Component biomarkers

Kohler, H.-R. and Triebskom, R. (1998) Assessment of the cytotoxic impact of heavy metals on soil invertebrates using a protocol integrating qualitative and quantitative components. Biomarkers, 3, 109-127. 

Component biomarkers are found more easily than food biomarkers, because food markers are included within component biomarkers. For example, plasma isofla-vones are measured as a marker of the exposure to isoflavones, although as they have an almost unique dietary source, soybean products and their derivatives. 

Component Biomarker Tissue/biofluid N Food survey Correlation coefficient (r) References... 

Particular attention is given to the development of new mechanistic biomarker assays and bioassays that can be used as indices of the toxicity of mixtures. These biomarker assays are typically based on toxic mechanisms such as brain acetylcholinesterase inhibition, vitamin K antagonism, thyroxin antagonism, Ah-receptor-mediated toxicity, and interaction with the estrogenic receptor. They can give integrative measures of the toxicity of mixtures of compounds where the components of the mixture share the same mode of action. They can also give evidence of potentiation as well as additive toxicity. 

With investigations of phytochemicals and functional foods, the outcome measure is generally going to be a biomarker of disease, such as serum cholesterol level as a marker of heart disease risk, or indicators of bone turnover as markers of osteoporosis risk. Alternatively, markers of exposure may also indicate the benefit from a functional food by demonstrating bioavailability, such as increased serum levels of vitamins or carotenoids. Some components will be measurable in both ways. For instance, effects of a folic acid-fortified food could be measured via decrease in plasma homocysteine levels, or increase in red blood cell folate. 

A range of biomarkers (biological markers) have been developed for the detection of microorganisms using both their genetic (DNA and RNA) and biochemical components. Most methods have originated from studies on pure isolates and have been adapted to identify and quantify either the total or a sub.set of the microbial biomass in a sample. In these methods,. specific taxonomic or pheno-... 

Mineral Oil Hydraulic Fluid. Limited studies were located that suggest biomarkers of exposure to mineral oil hydraulic fluids. No data that indicate quantitative or qualitative biomarkers of exposure to mineral oil hydraulic fluid were located. Mineral oil (hydrocarbons containing 15-30 carbon atoms per molecule) is a major component that is common to all mineral oil hydraulic fluids. Following exposure to food-grade mineral oil, most of the administered radioactivity was excreted in the feces as mineral oil (Ebert et al. 1966). Although the presence of mineral oil is a biomarker of exposure to mineral oil hydraulic fluids, it is also a biomarker of exposure to other readily available products that contain mineral oils. 

Organophosphate Ester Hydraulic Fluids. Interpretation of the biomarkers of exposure to organophosphate ester hydraulic fluids is complicated by the diversity of composition among the hydraulic fluids in this class. Erythrocyte acetylcholinesterase activity is a good biomarker of exposure to certain organophosphates (e.g., insecticides), but results are inconsistent with organophosphate components of... 

There is a growing need to better characterize the health risk related to occupational and environmental exposure to pesticides. Risk characterization is a basic step in the assessment and management of the health risks related to chemicals (Tordoir and Maroni, 1994). Evaluation of exposure, which may be performed through environmental and biological monitoring, is a fundamental component of risk assessment. Biomarkers are useful tools that may be used in risk assessment to confirm exposure or to quantify it by estimating the internal dose. Besides their use in risk assessment, biomarkers also represent a fundamental tool to improve the effectiveness of medical and epidemiological surveillance. 

Rather than comparing the spectrum from a bacterial mixture to the spectra of individual bacteria, spectra from mixtures (or pure cultures) can be examined for the presence of specific biomarker compounds. While the detection of a smaller number of maker ions provides less taxonomic specificity than a complete spectrum, taxonomic specificity is not the only basis for considering the components in a mixture of bacteria. 

B. frereana and B. papyrifera olibanum have very different terpenic composition from the others. B. frereana olibanum contains the same monoterpenes as olibanum from B. carteri, B. sacra or B. serrata, but is very poor in sesquiterpenes and contains none of the diterpenic biomarkers cited before. Two unidentified compounds (55 and 56) seem to be specific and the main diterpenes, present in high level, are four dimers of a-phellandrene. Dimer 3 (113) is the major component. On account of its absence in the other olibanum samples, it can be considered as characteristic of B. frereana olibanum. 

The result obtained by GC-MS, with the same SPME conditions, from the black thick balm of a crocodile mummy (sample 1400, Musee Guimet, Lyon, France) is presented in Figure 10.11. The composition of the extract is close to that of sample 1998 but phenolic compounds were not detected. The GC-MS chromatogram obtained with the same substance after acid methanolysis and silylation is presented in Figure 10.12. Except for the sesquiterpenoids eluted between 10 min and 22 min, the observed compounds originate from a beeswax. The biomarkers of this substance are hexadecanoic acids hydroxylated in position 14 or 15 and long chain hydrocarbons, acids and alcohols eluted between 50 min and 90 min. Diterpenoid or triterpenoid resin components are not observed. 

Due to the fact that JP-8 contains hundreds of aliphatic and aromatic hydrocarbons, in addition to various performance additives, this complex mixture poses a serious challenge for risk assessment. Exposure assessment is complicated by the fact that JP-8 may be encountered as a vapor, aerosol, or liquid, and possibly as combustible products, and each physical state may contain different chemical entities. However, progress has been made in the identification of JP-8 components that may serve as reliable and predictable biomarkers of exposure, particularly for dermal exposures [12,35,81,82,83,84],... 

The previous chapters have dealt mainly with LC/MS analysis involving short run times, many samples, and relatively small numbers of compounds in samples. What about samples containing very complex compound mixtures, for example, natural products, samples from biomarker discovery, protein digests, and QA/QC method development or metabolite identification samples requiring detection of every component Such workflows often require several analysis steps with different columns and different mobile phases and pH values to increase the separation probability by changing the selectivities of individual runs. 

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