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PubMed2002

Integrated approach to explore the potential of marine microorganisms for the production of bioactive metabolites.

During the last 10 years marine organisms have provided a large number of new natural products. Interesting compounds have mainly been derived from macroorganisms such as sponges, ascidians, corals and bryozoans. The number of secondary metabolites from marine microorganisms is smaller, but rapidly increasing. Because of the enormous difficulties involved in harvesting products from marine animals, and the fact that some of the bioactive compounds are produced by associated bacteria, the advantages of sustainable production of bioactive metabolites by bacteria or fungi, under the protection of natural resources, seem to be very attractive for the future. This review describes current progress in the isolation and identification of novel marine microorganisms, the discovery of new secondary metabolites, the biotechnological approaches to overproduce them, as well as the evaluation and characterization of their bioactivity.

Antineoplastic Agents↗
PubMed1995

Isolation and expression of three gibberellin 20-oxidase cDNA clones from Arabidopsis.

Using degenerate oligonucleotide primers based on a pumpkin (Cucurbita maxima) gibberellin (GA) 20-oxidase sequence, six different fragments of dioxygenase genes were amplified by polymerase chain reaction from arabidopsis thaliana genomic DNA. One of these was used to isolate two different full-length cDNA clones, At2301 and At2353, from shoots of the GA-deficient Arabidopsis mutant ga1-2. A third, related clone, YAP169, was identified in the Database of Expressed Sequence Tags. The cDNA clones were expressed in Escherichia coli as fusion proteins, each of which oxidized GA12 at C-20 to GA15, GA24, and the C19 compound GA9, a precursor of bioactive GAs; the C20 tricarboxylic acid compound GA25 was formed as a minor product. The expression products also oxidized the 13-hydroxylated substrate GA53, but less effectively than GA12. The three cDNAs hybridized to mRNA species with tissue-specific patterns of accumulation, with At2301 being expressed in stems and inflorescences, At2353 in inflorescences and developing siliques, and YAP169 in siliques only. In the floral shoots of the ga1-2 mutant, transcript levels corresponding to each cDNA decreased dramatically after GA3 application, suggesting that GA biosynthesis may be controlled, at least in part, through down-regulation of the expression of the 20-oxidase genes.

Amino Acid Sequence↗
PubMed1994

Selective inhibitors of cytochromes P450.

The balance between detoxification and bioactivation of a compound in a particular species or organ is highly dependent on the relative amounts and activities of the different forms of cytochrome P450 (P450) that are expressed. Therefore, knowledge of the catalytic specificities and regulation of individual P450 forms is of paramount importance in predicting and/or rationalizing species, strain, and individual differences in xenobiotic metabolism as well as metabolic interactions between compounds, both endogenous and exogenous. The emergence in recent years of a battery of isoform-selective chemical inhibitors that can be used in vitro and in vivo in experimental animals and humans has greatly facilitated the identification of individual cytochromes P450 responsible for specific bioactivation and detoxification reactions. Many of these inhibitors are mechanism-based and owe their selectivity to metabolism by the target enzyme. Such compounds have also proven valuable as probes of the catalytic mechanism of cytochromes P450, for identifying amino acid residues of importance for the various functions of the enzyme, for assessing the physiological roles of P450-derived oxidation products of endogenous compounds, in chemical-induced models of acute hepatic porphyria, and for studying protein turnover. The identification of isoform-selective, nontoxic inhibitors of individual human cytochromes P450 raises the real possibility of modulation of human drug metabolism for therapeutic purposes.

Animals↗
PubMed1982

Characterization of mutagenic coal fly ash and extracts.

Post-electrostatic precipitator (ESP) fly ash samples were collected from a coal-fired electric power generation plant under three modes of plant operation: normal operation, a low NOx-emission mode of combustion, and operation with the ESP shorted-out. Results of chemical and physical characterization of the ashes were compared with bacterial mutagenicity bioassay to determine parameters or compounds correlating with bioactivity. The general physical properties, ultimate composition, and trace elemental and radiochemical species determined did not correlate with the mutagenicity. Only the presence of aromatic hydrocarbons and chemically derivatizable polar organic compounds appeared to be associated with mutagenicity of the fly ash.

Carbon↗
PubMed2005

Asymmetric synthesis of novel tetrahydroquinoline derivatives with a sugar building block and their bioactivities.

Some novel spiro-tetrahydroquinolines were stereoselectively synthesized by using keto-sugar derived from sucrose as a building block in one pot under mild conditions. The in vitro immunobiological activity and cytotoxicity of these novel tetrahydroquinolines were investigated. The results implied that these spiro-compounds have obvious bioactivity and may be structurally modified to improve bioactivity further.

Antineoplastic Agents↗
PubMedDate not supplied

Protection by diethyldithiocarbamate, a CS2-liberating agent, against different models of experimentally-induced liver injury.

In experimental animals, diethyldithiocarbamate as well as carbon disulfide exert antihepatotoxic effects in different models of chemically-induced liver injury like carbon tetrachloride, chloroform, bromobenzene, dimethyl nitrosamine, furosemide, D-galactosamine, paracetamol, thioacetamide and trichloroethylene. On the other hand, both dithiocarb and CS2 are strong inhibitors of the microsomal mixed-function oxidase system which is involved in the bioactivation of these hepatotoxic agents. It is concluded that CS2 and CS2-producing agents as dithiocarb and disulfiram may inhibit metabolism of other xenobiotics and, thereby, not only protect against various hepatotoxic compounds that require bioactivation but also affect efficacy and duration of action of many drugs.

Animals↗
PubMed2006

Synthesis and anti-angiogenesis activity of coumarin derivatives.

A series of 7-diethylaminocoumarin compounds were synthesized and the cytotoxicities were tested against human umbilical vein endothelial cell (HUVEC) and some cancer cells. We found that the introduction of cyano groups at the 4-position will promote the bioactivity. In particular, compounds 9 and 10 strongly inhibited the proliferation of various cancer cell lines, and 12 and 15 showed a high selectivity for HUVEC. Therefore, these coumarin molecules can be utilized as lead compounds to develop potential nontoxic angiogenesis inhibitors and small molecular ligands to target HUVEC.

Angiogenesis Inhibitors↗
PubMed2026

Deciphering the Function and Structure of PA1216 as an S-Adenosyl-l-Methionine Binding Protein Using Differential Scanning Fluorimetry and Circular Dichroism.

Microbes produce bioactive secondary metabolites as toxins, pigments, or virulence factors. These specialized compounds are produced by nonribosomal peptide synthetases (NRPS), polyketide synthases (PKS), or hybrid NRPS/PKS pathways. The genes encoding NRPS and PKS reside in biosynthetic gene clusters (BGCs), some of which have no identified metabolite associated with them. Characterization of these orphan BGCs could provide insights into potential bioactive compounds that have yet to be discovered. Here, we characterize PA1216, a putative methyltransferase embedded within an NRPS BGC in Pseudomonas aeruginosa strain PAO1. We cloned, expressed, and purified PA1216, and developed an optimized differential scanning fluorimetry assay to measure its thermal stability, demonstrating concentration-dependent stabilization in the presence of established methyltransferase cofactors and inhibitors. We then adapted this assay for high-throughput screening of potential PA1216 substrates, identifying destabilizing compounds, including glycyl-glycine dipeptides, amino esters with aromatic or basic side chains, and N-Boc-protected amino acids. In contrast, sodium salts of organic acids stabilized PA1216. Lastly, we employed AlphaFold to construct a predictive model, revealing that PA1216 contains a Rossmann-like fold and a glycine-rich loop, typical of class I methyltransferases, and we corroborated these secondary structural elements using circular dichroism spectroscopy. Overall, these studies illuminate PA1216 function and establish a platform for characterizing cryptic gene clusters within secondary metabolic pathways.

Circular Dichroism↗
PubMed1996

Longimicins A-D: novel bioactive acetogenins from Asimina longifolia (annonaceae) and structure-activity relationships of asimicin type of annonaceous acetogenins.

Bioactivity-directed fractionation of the ethanol extract of Asimina longifolia led to the isolation of four novel bioactive annonaceous acetogenins: longimicins A-D (1-4). Compounds 1-4 represent the asimicin type of acetogenins; however, the locations of the adjacent bis-tetrahydrofuran (THF) ring moieties are shifted along the aliphatic chains compared to the known compounds of this type. They are the first examples among this type of acetogenins with the placements of the ring systems altered. Compounds 1-4 showed bioactivities in several bioassays, but they are less active than their structural isomers. Study of their structure-activity relationships (SAR) reveals that the position of the adjacent bis-THF ring moiety is essential for maximization of the bioactivities among these asimicin type annonaceous acetogenins.

Animals↗
PubMed1985

Identification of Gibberellins A(1), A(5), A(29), and A(32) from Immature Seeds of Apricot (Prunus armeniaca L.).

Gibberellins (GAs) A(1), A(5), and A(29) were identified, and also GA(32) was confirmed, as endogenous GAs of immature seeds (3-4 weeks after anthesis, 0.25-0.5 gram fresh weight) of apricot (Prunus armeniaca L.) based on capillary gas chromatography (GC), retention time (Rt), and selected ion monitoring (SIM), in comparison with authentic standards. Fractions subjected to GC-SIM were purified and separated using sequential solvent partitioning --> paper chromatography --> reverse phase C(18) high performance liquid chromatography (HPLC) --> bioassay on dwarf rice cv Tan-ginbozu. Two other peaks of free GA-like bioactivity (microdrop and immersion dwarf rice assays) were eluted from C(18) HPLC at Rts where GA(4/7) and GA(8) (or other GAs with similar structures) would elute. Also, three unidentified GA glucoside-like compounds (based on bioactivity on the immersion assay, and no bioactivity on the microdrop assay) were noted. There were very high amounts of GA(32) (112 ng of GA(3) equivalents per gram fresh weight), and minor amounts (0.5 ng of GA(3) equivalents) for each of GA(1) and GA(5), respectively, based on the microdrop assay.

Journal Article↗
PubMed2005

Cultivation conditions and selenium fertilization alter the phenolic profile, glucosinolate, and sulforaphane content of broccoli.

Broccoli is a food often consumed for its potential health-promoting properties. The health benefits of broccoli are partly associated with secondary plant compounds that have bioactivity; glucosinolates and phenolic acids are two of the most abundant and important in broccoli. In an effort to determine how variety, stress, and production conditions affect the production of these bioactive components broccoli was grown in the greenhouse with and without selenium (Se) fertilization, and in the field under conventional or organic farming procedures and with or without water stress. High-performance liquid chromatography/mass spectrometry was used to separate and identify 12 primary phenolic compounds. Variety had a major effect: There was a preponderance of flavonoids in the Majestic variety, but hydroxycinnamic esters were relatively more abundant in the Legacy variety. Organic farming and water stress decreased the overall production of phenolics. Se fertilization increased glucosinolates in general, and sulforaphane in particular, up to a point; above that Se fertilization decreased glucosinolate production. Organic farming and water stress also decreased glucosinolate production. These data show environmental and genetic variation in phenolics and glucosinolates in broccoli, and warn that not all broccoli may contain all health-promoting bioactive components. They further show that selection for one bioactive component (Se) may decrease the content of other bioactive components such as phenolics and glucosinolates.

Agriculture↗
PubMed2006

In vitro metabolism of (nitrooxy)butyl ester nitric oxide-releasing compounds: comparison with glyceryl trinitrate.

We investigated the in vitro metabolism of two (nitrooxy)butyl ester nitric oxide (NO) donor derivatives of flurbiprofen and ferulic acid, [1,1'-biphenyl]-4-acetic acid-2-fluoro-alpha-methyl-4-(nitrooxy)butyl ester (HCT 1026) and 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid 4-(nitrooxy)butyl ester (NCX 2057), respectively, in rat blood plasma and liver subcellular fractions compared with (nitrooxy)butyl alcohol (NOBA) and glyceryl trinitrate (GTN). HCT 1026 and NCX 2057 undergo rapid ubiquitous carboxyl ester hydrolysis to their respective parent compounds and NOBA. The nitrate moiety of this latter is subsequently metabolized to inorganic nitrogen oxides (NOx), predominantly in liver cytosol by glutathione S-transferase (GST) and to a lesser extent in liver mitochondria. If, however, in liver cytosol, the carboxyl ester hydrolysis is prevented by an esterase inhibitor, the metabolism at the nitrate moiety level does not occur. In blood plasma, HCT 1026 and NCX 2057 are not metabolized to NOx, whereas a slow but sustained NO generation in deoxygenated whole blood as detected by electron paramagnetic resonance indicates the involvement of erythrocytes in the bioactivation of these compounds. Differently from NOBA, GTN is also metabolized in blood plasma and more quickly metabolized by different GST isoforms in liver cytosol. The cytosolic GST-mediated denitration of these organic nitrates in liver limits their interaction with other intracellular compartments to possible generation of NO and/or their subsequent availability and bioactivation in the systemic circulation and extrahepatic tissues. We show the possibility of modulating the activity of hepatic cytosolic enzymes involved in the metabolism of (nitrooxy)butyl ester compounds, thus increasing the therapeutic potential of this class of compounds.

Animals↗
PubMed2001

Cyclopentenone prostaglandins: new insights on biological activities and cellular targets.

The cyclopentenone prostaglandins PGA2, PGA1, and PGJ2 are formed by dehydration within the cyclopentane ring of PGE2, PGE1, and PGD2. PGJ2 is metabolized further to yield Delta(12)-PGJ(2) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)). Various compounds within the cyclopentenone prostaglandin family possess potent anti-inflammatory, anti-neoplastic, and anti-viral activity. Most actions of the cyclopentenone prostaglandins do not appear to be mediated by binding to G-protein coupled prostanoid receptors. Rather, the bioactivity of these compounds results from their interaction with other cellular target proteins. 15-deoxy-Delta(12,14)-PGJ(2) is a high affinity ligand for the nuclear receptor PPARgamma and modulates gene transcription by binding to this receptor. Other activities of the cyclopentenone prostaglandins are mediated by the reactive alpha,beta-unsaturated carbonyl group located in the cyclopentenone ring. The transcription factor NF-kappaB and its activating kinase are key targets for the anti-inflammatory activity of 15d-PGJ2, which inhibits NF-kappaB-mediated transcriptional activation by PPARgamma-dependent and independent molecular mechanisms. Other cyclopentenone prostaglandins, such as Delta(7)-PGA1 and Delta(12)-PGJ2, have strong anti-tumor activity. These compounds induce cell cycle arrest or apoptosis of tumor cells depending on the cell type and treatment conditions. We review here recent progress in understanding the mechanisms of action of the cyclopentenone prostaglandins and their possible use as therapeutic agents.

Animals↗
PubMed2006

Clarifying the real bioactive constituents of garlic.

Compounds in garlic work synergistically to produce various effects, but, because of garlic's chemical complexity, processing methods yield preparations with differing efficacy and safety. Although thiosulfinates such as allicin have been long misunderstood to be active compounds due to their characteristic odor, it is not necessary for garlic preparations to contain such odorous compounds to be effective, and they decompose and disappear during any processing. Garlic exhibits hypolipidemic, antiplatelet, and procirculatory effects. It prevents cold and flu symptoms through immune enhancement and demonstrates anticancer and chemopreventive activities. In addition, aged garlic extract possesses hepatoprotective, neuroprotective, antioxidative activities, whereas other preparations may stimulate oxidation. Additional effects may be caused by S-allylcysteine, S-allyl mercaptocysteine), saponins, Nalpha-fructosyl arginine, and other substances formed during a long-term extraction process. Although not all of active ingredients of garlic are known, and allicin-like transient components are not directly active, ample research suggests that an allicin-free garlic preparation that is standardized with a bioavailable component such as S-allylcysteine, is active and various effects of garlic may be attributed to it. Furthermore, various chemical constituents in garlic products, including nonsulfur compounds such as saponins, may contribute to the essential biological activities of garlic. Further studies are needed to confirm their bioavailability and associated activities.

Antioxidants↗
PubMed2006

Bioecological and nutritional control of disease: prebiotics, probiotics and synbiotics.

A growing number of patients worlwide suffer acute and chronic diseases. Evidence supports the association of chronic diseases to modern lifestyle habits and malfunction of the immune system. Morbidity and mortality for patients affected of chronic diseases is unacceptably high despite advanced surgical and medical treatments. Nowadays there is an increasing interest in the bioecological and nutritional control of diseases. The use of prebiotics, probiotics and synbiotics, e.g. antioxidants, anti-inflammatory omega-3 lipid emulsions, bioactive fibers, lactic acid bacteria (LAB), etc, appears as a new tool for the treatment of disease. The effects of antioxidants and omega-3 lipid emulsions remain largely unexplored, but significant modulatory effects on neutrophils and morbidity have been observed. It is burning that these compounds are tried in patients including surgically and critically ill patients. Some bioactive fibers and some probiotic bacteria have demonstrated extraordinary efficacy to restore and maintain immunity and prevent complications. Lactic acid bacteria (LAB) have demonstrated ability to reduce or eliminate potential pathogen micro-organisms, as well as various toxins, mutagens and carcinogens; they also promote apoptosis, synthesize and release numerous nutrients, antioxidants, growth-factors, coagulation and other bioactive compounds, and modulate the innate and adaptive immune defence mechanisms. More recent studies suggest that LAB promote and maintain gastrointestinal (GI) motility and prevent GI paralysis and postoperative ileus and have the ability to inhibit inflammation. Further studies are needed to ascertain the molecular mechanisms by which pre-, pro- and synbiotics influence the outcome in a variety of acute and chronic diseases.

Forecasting↗
PubMed2000

Evaluation of the kinetics of beta-elimination reactions of selenocysteine Se-conjugates in human renal cytosol: possible implications for the use as kidney selective prodrugs.

This study was performed to evaluate whether selenocysteine Se-conjugates are substrates for human cysteine conjugate beta-lyase enzymes. By testing kidney cytosols of three different humans, we studied interindividual differences in beta-lyase enzymes in humans. A series of 22 selenocysteine Se-conjugates were tested in rat and human kidney cytosols to compare their ability to form selenol compounds by beta-elimination. All compounds appeared to be good substrates for rat and human cysteine conjugate beta-lyase enzymes. The beta-lyase activity toward the selenocysteine Se-conjugates was comparable with those of the known nephrotoxic cysteine S-conjugate S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine in rats and humans. In rat kidney cytosol, between 22- and 877-fold higher beta-elimination rates were observed compared with human kidney cytosol. Significant correlations (P <.0001) between three human kidney cytosols in beta-lyase activities were found within the tested series of 22 compounds. Specific beta-lyase activities and intrinsic clearances of beta-elimination reactions ranged up to 3-fold, indicating that there are quantitative rather than qualitative interindividual differences in beta-eliminating enzymes in humans. Furthermore, Se-alkyl selenocysteine conjugates showed a sterically dependent bioactivation to selenol compounds in humans but not in rats. The present study supports the hypothesis that selenocysteine Se-conjugates may be useful as prodrugs to target pharmacologically active selenol compounds (e.g., antitumor or chemoprotective) to the kidney in humans.

Aged↗
PubMed1994

Sulphation of N-hydroxy-4-aminobiphenyl and N-hydroxy-4-acetylaminobiphenyl by human foetal and neonatal sulphotransferase.

Sulphation of the genotoxic compounds N-hydroxy-4-aminobiphenyl (N-OH-4ABP) and N-hydroxy-4-acetylaminobiphenyl (N-OH-4AABP) was determined in cytosolic preparations of human foetal, neonatal and adult liver and foetal and neonatal adrenal gland. Sulphotransferase (ST) activity capable of sulphating these compounds was present in foetal liver and adrenal gland by 14 weeks of gestation. Sulphation of N-OH-4ABP was higher in foetal and neonatal adrenal cytosol than was sulphation of N-OH-4AABP and in general, N-OH-4ABP ST activity was also greater than that towards 1-naphthol. In foetal and neonatal liver cytosol the sulphation of N-OH-4ABP was also higher than that of N-OH-4AABP (approximately 2-fold). In adult liver cytosols, however, N-OH-4AABP ST activity was higher than that for N-OH-4ABP and 1-naphthol sulphation. Aromatic hydroxylamines and hydroxamic acids are known to be converted by sulphotransferase into reactive, electrophilic compounds capable of reacting with DNA. Our data show that the human foetus and neonate have the capacity to sulphate these compounds and thus is able to produce the reactive mutagenic metabolites. Therefore, this class of genotoxic compounds may be bioactivated by humans during development--a time when they are most vulnerable to the effects of genotoxins.

Adrenal Glands↗
PubMed1990

Structural specificity for biological activity of trichostatin A, a specific inhibitor of mammalian cell cycle with potent differentiation-inducing activity in Friend leukemia cells.

Biological activities of four chemically synthesized trichostatin-related compounds, (R)-trichostatin A, (S)-trichostatin A, (R)-trichostatic acid, and (S)-trichostatic acid, were investigated. Assays of differentiation-inducing activity in Friend leukemia cells and G2-arresting activity in the cell cycle of normal rat fibroblast cells were used as monitoring systems for comparing the bioactivities of these compounds. The results clearly showed that both of the enantiomers of trichostatic acid had no activity in both the assay systems. In the case of (S)-trichostatin A, the antipode of naturally occurring trichostatin A, 50% effective concentrations were determined to be 50-70-fold higher than those of (R)-trichostatin A. The relationship between this ratio and the value of enantiomeric excess strongly suggests that (S)-trichostatin A is also biologically inactive. These results indicate that the absolute configuration and the presence of the hydroxamate group of trichostatin A are essential for its biological activity.

Animals↗