Synthesis and Anticancer Activity of New 1-Thia-4-azaspiro[4.5]decane, Their Derived Thiazolopyrimidine and 1,3,4-Thiadiazole Thioglycosides

New 1-thia-azaspiro[4.5]decane derivatives, their derived thiazolopyrimidine and 1,3,4-thiadiazole compounds were synthesized. The thioglycoside derivatives of the synthesized (1,3,4-thiadiazolyl)thiaazaspiro[4.5]decane and thiazolopyrimidinethione compounds were synthesized by glycosylation reactions using acetylated glycosyl bromides. The anticancer activity of synthesized compounds was studied against the cell culture of HepG-2 (human liver hepatocellular carcinoma), PC-3 (human prostate adenocarcinoma) and HCT116 (human colorectal carcinoma) cell lines and a number of compounds showed moderate to high inhibition activities.

In-vitro anticancer and antimicrobial activities of PLGA/silver nanofiber composites prepared by electrospinning

In the present work, a series of 0, 1 and 7 wt% silver nano-particles (Ag NPs) incorporated poly lactic-co-glycolic acid (PLGA) nano-fibers were synthesized by the electrospinning process. The PLGA/Ag nano-fibers sheets were characterized using SEM, TEM and DSC analyses. The three synthesized PLGA/silver nano-fiber composites were screened for anticancer activity against liver cancer cell line using MTT and LDH assays. The anticancer activity of PLGA nano-fibers showed a remarkable improvement due to increasing the concentration of the Ag NPs. In addition to the given result, PLGA nano-fibers did not show any cytotoxic effect. However, PLGA nano-fibers that contain 1 % nano silver showed anticancer activity of 8.8 %, through increasing the concentration of the nano silver to 7 % onto PLGA nano-fibers, the anticancer activity was enhanced to a 67.6 %. Furthermore, the antibacterial activities of these three nano-fibers, against the five bacteria strains namely; E.coli o157:H7 ATCC 51659, Staphylococcus aureus ATCC 13565, Bacillus cereus EMCC 1080, Listeria monocytogenes EMCC 1875 and Salmonella typhimurium ATCC25566 using the disc diffusion method, were evaluated. Sample with an enhanced inhibitory effect was PLGA/Ag NPs (7 %) which inhibited all strains (inhibition zone diameter 10 mm); PLGA/Ag NPs (1 %) sample inhibited only one strain (B. cereus) with zone diameter 8 mm. The PLGA nano-fiber sample has not shown any antimicrobial activity. Based on the anticancer as well as the antimicrobial results in this study, it can be postulated that: PLGA nanofibers containing 7 % nano silver are suitable as anticancer- and antibiotic-drug delivery systems, as they will increase the anticancer as well as the antibiotic drug potency without cytotoxicity effect on the normal cells. These findings also suggest that Ag NPs, of the size (5-10 nm) evaluated in the present study, are appropriate for therapeutic application from a safety standpoint.

Synthesis, tumor inhibitory and antioxidant activity of new polyfunctionally 2-substituted 5,6,7,8-tetrahydronaphthalene derivatives containing pyridine, thioxopyridine and pyrazolopyridine moieties

2-Acetyl-5,6,7,8-tetrahydronaphthalene (1) was allowed to react with different aromatic aldehydes to produce the cyanopyridones 2a and 2b, which were treated with phosphorous pentasulfide to afford the corresponding thioxopyridine derivatives 3a and 3b, respectively. The reaction of 3a and 3b with ethyl bromoacetate afforded the ester derivatives 4a and 4b, while their condensation with hydrazine hydrate gave the corresponding pyrazolopyridine derivatives 5a and 5b. The reaction of the precursor 2-amino-5,6,7,8-tetrahydronaphthalene (6) with ethoxy methylenemalonic ester led to the formation of aminomethylenemalonate derivative 7. Cyclization of 7 in boiling diphenyl ether gave the derivative - ethyl 6,7,8,9-tetrahydro-4-hydroxybenzo[g]-quinoline-3-carboxylate (8) which was hydrolyzed to produce the corresponding carboxylic acid analogue 9. Further reaction of 3a with 3-chloropropane-1,2-diol and/or iodomethane produced the corresponding nicotinonitrile derivatives 10 and 11. Hydrazinolysis of derivative 11 gave the hydrazinyl derivative 12. Moreover, chlorination of compound 2a with phosphorous oxychloride led to 2-chloro nicotinonitrile derivative 13, which was refluxed with various amines to form the corresponding derivatives 5a, 14 and 15. Treatment of the pyrazolopyridine compound 5a with formic acid and acetic anhydride afforded the corresponding formamide and acetamide analogues 16 and 17, while its reaction with DMF-DMA yielded the corresponding formimidamide derivative 18. The pyridopyrazolo[1,5-a]pyrimidine derivative 19 was obtained by cyclization of 5a with acetyl acetone. The antioxidant activity evaluation of the newly synthesized compounds showed that the pyrazolopyridine derivative 5a exhibited scavenging potency higher than that obtained by ascorbic acid. Tumor inhibitory activity screening revealed that derivatives 8 and 10 showed promising potency against the liver cancer cells (HepG-2) compared to doxorubicin as a reference drug.

Chemical and antioxidant investigations: Norfolk pine needles (Araucaria excelsa)

Chemical investigations from a foliar extract of Araucaria excelsa (Lamb.) (Araucariaceae) resulted in the identification of seven phenolic metabolites including one flavananol, one flavananol 3-O-glycoside, four C-glycoside flavonoids, and one phenolic acid. Structures were elucidated by spectral determination including: UV, NMR and MS analysis. Moderate antioxidant activity was observed with a 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay in comparison with the reference antioxidant ascorbic acid.

Human cytochrome p450 enzymes of importance for the bioactivation of methyleugenol to the proximate carcinogen 1'-hydroxymethyleugenol

In vitro studies were performed to elucidate the human cytochrome P450 enzymes involved in the bioactivation of methyleugenol to its proximate carcinogen 1'-hydroxymethyleugenol. Incubations with Supersomes, expressing individual P450 enzymes to a high level, revealed that P450 1A2, 2A6, 2C9, 2C19, and 2D6 are intrinsically able to 1'-hydroxylate methyleugenol. An additional experiment with Gentest microsomes, expressing the same individual enzymes to roughly average liver levels, indicated that P450 1A2, 2C9, 2C19, and 2D6 contribute to methyleugenol 1'-hydroxylation in the human liver. A study, in which correlations between methyleugenol 1'-hydroxylation in human liver microsomes from 15 individuals and the conversion of enzyme specific substrates by the same microsomes were investigated, showed that P450 1A2 and P450 2C9 are important enzymes in the bioactivation of methyleugenol. This was confirmed in an inhibition study in which pooled human liver microsomes were incubated with methyleugenol in the presence and absence of enzyme specific inhibitors. Kinetic studies revealed that at physiologically relevant concentrations of methyleugenol P450 1A2 is the most important enzyme for bioactivation of methyleugenol in the human liver showing an enzyme efficiency (kcat/Km) that is approximately 30, 50, and > 50 times higher than the enzyme efficiencies of, respectively, P450 2C9, 2C19, and 2D6. Only when relatively higher methyleugenol concentrations are present P450 2C9 and P450 2C19 might contribute as well to the bioactivation of methyleugenol in the human liver. A 5-fold difference in activities was found between the 15 human liver microsomes of the correlation study (range, 0.89-4.30 nmol min(-1) nmol P450(-1)). Therefore, interindividual differences might cause variation in sensitivity toward methyleugenol. Especially lifestyle factors such as smoking (induces P450 1A) and the use of barbiturates (induces P450 2C) can increase the susceptibility for adverse effects of methyleugenol.

Human Cytochrome P450 Enzyme Specificity for Bioactivation of Safrole to the Proximate Carcinogen 1‘-Hydroxysafrole

In the present study, the cytochrome P450 mediated bioactivation of safrole to its proximate carcinogenic metabolite, 1'-hydroxysafrole, has been investigated for the purpose of identifying the human P450 enzymes involved. The 1'-hydroxylation of safrole was characterized in a variety of in vitro test systems, including Supersomes, expressing individual human P450 enzymes to a high level, and microsomes derived from cell lines expressing individual human P450 enzymes to a lower, average human liver level. Additionally, a correlation study was performed, in which safrole was incubated with a series of 15 human liver microsomes, and the 1'-hydroxylation rates obtained were correlated with the activities of these microsomes toward specific substrates for nine different isoenzymes. To complete the study, a final experiment was performed in which pooled human liver microsomes were incubated with safrole in the presence and absence of coumarin, a selective P450 2A6 substrate. On the basis of the results of these experiments, important roles for P450 2C9*1, P450 2A6, P450 2D6*1, and P450 2E1 were elucidated. The possible consequences of these results for the effects of genetic polymorphisms and life style factors on the bioactivation of safrole are discussed. Polymorphisms in P450 2C9, P450 2A6, and P450 2D6, leading to poor metabolizer phenotypes, may reduce the relative risk on the harmful effects of safrole, whereas life style factors, such as the use of alcohol, an inducer of P450 2E1, and barbiturates, inducers of P450 2C9, and polymorphisms in P450 2D6 and P450 2A6, leading to ultraextensive metabolizer phenotypes, may increase the relative risk.

Quenching of quercetin quinone/quinone methides by different thiolate scavengers: stability and reversibility of conjugate formation

Oxidation of flavonoids with a catechol structural motif in their B ring leads to formation of flavonoid quinone/quinone methides, which rapidly react with GSH to give reversible glutathionyl flavonoid adducts. Results of the present study demonstrate that as a thiol-scavenging agent for this reaction Cys is preferred over GSH and N-acetylcysteine. The preferential scavenging by Cys over GSH reported in the present study appeared not to provide a basis for detection of thiol-based flavonoid conjugates in biological systems. This is because physiological concentrations of GSH are substantially higher than those of Cys, which was shown to shift the balance of thiol conjugate formation in favor of glutathionyl adduct formation. Furthermore, the cysteinyl quercetin adducts, although not showing the reversible nature of the glutathionyl conjugates, appeared nevertheless to be unstable. Thus, as a biomarker for formation of reactive quercetin quinone/quinone methides in biological systems, detection of the glutathionyl conjugates or the N-acetylcysteinyl conjugates derived from them should still be the method of choice. At GSH levels that dominate the level of other cellular thiol groups, covalent addition of the quinone to other cellular thiol groups may be efficiently prevented. However, various tissues are known to contain higher levels of protein-bound sulfhydryl moieties than of nonprotein sulfhydryl groups, the latter consisting of especially GSH. Thus, the results of the present study indicate that in biological systems covalent addition of quercetin quinone methide to tissue protein sulfhydryl groups can be expected. The transient nature of these adducts, as shown for all three types of thiol quercetin adducts in the present study, will, however, also result in a transient nature of the protein-bound quercetin adducts to be expected. Because stability of the various thiol quercetin adducts appeared a matter of minutes to hours instead of days, this rapid transient nature of possible quercetin quinone methide adducts may also restrict the ultimate toxicity to be expected from the quercetin quinone/quinone methides.

The pro-oxidant chemistry of the natural antioxidants vitamin C, vitamin E, carotenoids and flavonoids

Natural antioxidants like vitamin C, vitamin E, carotenoids, and polyphenols like flavonoids, are at present generally considered to be beneficial components from fruit and vegetables. The anti-oxidative properties of these compounds are often claimed to be responsible for various beneficial health effects of these food ingredients. Together these studies provide the basis for the present rapidly increasing interest for the use of natural antioxidants as functional food ingredients and/or as food supplements. However, at higher doses or under certain conditions antioxidant-type functional food ingredients may exert toxic pro-oxidant activities. The present manuscript gives an overview of especially this pro-oxidative chemistry and toxicity of well-known natural antioxidants including vitamin C, vitamin E, carotenoids and flavonoids.

Identification of o-quinone/quinone methide metabolites of quercetin in a cellular in vitro system

Formation of quercetin quinone/quinone methide metabolites, reflected by formation of the glutathionyl quercetin adducts as authentic metabolites, was investigated in an in vitro cell model (B16F-10 melanoma cells). Results of the present study clearly indicate the formation of glutathionyl quercetin adducts in a tyrosinase-containing melanoma cell line, expected to be representative also for peroxidase-containing mammalian cells and tissues. The data obtained also support that the adducts are formed intracellular and subsequently excreted into the incubation medium and reveal for the first time evidence for the pro-oxidative metabolism of quercetin in a cellular in vitro model.

The regioselectivity of glutathione adduct formation with flavonoid quinone/quinone methides is pH-dependent

In the present study, the formation of glutathionyl adducts from a series of 3',4'-dihydroxy flavonoid o-quinone/p-quinone methides was investigated with special emphasis on the regioselectivity of the glutathione addition as a function of pH. The flavonoid o-quinones were generated using horseradish peroxidase, and upon purification by HPLC, the glutathionyl adducts were identified by LC/MS as well as (1)H and (13)C NMR. The major pH effect observed for the glutathione conjugation of taxifolin and luteolin quinone is on the rate of taxifolin and luteolin conversion and, as a result, on the ratio of mono- to diglutathione adduct formation. With fisetin, 3,3',4'-trihydroxyflavone, and quercetin, decreasing the pH results in a pathway in which glutathionyl adduct formation occurs in the C ring of the flavonoid, being initiated by hydration of the quinone and H(2)O adduct formation also in the C ring of the flavonoid. With increasing pH, for fisetin and 3,3',4'-trihydroxyflavone glutathione adduct formation of the quinone occurs in the B ring at C2' as the preferential site. For quercetin, the adduct formation of its quinone/quinone methide shifts from the C ring at pH 3.5, to the A ring at pH 7.0, to the B ring at pH 9.5, indicating a significant influence of the pH and deprotonation state on the chemical electrophilic behavior of quercetin quinone/quinone methide. Together the results of the present study elucidate the mechanism of the pH-dependent electrophilic behavior of B ring catechol flavonoids, which appears more straightforward than previously foreseen.

Structure-activity study on the quinone/quinone methide chemistry of flavonoids

A structure-activity study on the quinone/quinone methide chemistry of a series of 3',4'-dihydroxyflavonoids was performed. Using the glutathione trapping method followed by HPLC, (1)H NMR, MALDI-TOF, and LC/MS analysis to identify the glutathionyl adducts, the chemical behavior of the quinones/quinone methides of the different flavonoids could be deduced. The nature and type of mono- and diglutathionyl adducts formed from quercetin, taxifolin, luteolin, fisetin, and 3,3',4'-trihydroxyflavone show how several structural elements influence the quinone/quinone methide chemistry of flavonoids. In line with previous findings, glutathionyl adduct formation for quercetin occurs at positions C6 and C8 of the A ring, due to the involvement of quinone methide-type intermediates. Elimination of the possibilities for efficient quinone methide formation by (i) the absence of the C3-OH group (luteolin), (ii) the absence of the C2=C3 double bond (taxifolin), or (iii) the absence of the C5-OH group (3,3',4'-trihydroxyflavone) results in glutathionyl adduct formation at the B ring due to involvement of the o-quinone isomer of the oxidized flavonoid. The extent of di- versus monoglutathionyl adduct formation was shown to depend on the ease of oxidation of the monoadduct as compared to the parent flavonoid. Finally, unexpected results obtained with fisetin provide new insight into the quinone/quinone methide chemistry of flavonoids. The regioselectivity and nature of the quinone adducts that formed appear to be dependent on pH. At pH values above the pK(a) for quinone protonation, glutathionyl adduct formation proceeds at the A or B ring following expected quinone/quinone methide isomerization patterns. However, decreasing the pH below this pK(a) results in a competing pathway in which glutathionyl adduct formation occurs in the C ring of the flavonoid, which is preceded by protonation of the quinone and accompanied by H(2)O adduct formation, also in the C ring of the flavonoid. All together, the data presented in this study confirm that quinone/quinone methide chemistry can be far from straightforward, but the study provides significant new data revealing an important pH dependence for the chemical behavior of this important class of electrophiles.

Transferrin receptor-mediated gene transfer to the corneal endothelium

BACKGROUND

The application of gene therapy to prevent allograft rejection requires the development of noninflammatory vectors. We have therefore investigated the use of a nonviral system, transferrin-mediated lipofection, to transfer genes into the cornea with the aim of preventing corneal graft rejection.

METHODS

Rabbit and human corneas were cultured ex vivo and transfected with either lipofection alone or in conjunction with transferrin. The efficiency of transfection, localization, and kinetics of marker gene expression were determined. Strategies to increase gene expression, using chloroquine and EDTA, were investigated. In addition to a marker gene, a gene construct encoding viral interleukin 10 (vIL-10) was transfected and its functional effects were examined in vitro.

RESULTS

Transferrin, liposome, and DNA were demonstrated to interact with each other, forming a complex. This complex was found to deliver genes selectively to the endothelium of corneas resulting in gene expression. Treatment of corneas with chloroquine and EDTA increased the transfection efficiency eight-fold and threefold, respectively. We also demonstrated that constructs encoding vIL-10 could be delivered to the endothelium. Secreted vIL-10 was shown to be functionally active by inhibition of a mixed lymphocyte reaction.

CONCLUSIONS

Our data indicate that transferrin-mediated lipofection is a comparatively efficient nonviral method for delivering genes to the corneal endothelium. Its potential for use in preventing graft rejection is shown by the ability of this system to induce vIL-10 expression at secreted levels high enough to be functional.

Gene delivery to the corneal endothelium

Gene transfer to the corneal endothelium has potential for modulating rejection of corneal grafts. It can also serve as a convenient and useful model for gene therapy of other organs. In this article we review the work carried out in our laboratory using both viral and nonviral vectors to obtain gene expression in the cornea.

Peroxidase-catalyzed formation of quercetin quinone methide-glutathione adducts

The oxidation of quercetin by horseradish peroxidase/H(2)O(2) was studied in the absence but especially also in the presence of glutathione (GSH). HPLC analysis of the reaction products formed in the absence of GSH revealed formation of at least 20 different products, a result in line with other studies reporting the peroxidase-mediated oxidation of flavonoids. In the presence of GSH, however, these products were no longer observed and formation of two major new products was detected. (1)H NMR identified these two products as 6-glutathionylquercetin and 8-glutathionylquercetin, representing glutathione adducts originating from glutathione conjugation at the A ring instead of at the B ring of quercetin. Glutathione addition at positions 6 and 8 of the A ring can best be explained by taking into consideration a further oxidation of the quercetin semiquinone, initially formed by the HRP-mediated one-electron oxidation, to give the o-quinone, followed by the isomerization of the o-quinone to its p-quinone methide isomer. All together, the results of the present study provide evidence for a reaction chemistry of quercetin semiquinones with horseradish peroxidase/H(2)O(2) and GSH ultimately leading to adduct formation instead of to preferential GSH-mediated chemical reduction to regenerate the parent flavonoid.

Synthesis and anti-phlogistic potency of some new non-proteinogenic amino acid conjugates of "Diclofenac"

In search for more potent, particularly less ulcerogenic gastritis that hopefully replace the universal NSAID "Diclofenac", (2-[(2,6-dichlorophenyl)amino]-phenylacetic acid, C.A.S. 15307-86-5), twelve new non-proteinogenic amino acid conjugates of the drug, namely that of sarcosine, beta-alanine, D-leucine and D-phenylalanine, were synthesized and biologically screened for their anti-inflammatory, analgesic and ulcerogenic activity in rats. "Diclofenac" amino acid esters (IIa-d), were synthesized via the corresponding HOSu or HOBt active esters. Alkaline hydrolysis (NaOH) followed by acidification (KHSO4) or thioamide formation (Lawsson's Reagent, C.A.S. 19172-47-5), afforded the corresponding free acids IIIa-d or the thioamides IVa-d respectively. Interestingly, in contrary to the parent "Diclofenac", the synthesized candidates (except IIId), were entirely nonulcerogenic in rats. Further, they considerably retained a generalized anti-phlogistic activity. The major "Diclofenac" irritating gastric side effect was thus eliminated. Particularly, the sarcosine conjugate IIa and its thiomimic IVa exhibit promising therapeutic perspectives.

Synthesis and comparative anti-phlogistic potency of new proteinogenic amino acid conjugates of 2-[2,6-dichlorophenyl-1-amino]phenyl acetic acid "diclofenac"

New proteinogenic amino acids conjugates of 2-[2,6-dichlorophenyl-1-amino]phenyl acetic acid "Diclofenac", [I] were synthesized. Glycine methyl ester and L-methionine ethyl ester were coupled with [I] via the active ester method to give the corresponding 2-[2,6-dichlorophenyl-1-amino]benzyl carboxy N-amino acid ester of the type [IIa, b], respectively, which were hydrolyzed in alkaline medium to yield the free amino acids [IIIa, b]. Condensation of IIIa with glycine methyl ester using a modified classical carbodiimide (DCCI) method gave the corresponding, "Diclofenac" glycylglycine methyl ester [IVa]. Hydrolysis of compounds IVa gives the corresponding acid Va. Thionation of compounds IIb and IVa by reaction with Lewesson's Reagent (LR), afforded the corresponding thio-analogues (VIa and IVb). Interestingly, while retaining considerable comparative anti-phlogistic activity (anti-inflammatory and analgesic), the synthesized candidates proved to be practically nonulcerogenic in rats.