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Biomedical subjects

Peter Forgo

Publications and source records attributed to Peter Forgo.

17 recordsLinked to original sources
PubMed2006

Phenanthrenes and a dihydrophenanthrene from Tamus communis and their cytotoxic activity.

From the petroleum ether extract of the rhizomes of Tamus communis, the 7-hydroxy-2,3,4,8-tetramethoxyphenanthrene (1) was isolated, together with the known 2,3,4-trimethoxy-7,8-methylenedioxyphenanthrene (2), 3-hydroxy-2,4,-dimethoxy-7,8-methylenedioxyphenanthrene (3), 2-hydroxy-3,5,7-trimethoxyphenanthrene (4) and 2-hydroxy-3,5,7-trimethoxy-9,10-dihydrophenanthrene (5), through cytotoxic assay guidance. The structures were determined by means of HREIMS, (1)H NMR, JMOD and NOESY experiments. The cytotoxic effects of the isolated compounds were tested on cervix adenocarcinoma (HeLa) cells, with the MTT assay. The results demonstrated that, with the exception of 2, all these compounds displayed pronounced cytotoxic activity; especially 1 and 3 exhibited significant cell growth inhibitory effects, with IC(50)=8.52+/-0.70 and 3.64+/-0.12 microM, respectively.

Cell Survival↗
PubMed2006

Cytotoxic phenanthrenes from the rhizomes of Tamus communis.

From the fresh rhizomes of Tamus communis five phenanthrenes (1 - 5) were isolated under the guidance of cytotoxic assays in HeLa cells. The compounds were obtained from the highly active CHCl (3) fraction of the MeOH extract by using multistep chromatographic purifications, including VLC, preparative TLC, HPLC and gel filtration. The compounds were identified by means of EI-mass, UV and NMR spectroscopy as 7-hydroxy-2,3,4-trimethoxyphenanthrene (1), 2,7-dihydroxy-3,4-dimethoxyphenanthrene (nudol) (2), 2,7-dihydroxy-3,4,8-trimethoxyphenanthrene (3), 3,7-dihydroxy-2,4,8-trimethoxyphenanthrene (confusarin) (4), and 3,7-dihydroxy-2,4-dimethoxyphenanthrene (5). Compound 1 is a new natural product, and 2 - 4 were isolated for the first time from T. communis. In the cytotoxic assays, compounds 1 - 3 and 5 significantly inhibited the growth of HeLa cells (IC (50) = 0.97 - 20.18 microM). Compound 3, with an IC (50) value of 0.97 microM, is of special interest because of its high activity.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Leucovernine and acetylleucovernine, alkaloids from Leucojum vernum.

The fresh bulbs of Leucojum vernum provided seven tyrosine-derived alkaloids; two of them have not been reported before and are named leucovernine and acetylleucovernine. The five known alkaloids were N-demethylgalanthamine, hippeastrine, 9-O-demethylhomolycorine, 5alpha-hydroxyhomolycorine, and 11-hydroxyvittatine. These compounds have been isolated from this species for the first time. The structure determination was carried out by the combination of liquid-phase one- and two-dimensional NMR spectroscopy and high-resolution mass spectrometry.

Amaryllidaceae Alkaloids↗
PubMed2004

Vanadium(IV,V) complexes of D-saccharic and mucic acids in aqueous solution.

The vanadium(IV,V) complexes formed with two aldaric acids (D-saccharic or D-glucaric acid, and mucic or galactaric acid) in aqueous solution were characterised by employing pH-potentiometry, EPR, multinuclear NMR and UV-VIS spectroscopy. The stoichiometry and stability constants of the complexes formed were determined at 25 degrees C and ionic strength I= 0.2 mol dm(-3)(KCl). The spectral measurements revealed that vanadium(IV,V) coordinates first at the terminal COO(-) functions, forming mononuclear complexes. At pH > 3, through the metal ion-induced deprotonation and coordination of the neighbouring alcoholic functions, (COO(-), O(-)) coordinated dinuclear complexes are formed, which predominate in the pH range 4-8. In the basic pH range, the ligand molecules are displaced and binary metal hydroxo and oxo complexes are present. EPR measurements at room temperature and at 140 K proved that formation of the VO(iv) dimers is more enhanced at room temperature, but at 140 K their dissociation is favoured. An interesting pH-dependent cis-trans isomeric equilibrium was assumed and analysed by EPR and molecular modelling in the case of the complexes [(VO)(2)L(2)H(x)](x=-2 and -4). Joint evaluation of the pH-potentiometric and (51)V NMR measurements revealed that both aldaric acids are able to bind an excess of vanadium(V), through the formation of oligomeric 2:1 and 3:2 species, besides the 2:2 species formed with VO(IV).

Glucaric Acid↗
PubMed2004

Gradient enhanced selective experiments in the 1H NMR chemical shift assignment of the skeleton and side-chain resonances of stigmasterol, a phytosterol derivative.

The applicability of homonuclear gradient enhanced NMR experiments is demonstrated in the structure determination of steroid derivatives using stigmasterol as a model compound. High resolution 1H NMR spectra of steroids very often display well resolved multiplets usually in the low-field region, and these signals can be used as starting points in several selective NMR experiments to study scalar (J coupling), and dipolar (NOE) interactions. Selective excitation was carried out using a double pulsed-field gradient spin-echo sequence (DPFGSE) in which 180 degrees Gaussian pulses are sandwiched between sine shaped z-gradients. Scalar interactions were studied by homonuclear DPFGSE-COSY, DPFGSE-relay-COSY and DPFGSE-TOCSY experiments, while DPFGSE-NOESY was used to monitor spatial environment of the selectively excited proton. These methods provided unambiguous assignments for signals of the main skeleton and the side-chain of the steroid molecule. In addition, they allowed determination of the conformationally important homonuclear proton-proton coupling constants (J).

Magnetic Resonance Spectroscopy↗
PubMed2004

Alkaloids from Leucojum vernum and antiretroviral activity of Amaryllidaceae alkaloids.

Three alkaloids, lycorine, homolycorine and 2- O-acetyllycorine, were isolated from the bulbs of Leucojum vernum (Amaryllidaceae) and identified by means of NMR analysis. The alkaloids obtained from L. vernum and from other Amaryllidaceae species were studied in vitro for HIV-1 replication inhibitory activity on MT4 cells. The cytotoxicity of the compounds in uninfected cells was evaluated by using the MTT assay and the [ (3)H]thymidine incorporation test. The antiviral activities were determined by means of the p24 antigen assay and solid-phase reverse transcriptase testing. The results demonstrate that trisphaeridine, lycorine, homolycorine, and haemanthamine possess high antiretroviral activities (IC (50) = 0.4 - 7.3 microg/mL), accompanied by low therapeutic indices (TI (50) = 1.3 - 1.9).

Alkaloids↗
PubMed2003

Identification of tryptophan and beta-carboline as paralysins in larvae of the yellow mealworm, Tenebrio molitor.

Acidic methanolic, whole body extracts of larval Tenebrio molitor (Insecta, Coleoptera) and other juvenile insects are highly toxic to adults of the same species and other species: injection causes instant paralysis to death. Referring to their dramatic effect in mature insects, the responsible compounds have been designated as "paralysins." Two paralysins have already been identified in the flesh fly, Neobellieria bullata, i.e., beta-alanine-tyrosine (BAY) and 3-hydroxykynurenine (3HK). We report here the isolation, from larval T. molitor, of two additional paralysins, respectively, the essential amino acid, tryptophan (Trp), and the saturated beta-carboline, 1,2,3,4,-tetrahydro-beta-carboline-3-carboxylic acid (THCA).

Animals↗
PubMed2003

Inclusion complexes of ketosteroids with beta-cyclodextrin.

Inclusion complexes of several steroid derivatives with beta-cyclodextrin (7) were studied in dimethylsulfoxide solution. The investigated molecules were ketosteroids with different functional groups on the skeleton: 3beta-acetoxypregn-5-en-20-one (1), 3beta-acetoxypregna-5,16-dien-20-one (2), 3beta-acetoxyandrost-5-en-17-one (3), 3beta-hydroxyandrost-5-en-17-one (4), 5alpha-androstane-3,17-dione (5) and 17beta-hydroxyandrost-4-en-3-one (6). Complex formation was monitored by two-dimensional ROESY experiments through the detection of intermolecular dipolar interactions. In case of inclusion complex formation, the steroid molecule penetrates the cavity of the cyclodextrin and dipole-dipole interactions (ROEs) can be detected between the glucose H-3 and H-5 protons inside the cyclodextrin cavity and the steroid skeletal protons. Intermolecular interactions were detected in all six cases. However, ROESY experiments provided data indicating only partial immersion (A and B ring of the steroid skeleton) in case of 1, 2 and 6. On the contrary, compounds 3 and 5, showing the most correlation rich spectra, seem to fully immerse in the beta-cyclodextrin cavity.

Cyclodextrins↗
PubMed2003

Jatrophane diterpenoids from Euphorbia mongolica as modulators of the multidrug resistance of L5128 mouse lymphoma cells.

The dried aerial parts of Euphorbia mongolica afforded three new acylated polyhydroxy diterpenoids based on the jatrophane framework. The structures were established by means of a combination of 1D and 2D NMR techniques and mass spectrometry as (2S,3S,4R,5R,7S,8R,13S,15R)-5alpha,7beta,8alpha-triacetoxy-3beta-benzoyloxy-15beta-hydroxyjatropha-6(17),11E-diene-9,14-dione (1), (2S,3S,4R,5R,7S,8S,9S13S,15R)-5alpha,7beta,8alpha,9alpha,15beta-pentaacetoxy-3beta-benzoyloxyjatropha-6(17),11E-dien-14-one (2), and (2S,3S,4R,5R,7S,8S,9S13S,15R)-3beta,7beta,8alpha,9alpha,15beta-pentaacetoxy-5alpha-benzoyloxyjatropha-6(17),11E-dien-14-one (3). When the isolates were assayed for multidrug resistance-reversing activity in a rhodamine 123 exclusion test using L5178 mouse lymphoma cells, all compounds demonstrated a concentration-dependent effect in inhibiting the efflux pump activity of these tumor cells in the range 11.2-112 microM.

Animals↗
PubMed2003

New diterpenoids from the aerial parts of Salvia candelabrum.

The new diterpenoids, candesalvoquinone, 12- O-methylcandesalvone B, candesalvone B methyl ester with the 3,4-secoabietane skeleton, and candelabroquinone with the abietane skeleton were isolated from the aerial parts of Salvia candelabrum, together with the known compound candelabrone. The structures were established by mass spectroscopy and advanced two-dimensional NMR methods, including 1H-NMR, JMOD, 1H- 1H COSY, HSQC, HMBC and NOESY experiments.

Diterpenes↗
PubMed2003

Diterpenes from the aerial parts of Salvia candelabrum and their protective effects against lipid peroxidation.

A methanolic extract of the aerial parts of Salvia candelabrum was subjected to multiple chromatographic separation under the guidance of anti-lipid peroxidation assay. From the most active fractions seven abietane and seco-abietane diterpenes were isolated by preparative TLC purification. Besides candesalvoquinone, candelabroquinone, 12- O-methylcandesalvone B, candesalvone B methyl ester and candelabrone (all reported earlier), the known candesalvone B and the new candesalvolactone were identified. The structures were established by means of mass spectroscopy and advanced 2D NMR methods. All the identified compounds were evaluated for antioxidant activity in enzyme-dependent (IC (50) values 3.49 - 10.42 microM) and enzyme-independent (IC (50) values 1.40 - 13.40 microM) systems of lipid peroxidation. All compounds displayed marked concentration-dependent effects in both tests as compared with those of authentic ascorbic, rosmarinic and caffeic acids. The differences in antioxidant capacities observed in the enzyme-independent system allowed conclusions concerning structure-activity relationships.

Antioxidants↗
PubMed2002

Discovery and biological evaluation of a new family of potent modulators of multidrug resistance: reversal of multidrug resistance of mouse lymphoma cells by new natural jatrophane diterpenoids isolated from Euphorbia species.

The effects of 15 jatrophane diterpene polyesters (1-3 and 5-16) isolated from lipophilic extracts of Euphorbia serrulata, E. esula, E. salicifolia, and E. peplus (Euphorbiaceae) on the reversion of multidrug resistance of mouse lymphoma cells were examined. The structures of five new compounds (1-5) were elucidated by spectroscopic methods, including HRFABMS, ESIMS, (1)H-(1)H homonuclear and (1)H-(13)C heteronuclear correlations, long-range correlation spectra, and NOESY experiments. The stereochemistry and absolute configuration of one compound (3) were determined by X-ray crystallography. The structure-activity relationship is discussed.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

Syntheses and advanced NMR structure determination of androsteno-[17,16-d]-pyrimidine derivatives.

Reactions of 16-hydroxymethylene- and 16-aminomethylene-3beta-hydroxy-5-androsten-17-one with formamide and guanidine were carried out resulting in the formation of [16,17-d]-pyrimidine rings. Advanced two-dimensional NMR methods were used to investigate the structure of the products. Homonuclear-, and heteronuclear chemical shift correlation experiments yielded the complete 1H-, 13C- and 15N signal assignment for these compounds.

Androstenes↗
PubMed2002

Norditerpenoid alkaloids from Consolida orientalis and complete 1H and 13C NMR signal assignments of some lycoctonine-type alkaloids.

A new norditerpene alkaloid was isolated, 18-demethylpubescenine (1), in addition to four known compounds, 14-demethyltuguaconitine (2), takaosamine (3), gigactonine (4), and delcosine (5), from fresh, whole plants of Consolida orientalis. The structure of 1 was established by spectroscopic methods, including various 2D NMR techniques and HRESIMS. As a result of a detailed NMR study, complete 1H NMR chemical shift assignments for alkaloids 1-5 are presented herein, and some 13C NMR signal assignments for 2-4 have been revised.

Alkaloids↗
PubMed2002

Antiproliferative amaryllidaceae alkaloids isolated from the bulbs of Sprekelia formosissima and Hymenocallis x festalis.

Seven alkaloids were isolated from Sprekelia formosissima, and five from Hymenocallis x festalis. Tazettine, lycorine, haemanthidine and haemanthamine were evaluated for antiproliferative and multidrug resistance (mdr) reversing activity on mouse lymphoma cells. Lycorine, haemanthidine and haemanthamine displayed pronounced cell growth inhibitory activities against both drug-sensitive and drug-resistant cell lines, but did not significantly inhibit mdr-1 p-glycoprotein. Thus, the tested alkaloids are apparently not substrates for the mdr efflux pump. Assays for interactions with DNA and RNA revealed that the antiproliferative effects of lycorine and haemanthamine result from their complex formation with RNA.

Alkaloids↗