Lipophilic compounds

Sephadex A trade name for an insoluble hydrophilic substance prepared by cross-linking dextran, and used in gel filtration. It can also be linked to acidic or basic groups for ion exchange or to alkanes for the chromatography of lipophilic compounds. 

Excretion factors are often related to lipophilicity. More lipophilic compounds tend to be excreted by the Hver into the bile, resulting in elimination ultimately in the feces. As this is a relatively slow process, much of the radioactivity having a shorter half-life decays before being eliminated. Polar compounds are more likely to be excreted by the kidneys. 

Itraconazole. Itraconazole (18) is a highly lipophilic compound with a triazole stmcture. Compared to ketoconazole, itraconazole has a broader spectmm (including yispergillus spp.) (29,30) and an in vitro activity that is 10 times higher than ketoconazole for most species. 

Lindane is one of eight different hexachlorocyclohexane (HCH), C H Cl, isomers and its Chemical Abstract n.2cniQ is la, 2a 3P, 4a, 5a 6P-hexachlorocyclohexane [58-89-9] (y-HCH or y-BHC, ben2ene hexachloride) (80). Commercial products containing lindane are marketed as either a mixture of isomers or as the pure y-BHC isomer. Not unexpectedly, lindane is a highly stable lipophilic compound and it has been used extensively worldwide as an insecticide. In contrast, hexachloropentadiene, C Cl, is an extremely reactive industrial intermediate used as a chemical intermediate in the synthesis of a broad range of cyclodiene-derived pesticides, which include endosulfan, endrin, heptachlor, and several different organohalogen flame retardants (81). 

The metabolism of foreign compounds (xenobiotics) often takes place in two consecutive reactions, classically referred to as phases one and two. Phase I is a functionalization of the lipophilic compound that can be used to attach a conjugate in Phase II. The conjugated product is usually sufficiently water-soluble to be excretable into the urine. The most important biotransformations of Phase I are aromatic and aliphatic hydroxylations catalyzed by cytochromes P450. Other Phase I enzymes are for example epoxide hydrolases or carboxylesterases. Typical Phase II enzymes are UDP-glucuronosyltrans-ferases, sulfotransferases, N-acetyltransferases and methyltransferases e.g. thiopurin S-methyltransferase. 

Proton Pump Inhibitors and Acid Pump Antagonists retinoid X receptor (RXR) and is also activated by various lipophilic compounds produced by the body such as bile acids and steroids. PXR heterodimerized with RXR stimulates the transcription of cytochrome P450 3A monooxygenases (CYP3A) and other genes involved in the detoxification and elimination of the... 

The available evidence indicates that endosulfan can be metabolized in animals to other lipophilic compounds, which can rapidly enter tissues, and to more hydrophilic compounds that can be excreted. 

It is a lipophilic compound which removes intercellular lipids that are covalently linked to the cornified envelope surrounding epithelial cells [3]. It also enhances penetration of other agents. Resorcinol (m-dihydroxy benzene) is structurally and chemically similar to phenol. It disrupts the weak hydrogen bonds of keratin [4]. Lactic acid is an alpha hydroxy acid which causes corneocyte detachment and subsequent desquamation of the stratum corneum [5]. 

Salicylic acid (ortho hydroxybenzoic add) is a beta hydroxy acid agent. It is a lipophilic compound which produces desquamation of the stratum corneum via removal of intercellular lipids [3] (see salicylic acid section). Given its keratolytic effects, it has become an increasingly popular superficial peeling agent. Salicylic acid peels induce injury via thinning or removal of the stratum corneum. In addition, salicylic acid potentially enhances the penetration of TCA. 

After uptake, lipophilic pollutants tend to move into hydrophobic domains within animals or plants (membranes, lipoproteins, depot fat, etc.), unless they are biotransformed into more polar and water soluble with compounds having low Metabolism of lipophilic compounds proceeds in two stages ... 

Excretory processes for xenobiotics are best understood for mammals, with far less work having been done on birds, reptiles, and amphibians. Highly lipophilic compounds show little tendency to be excreted unchanged. In the absence of effective metabolism, they tend to have very long biological half-lives in depot fat. Thus, half-lives of about 1 year have been reported for p,p -DDE in birds, whereas higher... 

Principal Mechanisms of Uptake and Loss for Lipophilic Compounds... 

The following ranges of half-lives have been reported for vertebrate species, which are presumably related to rates of biotransformation as the original lipophilic compounds show little tendency to be excreted unchanged. 

Muramyl dipeptide derivatives have also been microencapsulated in lactide/glycolide copolymers for use alone as an immuno potentiator. L-lactide/glycolide copolymers were used to deliver MDP-B30, a lipophilic compound, from very small microspheres (less than 5 pm in diameter). The amount of MDP-B30 required for tumor growth inhibitory activity of mouse peritoneal macrophages was 2000 times less for the controlled release MDP-B30 microspheres than for the unen-capsulated drug (134). 

In addition to encapsulation within the aqueous phase of vesicles, amphiphilic and lipophilic compounds can interact with the bilayer. 

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