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PubMed2006

Recent developments in the analysis of brominated flame retardants and brominated natural compounds.

This article reviews recent literature on the analysis of brominated flame retardants (BFRs) and brominated natural compounds (BNCs). The main literature sources are reviews from the last five years and research articles reporting new analytical developments published between 2003 and 2006. Sample pretreatment, extraction, clean-up and fractionation, injection techniques, chromatographic separation, detection methods, quality control and method validation are discussed. Only few new techniques, such as solid-phase microextraction (SPME) or pressurized liquid extraction (PLE), have been investigated for their ability of combining the extraction and clean-up steps. With respect to the separation of BFRs, the most important developments were the use of comprehensive two-dimensional gas chromatography for polybrominated diphenyl ethers (PBDEs) and the growing tendency for liquid-chromatographic techniques for hexabromocyclododecane (HBCD) stereoisomers and of tetrabromobisphenol-A (TBBP-A). At the detection stage, mass spectrometry (MS) has been developed as well-established and reliable technology in the identification and quantification of BFRs. A growing attention has been paid to quality assurance. Interlaboratory exercises directed towards BFRs have grown in popularity and have enabled laboratories to validate analytical methods and to guarantee the quality of their results. The analytical procedures used for the identification and characterization of several classes of BNCs, such as methoxylated polybrominated diphenyl ethers (MeO-PBDEs) (also metabolites of PBDEs), halogenated methyl or dimethyl bipyrroles (DBPs), are reviewed here for the first time. These compounds were generally identified during the routine analysis of BFRs and have received little attention until recently. For each topic, an overview is presented of its current status.

Analytic Sample Preparation Methods↗

PubMed2001

Screening of natural compounds for inhibitory activity on colon cancer cell migration.

We examined the effects of 75 kinds of natural compounds, such as alkaloids, phenylpropanoids, flavonoids, steroids and terpenoids on the in vitro migration and proliferation of colon 26-L5 cells, in comparison with anti-cancer drugs used for chemotherapy. Twenty-three of the 75 compounds inhibited markedly tumor cell migration. Among the 23 compounds, evodiamine showed the most potent and selective inhibitory activity on tumor cell migration with an IC50 value of 1.25 microg/ml, which was about 20 times lower than that for tumor cell proliferation. The migratory inhibition reached about 70% at 10 microg/ml of evodiamine. On the other hand, most of anti-cancer drugs tested, except for paclitaxel, had little effect on tumor cell migration at the concentrations strongly inhibiting tumor cell proliferation. Paclitaxel suppressed tumor cell migration in a concentration-dependent manner and achieved about 70% inhibition at 10 microg/ml with a marginal effect on cell proliferation. These results suggest that evodiamine and paclitaxel may be regarded as leading compounds for anti-metastatic agents acting through the inhibition of tumor cell migration without cytotoxicity.

Animals↗

PubMed1998

Synthesis and biological activity of chimeric structures derived from the cytotoxic natural compounds dolastatin 10 and dolastatin 15.

The natural cytotoxic compounds dolastatins 10 and 15 exhibit great similarities in structure and in their biological activity profiles. Two compounds (1 and 2) formed by interchanging the dolaisoleuine residue of dolastatin 10 and the MeVal-Pro dipeptide of dolastatin 15 were synthesized in order to evaluate the possible equivalence of these units. These compounds can be considered as chimeras of dolastatins 10 and 15 formed by the N-terminal part of the former and the C-terminal part of the latter and vice versa. Both analogues exhibited a marked decrease in their cytotoxic activity but showed similar differential cytotoxicity with regard to the cell lines assayed compared with the parent compounds. HT-29 cell line was the least sensitive one. However, this activity was in the nanomolar level and close to that of vincristine. The differences in their effect on tubulin polymerization were less pronounced. We confirmed the already known crucial role of the Dil residue in this assay. The nonequivalence of the Dil unit and the MeVal-Pro dipeptide probably reflects modification in the relative positions of the N-dimethylamino and the phenyl moieties.

Animals↗

PubMed1995

Selective toxicity of compounds naturally present in food toward the transformed phenotype of human colorectal cell line HT29.

It has previously been observed that allyl isothiocyanate, a compound naturally present in the diet, is more cytotoxic toward the human colorectal adenocarcinoma cell line HT29 in its control transformed state than after exposure to sodium butyrate or to dimethylformamide, which slow growth and induce differentiation (detransformation). In the present study, a range of other dietary compounds were assayed for such selective toxicity. These compounds were chosen as constituents of foodstuffs that have been identified from epidemiologic studies as being potentially antitumorigenic and also as having anticarcinogenic activity in experimental models. Benzyl and phenethyl isothiocyanate, benzyl thiocyanate, and quercetin showed decreased toxicity towards HT29 after detransformation of the cells by one or both treatments, whereas no change was observed in the sensitivity to diallyl sulfide or diallyl disulfide. It is proposed that the presence of such selectively toxic compounds in the diet may inhibit the development of tumors by interfering with the growth of preneoplastic lesions while having little effect on normal cells. The cumulative effects of these inhibitions may contribute to the chemopreventive properties of the parent foodstuffs observed in epidemiologic studies.

Adenocarcinoma↗

PubMed2006

Cluster analysis as selection and dereplication tool for the identification of new natural compounds from large sample sets.

Cluster analysis of gas-chromatographic (GC) data of ca. 500 bacterial isolates was used as an aid in detection and identification of new natural compounds. This approach reduces the number of GC/MS analysis (dereplication) and concomitantly improves the selection of samples with high probability to contain unknown natural products. Lipophilic bacterial extracts were derivatized and analyzed by GC under standardized conditions. A program was developed to convert chromatographic data into a two-dimensional matrix. Based on the results of hierarchical cluster analysis samples were selected for further investigation by GC/MS and NMR. This approach avoided unnecessary analysis of similar samples. By this method, the unusual oligoprenylsesquiterpenes 1 and 2 as well as new aromatic amides 7 and 8 were identified.

Bacteria↗

PubMed2003

A natural compound (reuterin) produced by Lactobacillus reuteri for biological-tissue fixation.

The study was undertaken to examine the degree of tissue fixation by reuterin, a natural compound produced by Lactobacillus reuteri, at distinct fixation conditions (pH, temperature, and fixative concentration). Additionally, the rate of tissue fixation by reuterin was investigated using glutaraldehyde as a control. It was found by the Fourier transformed infrared spectroscopy and nuclear magnetic resonance spectroscopy that both mono- and di-aldehyde reuterin oligomers may be present in the acidic and basic aqueous reuterin solutions. Therefore, reuterin may crosslink biological tissues as glutaraldehyde (a di-aldehyde agent). The degree of tissue fixation by reuterin is significantly affected by its fixation conditions. Generally, with increasing the pH, temperature, or fixative concentration, the reduction in free-amino-group content, denaturation temperature, tensile strength, and resistance against enzymatic degradation of the reuterin-fixed tissue increased significantly. Also, the rate of tissue fixation by reuterin is significantly slower than that by glutaraldehyde. However, after fixation, it was noted that the reuterin-fixed tissue has comparable free-amino-group content, denaturation temperature, tensile strength, and resistance against enzymatic degradation as the glutaraldehyde-fixed tissue.

Aldehydes↗

PubMed1994

Applicability of diffusion methods required by the pharmacopoeias for testing antibacterial activity of natural compounds.

The diffusion methods required by various pharmacopoeias were investigated in comparison to the bioautographic TLC assay in regard to the applicability and the statistical evaluation for testing the antibacterial activity of natural substances. Naringenin as an example for a weakly effective lipophilic natural compound and tetracycline as standard were used. Data were analysed by linear regression and ANOVA. The comparison of the disk diffusion method, the hole-plate diffusion method, and the bioautographic TLC assay showed that nature and amount of substance influence to a great extent the selection of the test method. The evaluation of parallelism demanded by the pharmacopoeias may provoke problems in comparing natural substances with strongly effective antibiotics. The simultaneous influence of different variables was examined with the help of ANOVA. The bioautographic TLC assay showed for spotted compounds a comparable reproducibility and accuracy to the diffusion methods mentioned above.

Analysis of Variance↗

PubMed1994

Injuries to cultivated BJA-B cells by ajoene, a garlic-derived natural compound: cell viability, glutathione metabolism, and pools of acidic amino acids.

Ajoene (4,5,9-trithiadodeca-1,6,11-triene-9-oxide), a garlic-derived natural compound, which had been shown to have cytostatic/cytotoxic properties, was tested with a B cell lymphoma-derived cell line (BJA-B cells) in order to elucidate its mechanism of cytotoxic action. Viability of the cells was determined by the Trypan blue exclusion test and the colorimetric tetrazolium (MTT) assay, whereas metabolic disturbance was evaluated by measuring the pools of reduced (GSH), oxidized glutathione (GSSG) and the acidic amino acids, Glu and Asp. Fast uptake of ajoene was accompanied by an immediate reduction of the GSH and increase in the GSSG levels. The extent of these changes, as well as the further development of the metabolite pools, depended on the ajoene dose per cell. At a sublethal ajoene dose the GSH and GSSG pools rose at the later stages to levels much higher than in the control experiment. Bleb formation at the cytoplasmic membrane was a further rapid phenomenon, although injuries detected by Trypan blue exclusion developed only at a later stage. The MTT assay, performed in a parallel experiment (48 h after ajoene addition), showed, however, that reduction of cell viability was established at the very beginning of ajoene exposure. Altogether, the action of ajoene strongly resembled oxidative stress (i.e., interference with SH homeostasis and its pleiotropic consequences to cell physiology and metabolism.

Amino Acids↗

PubMed1995

[Assessment of the quality and certification of biologically active synthetic and natural compounds].

The paper summarizes the authors' experimental findings and analyzes the present status and trends of assessment of the quality and certification of biologically active synthetic and natural compounds. It is shown that methods for qualitative determination of the similarity and difference of their physicochemical properties should be developed to make their objective assessment.

Drug Compounding↗

PubMed1998

Enzymatic modification of natural compounds with pharmacological properties.

Glycosides of various classes of natural products are widely distributed in nature, where they are often present esterified with aliphatic and aromatic acids at specific OH's of their sugar moieties. Many of these compounds are pharmacologically important molecules or possess other interesting properties. For instance, ginsenosides (e.g., 3) are therapeutic dammarane-type oligoglycosides isolated from the water-soluble portion of the dried roots and leaves of Panax ginseng C.A. Meyer (Aralianceae), a plant widely used in traditional Chinese medicine. In recent years, we have exploited the regioselectivity of lipases and proteases in organic solvents for the synthesis of specific esters of ginsenosides as well as the selectivity of the beta-1,4-galactosyltransferase from bovine colostrum to obtain new glycosyl derivatives of these compounds. The application of these two enzymatic methodologies has also been exemplified with other natural compounds with pharmacological properties: digitonin (5), colchicoside (6), and flavonoid glycosides.

Acylation↗

PubMed2006

Prediction of human absorption of natural compounds by the non-everted rat intestinal sac model.

A major concern in natural drug research is that many substances with potent biological activity in vitro are unable to generate good activity in vivo owing to their poor water-solubility, poor permeability and/or poor stability. The permeability of drug candidates across the intestinal mucosa is one of the most important factors in defining drug bioavailability and biological activity. In order to screen promising compounds for further investigation, a non-everted rat intestinal sac model has been developed successfully to assay the permeability of natural compounds and to predict their human absorption. In this system, the drug solution was placed in non-everted intestinal sacs (NEIS), which were placed in an acceptor solution and the permeability of drug across intestine walls was determined. The feasibility of this method has been validated and demonstrated for 11 model compounds chosen from currently marketed drugs whose human fraction absorbed (Fa) data have been reported. The results of the studies indicate that a good relationship exists between the permeability of the model drugs and their corresponding Fa data. The permeability of 13 natural compounds was evaluated using this system. Only fraxinellone and vitexin-7-glucoside exhibited high intestinal permeability, and predictive of excellent human absorption, which awaits confirmation from further investigation in vivo. This model provides an alternative method to everted intestinal sacs for the evaluation of in vitro permeability in rats, and for estimating human absorption of drugs. It may therefore hold great promise for oral absorption screening of new drug candidates.

Animals↗

PubMed2004

An ex-vivo angiogenesis assay as a screening method for natural compounds and herbal drug preparations.

Angiogenesis is a fundamental component of complex biological processes, including oncogenesis. The aim of this work was to optimise and validate an ex-vivo angiogenesis assay as a quantitative (PC image) biological method for testing promising natural compounds and herbal drug preparations for their pro-/anti-angiogenic activity. The bioassay is based on the principle of wound healing and quantifies the effect of angiogenic agents on neovessel outgrowth of human placental vessels embedded in a three-dimensional fibrin matrix. The assay was validated by using known, well characterised pro- and anti-angiogenic effectors (basic fibroblast growth factor and carboxyamidotriazole, respectively), and an angiogenesis inhibitor of plant origin (green tea leaves extract) was used as a reference product to demonstrate the applicability of the assay for plant extracts. Other standardised plant extracts prepared from olive tree leaves and horse chestnut seeds were tested for their angiogenic potential, but showed only slight inhibitory or no activity, respectively. The results presented here indicate that this human ex-vivo angiogenic assay is "ready to use" for screening of herbal drug preparations and pure compounds.

Aesculus↗

PubMed2004

[Screening of natural compounds with hypolipidemic activity].

In the screening programme for natural hypolipidemic compounds 702 strains of soil microorganisms were tested and 25 of them were selected because of their ability to produce compounds inhibiting sterol synthesis in Hep G2 hepatoma cells. The compounds were estimated in the microbiological model with Tolypocladium inflatum 106 as the test microbe. The 2nd stage of the screening resulted in isolation of 13 strains producing compounds with high hypolipidemic activity, analogous to or higher than the activity of lovastatin in the experimental models.

Cell Line, Tumor↗

PubMed2005

A natural compound (ginsenoside Re) isolated from Panax ginseng as a novel angiogenic agent for tissue regeneration.

PURPOSE: The primary challenge for tissue engineering is to develop a vascular supply that can support the metabolic needs of the engineered tissues in an extracellular matrix. In this study, the feasibility of using a natural compound, ginsenoside Re, isolated from Panax ginseng in stimulating angiogenesis and for tissue regeneration was evaluated. METHODS: Effects of ginsenoside Re on the proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) were examined in vitro. Additionally, angiogenesis and tissue regeneration in a genipin-fixed porous acellular bovine pericardium (extracellular matrix; ECM) incorporated with ginsenoside Re implanted subcutaneously in a rat model were investigated. Basic fibroblast growth factor (bFGF) was used as a control. RESULTS: It was found that HUVEC proliferation, migration in a Transwell plate, and tube formation on Matrigel were all significantly enhanced in the presence of bFGF or ginsenoside Re. Additionally, effects of ginsenoside Re on HUVEC proliferation, migration, and tube formation were dose-dependent and reached a maximal level at a concentration of about 30 microg/ml. The in vivo results obtained at 1 week postoperatively showed that the density of neocapillaries and the tissue hemoglobin content in the ECMs were significantly enhanced by bFGF or ginsenoside Re. These results indicated that angiogenesis in the ECMs was significantly enhanced by loading with bFGF or ginsenoside Re. At 1 month postoperatively, vascularzied neo-connective-tissue fibrils were found to fill the pores in the ECMs loaded with bFGF or ginsenoside Re. CONCLUSIONS: The aforementioned results indicated that like bFGF, ginsenoside Re-associated induction of angiogenesis enhanced tissue regeneration, supporting the concept of therapeutic angiogenesis in tissue-engineering strategies.

Angiogenesis Inducing Agents↗

PubMed2006

New therapeutic approach for myeloid leukemia: induction of apoptosis via modulation of reactive oxygen species production by natural compounds.

The therapeutic approach to acute myeloid leukemia is based on chemotherapy, but the side effects of the drugs used and various complications, including infections and bleedings, are sometimes fatal. Recently, imatinib mesylate has shown remarkable efficacy and less toxicity as a molecularly targeted therapy in patients with chronic myeloid leukemia. Natural products appear to be safer than the current chemotherapeutic drugs, and we have therefore sought out new potential agents from various natural compounds with the ability to induce the apoptosis of myeloid leukemic cells.

Animals↗

PubMed2002

Biocompatibility study of biological tissues fixed by a natural compound (reuterin) produced by Lactobacillus reuteri.

Glutaraldehyde-fixed biological tissues have been used extensively to fabricate various bioprostheses. However, the tendency for glutaraldehyde to markedly alter tissue stiffness and promote tissue calcification is a well-recognized drawback of this crosslinking agent. To overcome the aforementioned deficiency with the glutaraldehyde-fixed bioprostheses, a fixation technique using a natural compound (reuterin) produced by Lactobacillus reuteri to crosslink biological tissues was developed by our group. It was reported that reuterin inhibits the growth of gram-positive and gram-negative bacteria as well as yeasts, fungi, and protozoa. The study was conducted to evaluate the biocompatibility of the reuterin-fixed tissues with or without ethanol sterilization implanted subcutaneously in a growing rat model. Fresh and the glutaraldehyde-fixed counterparts were used as controls. The results showed that both glutaraldehyde and reuterin are effective antimicrobial agents in the sterilization of biological tissues. The degrees in inflammatory reaction for the reuterin-fixed tissues with or without ethanol sterilization were significantly less than their glutaraldehyde-fixed counterparts throughout the entire course of the study. Additionally, the reuterin-fixed tissues have comparable tensile strengths and resistance against degradation as the glutaraldehyde-fixed tissues. The results obtained at 12-month postoperatively showed that the glutaraldehyde-fixed tissue without ethanol sterilization became significantly stiff and calcified. However, it was found that ethanol sterilization of the glutaraldehyde-fixed tissue may inhibit calcification. Additionally, reuterin fixation may inhibit tissue calcification as compared to glutaraldehyde fixation. These observations implied that the biocompatibility of the reuterin-fixed tissue is superior to the glutaraldehyde-fixed tissue.

Aldehydes↗

PubMed2006

Medical benefits of using natural compounds and their derivatives having multiple pharmacological actions.

The multiple pharmacological actions of a unique compound are a prerequisite for classifying drugs as highly efficacious, because the multiple pharmacological actions offer the possibility of treating various symptoms of chronic diseases as described below. 1) Sustained hyperglycemia induces macrovascular and microvascular complications in type 2 diabetes mellitus. Antihyperglycemic medication and the control of postprandial hyperglycemia are essentially important for normalizing plasma glucose level. Gymnemic acid IV isolated from Gymnema sylvestre (Asclepiadaceae) leaves has antisweet, antihyperglycemic, glucose uptake inhibitory, and gut glycosidase inhibitory effects. Most of these pharmacological effects may synergistically contribute to alleviating type 2 diabetes-related symptoms. 2) Diabetic skeletal and vascular smooth muscles are hypersensitive to chemical transmitters, cytokines and autacoids. The sensitivity of neuromuscular synapses is enhanced in diabetes, which seems to be closely associated with neuropathy as one of the diabetic complications. beta-Eudesmol found in Atractylodes lancea rhizome has a desensitizing channel blocking action to nicotinic acetylcholine receptors, anti-angiogenic action in vascular endothelium, and neuronal differentiation actions. These multiple pharmacological actions are favorable for treating angiogenic diseases possibly including the complications of diabetes, namely, retinopathy and nephropathy, and cancer. 3) Nipradilol is clinically utilized as a topical antiglaucoma drug. The ocular hypotensive effects of this compound are brought about by its alpha1 and beta-adrenergic receptor blocking actions, and nitric oxide (NO) releasing action. NO directly activates cyclooxygenases. All these pharmacologic effects are beneficial for treating glaucoma. The selectivity and specificity of drug action are required for treating acute diseases, infections or for acting as useful reagents. The pleiotropic actions of natural compounds and their derivatives serve as important clues for developing new drugs for various chronic diseases.

Adrenergic Antagonists↗

PubMed2004

A natural compound (reuterin) produced by Lactobacillus reuteri for hemoglobin polymerization as a blood substitute.

Stroma-free hemoglobin (Hb) has been modified by pyridoxylation and followed by polymerization with glutaraldehyde as a blood substitute. Nevertheless, the reaction rate of pyridoxylated Hb (PLP-Hb) with glutaraldehyde is too fast to control its molecular weight distribution. Additionally, it was reported that glutaraldehyde is cytotoxic even at low doses. To overcome these problems, another aldehyde, beta-hydroxypropionaldehyde (beta-HPA), was used in the study to polymerize hemoglobin (PLP-Hb). beta-HPA is a natural compound (reuterin) produced by Lactobacillus reuteri. It was found that the maximum degree of PLP-Hb polymerization by reuterin (RR-PLP-Hb) was approximately 40% if the formation of high molecular (> 500 kDa) polymers should be prevented. In contrast, at the same reaction condition, the glutaraldehyde-polymerized PLP-Hb solution became gel-like, due to overpolymerization. This indicated that the rate of PLP-Hb polymerization by reuterin was significantly slower than that by glutaraldehyde. With increasing the reaction temperature, PLP-Hb concentration, or reuterin-to-PLP-Hb molar ratio, the time to reach the maximum degree of PLP-Hb polymerization by reuterin became significantly shorter. Removal of unpolymerized PLP-Hb from the RR-PLP-Hb solution can be effectively achieved by a gel-filtration column. The P(50) value of the unmodified Hb solution was 14 torr, while that of the RR-PLP-Hb solution was 20 torr, an indication of lower oxygen affinity. Additionally, the oxygen-Hb dissociation curves for both test solutions had a sigmodial shape and a nearly 100% saturation at 100 torr. In the in vivo study, it was found that the animals treated with the RR-PLP-Hb solution all survived and remained healthy more than 3 months. In contrast, only one out of six rats survived for the control group treated with the unmodified Hb solution. Furthermore, it was found that the RR-PLP-Hb solution resulted in a significantly longer circulation time ( approximately 12 h) than the unmodified Hb solution ( approximately 1.5 h). These results suggest that the reuterin-polymerized PLP-Hb solution may be a new option in the development of blood substitutes.

Aldehydes↗