Metabolic assays high-content

Since its creation around 1973, modern high-pressure liquid chromatography (HPLC) has played a dominant role in the analysis of pharmaceuticals. It is used in many different applications for example, in content uniformity assays and stability-indicating methods, for the purity profiles of drug substances, or in the analysis of drug metabolism in animals and humans. The heart of all of these assays is the HPLC column. In this chapter, we will describe the fundamental properties of HPLC columns as well as how these properties influence column performance and separation characteristics in pharmaceutical assays. 

The intact cell assay of PAL gave us a tool to assess the possible interference of intermediates of phenyl-propanoid metabolism with PAL-activities in the tissue. It should be emphasized that in the experiments the inhibition of an enzyme already present is measured as opposed to an effect on the enzyme-content of the tissue. As Table 4 shows, derivatives of cinnamic acid, which are known to inhibit PAL in vitro (Eef. 4) also inhibit the intracellular PAL-activity. 7/hether feedback inhibition of PAL by cinnamic acid derivatives has a physiological significance in buckwheat is, however, questionable, as free derivatives from cinnamic acid do not accumulate in the tissue and may thus not be available in sufficiently high concentrations to cause inhibition of PAL. 

So far studies on the absorption, circulation, metabolism and excretion of vitamin Bg have been performed by feeding or injecting high amounts of radiolabelled PN. However, the contents of PN in the foods examined were low compared with those of the other vitamin Bg forms. Thus, information on the absorption, circulation, metabolism and excretion of vitamin Bg when animals or human consume usual foods should be obtained using enzymatic HPLC assay. 

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