Metabolite structure

Hampson, AJ, Hill WA, Zan Phillips M, Makriyannis A, Leung E, Eglen, RM, Bornheim LM. Anandamide hydroxylation by brain lipoxygenase metabolite structures and potencies at the cannabinoid receptor. Biophys. Biochim. Acta 1995 1259 173-179. 

Microbial Bioreactors Used in Metabolite Structure Elucidation 193... 

Owing to rapid development in analytical techniques, metabolite identification and structure elucidation have become possible even with trace levels of metabolites generated with in vitro or in vivo mammalian systems. However, the microbial bioreactor is still a valuable system for metabolite structure determination, especially when the metabolite of interest presents at a low level in in vitro or in vivo mammalian systems and the isolation from these matrices is hindered by the interference of other metabolites, the parent drug or endogenous compounds, or the structure determination requires appreciable amounts of samples due to structure complexity. 

Metabolite biosynthesis has demonstrated its utility in drug metabolite preparation and characterization, and contributed to drag discovery and development. Although metabolite biosynthesis is a prerequisite step for metabolite structure elucidation in many cases, it is complementary to chemical synthesis in large-scale metabolite preparations. The merits for using these techniques should be determined on a case-by-case fashion. New techniques, such as recombinant enzyme and microbial glucuronidation systems, would have a great impact on the field. 

The predicted metabolites are also the starting point for the phase II metabolic prediction, to find where glucuronidation could occur. All the probable metabolites obtained from CYP metabolism reactions are submitted to a possible phase II reaction catalyzed by UGTs, using the UGT structure(s) as a template. The accessibility component is computed in the UGTcavity to prioritize glucuronic acid transfer. The final metabolite structures are then reported in graphical output or saved to a file. 

Berger and coworkers [17] demonstrated the existence of macrocyclic substances capable of solubilizing alkali metal ions in nonpolar media, and described the formation of sodium and barium salts of a metabolite that had acid properties and was formed in a culture of an unspecified streptomyces. These salts were insoluble in water but dissolved in ether and benzene. The metabolite structure, originally called X 464 [17] and later nigericin [204]... 

Shan R etal., New metabolites with nematicidal and antimicrobial activities from the ascomycete Lachnum papyraceum (Karst.) Karst. VIII. Isolation, structure determination and biological activities of minor metabolites structurally related to mycorrhizin A,/yl rz zt>r 49 447- 52, 1996. 

Justino GC, Santos MR, Canario S, Borges C, Florencio MH, Mira L. 2004. Plasma quercetin metabolites Structure-antioxidant activity relationships. Arch Biochem Biophys 432 109-121. 

Hopfgartner, G., and Vilbois, F. (2000). The impact of accurate mass measurements using quadrupole/time-of-flight mass spectrometry on the characterisation and screening of drug metabolites Structure elucidation by LC-MS. Analusis 28 906-914. 

Hardman and Makarov, 2003), making the LTQ-Orbitrap especially suitable for small-molecule analyses. For most compounds, the relative intensities of ions in Orbitrap mass spectra are very similar to those spectra from LTQ (IT scan) (Fig. 5.5) (Sanders et al., 2005). As discussed above, this feature becomes very important for building MS/MS libraries and subsequent library searches for related structures (i.e., metabolites, structural analogues, degradants, etc.). Also highlighted in Fig. 5.5 are the excellent mass accuracies observed in the MS/MS mode, even for some very minor fragments. 

Pearce and Lushnikova [78] used semipreparative HPLC method for the isolation of the three omeprazole metabolites produced by the fungi. Incubation of Cunninghamella elegans ATCC 9245 and omeprazole allowed putative fungal metabolite to be isolated in sufficient quantities for structural elucidation. The metabolites structures were identified by a combination of LC/MS and NMR spectrometric experiments. These isolates are used as reference standards in the confirmatory analysis of mammalian metabolites of omeprazole. In the LC/MS and LC/MS/MS analysis, components were separated by reversed-phase HPLC on a Hypersyl HyPurity (15 cm x 4.6 mm, 5 /im) column. The mobile phase consisted... 

The identification of metabolite structures with LC/MS and LC/MS/MS techniques are an effective approach due to their ability to analyze trace mixtures from complex samples of urine, bile, and plasma. The key to structure identification approaches is based on the fact that metabolites generally retain most of the core structure of the parent drug (Perchalski et al, 1982). Therefore, the parent drug and its corresponding metabolites would be expected to undergo similar fragmentations and to produce mass spectra that indicate major substructures. 

Table 6.11 illustrates a representative buspirone metabolite structure database. Information on the structure, molecular weight, UV characteristics, RRT, and product ions of metabolites obtained from rat bile, urine, and liver S9 samples are compiled. Using this format, the predominant buspirone metabolite profile groups, As-B-P, A-B-Ps, and As-B-Ps are easily recognized. These profile groups indicate azaspirone decane dione and pyrimidine as metabolically active sites of attack and the presence of multiple substitution sites on each of these substructures. In many cases, the profile groups indicate the occurrence of metabolic reactions on more than one substructure. 

Figure 6.42 Product ion spectrum of CPT-11, the structural template for the identification of metabolite structures. (Reprinted with permission from Lokiec et al., 1996. Copyright 1996 American Association for Cancer Research.)...

Kerns, E. H. Rourick, R. A. Volk, K. J. Lee, M. S. 1997. Buspirone metabolite structure profile using a standard liquid chromatographic-mass spectrometric protocol. /. Chromatogr. B, 698,133-145. 

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