Formation Of Blue Pigment Research Articles

Formation mechanism of blue pigment in boiled lotus rhizome discs: Insight into the chelation of polyphenols and iron

Boiled lotus rhizome discs (BLRDs), as common processed products of lotus rhizome, have gained increasing attention from consumers and food manufacturers. However, the blue pigment formed during boiling affects its appearance and reduces the appetite of BLRDs. In this study, the effects of polyphenols and iron contents on blue pigment formation in BLRDs in different regions and months were investigated. Results revealed that blue variation was more serious in March and April of the second year in Wuhan, and polyphenols and iron contents in these two months were significantly higher than those in other months. Then, UPLC and UV–Vis analysis showed that polyphenols causing the formation of blue pigment in BLRDs were L-dopa, gallocatechin, catechin, epigallocatechin, chlorogenic acid and epicatechin, among which L-dopa (52.450 mg/100 g in fresh lotus rhizome (FLR)) and gallocatechin (36.210 mg/100 g in FLR) possessed the greatest effect. Moreover, the ESI-Q-TOF-MS analysis of L-dopa-iron chelate and gallocatechin-iron chelate suggested that the blue pigment of BLRDs was mainly in the form of bis-complexes under boiling conditions. The study on formation mechanism of blue pigment in BLRDs can provide a reference for lotus rhizome processing.

Synthesis and characterization of nano-ceramic pigment Co0.5Zn0.5Al2O4 via polyacrylamide gel method

Purpose The purpose of this paper is to synthesize and characterize nano-ceramic blue pigment Co0.5Zn0.5Al2O4 via polyacrylamide gel method. Generally, the high cost and the environmental toxicity of cobalt aluminate pigments lead them to become less common and cause problems in production process. To significantly reduce this problem, it is required to reduce the cobalt in the pigment and replace the cobalt with some amounts of zinc in the structure. Design/methodology/approach In this paper, calcination temperature and its effects on phase specification and color properties of final product were investigated. The powders were studied by using XRD, FESEM, TG/DTA, FTIR, UV-Vis and colorimetric in CIELab space, in which the calcination temperatures were set to 600°C, 800°C and 1,000 °C, and the inert atmosphere was air. Findings According to the XRD patterns, single-phase spinel structure with a good crystallinity was formed even in the low temperature. The infrared spectra displayed vibrations at about 500, 560 and 680 cm−1, which were ascribed to the spinel structure. FESEM images showed nanoscale particles with an average size of 32 nm. Regarding the Co2+ spin transitions in tetrahedral sites, the UV-Vis spectra presented three bands at 552, 598 and 628 nm. Practical implications The colorimetric data indicated the formation of blue pigments corresponding to negative values of b*. The color of pigments was affected by calcination temperature. Originality/value The characterization analysis shows that a blue pigment has been obtained in this research. Different degrees of blue color were obtained at different calcination temperatures.

Oxygen Consumption by Red Wines. Part II: Differential Effects on Color and Chemical Composition Caused by Oxygen Taken in Different Sulfur Dioxide-Related Oxidation Contexts.

Chemical changes caused by oxidation of red wines during 5 consecutive air-saturation cycles have been assessed. In order to investigate the existing relationship between the effects caused by O2 and the levels and consumption rates of wine SO2, the total oxygen consumed by the wines (16-25 mg/L) was subdivided into different nonmutually exclusive categories. The ones found most influential on chemical changes were the O2 consumed in the first saturation without equivalent SO2 consumption (O2preSO2) and the O2 consumed when levels of free SO2 were below 5 mg/L (radical forming O2). Chromatic changes were strongly related to both O2 categories, even though anthocyanidin degradation was not related to any O2 category. Radical forming O2 prevented both formation of red pigments and reduction of epigallocatechin and other proanthocyanidins, induced accumulation of phenolic acids, and caused losses of β-damascenone and whiskylactone without evidence of acetaldehyde formation. O2preSO2 seemed to play a key role in the formation of blue pigments and in the decrease of Folin index and of many important aroma compounds.

Influence of the composition of unripe genipap (Genipa americana L.) fruit on the formation of blue pigment.

The physical and chemical characteristics of unripe genipap fruits and the proximate and amino acid compositions of the endocarp and mesocarp of the unripe fruits were determined, placing special emphasis on the possible role of the protein-amino acid fraction on the formation of the typical blue pigment of the matrix. The two parts of the fruit analyzed have low energy (49.88kcal/100g for mesocarp and 43.48kcal/100g for endocarp) and high fiber content (7.88% for mesocarp and 16.76% for endocarp). The endocarp showed protein content (3.19%) five times higher than the mesocarp (0.62%), which may explain in part the greater amounts of blue pigment formed in the endocarp when compared to the mesocarp. Furthermore, the pH found in mesocarp (4.49) and endocarp (5.21) is within the optimum range for the formation of the blue pigment. A significant color change (ΔE (*) = 26.45) was observed in endocarp during its exposure to the air for 2h. Free aspartic and glutamic acids and cystine were the predominant amino acids in the mesocarp, while glutamic and aspartic acids and leucine were predominant in the endocarp. According to the results, the formation of blue pigment does not cause any change in the amino acid composition.

Influence of the stage of ripeness on the composition of iridoids and phenolic compounds in genipap (Genipa americana L.).

Genipap fruits, native to the Amazon region, were classified in relation to their stage of ripeness according to firmness and peel color. The influence of the part of the genipap fruit and ripeness stage on the iridoid and phenolic compound profiles was evaluated by HPLC-DAD-MS(n), and a total of 17 compounds were identified. Geniposide was the major compound in both parts of the unripe genipap fruits, representing >70% of the total iridoids, whereas 5-caffeoylquinic acid was the major phenolic compound. In ripe fruits, genipin gentiobioside was the major compound in the endocarp (38%) and no phenolic compounds were detected. During ripening, the total iridoid content decreased by >90%, which could explain the absence of blue pigment formation in the ripe fruits after their injury. This is the first time that the phenolic compound composition and iridoid contents of genipap fruits have been reported in the literature.

Green pigmentation and pH change of homogenized garlic

pH of greening garlic was stable below 6.25 during storage at 30°C for 12 h. pH of non-greening garlic increased for 2 h and stayed above 6.28. Garlic homogenate concentrations influenced absorbance at 590 nm (blue) and pH. Blue pigment formation was proportional to garlic concentrations up to 30% with a pH drop. Absorbance at 590 nm and pH decreased at a slow rate as the garlic concentration increased. Absorbance values at 440 nm (yellow) increased in proportion to concentrations of garlic in direct relationship with changes in pH. An inverse relationship between blue pigment formation and pH decline was observed.

Simple and Efficient Rout for Synthesis of Spinel Nanopigments

Nano‐sized CoxMg1−xAl2O4 (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8, and 1) inorganic pigments were synthesized via combustion method using β‐alanine, as a single and novel fuel, at 800°C in open furnace. The obtained powders were characterized by means of X‐ray diffraction (XRD), energy dispersive X‐ray (EDX) elemental analysis, diffuse reflectance spectrum (DRS), CIE L*a*b* color measurements, and scanning electron microscope (SEM). XRD patterns show that all calcined powders have single phase cubic spinel structure. EDX analysis revealed the composition of desired spinels. The diffuse reflectance spectra of the CoxMg1−xAl2O4 (x > 0) pigments confirmed the presence of tetrahedrally coordinated Co2+ ions in the spinel lattice. The colorimetric data pointed out the formation of blue pigments (for x > 0), corresponding to highly negative values of b*, and the bluest color was produced for x = 0.8 and 1. SEM images showed nanoparticles with less than 30 nm crystallite size and flakes‐like appearance of all synthesized powders.

Identification of Candidate Amino Acids Involved in the Formation of Blue Pigments in Crushed Garlic Cloves (Allium sativum L.)

The color-forming ability of amino acids with thiosulfinate in crushed garlic was investigated. We developed reaction systems for generating pure blue pigments using extracted thiosulfinate from crushed garlic and onion and all 22 amino acids. Each amino acid was reacted with thiosulfinate solution and was then incubated at 60 degrees C for 3 h to generate pigments. Unknown blue pigments, responsible for discoloration in crushed garlic cloves (Allium sativum L.), were separated and tentatively characterized using high-performance liquid chromatography (HPLC) and a diode array detector ranging between 200 and 700 nm. Blue pigment solutions exhibited 2 maximal absorbance peaks at 440 nm and 580 nm, corresponding to yellow and blue, respectively, with different retention times. Our findings indicated that green discoloration is created by the combination of yellow and blue pigments. Eight naturally occurring blue pigments were separated from discolored garlic extracts using HPLC at 580 nm. This suggests that garlic discoloration is not caused by only 1 blue pigment, as reported earlier, but by as many as 8 pigments. Overall, free amino acids that formed blue pigment when reacted with thiosulfinate were glycine, arginine, lysine, serine, alanine, aspartic acid, asparagine, glutamic acid, and tyrosine. Arginine, asparagine, and glutamine had spectra that were more similar to naturally greened garlic extract.

Blue pigments based on Co xZn 1− xAl 2O 4 spinels synthesized by the polymeric precursor method

The Co x Zn 1− x Al 2O 4 system ( x = 0; 0.1; 0.3; 0.5; 0.7; 0.9 and 1) was synthesized by the polymeric precursor method and characterized by the techniques XRD, TG-DTA, IR, UV–vis and colorimetry. The XRD patterns displayed the characteristic peaks of the spinel structure and a good crystallinity. The DTA curves showed an exothermic peak corresponding to the enthalpy of the transition taking place at about 700 °C. The infrared spectra displayed vibrations at about 650, 550, 540, 520, 500, 490 cm −1, which were ascribed to the spinel structure. The UV–vis spectra presented three bands at 550, 580 and 620 nm attributed to the Co 2+ spin transitions in tetrahedral sites. The colorimetric data point out the formation of blue pigments, corresponding to highly negative values of b ∗. The lightness, coordinate L ∗, increases with the heat treatment temperature. These facts reveal that Co x Zn 1− x Al 2O 4 is a promising system that can be employed to obtain ceramic blue pigments.

Enzymatic properties of human CYP2W1 expressed in Escherichia coli

The human genome project revealed a new member of the P450 family 2, CYP2W1, which has orthologous form in other vertebrate species, suggesting CYP2W1’s significant physiological function. Recently, it was reported that CYP2W1 can metabolize arachidonic acid. In this study, we isolated human CYP2W1 cDNA, and successfully expressed truncated CYP2W1 lacking N-terminal 20 amino acids in Escherichia coli cells. In the bicistronic expression system for human CYP2W1 and NADPH-P450 reductase, the formation of blue pigment, indigo, was observed in bacterial cultures. Based on this result, we revealed that CYP2W1 catalyzes the oxidation of indole. In addition, CYP2W1 showed monooxygenase activity towards 3-methylindole and chlorzoxazone. However, no activity was observed towards fatty acids including arachidonic acid. Further analysis using an E. coli expression system will reveal substrate specificity of CYP2W1 and why this P450 isoform is universally conserved in vertebrates.

Exploiting the versatility of human cytochrome P450 enzymes: the promise of blue roses from biotechnology.

The cytochrome P450 (P450) enzymes involved in drug metabolism are among the most versatile biological catalysts known. A small number of discrete forms of human P450 are capable of catalyzing the monooxygenation of a practically unlimited variety of xenobiotic substrates, with each enzyme showing a more or less wide and overlapping substrate range. This versatility makes P450s ideally suited as starting materials for engineering designer catalysts for industrial applications. In the course of heterologous expression of P450s in bacteria, we observed the unexpected formation of blue pigments. Although this was initially assumed to be an artifact, subsequent work led to the discovery of a new function of P450s in intermediary metabolism and toxicology, new screens for protein engineering, and potential applications in the dye and horticulture industries.

Studies on the Blue Pigments Produced from Genipin and Methylamine. I. Structures of the Brownish-Red Pigments, Intermediates Leading to the Blue Pigments.

During the course of studies on the blue pigment formation by the reaction of genipin with methylamine, nine red to brownish-red intermediary pigments were obtained under conditions excluding oxygen. They were identified as monomer, dimer, trimer and tetramer of 2-methyl-4-carbomethoxy-2-pyrindine derivatives on the basis of spectroscopic evidence.

Studies on the Blue Pigments Produced from Genipin and Methylamine. II. On the Formation Mechanisms of Brownish-Red Intermediates Leading to the Blue Pigment Formation.

The mechanisms of the formation of brownish-red pigments having a 2-methyl-4-carbomethoxy-2-pyrindine nucleus as a basic skeleton by reaction of genipin with methylamine under an atmosphere of inert gas are discussed based on the isolation of 5, 6-dihydro-2-methyl-4-carbomethoxy-8-hydroxymethyl-2-pyrindine as a precursor and on comparisons of the results obtained from the reactions of genipin congeners and methylamine. The origin of the extra methyl group at C-6 in the structures of some of the brownish-red pigments was clarified to be the carbon atom of the hydroxymethyl group at C-8 of genipin by using deuterium-labelled genipin.

Hydrophobic blue pigment formation from phosphatidylgenipin.

Phosphatidylgenipin, synthesized via the transphosphatidylation reaction of 1,2-dipalmitoyl-3-sn-phosphatidylcholine to genipin by phospholipase D, was found to react with L-phenylalanine in chloroform and gave a clear blue solution. This blue solution was also formed in following organic solvents: ethanol, ethyl acetate, diethyl ether, benzene, and hexane. However, genipin and L-phenylalanine did not give any colored product under the same conditions. The blue pigment resulted from phosphatidylgenipin and L-phenylalanine showed lambda max at 615 nm in chloroform, and had a similar blue color to an aqueous solution of the natural blue pigment "gardenia blue." This is an example for the preparation of a hydrophobic pigment from a phosphatidyl derivative of a water-soluble compound.

Blue Pigment Formation byClerodendron trichotomumcallus

Blue pigment-producing callus was induced from fruit of Clerodendron trichotomum Thunb. on Linsmaier and Skoog (LS) medium with 10 μM 2,4-dichlorophenoxyacetic acid (2,4-D). Callus grew on LS medium with either 2,4-D or 1-naphthaleneacetic acid (NAA) on subculture. Callus growth and blue pigment formation were much improved by selection on LS gellan gum medium with 2 μM NAA. Kinetin and benzyladenine (1 μM) inhibited blue pigment formation. One of the blue pigments was confirmed to be trichotomine by HPLC, TLC, and NMR spectra; two others were presumed to be trichotomine G1 and N,N′-di(D-glucopyranosyl)trichotomine on the basis of comparison with the blue pigments from C. trichotomum fruit on HPLC.

Kinetic aspects of the blue pigment formation in a maillard reaction between D-xylose and glycine.

The production of blue pigments in the early stage of a Maillard reaction between d-xylose and glycine was kinetically analyzed to be associated with the mechanism for polymerization. An ion-pairing and reversed-phase HPLC method was developed for quantitatively tracing the blue pigment formation. The experiment with varied composition revealed that the reaction obeyed the following relationship: v =s k [d-xylose]2 · [glycine]2This equation could also be derived according to the stationary state theory. Based on Arrhenius plots, the activation energy was found to be 17.5 kcal/mol. The application of the transition state theory provided — 17.4cal/deg/mol for the activation entropy. A reaction scheme for the production of blue pigments is proposed on the basis of this kinetic analysis.

Brilliant skyblue pigment formation from gardenia fruits

It is well known that blue pigment is formed by the reaction of amino acids with genipin, the hydrolyzate of geniposide from gardenia fruits. We studied the effect of the amino acid on blue pigment formation and found a linear relationship between the molecular weight of the neutral amino acid and the λ max of the blue pigment formed. Thin layer chromatographic analysis revealed brilliant skyblue components of the blue pigments formed from glycine, alanine, leucine, phenylalanine and tyrosine. Furthermore, a brilliant skyblue color was obtained by a reverse phase column chromatography (HP-20) of blue pigments formed from glycine, leucine and phenylalanine. The λ max of these purified pigments lay above 600 nm, and the peaks were sharper than those of crude pigments. After standing for two weeks at 40°C in 40% ethanol solution, the brilliant skyblue pigment formed from genipin and glycine remained stable, losing none of its initial absorbance.

Continuous blue pigment formation by gardenia fruit using immobilized growing cells

Bacillus subtilis no. 24 was used as a microorganism which hydrolyzes geniposide and forms a blue pigment. This microorganism possessed β-glucosidase activity during aerobic growth (log phase) and assimilated geniposide as a carbon source. The growth of this cell was depressed by genipin formed by the hydrolysis of geniposide. Blue pigment was formed continuously for 20 d in medium containing geniposide, yeast extract and Polypepton, using growing cells immobilized in calcium-alginate gel.

Microbiological transformation of pyridine N-oxide and pyridine by Nocardia sp.

A Nocardia sp., which utilises pyridine N-oxide (PNO), 2-hydroxypyridine, and pyridine as sole sources of carbon, nitrogen, and energy, has been isolated from soil by enrichment on PNO. PNO-adapted cells rapidly oxidized PNO and 2-hydroxypyridine; pyridine was oxidized very slowly. 2-Hydroxy pyridine- and pyridine-adapted cells oxidized their respective substrates, but PNO was not oxidized. Dihydroxypyridines did not accumulate during growth of the organism, but the formation of blue pigments during fermentation of PNO and 2-hydroxypyridine suggested their transient participation. The pigment has been characterized as 4,5,4′,5′-tetrahydroxy-3,3′-diazadiphenoquinone-(2,2′). No pigment was formed during pyridine metabolism. 2,5-Dihydroxypyridine was oxidized by PNO- and 2-hydroxypyridine-adapted but not by pyridine-adapted cells. Succinic semialdehyde was characterized as the intermediate of pyridine metabolism from semicarbazide-inhibited cultures; it was rapidly oxidized by pyridine-adapted cells. Pyridine N-oxide is therefore metabolized in this Nocardia sp. via 2-hydroxypyridine and 2,5-dihydroxypyridine, but these compounds do not serve as intermediates of pyridine metabolism.

The Bacterial Oxidation of Nicotine: VII. PARTIAL PURIFICATION AND PROPERTIES OF 2,6-DIHYDROXYPYRIDINE OXIDASE

Abstract An inducible oxidase from Arthrobacter oxydans that catalyzes the oxidation of 2,6-dihydroxypyridine was purified about 50-fold. Reduced pyridine nucleotide is required for oxidase activity; no requirement for ferrous, ferric, or other cation could be demonstrated. Artificial electron acceptors do not substitute for oxygen in the reaction. The oxidase catalyzes the anaerobic reduction of methylene blue by NADH. 2,6-Dihydroxypyridine increases the rate of the anaerobic reaction but is not altered during the reaction. The purified oxidase preparation has absorption maxima at 384 and 455 nm. The maxima disappear during the anaerobic reaction. These and other data suggest that the oxidase is a monooxygenase of molecular weight about 89,000 having a flavin prosthetic group. The only detectable product of the oxidase reaction is a blue pigment. Its formation is decreased or eliminated when oxidase is supplemented with a second enzyme fraction (cleavage enzyme). Blue pigment is not a substrate for the cleavage enzyme. It is proposed that the normal metabolic sequence is the oxidation of 2,6-dihydroxypyridine to a trihydroxypyridine, mediated by the oxidase, followed by pyridine ring cleavage in a second reaction. The over-all stoichiometry of the oxidase reaction, corrected for oxygen utilized in blue pigment formation, is 2,6-dihydroxypyridine:NADH:O2 = 1:1:1.