Purification and characterisation of leukotriene A4 hydrolase from rat neutrophils

Leukotriene A4 hydrolase was rapidly and extensively purified from rat neutrophils using anion exchange and gel filtration high-pressure liquid chromatography. The enzyme which converts the allylic epoxide leukotriene A4 to the 5,12-dihydroxyeicosatetraenoic acid leukotriene B4 was localized in the cytosolic fraction and exhibited an optimum activity at pH 7.8 and an apparent Km for leukotriene A4 between 2 X 10(-5) and 3 X 10(-5) M. The purified leukotriene A4 hydrolase was shown to have a molecular weight of 68 000 on sodium dodecylsulfate polyacrylamide gel electrophoresis and of 50 000 by gel filtration. The molecular weight and monomeric native form of this enzyme are unique characteristics which distinguish leukotriene A4 hydrolase from previously purified epoxide hydrolases.     

Steryl epoxide, secobutanolide and butanolides from the stem wood of Machilus zuihoensis

A steryl epoxide, machillene (1), a secobutanolide, secomahubanolide (2), and two butanolides, zuihoenalide (3), and 3-(1-methoxyoctadecyl)-5-methylene-5H-furan-2-one (4), together with 12 known compounds, were isolated from stem wood of Machilus zuihoensis. Their structures were determined by means of spectroscopic analyses. Machillene (1) showed cytotoxic activity against NUGC-3 and HONE-1 cancer cell lines in vitro.     

Cytotoxic and antimicrobial metabolites from marine lignicolous fungi, Diaporthe sp

A new compound (1), named diaporthelactone, together with two known compounds (2 and 3) were isolated from the culture of Diaporthe sp., a marine fungus growing in the submerged rotten leaves of Kandelia candel in the mangrove nature conservation areas of Fugong, Fujian Province of China. The new compound was elucidated to be 1,3-dihydro-4-methoxy-7-methyl-3-oxo-5-isobenzofuran-carboxyaldehyde (1), which showed cytotoxic activity against KB and Raji cell lines (IC50 6.25 and 5.51 microg mL(-1), respectively). Two known compounds, 7-methoxy-4,6-dimethyl-3H-isobenzofuran-1-one (2) and mycoepoxydiene (3), were also demonstrated to exhibit cytotoxic activities for the first time. All three compounds were assessed for antimicrobial activity.     

4,5-Diaryl-1H-pyrrole-2-carboxylates as combretastatin A-4/lamellarin T hybrids: synthesis and evaluation as anti-mitotic and cytotoxic agents

The 4,5-diarylated-1H-pyrrole-2-carboxylates 3-8 have each been prepared as hybrids of the potent anti-mitotic agent combretastatin A-4 (1) and the similarly active marine alkaloid lamellarin T (2). The key steps involved selective lithium-for-halogen exchange at C5 within the N-PMB protected 4,5-dibromopyrrole 22 and Negishi cross-coupling of the derived zincated species with the relevant aryl iodide. The ensuing 5-aryl-4-bromopyrrole then engaged in Suzuki-Miyaura cross-coupling with the appropriate arylboronic acid to give the 4,5-diarylated pyrroles 4, 6 and 8. TFA-promoted removal of the N-PMB group within these last compounds then gave the N-unsubstituted congeners 3, 5 and 7. Compounds 3-8 have all been evaluated for their anti-mitotic and cytotoxic properties and two of them, 3 and 5, display useful activities although they are less potent than combretastatin A-4.     

Amino substituted derivatives of 5'-amino-5'-deoxy-5'-noraristeromycin

The potent antiviral potential of 5'-amino-5'-deoxy-5'-noraristeromycin (2) is limited by associated toxicity. To seek derivatives of 2 that circumvent this undesirable property, three amino substituted derivatives (acetyl, 3; formyl, 4; and methyl, 5) of 2 have been prepared in 4-7 steps from the same intermediate, (1S,4R)-4-(6-chloropurin-9-yl)cyclopent-2-en-1-ol (6). Key steps involved an improved Pd(0)-catalyzed allylic azidation and a novel Pd(0)-catalyzed allylic amidation. The three target compounds were evaluated against a large number of viruses and found to be inactive except for a very weak effect of 5 on human cytomegalovirus, varicella zoster virus, and Epstein-Barr virus. There was also no noteworthy cytotoxicity associated with the new derivatives. Thus, these results indicate variation of the cyclopentyl amine of 2 does not offer a means to improve upon its antiviral potential.     

Cytotoxic bromoindole derivatives and terpenes from the Philippine marine sponge Smenospongia sp

A detailed chemical analysis of a Philippine marine sponge Smenospongia sp. has been performed. This study yielded four new metabolites, 5-bromo-L-tryptophan (1), 5-bromoabrine (2), 5,6-dibromoabrine (3) and 5-bromoindole-3-acetic acid (4). The pyrroloiminoquinone alkaloid, makaluvamine O (5) as well as 5,6-dibromotryptamine (6), aureol (7) and furospinulosin 1 (8) were also isolated. Although 1 and 4 have been synthesized previously, this is the first report on the isolation of these compounds from a natural source. The furanosesterterpene furospinulosin 1 (8) was obtained for the first time from the genus Smenospongia. The structures of all compounds were established by spectroscopic methods (UV, IR, 1D and 2D NMR, MS, [alpha]D). The cytotoxic potential of 1-8 was evaluated in a panel of isogenic HCT-116 human colon tumor cell lines.     

Solubilization and partial purification of leukotriene C4 synthase from guinea-pig lung: a microsomal enzyme with high specificity towards 5,6-epoxide leukotriene A4

Enzymic activities catalyzing allylic epoxide, leukotriene A4, to leukotriene C4 by conjugation with glutathione were present mainly in microsomal fractions of spleens and lungs of guinea pigs and rats. Leukotriene C4 (LTC4) synthase was solubilized from the microsomes of guinea-pig lung by the new procedures of a combination of 3-[3-cholamidopropyl)dimethylammonio)-1-propanesulfonate (CHAPS), digitonin and KCl. The enzyme was partially purified by two steps of column chromatography which resulted in a complete resolution of the enzyme from glutathione S-transferases (EC 2.5.1.18). The partially purified LTC4 synthase showed a Vmax value of 40 nmol/min per mg, and the apparent Km values for LTA4 and glutathione were 36 microM and 1.6 mM, respectively. The enzyme was unstable, and half of the activity was lost by incubation at 37 degrees C for 3 min. Glutathione at 10 mM completely protected the enzyme against this inactivation, while other sulfhydryl-group-reducing reagents were ineffective. The partially purified enzyme revealed a high specificity towards 5,6-epoxide leukotrienes (LTA4 and its methyl ester), while rat cytosolic glutathione S-transferases catalyzed conjugation of glutathione to various positional isomers of epoxide leukotrienes.     

Cytotoxicity and apoptosis induction of some selected marine bacteria metabolites

AIMS: To study the potential apoptosis effects of cytotoxic marine bacterial metabolites on human HeLa cell line. METHODS AND RESULTS: After HeLa cells were routinely cultured, tetrazolium-based colorimetric assay for cytotoxicity was performed to screen the marine bacteria extracts showing 12 strains active. To find the potential active strain with apoptosis mechanism, a battery of apoptosis assays, including AO/EB staining, TUNEL assay (terminal-deoxynucleotidyl transferase mediated nick end labelling), gel electrophoresis and flow cytometry, were used to determine whether apoptosis was involved in HeLa cell cytotoxicity of marine bacterial extracts. The results indicated that four strains could induce cell shrinkage, cell membrane blebbing, formation of apoptotic body and DNA fragmentation. CONCLUSIONS: Crude extracts of 12 of 153 strains of marine bacteria showed cytotoxic effects with ID50 ranged from 77.20 to 199.84 microg ml(-1), in which eight strains of bacteria were associated bacteria. The metabolites in the strains of QD1-2, NJ6-3-1, NJ1-1-1 and SS6-4 were able to induce HeLa cells apoptosis. Furthermore, the assessment by flow cytometry indicated that the hypodiploid apoptotic cells increased in a time-dependent manner, suggesting that induced apoptosis occurred from 24 h to 48 h after the extracts treatment. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results suggested that the compounds from fermentation in these four marine bacterial strains could be candidates for developing apoptosis specific anti-tumour agents with lower toxicity. This study indicated that associated marine bacteria could be good source to find cytotoxic metabolites, and some cytotoxic marine bacterial metabolites could have apoptosis mechanisms.     

Antitumor agents. Part 215: antitubulin effects of cytotoxic B-ring modified allocolchicinoids

N-Acetylcolchinol methyl ether 1 served as the starting material to prepare the chloroacetamide (3) and epoxide (5) analogues. Both 3 and 5 were potent inhibitors of tubulin polymerization in vitro. Compound 3 was also 4-fold more cytotoxic than colchicine against the 1A9 tumor cell line and showed a unique cross-resistance profile.     

Leukotriene A4 hydrolase in human leukocytes. Purification and properties

Leukotriene A4 hydrolase, a soluble enzyme catalyzing hydrolysis of the allylic epoxide leukotriene A4 to the dihydroxy acid leukotriene B4, was purified to apparent homogeneity from human leukocytes. The enzymatic reaction obeyed Michaelis-Menten saturation kinetics with respect to varying concentrations of leukotriene A4. An apparent KM value ranging between 20 and 30 microM was deduced from Eadie-Hofstee plots. Physical properties including molecular weight (68,000-70,000), amino acid composition, and aminoterminal sequence were determined. It was indicated that leukotriene A4 hydrolase is a monomeric protein, distinct from previously described epoxide hydrolases in liver.     

Antifungal 3,5-disubstituted furanones: From 5-acyloxymethyl to 5-alkylidene derivatives

5-Acetoxymethyl-3-(4-bromophenyl)-2,5-dihydrofuran-2-one previously described as highly antifungally active was found to provide the corresponding 5-methylene derivative via an unusual DMSO-promoted elimination of the ester group at C5 under antifungal assay conditions. Since the latter possessed nearly the same antifungal effect as that originally reported for the former, the 5-acetoxymethyl furanone just served as a precursor of the actual antifungally active species. A few series of compounds with alkyloxy, aryloxy and alkylidene substituents at C5 of the parent furanone structure were therefore prepared and evaluated. In line with the ease of elimination of the substituent from C5, low activities of the 5-alkoxy compounds were observed. On the other hand, their 5-aryloxymethyl congeners were found to be capable of liberating the antifungally active 5-methylene furanone into the testing medium. The antifungal effect of the 5-alkylidene derivatives was highly sensitive to substitution of the alkylidene moiety; a substituent in the allylic position was necessary for a compound to retain high activity. Parallel evaluation of cytostatic activity showed moderate activities of the antifungally active derivatives against HeLa S3 and CCRF-CEM lines. Cell cycle analysis of CCRF-CEM cells following the treatment with 5-methylene-3-(4-bromophenyl)-2,5-dihydrofuran-2-one revealed that this compound is a necrotic agent.     

Asymmetric epoxidation of alpha-olefins having neighboring sugar chiral templates and alternating copolymerization with dicarboxylic anhydrides

Sugar-substituted epoxides 5-8 were synthesized by asymmetric epoxidation (in CH(2)Cl(2)/water) of alpha-olefins having neighboring sugars (1-4) by use of an achiral oxidant (MCPBA), in which the sugar moiety acted as a chiral template. The diastereoselectivities depend on the methylene spacer between vinyl group and carbohydrate derivatives. The methylene spacer between sugar and vinyl groups influenced the diastereoselectvity. In the case of epoxidation of 4 at 27 degrees C for 24 h, the diastereoselectivity was the highest (99/1). Copolymerizations of 5-8 with succinic anhydride were attained at 100 degrees C for 72 h to give poly(ethylene succinate) having pendant carbohydrate [poly(SAn-alt-5), M(n) = 1.4 x 10(3); poly(SAn-alt-6), M(n) = 2.2 x10(3); poly(SAn-alt-7), M(n) = 2.9 x 10(3); poly(SAn-alt-8), M(n) = 1.8 x 10(3)]. The methylene spacer between sugar and epoxide has an effect on the reactivity of epoxide in copolymerization as well as the diastereoselectivity. Alternating copolymerization of 7 and glutaric anhydride gave a polyester of M(n) 4.2 x10(3).     

Mutagenicity of various chemicals including nickel and cobalt compounds in cultured mouse FM3A cells

Employing a suspension culture of FM3A cells, we examined the cytotoxic and mutagenic effects of various chemical compounds. Mutagenicity of various types of mutagens (MNNG, ENNG, sterigmatocystin, mitomycin C, Trp-P-1, and X-rays) was sensitively detected by this assay. Mutagenicity of Trp-P-2 was detected in the presence of an activating enzyme system. Nickel(II) and cobalt(II) compounds (NiCl2, Ni(CH3COO)2, nickel complex [(C2H5)4N]2 [NiCl4], CoCl2, and a cobalt complex [(C2H5)4N]2-[CoCl4]) were cytotoxic to FM3A cells at concentrations of over 1 X 10(-4) M, and produced 2-6-fold increases of the control in the average number of 6-thioguanine-resistant (6TGr) colonies over a very narrow concentration range of 2-4 X 10(-4) M. Comparison of the mutagenicity of various chemical compounds suggested that some of the nickel(II) and cobalt(II) compounds were very weak mutagens.     

Synthesis and in vitro cytotoxicity of 5-substituted 2-cyanoimino-4-imidazodinone and 2-cyanoimino-4-pyrimidinone derivatives

A series of 5-substituted 2-cyanoimino-4-imidazodinone and 2-cyanoimino-4-pyrimidinone derivatives were synthesized and their anticancer cytotoxicity were evaluated in in vitro assay. It was found that the bulky aryl functionality in the 5-position of the 2-cyanoimino-4-imidazolidinone compounds was essential for the cytotoxicity of these heterocyclic compounds. Some of the derivatives exhibited modest cytotoxicity against a variety of cancer cell lines. One of the derivatives, [1-[6-(4-chlorophenoxy)hexyl]-5-oxo-4-phenyl-3-(4-pyridyl)tetrahydro-1H-2-imidazolyliden]aminomethanenitrile (Compound 11), exhibited the most potent cytotoxic activity with IC(50) in the nanomolar range. The cytotoxicity of these derivatives was selection with no apparent toxic effect toward normal fibroblasts.     

Isolation of apoptosis- and differentiation-inducing substances toward human promyelocytic leukemia HL-60 cells from leaves of Juniperus taxifolia

A chloroform extract of the leaves of Juniperas taxifolia exhibited a marked antiproliferative effect on human promyelocytic leukemia HL-60 cells at a concentration of 2.5 microg/ml. Deoxypodophyllotoxin (4) was identified in the extract as an outstanding antiproliferative compound, and five diterpenes (1-3, 5, and 6) were isolated as known compounds with weak or no cytotoxicity. These compounds were examined for their respective apoptosis- and differentiation-inducing activities toward HL-60 cells by DNA fragmentation and NBT-reducing assays, respectively. Among them, 7alpha-hydroxysandaracopimaric acid (6) was found to have a potent differentiation-inducing activity in a dose-dependent manner at 0.125-2 microg/ml (0.39-6.29 microM), together with apoptosis-inducing activity at concentrations of more than 2.5 microg/ml (7.86 microM). Deoxypodophyllotoxin (4) that exerted cytotoxic and apoptosis-inducing activities at 2 ng/ml (5 nM) did not induce differentiation at the same concentration, and the other diterpenes (1-3 and 5) showed no effect on cell differentiation, even at 5 microg/ml. It was thus demonstrated for the first time that 7alpha-hydroxysandaracopimaric acid was an effective differentiation-inducing compound toward HL-60 cells.     

Search for antimetabolites among 5-trimethylsilyluracil nucleosides and their nonglycoside analogs]

The reaction of 2'-deoxy-5-trimethylsilyl(Tms)uridine with methanesulfonyl chloride led to the corresponding 3',5'-di-O-mesyl derivative, which was treated with lithium toluylate in DMF to give 2,3'-anhydro-1-(2-deoxy-5-O-p-toluyl-beta-D-xylofurano- syl)-5-Tms-uracil. Under these conditions 1-(2,3-dideoxy-5-O-p-toluyl-alpha-D- glycero-pent-2-enofuranosyl)-5-Tms-uracil was obtained from 1-(2-deoxy-alpha-D-ribofuranosyl)-5-Tms-uracil. Interaction of 2,3'-anhydronucleoside with LiN3 in DMF and successive deacylation with MeONa-MeOH gave 3'-azido-2',3'-dideoxy-5-Tms-uridine. Hydrogenation of this compound with 10% Pd/C in ethanol gave 3'-azido-2',3'-dideoxy-5-Tms-uridine. From 2,4,5-tris-Tms-uracil and 2,3-didehydrofurane in 1,2-dichloroethane in the presence of SnCl4 1-(2-tetrahydrofuranyl)-5-Tms-uracil was prepared. In a similar way 1-[(1,3-dioxy-2-propoxy)methyl]-5-Tms-uracil was synthesized by condensation of silylated uracil with 1,3-dibenzyloxy-2-acetoxymethylglycerol followed by the hydrogen transfer hydrogenolysis with cyclohexene--20% Pd(OH)2/C. None of the compounds exhibits cytotoxic activity against CaOv in vitro. The acycloderivative in concentration of 250 micrograms/ml has no effect on the HSV-1 and vaccinia virus replication in vitro. 3'-Azidonucleoside in dose of 100-750 mg/kg as well as 1-(2-tetrahydrofuranyl)-5-Tms-uracil in dose of 160-800 mg/kg were devoid of antitumour activity against P388 in vivo.     

Epoxide hydrolases: biochemistry and molecular biology

Epoxides are organic three-membered oxygen compounds that arise from oxidative metabolism of endogenous, as well as xenobiotic compounds via chemical and enzymatic oxidation processes, including the cytochrome P450 monooxygenase system. The resultant epoxides are typically unstable in aqueous environments and chemically reactive. In the case of xenobiotics and certain endogenous substances, epoxide intermediates have been implicated as ultimate mutagenic and carcinogenic initiators Adams et al. (Chem. Biol. Interact. 95 (1995) 57-77) Guengrich (Properties and Metabolic roles 4 (1982) 5-30) Sayer et al. (J. Biol. Chem. 260 (1985) 1630-1640). Therefore, it is of vital importance for the biological organism to regulate levels of these reactive species. The epoxide hydrolases (E.C. 3.3.2. 3) belong to a sub-category of a broad group of hydrolytic enzymes that include esterases, proteases, dehalogenases, and lipases Beetham et al. (DNA Cell Biol. 14 (1995) 61-71). In particular, the epoxide hydrolases are a class of proteins that catalyze the hydration of chemically reactive epoxides to their corresponding dihydrodiol products. Simple epoxides are hydrated to their corresponding vicinal dihydrodiols, and arene oxides to trans-dihydrodiols. In general, this hydration leads to more stable and less reactive intermediates, however exceptions do exist. In mammalian species, there are at least five epoxide hydrolase forms, microsomal cholesterol 5,6-oxide hydrolase, hepoxilin A(3) hydrolase, leukotriene A(4) hydrolase, soluble, and microsomal epoxide hydrolase. Each of these enzymes is distinct chemically and immunologically. Table 1 illustrates some general properties for each of these classes of hydrolases. Fig. 1 provides an overview of selected model substrates for each class of epoxide hydrolase.     

The effect of 4beta and 19 ester functionalities on some electrophilic addition reactions of delta5-steroids

The reactions of 3beta-acyloxyandrost-5-enes with bromine/silver acetate (Petrow reaction) and mercury(II) trifluoroacetate (modified Treibs oxidation) have been used previously to effect allylic oxidation on these substrates en route to biologically active compounds. In both these reactions, which involve electrophilic addition to the delta5-bond, the 3-acyloxy substituent plays a significant role. In this report, the effect of introducing other substituents proximate to the delta5-bond has been studied by using derivatives of 3beta-acetoxyandrost-5-en-17-one (1), namely, 3beta,4beta-diacetoxyandrost-5-en-17-one (13), 3beta,19-diacetoxyandrost-5-en-17-one (14), 3beta-acetoxyandrost-5-ene-7,17-dione (15), and 3beta-acetoxy-4,4-dimethylandrost-5-en-17-one (17). Our results indicate that in both sets of reactions the effect of the introduced functional groups was pronounced. In the Petrow reaction, electrophilic addition rather than allylic oxidation on the diacetates was observed. With the Treibs reaction, allylic oxidation on the diacetates occurred. The 7-keto and 4,4-dimethyl steroids proved to be poor substrates in both reactions.     

Total synthesis of junionone, a natural monoterpenoid from Juniperus communis L., and determination of the absolute configuration of the naturally occurring enantiomer by ROA spectroscopy

Recently, we reported a novel access to 2,2-diethyl-3-[(E/Z)-prop-1-en-1-yl]cyclobutanone by an intramolecular nucleophilic substitution with allylic rearrangement (S(N)i') of (E)-6-chloro-3,3-diethylhept-4-en-2-one. The ring closure reaction was found to proceed with selective syn-displacement of the leaving group. This method was now applied to the total synthesis of junionone, an olfactorily interesting cyclobutane monoterpenoid isolated from Juniperus communis, L. S(N)i' Ring closure of the ketone enolate of (E)-3,3-dimethyl-5-[(2R,3R)-3-methyloxiran-2-yl]pent-4-en-2-one (R,R)-(E)-4' proceeded only after the epoxide moiety had been activated by Lewis acid and led to the junionone precursors (3R)- and (3S)-3-[(1E,3R)-3-hydroxybut-1-en-1-yl]-2,2-dimethylcyclobutanone (S/R,R)-(E)-3. The ratio of syn- and anti-conformers in the transitory molecular arrangement was found to depend on the nature of the Lewis acid. The absolute configuration of both the synthetic as well as the natural junionone, isolated from juniper berry oil, was determined by Raman Optical Activity (ROA) spectroscopy. Our experiments led to a novel synthetic route to both (+)- and (-)-junionone, the first determination of the absolute configuration of natural junionone, and to the development of a practical ROA procedure for measuring milligram quantities of volatile liquids.     

In vitro assessment of cytotoxicity and carcinogenic potential of chemicals: evaluation of the cytotoxicity induced by 58 metal compounds in the Balb/3T3 cell line

A new, mechanistically based, in vitro strategy involving Balb/c 3T3 clone A 31-1-1 mouse embryo fibroblasts has been proposed for the determination of the carcinogenic potential of inorganic chemicals, in order to establish priority of metal compounds to be tested and, whenever possible, to compare the in vitro results with the corresponding in vivo data. As a first step in this research, this study reports on the cytotoxic effects of 58 metal compounds in the Balb/3T3 cell line. After harmonisation and standardisation of the Balb/3T3 protocol, cells were exposed for 72 hours to a fixed dose (100 microM) of 58 individual compounds. The cytotoxicity induced by some metal compounds was found to be related to their chemical form (for example, Cr(NO(3))(3) and Na(2)CrO(4)), suggesting that the Balb/3T3 cell line is a valuable cellular model in relation to this aspect of metal speciation. The results of the systematic study on the metal-induced cytotoxic effects in the Balb/3T3 cell line could be arbitrarily classified into three groups according to the degree of cytotoxicity. Group I includes 26 species that induced no observable effect or only a slight cytotoxic effect; Group II includes 13 metal compounds that exhibited an obvious degree of cytotoxicity; and Group III includes 19 metal species that displayed a strong cytotoxic response. Metal compounds of Groups II and III are considered to be of the highest priority for setting of dose-effect relationships for a subsequent in vitro study on metal-induced concurrent cytotoxicity and morphological transformation in the Balb/3T3 cell line.