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PubMed2002

An approach to furolabdanes and their photooxidation derivatives from R-(+)-sclareolide.

A synthetic route to furolabdanes from commercially available R-(+)-sclareolide is reported, with the specific aim of preparing (12R and 12S,15xi)-12,15-dihydroxylabda-7,13-dien-16,15-olides (3 and 5) and (12R and 12S,16xi)-12,16-dihydroxylabda-7,13-dien-15,16-olides (4 and 6). The key points of our approach are the use of Weinreb's amide 11 to join the furan ring to the terpenic unit. Photooxidation of the furan moiety of compounds 15 and 16, and of their acetates 19 and 20, has been used to built the hydroxybutenolide fragment. In this way the four possible isomers at the butenolide moiety, compounds 3-6, and their C-12 acetyl derivatives 21-24 have been obtained. On the basis of comparison of the spectral data ((1)H NMR) of the synthetic peracetates 25-28 (derived from 21-24) with the reported data for the peracetate 2 (derived from the natural product 1), the relative configuration at carbon C-12 of the natural product has been corrected. Furthermore, the absolute configuration of the natural product 1, considered to belong to the enantio-series, has to be changed to the normal-series on the basis of the optical rotation obtained for the synthetic derivative.

Asteraceae↗

PubMed2002

In vitro cytotoxic activity of phenanthroindolizidine alkaloids from Cynanchum vincetoxicum and Tylophora tanakae against drug-sensitive and multidrug-resistant cancer cells.

Two known phenanthroindolizidine alkaloids, (-)-(R)-13aalpha-antofine (1) and (-)-(R)-13aalpha-6-O-desmethylantofine (2), and two new natural products, (-)-(R)-13aalpha-secoantofine (3) and (-)-(R)-13aalpha-6-O-desmethylsecoantofine (4), were isolated from Cynanchum vincetoxicum. The structures of all compounds were established by means of NMR methods including COSY, NOESY, HSQC, and HMBC experiments, supported by HRMS and optical rotation data. Cytotoxic activity of the isolated alkaloids, and of three other alkaloids previously isolated from Tylophora tanakae, (-)-(R)-13aalpha-tylophorine (5), (-)-(R)-13aalpha-7-O-desmethyltylophorine (6), and (+)-(S)-13abeta-isotylocrebrine (7), was assessed in vitro using a drug-sensitive KB-3-1 and a multidrug-resistant KB-V1 cancer cell line. Structure-activity relationships in this series of alkaloids are discussed. The IC(50) values of some of the alkaloids are in the low nanomolar range, being thus comparable to the activity of clinically used cytotoxic drugs. Previously reported adverse side effects of these alkaloids could possibly be overcome by modern tissue-specific drug targeting techniques.

Alkaloids↗

PubMed2002

Microbial and chemical transformation studies of the bioactive marine sesquiterpenes (S)-(+)-curcuphenol and -curcudiol isolated from a deep reef collection of the Jamaican sponge Didiscus oxeata.

Microbial and chemical transformation studies of the marine sesquiterpene phenols (S)-(+)-curcuphenol (1) and (S)-(+)-curcudiol (2), isolated from the Jamaican sponge Didiscus oxeata, were accomplished. Preparative-scale fermentation of 1 with Kluyveromyces marxianus var. lactis (ATCC 2628) has resulted in the isolation of six new metabolites: (S)-(+)-15-hydroxycurcuphenol (3), (S)-(+)-12-hydroxycurcuphenol (4), (S)-(+)-12,15-dihydroxycurcuphenol (5), (S)-(+)-15-hydroxycurcuphenol-12-al (6), (S)-(+)-12-carboxy-10,11-dihydrocurcuphenol (7), and (S)-(+)-12-hydroxy-10,11-dihydrocurcuphenol (8). Fourteen-days incubation of 1 with Aspergillus alliaceus (NRRL 315) afforded the new compounds (S)-(+)-10beta-hydroxycurcudiol (9), (S)-(+)-curcudiol-10-one (10), and (S)-(+)-4-[1-(2-hydroxy-4-methyl)phenyl)]pentanoic acid (11). Rhizopus arrhizus (ATCC 11145) and Rhodotorula glutinus (ATCC 15125) afforded (S)-curcuphenol-1alpha-D-glucopyranoside (12) and (S)-curcudiol-1alpha-D-glucopyranoside (13) when incubated for 6 and 8 days with 1 and 2, respectively. The absolute configuration of C(10) and C(11) of metabolites 7-9 was established by optical rotation computations. Reaction of 1 with NaNO(2) and HCl afforded (S)-(+)-4-nitrocurcuphenol (14) and (S)-(+)-2-nitrocurcuphenol (15) in a 2:1 ratio. Acylation of 1 and 2 with isonicotinoyl chloride afforded the expected esters (S)-(+)-curcuphenol-1-O-isonicotinate (16) and (S)-(+)-curcudiol-1-O-isonicotinate (17), respectively. Curcuphenol (1) shows potent antimicrobial activity against Candida albicans, Cryptococcus neoformans, methicillin-resistant Staphylococcus aureus, and S. aureus with MIC and MFC/MBC ranges of 7.5-25 and 12.5-50 microg/mL, respectively. Compounds 1 and 3 also display in vitro antimalarial activity against Palsmodium falciparium (D6 clone) with MIC values of 3600 and 3800 ng/mL, respectively (selectivity index >1.3). Both compounds were also active against P. falciparium (W2 clone) with MIC values of 1800 (S.I. >2.6) and 2900 (S.I. >1.6) ng/mL, respectively. Compound 14 shows anti-hepatitis B virus activity with an EC(50) of 61 microg/mL.

Animals↗

PubMed2003

Chemical and biological investigation of the fungus Pulveroboletus ravenelii.

Two new compounds, pulveraven A (1) and pulveraven B (2), as well as vulpinic acid (3) and its previously unreported polymorph were isolated from the fruiting body of Pulveroboletus ravenelii. The structures were determined using a combination of NMR, MS, IR, optical rotation, molecular modeling, and X-ray analysis. The isolates were evaluated for antimicrobial activity as well as their potential to inhibit cyclooxygenase (COX) activity and carcinogen-induced preneoplastic lesion formation with mouse mammary organ culture (MMOC).

Agaricales↗

PubMed2003

New lysophosphatidylcholines and monoglycerides from the marine sponge Stelletta sp.

Two new lysophosphatidylcholines (1, 2) and four new monoglycerides (5-8) were isolated from the marine sponge Stelletta sp. by bioactivity-guided fractionation. The planar structures of the new compounds were established on the basis of NMR and MS analyses. The stereochemistry was defined by comparison of the optical rotation. The compounds were evaluated for cytotoxicity against a small panel of five human tumor cell lines.

Animals↗

PubMed2003

Molecular structure and stereochemistry of silybin A, silybin B, isosilybin A, and isosilybin B, Isolated from Silybum marianum (milk thistle).

Two pairs of diastereoisomeric flavonolignans, silybin A, silybin B, isosilybin A, and isosilybin B, were successfully separated from Silybum marianum by sequential silica gel column chromatography, preparative reversed-phase HPLC, and recrystallization. Complete stereochemical assignments at C-2, C-3, C-7', and C-8' of these flavonolignans have been achieved. On the basis of X-ray crystallographic analysis and optical rotation data, coupled with comprehensive (1)H and (13)C NMR spectral data interpretation including COSY, HMQC, and HMBC, the stereochemistry of these diastereoisomers was determined unambiguously as silybin A (4), 2R, 3R, 7'R, 8'R; silybin B (5), 2R, 3R, 7'S, 8'S; isosilybin A (6), 2R, 3R, 7'R, 8'R; and isosilybin B (7), 2R, 3R, 7'S, 8'S.

Drugs, Chinese Herbal↗

PubMed2003

Dibenzylbutyrolactone and dibenzylbutanediol lignans from Peperomia duclouxii.

Nine new lignans (1-9), including five dibenzylbutyrolactones and four dibenzylbutanediols, were obtained from an ethyl acetate extract of the whole plants of Peperomia duclouxii. The structures of 1-9 were determined by spectroscopic methods (mainly extensive 1D and 2D NMR experiments and by mass spectral measurements). The absolute structures were elucidated as 2S,3S from their optical rotations and by chemical transformations.

4-Butyrolactone↗

PubMed2004

New cytotoxic metabolites from a marine sponge Homaxinella sp.

Three new butenolides (1-3), a new cyclopentenone derivative (4), and a known alcohol (5) were isolated from a marine sponge Homaxinella sp. by bioactivity-guided fractionation. The planar structures were established on the basis of NMR and MS analyses. The stereochemistry of the butenolides and cyclopentenone derivative was defined on the basis of optical rotation and CD spectroscopy. The compounds were tested for cytotoxicity against a panel of five human solid tumor cell lines and displayed marginal to significant activity.

Alcohols↗

PubMed2004

Syncarpamide, a new antiplasmodial (+)-norepinephrine derivative from Zanthoxylum syncarpum.

A new (+)-norepinephrine derivative, syncarpamide (1), along with a known coumarin, (+)-S-marmesin (2), and one known alkaloid, decarine (3), have been isolated from the stem of Zanthoxylum syncarpum. The structure of compound 1 was elucidated on the basis of 1D and 2D NMR, MS, IR, optical rotation, and CD analyses. Its absolute stereochemistry was elucidated by synthesis of its enantiomer and subsequent comparison of CD data. Characterizations of compounds 2 and 3 were based on spectral analysis and comparison with reported data. Compounds 1 and 3 showed antiplasmodial activity, with IC(50) values of 2.04 and 1.44 microM against Plasmodium falciparum D(6) clone and 3.06 and 0.88 microM against P. falciparum W(2) clone, respectively. Compound 3 showed cytotoxicity at 56.42 microM, whereas compound 1 was not cytotoxic at 10.42 microM. Compound 1 was tested for hypotensive activity, but no activity was observed. Compound 2 showed no antiplasmodial or antimicrobial activities.

Animals↗

PubMed2004

Isolation of a library of aromadendranes from Landolphia dulcis and its characterization using the VolSurf approach.

A library of nine aromadendrane-type sesquiterpenes (1-9), including eight new natural products (1-5 and 7-9), was isolated from Landolphia dulcis var. barteri along with a previously described cadinane derivative (10) and a new muurolane derivative (11). The structures of all compounds were established by means of NMR methods including COSY, NOESY, HSQC, and HMBC experiments, supported by HRMS and optical rotation data. Virtual characterization of the aromadendrane library (1-9) was performed using chemoinformatics tools. 3D molecular fields were calculated with the GRID program using low-energy structures obtained with the MMFF force field. VolSurf descriptors were calculated from the GRID maps and subsequently analyzed by multivariate statistics. The analysis disclosed the presence of a common motif for possible interactions of the aromadendranes with a putative target receptor. At the same time, a considerable chemical diversity within the library was disclosed, despite a close biosynthetic relationship of its members. The results can be interpreted in terms of evolutionary optimization of structures of secondary metabolites for interaction with macromolecular targets and are of interest in terms of assessment of potential "drug-likeness" of natural products.

Apocynaceae↗

PubMed2005

Cytotoxic bisindole alkaloids from a marine sponge Spongosorites sp.

Three new bisindole alkaloids of the hamacanthin class (1-3) and one new bisindole alkaloid of the topsentin class (6) were isolated along with known bisindole alkaloids (4, 5, 7-11) from the MeOH extract of a marine sponge Spongosorites sp. by bioactivity-guided fractionation. The planar structures were established on the basis of NMR, MS, and IR spectroscopic analyses. Configurations of compounds 1-4 were derived from 1H NMR data and optical rotation. Compounds 1, 4, 5, and 11 showed moderate to significant cytotoxicity against five human tumor cell lines, and compounds 1-5 showed weak antibacterial activity against clinically isolated methicillin-resistant strains.

Animals↗

PubMed2004

Cytotoxic furanosesterterpenes from a marine sponge Psammocinia sp.

Three new (1-3) and seven known (4-10) cytotoxic furanosesterterpenes were isolated from a marine sponge Psammocinia sp. by bioactivity-guided fractionation. The structures were established on the basis of NMR and MS analyses. The geometry and absolute configuration were determined on the basis of optical rotation, NMR, and CD data. These compounds were evaluated for cytotoxicity against a small panel of five human tumor cell lines, and most of the compounds showed toxicity to SK-MEL-2. The mixture of compounds 7 and 8 displayed significant inhibition of DNA replication and moderate antioxidant profile.

Animals↗

PubMed2005

Isolation and structure elucidation of the new fungal metabolite (-)-xylariamide A.

Chemical investigations of the terrestrial microfungus Xylaria sp. have afforded the new natural product (-)-xylariamide A (1). The gross structure of 1 was determined by interpretation of 1D and 2D NMR, UV, IR, and MS data. Confirmation of the structure and the absolute stereochemistry of 1 were determined by the total synthesis of (+)-xylariamide A (2). Synthetic 2 was produced by N,O-bis(trimethylsilyl)acetamide-induced coupling of 3-chloro-L-tyrosine (3) with (E)-but-2-enedioic acid 2,5-dioxo-pyrrolidin-1-yl ester methyl ester (4). Optical rotation comparison of 1 with 2 indicated that the natural product (1) contained 3-chloro-D-tyrosine. Both enantiomers of xylariamide A were tested in a brine shrimp lethality assay, and only the natural product (1) showed toxicity.

Animals↗

PubMed2006

Bioactive secolignans from Peperomia dindygulensis.

Thirteen secolignans, including eight new ones (1-8), were isolated from the EtOAc extract of Peperomia dindygulensis. The structures were mainly elucidated by 1D and 2D NMR and MS experiments, the relative configurations were determined by NOE correlations, and the absolute configurations were established by the optical rotations and CD spectra. Cytotoxicity and MDR (multidrug resistance) reversal activity of the isolated compounds were examined. Compounds 6 and 7, peperomins B (10) and E (12), showed moderate to strong growth inhibitory activity against a malignant lung tumor cell (VA-13) with IC(50) values of 15.2, 13.5, 13.9, and 1.93 microM, respectively, and also inhibited the growth of a normal lung fibroblast cell (WI-38) at the same levels. Compound 7 and peperomin E (12) exhibited inhibitory activity against a liver tumor cell (HepG2) with IC(50) values of 22.3 and 12.1 microM. Compounds 5 and 7 and peperomins A, B, C, and E (9-12) enhanced calcein accumulation in MDR 2780 cells at 25 microg/mL. Compounds 2, 3, 7, and peperomin E (12) showed inhibitory activity on induction of the intercellular adhesion molecule-1 (ICAM-1).

Antineoplastic Agents, Phytogenic↗

PubMedDate not supplied

Isolation and pharmacological characterization of vernolepin.

Vernolepin, a sesquiterpene lactone, was isolated from the dried fruit of Vernonia amygdalina Del. The different steps used during the extraction were: continuous extraction with chloroform, partition of the chloroform-extract between pertroleum ether and 10% aqueous methanol, column chromatography of the methanol extract, isolation of the active fractions by pharmacological and chemical characterization. Vernolepine was obtained as colorless prisms and identified by melting point, uv, ir, 1H nmr, optical rotation, and mass spectrometry. The total content of the dried fruit was 0.09% vernolepin. The first pharmacological characterization of vernolepin revealed: (1) a competitive antagonism against histamine in guinea pig ileum (pA2 = 5.61; 15 min incubation); (2) a biphasic enhancement/inhibition of coaxial stimulation of guinea pig ileum; (3) an antiaggregating and disaggregating activity against rabbit platelet aggregation induced by arachidonic acid (1 X 10(-4) g/ml; 3.3 X 10(-4)M) or ADP (4 X 10(-6) g/ml; 1 X 10(-5)M) without inhibition of cyclo-oxygenase or lipoxygenase. All these reactions were time dependent and occurred at concentrations of 5 X 10(-6) to 1 X 10(-5) g/ml vernolepin (1.8 to 3.5 X 10(-5)M).

Africa↗

PubMedDate not supplied

Oxidation of rotenone by Polyporus anceps laccase.

The extracellular laccase produced by Polyporus anceps transforms rotenone to a single, more polar product. This transformation occurs in incubation mixtures containing chlorpromazine, laccase, and rotenone where rotenone serves as a pseudosubstrate for the enzyme. Chlorpromazine, the true substrate, serves as a cycling redox component of the system forming a radical-cation species that abstracts an electron from rotenone in the oxidation process. Physicochemical properties of the product were determined on an analytically pure sample obtained by preparative hplc. High resolution ms, high-field pmr and cmr, uv, and optical rotation analyses indicated that rotenone had been transformed to 6a beta, 12a beta-rotenolone by P. anceps laccase.

Basidiomycota↗

PubMedDate not supplied

Mutagenic perylenequinone metabolites of Alternaria alternata: altertoxins I, II, and III.

The mold genus Alternaria is a widely distributed plant pathogen. Some of these species, e.g., A. alternata, are common decay organisms of fruits and vegetables. Two novel perylene oxide metabolites, altertoxins II and III, have been identified in extracts of A. alternata isolates that exhibit mutagenic responses in the Ames Salmonella typhimurium assay. These identifications were based on mass, optical rotational, and 1H- and 13C-nmr spectral studies. Previous reports of related perylene dione mycotoxins have been clarified.

Alternaria↗

PubMedDate not supplied

2,3-Dehydrococaine: not a direct precursor of cocaine in Erythroxylum coca.

(+/-)-3-[4(-3)H]Benzoyloxy-2-[carbonyl-13C, 14C]carbomethoxy-2-tropene (2,3-dehydrococaine) was synthesized from Ba [13C, 14C]CO3 and [4(-3)H]benzoic acid. This labeled compound (3H/14C 0.65) was administered to Erythroxylum coca plants for 3 and 15 days. After these times, cocaine was isolated and was found to have a 3H/14C ratio quite different from the administered dehydrococaine (3.0 and 10.6 for the 3- and 15-day feeding experiments, respectively). Degradations of the cocaine indicated that tritium was all located in the 4-position of its benzoyl moiety. 13C-nmr spectroscopy indicated enrichment of the carbomethoxy group of cocaine, consistent with the observed specific incorporation of the 14C. From the 3-day feeding experiment unmetabolized dehydrococaine was isolated having the same specific activity and 3H/14C ratio as the administered compound. Also from this feeding experiment 2-carbomethoxy-3-tropinone was isolated having about 1/3 the specific activity (14C) of the administered dehydrococaine and having a (-) optical rotation. These results indicate that cocaine is not formed by the direct reduction of dehydrococaine. The results indicate that cocaine is not formed by the direct reduction of dehydrococaine. The results are rationalized by proposing initial hydrolysis of the dehydrococaine to benzoic acid and 2-carbomethoxy-3-tropinone. The latter compound is then reduced to methyl ecgonine, which is then esterified with benzoic acid to yield cocaine. The change in the 3H/14C ratio is due to the fact that only the (+) enantiomer of 2-carbomethoxy-3-tropinone is converted to cocaine, and that different pool sizes of the non-labeled intermediates exist in the plant.

Chemical Phenomena↗