Chemical marker compounds

The chemometric principle was used to derive a guideline for obtaining a simple yes or no answer about the sterility of food particulates heated at aseptic processing temperatures. A quadratic temperature pulse model was used to estimate bacterial destruction from the fractional yield of thermally produced chemical marker compounds (2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one, M-1, and 4-hydroxy-5-methyl-3(2H)-furanone, M-2) and the rate constants and the activation energies of the chemical and bacterial systems. The model yielded a conservative estimate of lethality at the center of meat-balls heated under different time-temperature conditions. A scheme for determining the minimum marker yield for a designated F -value is provided. 

Several chemical marker compounds formed at sterilizing temperatures from precursor compounds inherently present in the foods have been reported (Kim and Taub, 1993 Kim et al, 1994). In order to apply these chemical markers to real processing conditions, where lethality accumulates under nonisothermal conditions, accurate informations about the reaction rate constants and their temperature dependence (activation energy or Z-value) are needed. The variability of the precursor concentration within the particulates and among different particulates also needs to be considered carefully. 

This overview deals with some of the chemical marker compounds suited to the requirements of quality control laboratories in the citrus industry. Chemical markers include ascorbic acid, dehydroascorbic acid, hydroxymethylfurfural, furfural, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, 4-vinyl guaiacol and a-terpineol. Some of these compounds might be applied as useful tools in evaluating quality deterioration due to unsuitable manufacturing and storage as well as for the computation and optimization of the manufacturing processes and parameters. Since they are all chemically reactive compounds, careful evalution of kinetics of these compounds is necessary. 

The methacrylic backbone structure makes the spherical Toyopearl particles rigid, which in turn allows linear pressure flow curves up to nearly 120 psi (<10 bar), as seen in Fig. 4.45. Toyopearl HW resins are highly resistant to chemical and microbial attack and are stable over a wide pH range (pH 2-12 for operation, and from pH 1 to 13 for routine cleaning and sanitization). Toyopearl HW resins are compatible with solvents such as methanol, ethanol, acetone, isopropanol, -propanol, and chloroform. Toyopearl HW media have been used with harsh denaturants such as guanidine chloride, sodium dodecyl sulfate, and urea with no loss of efficiency or resolution (40). Studies in which Toyopearl HW media were exposed to 50% trifluoroacetic acid at 40°C for 4 weeks revealed no change in the retention of various proteins. Similarly, the repeated exposure of Toyopearl HW-55S to 0.1 N NaOH did not change retention times or efficiencies for marker compounds (41). 

The survival of a-boswellic acid, p-boswellic acid and their O-acetates, which have been isolated only from frankincense, has been demonstrated in archaeological samples [99,107,113]. These compounds are considered as very useful specific chemical markers for the identification of frankincense in resinous archaeological materials. 

Several studies have dealt with the problem of discriminating between mastic and dammar, and three marker compounds of mastic have been identified moronic, masticadienonic and acetyl masticadienolic acids [42], The chemical structure of (iso)masticadienonic acid and 3-0-acetyl-3-epi(iso)masticadienonic acid is characterized by a side chain, as for dammarane molecules, but with a carboxylic acid end group (Table 12.1). Under pyrolysis conditions this side chain is susceptible to cleavage as demonstrated by the presence, among the pyrolysis products of mastic, of 2-methyl-pent-2,4-dienoic acid, that perfectly matches with the chemical structure of the side chain end. In addition 3-(9-acetyl-3-epi-(iso)masticadienolic acid also loses the acetyl group and, in contrast to masticadienonic acid, is not detected at all. 

Botanical raw materials and their extracts therefore usually contain complex mixtures of several chemical constituents. For a large majority of botanical plant material and extracts of these used as dietary supplements, it is not known with certainty which of the various components is responsible for the purported pharmacological effect. It is generally believed that several constituents act synergistically to provide the purported effect. In actual practice, two or more of the chemical constituents present in the plant material are identified as marker compounds that are characteristic of the plant material to be tested, for identification and monitoring of the stability of the extracts. 

There are inherent problems associated with enzyme-mediated methods, regardless of the method used. The right conditions must be met, of course, for the enzyme action to take place. Unlike fluorochromes or gold particles (two other marker compounds), enzymes need to act chemically for the assay to work. Also, the enzyme action must only represent the marker molecule. Endogenous enzyme or enzyme-like activity can create problems only realized in systems that use enzymes. Also, the use of enzymes demands more attention to detail because of the increase in sensitivity that is often obtained. The problem of unwanted reactivity is enhanced in enzyme-mediated reactions more so than in others, in part because of the additional level of sensitivity brought about by the continuous action on a substrate. 

For groups experienced in trace analysis of chemical markers for bacteria, currently samples are analyzed almost exclusively by GC-MS/MS. GC-MS/MS assays are now well established and a wide range of clinical and environmental samples have been analyzed. However, application in the pharmaceutical industry requires further evaluation. For example, Mur is released by hydrolysis and analyzed as an alditol acetate 3-OH FAs after methanolysis are converted to methyl trimethylsilyl derivative. Detailed analytical procedures have been described elsewhere for Mur [3,4,7, 8,11] and for 3-OH FAs [2, 5,12,13]. The compounds of interest contain active... 

The precision of MS assays is in the range typical of most clinical assays (i.e., under 5-15%). The best choice of internal standard is the stable-isotope-labeled form (preferably 13C) of the compound of interest (e.g., P-hydroxy myristic acid or muramic acid). Specific trace detection of chemical markers in complex matrices requires appropriate negative controls. Procedures are often described that do not employ the mass spectrometer and false positives are often reported. The mere analysis of blank filters or water blanks is not satisfactory since chemical noise contributed by the sample is much greater and is not accounted for with this form of control. 

Immunoblotting techniques involve the identification of a protein target via antigen-antibody-specific reactions. Proteins are typically separated by electrophoresis in polyacrylamide gels, and then transferred ( blotted ) onto chemically resilient membranes (e.g., nitrocellulose, polyvinylidene difluoride) where they bind in the pattern they took in the gel. The membrane is overlaid with a primary antibody directed to the specific target, then with a secondary antibody (anti-immunoglobulin) labeled with radioisotopes, enzymes or other marker compounds. 

By virtue of where, when, and how the various organic matter inputs were formed and transported to the underlying sediments, it is possible to exploit specific chemical and isotopic characteristics to make inferences about the sources and composition of sedimentary organic matter. Much of this information is inaccessible at the bulk level. For example, bulk elemental compositions and stable carbon isotopic compositions are often insufficiently unique to distinguish and quantify sedimentary inputs. Abundances and distributions of source-specific organic compounds ( biomarkers ) can help to identify specific inputs. However, this molecular marker approach suffers from the fact that the source diagnostic marker compounds are... 

Marker compound-chemically defined constituents of an herbal drug, which are of interest for control purposes, independent of whether they have any therapeutic activity or not. 

Chemical contamination of some groundwater and surface-water supplies may have occurred as a result of point-source, waste disposal practices located near State College, PA and the Pennsylvania State University. The compound, unidentified, but having a consistent retention time for elution in the analytical method used for tracing and quantification, will be further described as a marker compound in order to properly focus on the dispersal aspects of this problem. It... 

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