Monohydroxylation and esterification as determinants of the effects of cis- and trans-9-octadecenoic acids on the permeation of hydrocortisone and 5-fluorouracil across hairless mouse skin in vitro

The effects of cis-9-octadecenoic acid (oleic acid) and of a group of chemically related cis- (ricinoleic acid) and trans- (ricinelaidic acid) 12-monohydroxylated derivatives and their corresponding ethyl and methyl esters on the skin permeation of model hydrophobic (hydrocortisone, log K=1.61) and hydrophilic (5-fluorouracil, log K=-0.89) drugs was investigated in vitro using excised hairless mouse skin. Drug solutions were prepared in propylene glycol, with and without the addition of a fatty acid to a level of 5%. Whereas the addition of oleic acid markedly enhanced the transdermal flux of both drugs relative to a sample in propylene glycol alone (hydrocortisone approximately 1800-fold; 5-fluorouracil approximately 330-fold), that of a cis- or trans-12-monohydroxylated analog of oleic acid resulted in only a small increase (1.4-2.7-fold for hydrocortisone; 4.4-6.6-fold for 5-fluorouracil). On the other hand, the methyl and ethyl esters of cis- and trans-12-hydroxy-9-octadecenoic acid exerted a much greater enhancing effect (327-720-fold for hydrocortisone, 42-74-fold for 5-fluorouracil) than the corresponding parent fatty acids. Furthermore, whereas the ethyl esters were found to have a greater effect on the skin permeation of hydrocortisone than the methyl esters, the reverse was true with regards to 5-fluorouracil. Additionally, the esters of trans-12-hydroxy-9-octadecenoic acid promoted permeation to an extent comparable to that achieved with their cis-counterparts.     

Enhancing effects of medium chain aliphatic alcohols and esters on the permeation of 6-carboxyfluorescein and indomethacin through rat skin

Medium chain aliphatic alcohols (C8-C12) and methyl or propyl esters of medium chain fatty acids (C8-C12) enhanced the permeation of 6-carboxyfluorescein (6-CF) and indomethacin (IND) through excised rat skin. The enhancing effects of the aliphatic alcohols for 6-CF and IND decreased with the increase in carbon chain length. The dependence on the carbon chain length was different from that exhibited by medium-chain fatty acids previously reported. In the case of fatty acid esters, the enhancing effects were lower than those of aliphatic alcohols and fatty acids. The relationship between the enhancing effects and the total number of carbon atoms in the esters was different for 6-CF and IND. The dependence on the total number of carbon atoms was similar to that in the aliphatic alcohols for 6-CF, and greater effects were observed in the shorter esters. On the other hand, no definite trends were observed for IND. Although the relationships between the structure and skin permeation-enhancing effect of the aliphatic alcohols and fatty acid esters used in this study are not yet fully understood, they are possible candidates as permeation enhancers for hydrophilic and lipophilic drugs. Further experiments, including examination of the location and environment of the lipophilic carbon chain and hydrophilic groups of such enhancers in the stratum corneum, are needed to optimize transdermal delivery systems containing them.     

Enhancing Effects of Medium Chain Aliphatic Alcohols and Esters on the Permeation of 6-Carboxyfluorescein and Indomethacin through Rat Skin

Medium chain aliphatic alcohols (C8-C12) and methyl or propyl esters of medium chain fatty acids (C8-C12) enhanced the permeation of 6-carboxyfluorescein (6-CF) and indomethacin (IND) through excised rat skin. The enhancing effects of the aliphatic alcohols for 6-CF and IND decreased with the increase in carbon chain length. The dependence on the carbon chain length was different from that exhibited by medium-chain fatty acids previously reported. In the case of fatty acid esters, the enhancing effects were lower than those of aliphatic alcohols and fatty acids. The relationship between the enhancing effects and the total number of carbon atoms in the esters was different for 6-CF and IND. The dependence on the total number of carbon atoms was similar to that in the aliphatic alcohols for 6-CF, and greater effects were observed in the shorter esters. On the other hand, no definite trends were observed for IND. Although the relationships between the structure and skin permeation-enhancing effect of the aliphatic alcohols and fatty acid esters used in this study are not yet fully understood, they are possible candidates as permeation enhancers for hydrophilic and lipophilic drugs. Further experiments, including examination of the location and environment of the lipophilic carbon chain and hydrophilic groups of such enhancers in the stratum corneum, are needed to optimize transdermal delivery systems containing them.     

Comparative bioavailability of eicosapentaenoic acid and docasahexaenoic acid from triglycerides, free fatty acids and ethyl esters in volunteers

Comparative Bioavailability of Eicosapentaenoic Acid and Docosahexaenoic Acid from Triglycerides, Free Fatty Acids and Ethyl Esters in Volunteers. The bioavailability of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from triglycerides, free fatty acids and ethyl esters was investigated in 8 female volunteers in a randomized triple cross-over trial with baseline control. EPA/DHA was administered in capsules in form of triglycerides (1.68/0.72 g), free fatty acids (1.35/1.065 g) and ethyl esters (1.86/1.27 g). The resulting EPA/DHA plasma levels were determined and evaluated. The mean relative bioavailability of EPA/DHA compared to triglycerides was 186/136% from free fatty acids and 40/48% from ethyl esters. Maximal plasma levels were about 50% higher with free fatty acids and about 50% lower with ethyl esters as compared to triglycerides. The tolerability of the free fatty acids was much worse than that of triglycerides and ethyl esters. The main side effect was eructation.     

Possible involvement of long chain fatty acids in the spores of Ganoderma lucidum (Reishi Houshi) to its anti-tumor activity

During our isolation of biologically active substances from the spores of Ganoderma lucidum (Reishi Houshi, G. lucidum) guided by the inhibitory activity on HL-60 cell proliferation, NMR spectroscopic and mass spectrometric data indicate the substance contains a mixture of several long chain fatty acids. Hence, in this study, we have examined the inhibitory effects of an ethanolic extract of the spores of G. lucidum as the spore extract, on the proliferation of various human cancer cell lines by comparison with several authentic long chain fatty acids. Of the fatty acids we examined nonadecanoic acid (C19:0) showed the highest inhibitory activity for HL-60 cell proliferation with IC(50) values of 68+/-7 microM followed by heptadecanoic acid (C17:0, 120+/-23 microM), octa- (C18:0, 127+/-4 microM) and hexadecanoic acids (C16:0, 132+/-25 microM), respectively. The corresponding unsaturated fatty acids containing one double bond such as cis-10-nonadecenoic acid (C19:1), cis-9-octadecenoic acid (C18:1), cis-10-heptadecenoic acid (C17:1) and cis-9-hexadecenoic acid (C16:1) were less effective. The ethanolic extract of spores of G. lucidum were shown by annexin-V FITC/PI double staining to induce apoptosis of HL-60 cells in a similar way to cis-10-nonadecenoic acid (C19:1). These unsaturated fatty acids probably inhibit tumor necrosis factor production induced by lipopolysaccharide in a mouse macrophage preparation. Our results suggest the spores of G. lucidum contain 19-carbon fatty acids as one of the components for characteristics of its physiological effects.     

Formation of fatty acid ethyl esters during chronic ethanol treatment in mice

Ethyl esters of long-chain fatty acids are formed in the liver and brain of mice after 1-6 days of ethanol intoxication. This observation extends the reports of Lange and co-workers who detected these compounds as unusual metabolites of ethanol in human tissues [E. A. Laposata and L. G. Lange, Science 231, 497 (1986)]. Ethyl esters of oleic and linoleic acids, and, in smaller amounts, ethyl esters of palmitic and stearic acids were found in the livers of mice that had been treated with ethanol by inhalation. In the brain, only the esters of unsaturated fatty acids were found, in lower amounts than in liver. All the fatty acid ethyl esters seemed to have reached steady-state levels in the tissues after 3 or 4 days of alcohol treatment. When incorporated into synaptosomal plasma membranes in vitro, in intramembrane concentrations estimated to resemble those observed in the mice, these esters reduced the fluorescence anisotropy, i.e. they disordered the membranes.     

Composition of the lipophilic fraction of stinging nettle (<Emphasis Type="Italic">Urtica dioica</Emphasis> L. and <Emphasis Type="Italic">U. urens</Emphasis> L.) homeopathic matrix tinctures

The composition of lipophilic fractions of homeopathic matrix tinctures of Urtica dioica L. (I) and U. urens L. (II) derived from freshly collected plants and dried (desiccated) material (herb and roots) was studid using GC-MS techniques. The analyses of n-hexane extracts of tincture I revealed 43 compounds (of which 27 were identified) whereas the analysis of the extract of tincture II revealed 28 compounds (21 identified). The extract from I contains fatty acids in the form of ethyl esters, terpenoids (apiol, eugenol), squalene, and some other substances. The main fatty acids are palmitic, linolenic, and nonadecanoic. Tincture of I obtained from a desiccated raw material contains ethyl esters of linoleic and 2,3-benzofurandicarboxylic acids, which are not found in II. Tincture obtained from freshly collected material contains greater amounts of ethyl esters of oleic, 9-oxononanoic, 4-hydroxy-3-methoxybenzoic acids, 3-ethyl-4-methyl-(1H)-pyrrol-2,5-dione, 5,6,7,7a-tetrahydro-2(4H)-benzofuranone, and eugenol. The extract of tincture II contains significant amounts of palmitic, linoleic, and linolenic acids and 3,7,11,15-tetramethyl-2-hexadecen-1-ol. Some of the identified substances, including ethyl esters of heptadecenoic, arachic, 8,11-eicosadienoic, heneicosanoic, and behenic acids were detected only in the tincture from dried (desiccated) raw material. The lipophilic fraction of matrix tinctures from U. dioica root contain large amounts of linoleic, linolenic, and nonadecanoic acids and their isomers in addition to palmitic, myristic, 9-oxononanoic, and pentadecanoic acids. The content of identified components was greater in the tinctures from freshly collected material (except for squalene, the concentration of which increases by a factor of about four in the tincture prepared from desiccated material). Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 42, No. 12, pp. 26–29, December, 2008.     

Fatty acid amide hydrolase, an enzyme with many bioactive substrates. Possible therapeutic implications

During the last eight years a number of bioactive lipid mediators, the amides or esters of long chain fatty acids, have been discovered or re-discovered. These are: anandamide (N-arachidonoyl-ethanolamine, AEA) and 2-arachidonoylglycerol (2-AG), two endogenous agonists of cannabinoid receptors; oleamide (cis-9-octadecenoamide), a putative endogenous sleep-inducing factor; N-palmitoylethanol amine (PEA), a compound with promising anti-inflammatory and immune-modulatory activity. These compounds are all substrates for the same hydrolytic enzyme, fatty acid amide hydrolase (FAAH), whose molecular characterization was obtained in 1996. The molecular and enzymatic properties, tissue distribution, substrate recognition properties, physiological regulation and biological role of FAAH are discussed in this article, with special emphasis on the possible pharmacological manipulation of the activity of this enzyme with therapeutic purpose.     

Synthesis and hypolipidaemic evaluation of a series of alpha-asarone analogues related to clofibrate in mice

A series of alpha-asarone analogues related to clofibrate, containing an acetic acid group at C-2 of the aromatic ring, has been prepared as the acids or as the ethyl and methyl esters. The corresponding alcohols were also synthesized by reduction of the ethyl esters. The compounds were examined in hyperlipidaemic male mice to evaluate their ability to modify serum lipoprotein cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides after oral administration of 40 and 80 mg kg(-1) for 6 days. Except for methyl 2-methoxy-5-nitro-4-(2-propenyl)phenoxyacetate at either dose, these clofibrate-related phenoxyacetic acid derivatives were found to have significant hypocholesterolaemic activity. Levels of low-density lipoprotein cholesterol and triglycerides were significantly reduced and those of high-density lipoprotein cholesterol were elevated. 2-Methoxy-5-nitro-4-(2-propenyl)phenoxyacetic acid was active at both doses in all the tests. Clofibrate (150 mg kg(-1)) was more potent at reducing low-density lipoprotein cholesterol. No activity was detected for the alcohol derivatives. These preliminary results suggest that this class of compound might have more promise as potential hypolipidaemic agents than other alpha-asarone derivatives. Further investigation and characterization should be performed to determine the mode of action of these agents on lipid metabolism.     

Acute toxicity of fatty acids to the freshwater green alga Selenastrum capricornutum

The acute toxicity of fatty acids (C14 to C18) commonly found in wood was determined by the standard algal growth inhibition test using the freshwater green alga Selenastrum capricornutum. Toxicity, quantified as IC50 values, varied depending on the number of total carbons and double bonds. Of the tested acids, oleic (cis-9-octadecenoic) acid showed the highest toxicity (72-h IC50 = 0.47 mg/L) to the alga, and triolein, a triglyceride of oleic acid, showed no apparent toxicity. Further examination of a series of C18:1 acids with a double bond at the 6, 11, or 12 position revealed that both double-bond position and cis or trans configuration affected toxicity. The 72-h IC50 data for these fatty acids and related compounds seemed to correlate well with the melting point (mp), showing two separate linear relationships: at mp < 35 degrees C toxicity increased with increasing melting point, and at mp > 40 degrees C toxicity decreased with melting point.     

Structure-activity studies of carbamate and other esters: agonists and antagonists to nicotine

A number of aromatic, cycloalkyl, and heterocyclic carbamic acid esters, thiocarbamic acid esters, and carboxylic acid esters of di- and trial-kylaminoalkyl and heterocyclic amino alcohols have been synthesized and tested for their pharmacologic and receptor binding characteristics at the nicotine receptor. Receptor binding was measured in rat brain membranes using (-)-3H-nicotine or 3H-methylcarbamylcholine as radioligands. The compounds were tested for their ability to produce seizures and prostration and to antagonize the nicotine-induced prostration and seizures as well as the hypertensive action of nicotine in rats. Among the potent agonists were the N-methylcarbamyl and N-methylthiocarbamyl esters of choline (trimethylaminoethanol), with the tertiary amino derivatives between considerably less potent than the quaternary. Potent antagonists included trimethylaminoethyl benzoate, 3-quinuclidinyl benzoate, and trimethylaminoethyl esters of phenyl and phenylthiocarbamic acids. One of the most potent antagonists to nicotine was alpha-lobeline.     

Toxicity of epoxy fatty acids and related compounds to cells expressing human soluble epoxide hydrolase

Soluble epoxide hydrolase (sEH) is suggested to alter the mode of action and increase the toxic potency of fatty acid epoxides. To characterize the structural features necessary for sEH-dependent epoxy fatty acid toxicity, 75 aliphatic compounds were assayed for cytotoxicity in the presence and absence of sEH. Three groups of aliphatic epoxide-diol pairs were described by their observed differential toxicity. Group I compounds were typified by terminal epoxides whose toxicity was reduced in the presence of sEH. Group II compounds were toxic in either their epoxide or diol form, but toxicity was unaffected by sEH. Group III compounds exhibited sEH-dependent toxicity and were therefore used to investigate the structural elements required for cytotoxicity in this study. The optimal structure for group III compounds appeared to be a fatty acid 18-20 atoms long (e.g., a carbon backbone plus a terminal heteroatom) with an epoxide positioned between C-7 and C-12. In the absence of sEH, replacement of epoxides with a vicinal diol was required for toxicity. While diol stereochemistry was unimportant, vicinal diol-induced toxicity exhibited fewer positional constraints to toxicity than sEH-dependent epoxide toxicity. Tested fatty acids and esters with neither an epoxide nor a vicinal diol were not toxic. These data support the hypothesis that long-chain epoxy fatty acid methyl esters are potential pro-toxins metabolized by sEH to more toxic diols. Furthermore, our results suggest that the endogenous compounds, leukotoxin methyl ester, 9,10(Z)-epoxyoctadec-12(Z)-enoic acid methyl ester, and isoleukotoxin methyl ester, 12, 13(Z)-epoxyoctadec-9(Z)-enoic acid methyl ester, are structurally optimized to elicit the observed effect.     

Antifungal properties of halofumarate esters

Alkyl esters (C1--C4) of the four halofumaric acids were tested for antifungal activity against Candida albicans, Aspergillus niger, Mucor mucedo, and Trichophyton mentagrophytes at pH 5.6 and 7.0 in the absence and presence of 10% beef serum in Sabouraud dextrose agar. The most toxic compound to each organism was: C. albicans, ethyl iodofumarate (0.054 mmole/liter); A. niger, methyl bromofumarate (0.090 mmole/liter); M. mucedo, methyl fluorofumarate (0.037 mmole/liter); and T. mentagrophytes, ethyl iodofumarate (0.020 mmole/liter). The order of overall activity of the six most toxic compounds was: ethyl iodofumarate greater than ethyl chlorofumarate greater than methyl iodofumarate = methyl bromofumarate greater than methyl chlorofumarate greater than bromofumarate.     

Omega-3 fatty acid preparations--a comparative study

Fifteen food supplements and 1 medicine, formulated as soft capsules and containing omega-3 fatty acids, were evaluated with different tests, including desegregation, determination of the anisidine and peroxide values and assay of the omega-3 acids according to the European Pharmacopoeia. All the products contained purified fish oil rich in omega-3 fatty acids, mainly eicosapentaenoic acid (C20:5; EPA) and docosahexaenoic acid (C22:6; DHA), and available as triglycerides, ethyl esters or free fatty acids. The medicinal product complied with the fixed requirements whereas 7 of the 15 food supplements deviated from 1 or more of the criteria with regard to the peroxide value and the content of 1 or more of the fattty acids.     

Negative Ames tests of epoxide fatty methyl esters derived from hemolysis of linoleic acid hydroperoxides

Five isomeric epoxyhydroxyene and epoxyoxoene fatty esters derived from hemolytic decomposition of linoleic acid hydroperoxide were tested for mutagenicity by the "Ames' top-agar incorporation method using S-9 mix derived from livers of male rats pretreated with Aroclor 1254. The epoxide fatty esters tested--methyl trans-12,13-epoxy-erythro-11-hydroxy-cis(trans)-9-octadecenoate and methyl trans-12,13-epoxy-threo-11-hydroxy-cis(trans)-9-octadecenoate (each composed of approximately 80% cis-9-ene and 20% trans-9-ene), methyl trans-12,13-epoxy-9-oxo-(trans-10-octadecenoate, methyl trans-12,13-epoxy-9-hydroxy-trans-10-octadecenoate and methyl cis-12,13-epoxy-9-oxo-trans-10-octadecenoate--had structural characteristics similar to certain potent mutagens. However, these esters were not mutagenic in Salmonella typhimurium strains TA100, TA98 or TA1537 at concentrations up to 2000 micrograms/test plate. Under the same test conditions, the methyl ester of hydroperoxy linoleic acid, from which these epoxides were derived, was weakly mutagenic in strain TA100 and possibly also in strain TA98.     

Fluorinated retinoic acids and their analogues. 1. Synthesis and Biological activity of (4-methoxy-2,3,6-trimethylphenyl)nonatetraenoic acid analogues.

(4-Methoyx-2,3,6-trimethylphenyl)nonatetraenoic acids, esters, and amides (analogues of retinoic acid) bearing a fluorine atom(s) or a trifluoromethyl group on the polyene side chain were synthesized. The biological activities of these compounds and of 10-, 12-, and 14-fluororetinoic acid esters were evaluated in vivo in a chemically induced mouse papilloma test; the toxicities were assessed in an in vivo mouse hypervitaminosis A test. Antipapilloma activity greater than the parent nonfluorinated ester was found for 1c (ethyl 12-fluororetinoate) and 23 and 39 (aromatic 4- and 6-fluororetinoid esters, respectively). A similar increase in antipapilloma activity was observed for 71 and 72, the aromatic 4- and 6-fluororetinoic acids, respectively, relative to 2 and for 73 (aromatic 4-fluororetinoid amide) relative to 4.     

Synergistic antiviral effect of xanthates and ionic detergents

Xanthate compounds have been shown to exhibit antiviral activity against various DNA and RNA viruses under acidic pH conditions. It is now possible to utilize the unique broad range antiviral spectrum of these compounds under physiological pH conditions (pH 7.4) by simultaneous administration of certain ionic detergents. When used in conjunction with tricyclodecan-9-yl-xanthate (D609), sodium deoxycholate, sodium dodecylsulfate and certain fatty acids, which have no antiviral activity of their own, inhibit the replication of various DNA and RNA viruses (such as herpes simplex, vesicular stomatitis and Coxsackie B 4) in vitro at pH 7.4. Among saturated fatty acids of various chain lengths there was a marked size restriction in that the efficiency of undecanoic acid (11 C atoms) was three orders of magnitude greater than that of shorter (6 C atoms) or longer (18 C atoms) monocarbonic acids. Dose-response kinetics revealed a synergistic interaction between the xanthate and the monocarbonic acid. A dose that inhibited the replication of herpesvirus by a factor of 1000 still permitted mitotic activity in uninfected growing control cultures.     

Antipyretic activity of new compounds 4-(3-oxo-1,2-benzisothiazolin-2-yl)phenylalkanoic acids, their esters, amides and 1,1-dioxide derivatives

Antipyretic activity of new compounds, 4-(3-oxo-1,2-benzisothiazolin-2-yl)phenylalkanoic acids, their esters, amides and 1,1-dioxide derivatives has been studied. The acid compound of the benzoic series (I:a), tested at graded doses, exerted a noticeable antipyretic action; it had two times the "potency" of benzisothiazolone but an almost equal "efficacy". Its "potency" however was not proportional to the development of gastric lesions and to the acute toxicity. A decreased pharmacological activity has been observed in phenylalkanoic acids in the following order: R = COOH greater than CH2COOCH greater than CH(CH3)COOH greater than CH(C2H5)COOH, probably due to their increasing lipophilic character. By contrast among 1,1-dioxide derivatives the most effective in preventing pyrogen-induced fever was the ethyl ester (V:c) of benzoic series which appeared to be as active as paracetamol. The interest arising from these observations is here after discussed.     

Activation of carboxylic acids by pyrocarbonates

Activation of carboxylic acids was achieved via dialkyl pyrocarbonates (ROCO₂O, R= C₂H₅, i-C₃H₇, sec-C₄H₉, tert.-C₄H₉) in aprotic solvents in the presence tertiary amines. A convenient procedure for the preparation of carboxylic acid anhydrides from carboxylic acids and di-tert.-butyl pyrocarbonate in the presence of pyridine is reported. Analogously, di-isopropyl- or diethyl pyrocarbonate may be used in the presence of N-methylmorpholine (triethylamine). With pyridine, di-isopropyl- or diethyl pyrocarbonate carboxylic acids form isopropyl- or ethyl esters, respectively. A wide variety of esters were prepared in good yields in a one-pot procedure from carboxylic acids, including N-protected amino acids, and alcohols or from phenols by means of di-tert.-butyl pyrocarbonate in the presence of pyridine (Boc₂O-pyridine system). t-Butyl esters of carboxylic acids were obtained by the same procedure with 4-dimethylarninopyridine. In the absence of carboxylic acid, with 4-dimethylaminopyridine Boc₂O and alcohols generate alkyl tert.-butyl carbonates.