Lipoidal solubility

It is generally agreed that the contact-insecticidal activity of the DDT type of compound depends on at least one toxic component and the CC13 group or some other lipoid-soluble group for penetration. Beyond this point, there is a lack of agreement as to the exact mechanism by which the contact insecticides exert their action. 

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... 

It must be able to enter the sap by diffusion through the leaf or root cuticle. Hence some degree of lipoid solubility is desirable. Larger molecular size will be disadvantageous. 

Figure 15. Relationship between peripheral a-adrenoceptor activity, lipoid solubility, and centrally mediated cardiodepressor activity. Abscissa natural logarithms of the product of relative activity on peripheral a-adrenoceptors as derived from blood pressure decreases in spinal rats multiplied by percentage of distribution between octanol/buffer (Figure 4). Ordinate natural logarithms of the relative CNS activity as derived from bradycardia test in vagotomized...

A passage of the blood-brain barrier has, however, not to be expected due to their polarity and molecular size. Due to the particular structure of the brain capillaries only lipoid-soluble low molecular substances are able to enter the brain vessels from the blood. This fact is called the blood-brain or blood-liquor barrier which indeed cannot be overcome by polymers but by free low-molecular active substances like mezcalin or aminoantipyrine. 

Together with sorbic acid, benzoic acid also acts as a membrane perturbing agent (Hazan, Levine, and Abeliovich, 2004). Disruption of the OM by organic acids involves the action of dissociated as well as undissociated forms (Alakomi et al., 2000). High lipoid solubility and the ability to form membrane polar/hydrogen unions are responsible for benzoic interaction with cell membranes and the modification of membrane properties (Otero-Losada, 2003). 

The compound 2,2-bis(p-fluorophenyl)-l,l,l-trichloroethane (DFDT, 17) prepared by the condensation of chloral and fluorobenzene is, like DDT, a compound of high lipoid solubility. It is rarely used in plant protection, but rather against flies and lice. Its use is rather restricted, mainly owing to the high price of fluorobenzene (Bradlow and Vanderwerf, 1947). 

If the chlorine atoms of the trichloromethyl group are gradually exchanged by fluorine atoms, the lipoid solubility of the compound and, at the same time, its... 

McCallan and Wilcoxon (1936) were the first to report that fungal spores can solubilise copper. In the bathing medium of Neurospora sitophilus spores they detected malic acid and certain amine acids which were able to dissolve copper even from dry deposits of Bordeaux mixture. In this case, complex compounds of the copper(II) ions are formed and, as shown already by the investigations of Bodnar and Terenyi (1930), the fungicidal action of copper(II) complexes proved to be superior to that of copper(II) ions. Horsfall et al. (1937) made similar observations. This phenomenon can be explained by the much higher lipoid solubility of copper(II) complexes (Horsfall, 1957 Durkee, 1958) which allows them to penetrate the cell more easily. They dissociate in the cell, and copper(II) ions are liberated. Thus, complex-forming compounds seem to aid the transport of the... 

Powell (1946) and Mason (1948) found that the 2 1 complex of 8-hydroxyquinoline with copper, oxine-copper, has a stronger fungicidal action than 8-hydroxyquinoline. Albert et al. (1953) attributed this to the fact that the organic part of the compound makes copper lipoid-soluble and thus accelerates its penetration into the cell. Inside the cell the 2 1 complex dissociates into a 1 1 complex and free 8-hydroxyquinoline. The active toxic agent is the ionised 1 1 complex of nonlipoid properties, which reacts with the enzymes in the fungus and blocks their function. This theory is also supported by the research work of McNew and Gershon (1969). 

In addition to solubility in water, the lipoid solubility and basicity of the compound play important roles in the development of action, the former influencing uptake through the leaves, the latter colloidal adsorption by the soil. These properties also determine the mode of application of each compound, that is, whether it is applied pre- or postemergence. 

Crystals, mp 50, bp0J 160-162. Possesses water and lipoid solubility. LDm orally in rats 62 mg/kg, E. W. Schafer, Toxicol. AppL Pharmacol 21, 315 (1972). 

Among the booster explosives, we find trinitrophenylmethylnitramine, commonly called tetryl or tetralite. An outstanding example of an alkylated compound in the field of flavors is vanillin. Alkylation plays a striking part in the preparation of hypnotics, e.g., barbital (Veronal), pheno-barbital (Luminal), and Amytal, rendering them lipoid-soluble. 

Introduction of a lipophilic functional moiety at C-3 position renders a marked and pronounced enhaneement in the diuretic potency. For instance aralkyl, haloalkyl, or thioether substitution, enhanees the lipoidal solubility of the moleeule to a eonsiderable extent thereby produeing eompounds with a much longer duration of aetion. 

The lowering of the lipoidal solubility eharacteristic feature in the drug molecule still retained an effeetive Hj-antagonism peripherally. It also drastically squeezed in the t 2 to 1.7 hours only when eompared to 4.6 hours for the parent molecule tripolidine. 

It is, however, pertinent to state here that even though sulphanilamide has sufficient lipid solubility (10.5%) to cross the bacterial membrane, 99.7% of the total available molecules would usually remain in the molecular (inactive) state once inside. Based on the above statement of facts the existing difference in the lipoidal solubility between the two aforesaid drugs would certainly permit the scope of prediction that sulfadiazine should possess a distinct longer biological half-life. 

Antidotal substances with higher lipoid solubility, which penetrate the CNS more readily, might be expected to have greater antidotal activity, since some of the more severe effects of ChE inhibitor poisoning (such as apnea and seizures) are mediated in the CNS. 

Among the three 2-halo-acetamides, chloro-, bromo- and iodo-acetamide, 2-chloracetamide is the one with the lowest antimicrobial efficacy, although because of the high electronegativity of the chloro atom, it is the more reactive compound. But its lipoid solubility is much lower than that of bromo- and iodo-acetamide. Comparison data of the three 2-halo-acetamides are listed in Table 76. Nevertheless 2-chloracetamide only has gained significant importance as a preservative for the protection of aqueous functional fluids because of its good water solubility and in consequence its favourable partition coefficient. 

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