Abstract: An inestimable role in the organic life is played by carbohydrates. Monosaccharides and their derivates constitute the building blocks of various biomolecules like DNA and RNA, ATF, cellulose, chitin and starch which are indispensable for the living organisms. Among all prebiotic carbohydrates the main emphasis is placed on ribose. Indeed, the RNA-world (Gesteland and Atkins, 1993) is one of the most reasoned hypotheses on the prebiotic chemical evolution and the origin of life. In this work we investigated the possibility of formation of different monosaccharides from the simplest substrate—formaldehyde (hereinafter, FA), in the aqueous solution in possible prebiotic conditions. We demonstrated that glycolaldehyde (hereinafter, GA) could be formed in aqueous FA solution under the UV-irradiation (Pestunova et al., 2005). From the other hand higher monosaccharides were shown to be synthesized via condensation of formaldehyde and lower carbohydrates catalyzed by phosphates in neutral aqueous solution at mild temperatures. (Simonov et al., 2007). In order to combine these processes an experimental photo-catalytic flow installation was designed. The starting solution for all experiments contained FA with different concentrations and a catalyst-homogeneous phosphates (Na2HPO4 + KH2PO4), at pH = 8. That is, the sole substrate for the synthesis of monosaccharides was FA known to be an abundant compound of the prebiotic environment. The consecutive photosynthesis of GA and catalytic condensation of FA with lower monosaccharides resulted in the formation of significant amounts of higher monosaccharides. The HPLC analysis of the reaction mixture revealed that erythrulose (tetra-ketose) and 3-pentulose (penta-3-ketose) with maximum yields of 10% and 5%, respectively, were the major products of the process. At the same time the isomerization of 3-pentulose results in the formation of reasonable amounts of ribulose (4% yield). Finally, under the catalytic action of phosphates ribulose is isomerized into ribose and arabinose. The detected concentration of ribose in the reaction mixture was not very high. Nevertheless, it is the first evidence of the possibility of the synthesis of these vitally important monosaccharides from FA in putative prebiotic conditions. In addition to monosaccharides pyruvaldehyde was identified in the reaction mixture. Pyruvic acid was identified in trace amounts. The importance of these compounds for the prebiotic chemistry is discussed in detail in the series of works by Weber (1998). In conclusion we would like to note that the investigated reactions do not require any complex substrates, extreme conditions and proceed readily in neutral aqueous media. Thus, the combination of the photochemical and catalytic process can be considered as a putative route to the monosaccharides and their derivates on prebiotic Earth.

Cite: Simonov A. , Delidovich I. , Pestunova O. , Snytnikov V. , Parmon V.
Putative Prebiotic Photocatalytic Synthesis of Monosaccharides in Aqueous Solution of Formaldehyde
Origins of Life and Evolution of Biospheres. 2009. V.39. N3-4. P.268-269. WOS РИНЦ

Identifiers:

Web of science:	WOS:000267033300092
Elibrary:	19559313

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