Absence Of Carbonyl Group Research Articles

Genoprotective Effect of Some Flavonoids against Genotoxic Damage Induced by X-rays In Vivo: Relationship between Structure and Activity.

Flavonoids constitute a group of polyphenolic compounds characterized by a common gamma-benzo- pyrone structure considered in numerous biological systems to possess antioxidant capacity. Among the different applications of flavonoids, its genoprotective capacity against damage induced by ionizing radiation stands out, which has been related to antioxidant activity and its chemical structure. In this study, we determined the frequency of appearance of micronucleus in vivo by means of the micronucleus assay. This was conducted in mice treated with different flavonoids before and after exposure to 470 mGy X-rays; thereafter, their bone marrow polychromatophilic erythrocytes were evaluated to establish the structural factors enhancing the observed genoprotective effect. Our results in vivo show that the presence of a monomeric flavan-3-ol type structure, with absence of carbonyl group in position C4 of ring C, absence of conjugation between the carbons bearing the C2 = C3 double bond and the said ring, presence of a catechol group in ring B and characteristic hydroxylation in positions 5 and 7 of ring A are the structural characteristics that determine the highest degree of genoprotection. Additionally, a certain degree of polymerization of this flavonoid monomer, but maintaining significant levels of monomers and dimers, contributes to increasing the degree of genoprotection in the animals studied at both times of their administration (before and after exposure to X-rays).

Interaction of chlorogenic acid with model lipid membranes and its influence on antiradical activity

Chlorogenic acid (CGA) is a strong phenolic antioxidant with antibacterial properties composed by a caffeoyl ester of quinic acid. Although a number of benefits has been reported and related to interactions with the red blood cell membranes, details on its membrane action and how composition and membrane state may affect it, is not yet well defined.In this work, the interaction of CGA with lipid monolayers and bilayers composed by 1,2-dimiristoyl-sn-glycero-3-phosphocholine (DMPC); 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (14:0 diether PC); 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-di-O-hexadecyl-sn-glycero-3-phosphocholine (16:0 diether PC) were studied at different surface pressures (π). The kinetics of interaction was found to be more rapid in DMPC than in the absence of carbonyl groups. Measurements by FTIR-ATR at different water activities confirm specific interactions of CGA with carbonyl and phosphate groups affecting water level along hydrocarbon region.The antioxidant activity of CGA in the presence of DMPC unilamellar vesicles, evidenced by the absorbance reduction of the radical cation ABTS•+, is significantly different with respect to aqueous solution. The influence of CGA on antiradical activity (ARA) with lipid membranes depending on the hydration state of the lipid interface is discussed.

Yellowing and brightness reversion of celluloses: CO or COOH, who is the culprit?

Literature is strongly contradictory about the molecular reasons for yellowing and brightness reversion of pure (lignin- and hemicellulose-free) celluloses, such as in highly bleached pulps, bacterial cellulose, or cotton linters. While oxidized groups—carbonyls (CO) and carboxyls (COOH)—have been recognized as the initiators of yellowing, they are generally always found together; thus, their effects are permanently superimposed in real-world cellulose. For this reason, their individual contributions could not be reliably determined. To tackle this conundrum, we have used a two-stage study: the employment of glucopyranose-derived model compounds and the use of special cellulosic pulps. Both substrates had either only carbonyl functions, only carboxyl functions, or defined ratios of both functionalities present at the same time. The model compounds alone already provided strong indications of the CO-related and COOH-related effects, and further confirmation was obtained by the pulp study. Here, in regard to the polymer case, the carbonyl groups are the minimum functional unit in cellulose responsible for chromophore generation (termed as the “CO effect”). The carbonyl groups are the precursors for the chromophores that are formed later upon yellowing/aging. Chromophore formation increases strictly linearly with the carbonyl content at a constant given carboxyl content. Carboxyl groups alone (i.e., in the absence of carbonyl groups) are fully innocent regarding the color generation. However, they have a strong promotive action when carbonyl groups are present (termed as the “COOH effect”), which includes acidic catalysis and an additional activation by electronic effects. The general roles of CO and COOH are the same for all aging types (e.g., thermal, acidic, or alkaline), while the respective rates of chromophore generation evidently depend on various parameters such as the temperature, medium, and pH value.Graphical abstract

Deacidification of organic liquid products by fractional distillation in laboratory and pilot scales

This work aims to investigate the de-acidification of organic liquid products, obtained by catalytic cracking of palm oil (Elaeis guineensis Jacq) using Na2CO3 as catalyst, by fractional distillation. The distillation of OLP carried out in laboratory, using columns of different heights with and without reflux, and in pilot scale. OLP and distillation fractions physicochemical characterized for density, kinematic viscosity, acid value, saponification value, refractive index, ester index, free fatty acids, flash point, and copper strip corrosion. The OLP analyzed by GC–MS and FT-IR, and light diesel-like fractions by FT-IR, NMR, and GC–MS. The experiments carried out in laboratory scale with and without reflux showed biofuels (distillates) yields between 62.15 and 76.41% and 71.65 and 89.44% (wt.), respectively, while that in pilot scale was 32.68% (wt.). For the experiments in laboratory scale, the yields of distillates decrease exponentially with column height, with and without reflux, while those of bottoms products increase exponentially. In addition, the yields of distillates and gas increase with increasing Na2CO3 content, while that of bottom products decrease. The yield of light diesel-like fractions, with and without reflux ranged between 48.82 and 63.18, and 20.23 and 21.43% (wt.), respectively. The column height had no significant effect on the density of distillation fractions, with and without reflux. The densities of gasoline, kerosene, and light diesel with reflux, superpose exactly those of kerosene, light diesel, and heavy diesel without reflux. The kinematic viscosity of distillation fractions decreases with increasing column height for the experiments with and without reflux, while the acid values decrease. For the distillation experiments in pilot scale, the acid values of gasoline, kerosene, and light diesel-like fractions were 0.33, 0.42, and 0.34mg KOH/g. FT-IR of distillation fractions in pilot scale and NMR of light diesel-like fraction in laboratory scale, column height of 50cm, under reflux identified the presence of aliphatic hydrocarbons and the absence of carbonyl groups. The GC–MS analysis identified in OLP composition 92.84% (area.) hydrocarbons and 7.16% (area.) oxygenates. The light diesel-like fraction contains 100% hydrocarbons with an acid value of 0.34mg KOH/g, density of 0.7862g/cm3, and kinematic viscosity of 1.52mm2s−1, proving the feasibility of OLP de-acidification by fractional distillation.