Hydrophobic compounds INDEX

Many bixxer compounds contain both hydrophobic and hydrophilic sites which can alter cell membranes through penetration. There is a correlation between bitter intensity and hydrophobicity-solubility indexes such as fee octanol/water partition coefficient, lo (7). Penetration may directly affect cAMP phosphodiesterase as part of fee transduction process (see below). A bitter receptor protein may be involved wife certain bitters, such as specific structural requirements wife fee bitter tasting dipeptides and denatonium salts (27). The latter is used in some consumer products to avoid accidental ingestion. A receptor mechanism is also supported by fee existence of a genetic "taste blindness" for some bitter materials (see below). 

One study of PAH elimination with lobsters (Homarus americanus) showed an interesting pattern (Uthe and Musial 1986). Lobsters that were captured from a polluted area of Sydney Harbor, Nova Scotia, Canada and held for 12 mon in a relatively clean aquarium system retained a large percentage of some of the PAHs in their tissues. The results showed a relationship between the percentage decline and PAH water solubility (an index of hydrophobicity) (Fig. 10). For the more water-soluble PAHs (e.g., fluoranthene and pyrene), the lobsters lost about 80% of their initial body burden, whereas for the more hydrophobic compounds (e.g., benzo[a]py-... 

As in isocratic mode, the estimate of log P is indirect and based on the construction of a linear retention model between a retention property characteristic of the solute (logkw) and a training set with known logP ci values. To assess the most performing procedures, the three hydrophobicity indexes (( )o, CHI and logkw) were compared on the basis of the solvation equation [41]. These parameters were significantly inter-related with each other, but not identical. Each parameter was related to log P with values between 0.76 and 0.88 for the 55 tested compounds fitting quality associated with the compound nature. 

An electronic parameter that often correlates with metabolic rates is the electrophilic (or nucleophilic) superdelocalizability. This quantity is a reactivity index formulated by Fukui and colleagues as an orbital-weighted electron density.145 The total electrophilic superdelocalizability, 2SE, summed over all atoms in a molecule, exhibits a parallelism with the hydrophobic parameter, log P, in several series of compounds such as PAHs and aliphatic amines, where it is probably approximating molecular volume. 

Fig. 12.19) that seemed to have the widest range of coefficients for the molecular descriptors in the solvation equation. Table 12.10 shows the solvation equations obtained and their normalised coefficients. The equations were obtained from the chromatographic hydrophobicity index data (CHI) of the compounds listed in Table 12.7 by using a 2.5 min linear gradient of the oi anic solvent from 0 to 1009F with 2 ml/min flow rate. The columns used were 4.6 x 50 mm short columns. The application of this fast gradient method makes it possible to obtain CHI values in a given HPLC system in 5 min. 

Recent studies have made it possible to classify water-organic solvent systems in CCC for separation of organic substances on the basis of the liquid-phase density difference, the solvent polarity, and other parameters from the point of view of stationary-phase retention in a CCC column [1,3-9]. Ito [1] classified some liquid systems as hydrophobic (such as heptane-water or chloroform-water), intermediate (chloroform-acetic acid-water and n-butanol-water) and hydrophilic (such as n-butanol-acetic acid-water) according to the hydrophobicity of the nonaqueous phase. Thirteen two-phase solvent systems were evaluated for relative polarity by using Reichardt s dye to measure solvachromatic shifts and using the solubility of index compounds [6]. 

Siwek and Sliwiok applied connectivity, Wiener index, and Balaban index to evaluate hydrophobicities (log fe(v) of selected isomer ketones, by using an RP-HPLC technique. Topological indices do not correlate well with log kdf, for a large group of compounds " ... 

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