Lucigenine

A number of chemiluminescent reactions may proceed through unstable dioxetane intermediates (12,43). For example, the classical chemiluminescent reactions of lophine [484-47-9] (18), lucigenin [2315-97-7] (20), and transannular peroxide decomposition. Classical chemiluminescence from lophine (18), where R = CgH, is derived from its reaction with oxygen in aqueous alkaline dimethyl sulfoxide or by reaction with hydrogen peroxide and a cooxidant such as sodium hypochlorite or potassium ferricyanide (44). The hydroperoxide (19) has been isolated and independentiy emits light in basic ethanol (45). 

Classical chemiluminescence from lucigenin (20) is obtained from its reaction with hydrogen peroxide in water at a pH of about 10 Qc is reported to be about 0.5% based on lucigenin, but 1.6% based on the product A/-methylacridone which is formed in low yield (46). Lucigenin dioxetane (17) has been prepared by singlet oxygen addition to an electron-rich olefin (16) at low temperature (47). Thermal decomposition of (17) gives of 1.6% (47). 

Unloaded silica does not recover HPA from aqueous solution. The surface of silica gel modified with quarternary ammonium salts (QAS) gets anion-exchange properties. The aim of the work is the elaboration of solid-phase reagents on the base of ion associate of HPA with QAS immobilized onto silica surface for the determination of phosphoms and organic reductants. Heterocyclic (safranine and lucigenine) and aliphatic (trinonyloctadecyl ammonium iodide and tetradecyl ammonium nitrate) compounds have been examined as QAS. 

Two techniques for sorption-spectroscopic determination of ascorbic acid have been proposed. The first one is the recovery by silica modified with tetradecyl ammonium nitrate of blue form of molibdophosphoric HPA in the presence of vitamin C. And the second one is the interaction between the ascorbic acid in solution and immobilized on silica ion associate of molibdophosphoric acid with lucigenine. The detection limits of vitamin C are 0.07 and 2.6 mg respectively. The techniques were successfully applied to the determination of ascorbic acid in fmit juices. 

Rost, M., Karge, E., and Klinger, W. (1998). What do we measure with luminol-, lucigenin- and penicillin-amplified chemiluminescence 1. Investigations with hydrogen peroxide and sodium hypochlorite. J. Biolumin. Chemilumin. 13 355-363. 

Storch, J., and Ferber, E. (1988). Detergent-amplified chemiluminescence of lucigenin for determination of superoxide anion production by NADPH oxidase and xanthine oxidase. Anal. Biochem. 169 262-267. 

Huber C., Krause C., Werner T., Wolfbeis O.S., Serum chloride optical sensors based on dynamic quenching of the fluorescence of photo-immobilized lucigenin, Microchimica Acta 2003 142 245-253. 

The 02, radical can act as an oxidant as well as a reductant and chemical estimates of its production can also be based on its ability to oxidize epinephrine to adren-ochrome [62], These chemical methods have the additional advantage of not requiring highly specialized equipments. Also based on its redox property, the 02 radical can be determined by chemiluminescence methods through the measurement of the intensity of the fluorescence radiation emitted after chemical oxidation of 02 by, e.g., lucigenin [63-67], These methods, however, are limited by the poor selectivity and lack of capability for in-vivo performance. 

Me Capra in particular proposed n> that the chemiluminescence reactions of a large number of organic compounds had this concerted dioxetane decomposition step as key reaction in the production of electronically excited products, namely acridinium salts 25,26,27) indolylperoxides 28>, activated oxalic esters 29>, diphenyl carbene 30>, tetrakis-dimethylamino-ethylene 31 32>, lucigenin 33>, and substituted imidazoles 23>. 

Lucigenin 71 chemiluminescence is more complicated than that of luminol and related compounds due to the presence in the reaction mixture of several species capable of emission 135>. N-Methylacridone 72, however, has been established as the primary excited product (for references see 0 p. 90) from which energy transfer occurs to the other species 3>. 

Because of the close relations between lucigenin, N-alkylacridones, and other 9-substituted acridines, it appears appropriate to consider the chemiluminescence reactions of all these compounds simultaneously. 

In view of the increasing interest in the radical ion chemiluminescence 71 has also been investigated to see whether radical ions play an essential role here, especially by E. G. Janzen et al. 136,137,138) The reaction pathway to N-methylacridone 72 was thought to proceed perhaps via a homolytic cleavage of the lucigenin carbinol base 74, yielding N-methylacridone radical anion 75. 

ESR spectroscopy, however, revealed that 75, which one may call a ketyl radical, was not present in alkaline solutions of 77 in absence of oxidizing agents. The signal actually observed was that of 9-hydroxy-N,N -dimethyl-9,9 -biacridan radical 76. It was suggested that this radical was formed by one-electron transfer from N-methyl-acridone radical anion 75 to lucigenin monocarbinol 77, or by addition of hydroxide ion to lucigenin radical cation 78 (formed from lucigenin by one-electron transfer by the ketyl 75). 

The lucigenin radical 78 is not involved, according to Janzen and coworkers 136), in the direct formation of this cyclic peroxide one would, however, expect a reaction of 78 with oxygen radical anion to be a possible way of forming the cyclic peroxide, although lucigenin radicals were not detected in the presence of hydrogen peroxide. 

The dioxetane derivative 79 may be formed as intermediate in the brilliant chemiluminescence reaction between 10,10 -dimethyl-9,9 -bi-acridylidene and excited-singlet oxygen 125>. Chemiluminescence also occurs when potassium cyanide is added to lucigenin solutions in the... 

Quenching in lucigenin fluorescence (and similar effects should operate in lucigenin and acridine chemiluminescence in general) has recently been investigated by Hercules 143>. 

Figure 5 Chemical structure of lucigenin (10,10 - dimethyl-9,9 -biscridinium (nitrate)).

One of the more efficient CL substances, lucigenin (10,10 -dimethyl-9,9 -biscridinium nitrate), was discovered by Gleu and Petsch in 1935 (Fig. 5). They observed an intense green emission when lucigenin was oxidized in an alkaline medium [72], Other acridinium derivatives were shown to produce CL emission upon hydrogen peroxide oxidation of aqueous alkaline solutions. The main reaction product was /V-mcthylacridone, acting as an active intermediate in the mechanism proposed by Rauhut et al. [73, 74] (Fig. 6). 

For analysis in solutions, the most frequently used CL reaction is alkaline oxidation of luminol and lucigenin in the presence of hydrogen peroxide as oxidant, although sodium hypochlorite, sodium perborate, or potassium ferricyanide may also be used. CL reactions involving alkaline oxidation have been used to indicate acid-base, precipitation, redox, or complexometric titration endpoints either by the appearance or the quenching of CL when an excess of titrant is present [114, 134], An example of these mechanisms is shown in Figure 14. 

Lucigenin oxidation in alkaline H202 425 nm Blue-green 0.016... 

Chemiluminescence from lucigenin is observed even without the catalytic transition metal ions but it is more intense when these ions are used. In aqueous or predominately aqueous solutions the CL yield is 0.01-0.02, which makes it a slightly better emitter than luminol [35], The emission of lucigenin is also catalyzed by Pb(II), Bi(III), Tl(III), and Hg(I) ions, which do not catalyze the CL of luminol [36],... 

Lucigenin is often used to facilitate the measurement of reactive oxygen species in immunological studies, because it enhances the cellular CL intensity [37], Both luminol and lucigenin can be used to measure reactive oxygen how-... 

Figure 5 Chemiluminescent reaction of lucigenin proceeding via a dioxetane intermediate.

Several N-methyl-9-acridinecarboxylic acid derivatives (e.g., 10-methyl-9-acridinecarboxylic chloride and esters derived therefrom [39]) are chemiluminescent in alkaline aqueous solutions (but not in aprotic solvents). The emission is similar to that seen in the CL of lucigenin and the ultimate product of the reaction is N-methylacridone, leading to the conclusion that the lowest excited singlet state of N-methylacridone is the emitting species [40], In the case of the N-methyl-9-acridinecarboxylates the critical intermediate is believed to be either a linear peroxide [41, 42] or a dioxetanone [43, 44], Reduced acridines (acridanes) such as N-methyl-9-bis (alkoxy) methylacridan [45] also emit N-methylacridone-like CL when oxidized in alkaline, aqueous solutions. Presumably an early step in the oxidation process aromatizes the acridan ring. 

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