Solubility tests test compounds

An also frequently occurring problem may be the low solubility of test compounds in aqueous solvents. Organic cosolvents, such as DMSO or ethanol can be used however, due to limited cell viability, final concentrations above 1 % have to be avoided. 

Group I. This includes the lower members of the various homologous series (4-5 atoms in a normal chain) that contain oxygen and/or nitrogen in their structures they are soluble iu water because of their low carbon content. If the compound is soluble in both water and ether, it would also be soluble in other solvents so that further solubility tests are generally unnecessary the test with sodium bicarbonate solution should, however, be performed (see Section XI,6). 

Data sets on toxicity to aquatic organisms vary considerably from compound to compound, with dibutyltin being the best studied. Results of toxicity tests for all compounds are summarized in Figure 2. Values for all but one test on the octyltins have been set at the solubility of the compounds, since no toxicity was observed below the solubilities derivation of PNECs for the octyltins are, therefore, more precautionary than for the other compounds. 

These batch procedures for enrichment and successive transfer may be replaced by the use of continuous culture. This may be particularly attractive when the test compound is toxic, when it is poorly soluble in water, or where the investigations are directed to substrate concentrations so low that clearly visible growth is not to be expected. These problems remain, however, for subsequent isolation of the relevant organisms. One considerable problem in long-term use arises from growth in the tubing of the pump system that is used to administer the medium and should be renewed periodically. 

Compound la with no substitution, showed good activity with increased hpophihcity activity. Further increases in lipophihcity led to a decrease in activity. Replacement of a proton of the methyl group by a hpophobic group (chloro) resulted in a further decrease in activity. The order of activity of substituents at the first position was methyl, ethyl, unsubstituted, propyl, and chloromethyl. Compounds with a small substituent at Ci seem to provide optimum activity. As the test compounds could not be converted to water soluble form, in vitro evaluation for antihistaminic activity could not be performed. 

Although a lipoid-soluble group characterizes many contact insecticides, simple oil-solubility of a compound is not always a criterion of activity. Busvine (14) tested a series of DDT analogs and found that solubility in oil was not essential to activity. Kirkwood... 

Here, we briefly describe the automated Caco-2 assay used at the research site in AstraZeneca R D Molndal. The solubility of the test compounds is measured (or theoretically predicted) before they are run in the Caco-2 assay. In order to be able to make correct determinations of the permeability coefficient, the substance must be dissolved when added to cell monolayer in the transport experiment. Compounds with insufficient solubility are therefore not tested. We generally apply a test concentration of 10 pM, but in specific projects or under certain circumstances a concentration of only 1 pM is applied. The test compounds are first prepared in DM SO solution (1 mM) on a parent plate and are then diluted in transport buffer to give a final drug concentration of 10 pM (solution containing 1% DMSO) when added to the cell monolayers. 

If your compound does not happen to dissolve in CC14, you still have a shot because deuterium atoms do not give PMR signals. This is logical, since they re not protons. The problem is that deuterated solvents are expensive, so do NOT ask for, say, D20 or CDC13, the deuterated analogs of water and chloroform, unless you re absolutely sure your compound will dissolve in them. Always use the protonic solvents — H20 or CHC13 here — for the solubility test. There are other deuterated solvents, and they may or may not be available for use. Check with your instructor. 

Prepare a stock solution of the test compound at a concentration of 50 mg ml-1 in an appropriate solvent. It may be necessary to prepare a lower concentration of stock solution, depending on the solubility of the test compound. 

Preliminary Cytotoxicity Testing. An essential first step is to carry out a preliminary study to evaluate the toxicity of the test material to the indicator cells, under the conditions of the main mutagenicity test. When selecting dose levels, the solubility of the test compound, the resulting pH of the media, and the osmolality of the test solutions all need to be considered. The latter two parameters have been known to induce false positive effects in in vitro mammalian tests (Brusick, 1986). The experimental procedure is carried out as follows. 

Prepare treatment medium containing various concentrations of test compound 19.7 ml of Eagle s medium (without serum) plus 300 pi of stock concentration of compound in a preferred solvent (e.g., water, ethanol, DMSO, etc.). The final concentration of solvent other than water should not exceed 1% v/v. Normally a range of 0-5000 pg ml-1 (final concentration) is covered. For a sparingly soluble compound, the highest concentration will be the lowest at which visible precipitation occurs. Similarly, if a compound has a marked effect on osmolality, concentrations should not be used that exceed 500 milliosmoles (mosm) per kg. In addition, a pH range of 6.5-7.5 should be maintained. 

It is technically possible, but very difficult, to measure the exact frequency of a radio signal, and in practice the frequency of the energy absorbed by a test compound (usually called the resonance frequency) is measured relative to that of a reference compound. This reference may be mixed with the sample (direct referencing), or if contamination of the sample is undesirable it may be placed in a separate container within the sample tube (external referencing). In proton and 13C NMR, the reference compound usually used is TMS (tetra-methyl silane) or its water-soluble derivative DSS (2,2-dimethylsilapentane 5-sulphonic acid). These compounds give a sharp proton peak at the right-hand side of a typical NMR spectrum (Figure 2.39). 

Single Test Compound Clustering with Several Marketed Drugs on the Basis of the Similarity of In Vitro Profile Results Including Human Absorption, Oral Bioavailability, Permeability, Solubility, Log D, and Metabolic Stability Characteristics... 

Solubility screens using LC/MS detection do not require an ultra-pure sample of the test compound due to the selective detection of the mass spectrometer. Mass spectrometric detection offers high selectivity and low detection limits, which eliminates the need to develop complex chromatographic methods. The LC/MS-based solubility screen surpasses the traditional HPLC/UV-based equilibrium solubility assay with increased throughput, minimal manual intervention, and high sensitivity and selectivity. 

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