2, 5‐Diketopiperazines (Cyclic Dipeptides) in Beef: Identification, Synthesis, and Sensory Evaluation

Chen, M.Z.; Dewis, Mark L.; Kraut, Kenneth J.; Merritt, Debra; Reiber, L.; Trinnaman, Laurence; Costa, Neil C. Da

doi:10.1111/j.1750-3841.2009.01062.x

Cited by 43 publications

(33 citation statements)

References 14 publications

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“…Briefly, pyrograms were measured for 200 ± 20 μg sediment using a FrontierLabs PY-2020iD oven (450°C) connected to an Agilent 7890A-5975C GC/MS system. Peak integration and identification were performed using a data processing pipeline under "R" computational environment [R-Development-Core-Team, 2011], the software "NIST MS Search version 2.0" containing the library "NIST/EPA/NIH 2011" [National Institute of Standards and Technology, 2011] and additional spectra from published studies [Faix et al, 1991;Nguyen et al, 2003;Meredith et al, 2008;Buurman et al, 2009;Chen et al, 2009;Schellekens et al, 2009;Gupta and Cody, 2011;Fabbri et al, 2012;Sessions et al, 2013;Schellekens et al, 2014]. Peaks extracted by the data processing pipeline were 492 and 617 for the sediment records of Dragsjön and Lång-Älgsjön, respectively.…”

Section: Conventional Om Variables and Molecular Characterization By mentioning

confidence: 99%

Investigating molecular changes in organic matter composition in two Holocene lake‐sediment records from central Sweden using pyrolysis‐GC/MS

et al. 2017

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Organic matter (OM) is a key component of lake sediments, affecting carbon, nutrient, and trace metal cycling at local and global scales. Yet little is known about long‐term (millennial) changes in OM composition due to the inherent chemical complexity arising from multiple OM sources and from secondary transformations. In this study we explore how the molecular composition of OM changes throughout the Holocene in two adjacent boreal lakes in central Sweden and compare molecular‐level information with conventional OM variables, including total carbon, total nitrogen, C:N ratios, δ13C, and δ15N. To characterize the molecular OM composition, we employed a new method based on pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), which yields semiquantitative data on >100 organic compounds of different origin and degradation status. We identify large changes in OM composition after deglaciation (circa 8500 ± 500 B.C.), associated with early landscape development, and during the most recent 40–50 years, driven by degradation processes. With molecular‐level information we can also distinguish between natural landscape development and human catchment disturbance during the last 1700 years. Our study demonstrates that characterization of the molecular OM composition by the high‐throughput Py‐GC/MS method is an efficient complement to conventional OM variables for identification and understanding of past OM dynamics in lake‐sediment records. Holocene changes observed for pyrolytic compounds and compound classes known for having different reactivity indicate the need for further paleo‐reconstruction of the molecular OM composition to better understand both past and future OM dynamics and associated environmental changes.

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Section: Conventional Om Variables and Molecular Characterization By mentioning

confidence: 99%

Investigating molecular changes in organic matter composition in two Holocene lake‐sediment records from central Sweden using pyrolysis‐GC/MS

et al. 2017

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“…They were identified in mammals, e.g., in rat and monkey brains, human central nervous system, gastrointestinal tract and blood (Prasad 1988). Besides the widespread DKP biosynthesis, they occur as chemical degradation products in e.g., roasted coffee (Ginz and Engelhardt 2000), stewed beef (Chen et al 2009) and beer (Gautschi et al 1997). The identified DKPs were described to cause a bitter taste in these foods.…”

Section: Introductionmentioning

confidence: 99%

Enzymatical and microbial degradation of cyclic dipeptides (diketopiperazines)

2013

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Diketopiperazines (DKPs) are cyclic dipeptides, representing an abundant class of biologically active natural compounds. Despite their widespread occurrence in nature, little is known about their degradation. In this study, the enzymatical and microbial cleavage of DKPs was investigated. Peptidase catalyzed hydrolysis of certain DKPs was formerly reported, but could not be confirmed in this study. While testing additional peptidases and DKPs no degradation was detected, indicating peptidase stability of the peptide bond in cyclic dipeptides. Besides confirmation of the reported degradation of cyclo(l-Asp-l-Phe) by Paenibacillus chibensis (DSM 329) and Streptomyces flavovirens (DSM 40062), cleavage of cyclo(l-Asp-l-Asp) by DSM 329 was detected. Other DKPs were not hydrolyzed by both strains, demonstrating high substrate specificity. The degradation of cyclo(l-Asp-l-Phe) by DSM 40062 was shown to be inducible. Three strains, which are able to hydrolyze hydantoins and dihydropyrimidines, were identified for the degradation of DKPs: Leifsonia sp. K3 (DSM 27212) and Bacillus sp. A16 (DSM 25052) cleaved cyclo(dl-Ala-dl-Ala) and cyclo(l-Gly-l-Phe), and Rhizobium sp. NA04-01 (DSM 24917) degraded cyclo(l-Asp-l-Phe), cyclo(l-Gly-l-Phe) and cyclo(l-Asp-l-Asp). The first enantioselective cleavage of cyclo(dl-Ala-dl-Ala) was detected with the newly isolated strains Paenibacillus sp. 32A (DSM 27214) and Microbacterium sp. 40A (DSM 27211). Cyclo(l-Ala-d-Ala) and cyclo(l-Ala-l-Ala) were completely degraded, whereas the enantiomer cyclo(d-Ala-d-Ala) was not attacked. Altogether, five bacterial strains were newly identified for the cleavage of DKPs. These bacteria may be of value for industrial purposes, such as degradation of undesirable DKPs in food and drugs and production of (enantiopure) dipeptides and amino acids.

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“…2a). Many literatures were reported on the mass spectrometric analysis of DKPs (Chen et al 2009(Chen et al , 2004Furtado et al 2007;Guo et al 2009a, b;Ryan et al 2009). But the exclusive cyclic dipeptide radical ion (M ?• ) has scarcely been reported, which is important for understanding gas-phase molecular reactivity and chemical properties of DKPs.…”

Section: Resultsmentioning

confidence: 97%

Synchrotron vacuum ultraviolet (VUV) photo-induced fragmentation of cyclic dipeptides radical cations

et al. 2011

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Cyclic dipeptides, due to their chemical properties and various bioactivities, are very attractive for medicinal chemistry. Fragmentations of three simple cyclic dipeptides including cyclo(Gly-Gly), cyclo(Ala-Ala) and cyclo(Gly-Val) in the gas-phase are determined with synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (VUV PIMS) and theoretical calculations. Cyclo(Gly-Gly) and cyclo(Ala-Ala) show the similar fragmentation pathways. The primary decomposition reactions of cyclo(Gly-Gly) and cyclo(Ala-Ala) radical cations are found to be HNCO loss and CO elimination. The appearance energies (AEs) of fragment ions [CH2NHCOCH2]+• and [CH3CHNHCOCHCH3]+• are measured to be 10.21 and 9.66±0.05 eV, respectively, which are formed from cyclo(Gly-Gly) and cyclo(Ala-Ala) radical cations with HNCO elimination. Due to the stabilization of the radical cation of cyclo(Gly-Val) with isopropyl side group, the dominant fragment ion m/z 114 assigned as [C4H6N2O2]+• is produced by γ-H migration and i cleavage to lose propylene. The ionization energies (IEs) of three cyclic dipeptides decrease in the order cyclo(Gly-Gly) (9.33±0.05 eV)>cyclo(Ala-Ala) (9.21±0.05 eV)>cyclo(Gly-Val) (9.09±0.05 eV) from measurements of photoionization efficiency spectra. It implies that IEs of cyclic dipeptides are affected by substituent groups and symmetrical characterization of molecular structures. These observations of the chemical properties of cyclic dipeptides radical ion (M+•) may be important for understanding gas-phase molecular reactivity of 2,5-diketopiperazines and guiding diketopiperazine-based drug design.

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2, 5‐Diketopiperazines (Cyclic Dipeptides) in Beef: Identification, Synthesis, and Sensory Evaluation

Cited by 43 publications

References 14 publications

Investigating molecular changes in organic matter composition in two Holocene lake‐sediment records from central Sweden using pyrolysis‐GC/MS

Investigating molecular changes in organic matter composition in two Holocene lake‐sediment records from central Sweden using pyrolysis‐GC/MS

Enzymatical and microbial degradation of cyclic dipeptides (diketopiperazines)

Synchrotron vacuum ultraviolet (VUV) photo-induced fragmentation of cyclic dipeptides radical cations

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