebaum (1979) Naturally Occuring Carcinogens, Mutagens and Modulators of Carcinogenesis; Shephard et al., Food Chem.

Characterization of potentially mutagenic products from the nitrosation of piperine.

Piperine is the main pungent principle of pepper, a spice consumed by people all over the world. It is the trans-trans isomer of 1-piperoylpiperidine and contains the methylene dioxy moiety. It is known to give unidentified mutagenic products on reaction with nitrite.

Urea-acetylene dicarboxylic acid reaction: a likely pathway for prebiotic uracil formation.

A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid (ADCA) may have played a role in chemical evolution.

A possible prebiotic synthesis of thymine: uracil-formaldehyde-formic acid reaction.

When uracil is reacted with formaldehyde and formic acid in dilute aqueous solutions at 100-140 degrees C, 5-hydroxymethyluracil (5-HMU), methylenebiuracil (MBU) and thymine are formed. It has been shown that 5-HMU is an intermediate in the formation of MBU and thymine. In the presence of formic acid, 5-HMU gives MBU, thymine and in some cases uracil.

Methyleneaminoacetonitrile: possible role in chemical evolution-II.

Methyleneaminoacetonitrile (MAAN) when reacted with other amino acids, gives rise to the formation of peptides in addition to the usual hydrolytic products. It acts as a precursor of glycine and also as a dehydration condensing agent. It has been shown that MAAN is easily formed by the reaction of hydrogen cyanide, ammonia and formaldehyde as well as by the reaction of formaldehyde with aminoacetonitrile, in dilute ammoniacal solution.

Transformation of some hydroxy amino acids to other amino acids.

It has been observed that beta-hydroxy-alpha-amino acids are transformed into other amino acids, when heated in dilute solutions with phosphorous acid, phosphoric acid or their ammonium salts. It has been shown that as in the case of previously reported glycine-aldehyde reactions, glycine also reacts with acetone to give beta-hydroxyvaline under prebiologically feasible conditions. It is suggested, therefore, that the formation of beta-hydroxy-alpha-amino acids and their transformation to other amino acids may have been a pathway for the synthesis of amino acids under primitive earth conditions.