New strictosidine β-glucosidase from Strychnos mellodora

A stable strictosidine glucosidase was isolated from dried powdered material of Strychnos mellodora. The kinetic parameters K_m and V_max of the purified glucosidases from Catharanthus roseus and S. mellodora towards strictosidine, dolichantoside and palicoside were determined and compared.     

Tetrahydro-β-Carboline alkaloids from Carthamus tinctorius L. with tyrosinase inhibitory activity

Phytochemical research on the dry flower of Carthamus tinctorius L. led to the isolation of two new epimeric tetrahydro-β-carboline alkaloids (1 and 2), together with three known analogues (3–5). Their planar structures were determined by comprehensive 1D, 2D-NMR, and HR-ESI–MS spectroscopic data analyses. The absolute configurations of alkaloids 1 and 2 were assigned by comparing their experimental electronic circular dichroism (ECD) curves with the calculated ECD data. To investigate their impact on melanogenesis, all of the alkaloids isolated were tested for their tyrosinase inhibitory activity and alkaloid 4 was found to inhibit tyrosinase with an IC₅₀ value of 0.17 mM, compared with 0.18 mM for arbutin. The putative binding interactions between the compounds and tyrosine were studied by molecular docking to provide an explanation for their inhibitory activities, and the results obtained indicated that hydrophobic interactions played a very significant role in the combination.     

Gardovatine,a novel Strychnos–Strychnos bisindole alkaloid with cytotoxicity from Gardneria oveta

Gardovatine (1), the first Strychnos–Strychnos alkaloid with a C₃/C₇ cleaved backbone, was isolated from twigs and leaves of Gardneria ovate, together with an analogue divarine (2). The structure was established by extensive spectroscopic methods. Both compounds showed potential cytotoxicities against five human cancer cell lines.     

β-Carboline alkaloids from the leaves of Trigonostemon lii Y.T. Chang

A phytochemical work on the alkaloid constituents from Trigonostemon lii Y.T. Chang was conducted to give six new β-carboline alkaloids, trigonostemines A-F (1-6) and eight known β-carboline alkaloids (7-14). Their structures were elucidated by extensive spectroscopic techniques including 2D NMR experiments and mass spectrometry. All of the compounds were evaluated for their cytotoxic activities against the HL-60, SMMC-7721, A-549, MCF-7, and SW480 human cancer cell lines. Trigonostemines A and B (1 and 2) exhibited stronger inhibitory activities than the positive control (cisplatin) in some cell lines.     

LC–SPE–NMR–MS analysis of Strychnos usambarensis fruits from Rwanda

The novelty of the present work lies in the characterization of akagerine and palicoside in Strychnos usambarensis fruits by a hyphenated analytical method combining high-performance liquid chromatography coupled with solid-phase extraction (SPE), mass spectrometry (HPLC–MS) and NMR spectroscopy. Akagerine was already known in S. usambarensis roots but palicoside is described for the first time in the species.     

Effect of 1-Trichloromethyl-l,2,3,4-Tetrahydro-β-Carboline (TaClo) on Human Serotonergic Cells

The tryptamine-derived dopaminergic neurotoxin 1-trichloromethyl-l,2,3,4-tetrahydro--carboline ('TaClo'), which was found to occur in humans after intake of the hypnotic chloral hydrate, was also shown to strongly disturb serotonergic cells. Incubation experiments using the human serotonergic cell line JAR clearly revealed TaClo to significantly reduce serotonin (5-HT) uptake (IC₅₀ = 59 M) and to induce a distinct loss of cellular viability at increasing TaClo concentrations. In contrast to well-known serotonergic neurotoxins such as amphetamines, however, TaClo toxicity is not mediated by the 5-HT transporter (5-HTT). In the presence of the specific 5-HTT inhibitor imipramine, the uptake of TaClo into JAR cells was not reduced, hinting at an exclusively passive penetration of this highly lipophilic -carboline through cell membranes. Similar toxic effects towards JAR cells were also observed for the 5-HT-related TaClo analog 6-hydroxy-l-trichloromethyl-l,2,3,4-tetrahydro--carboline ('6-OH-TaClo') (IC₅₀ = 26 M). The dopamine-derived alkaloid-type heterocycle 6,7-dihydroxy-l-trichloromethyl-1,2,3,4-tetrahydroisoquinoline ('DaClo'), by contrast, was found to be less toxic, showing only a weak inhibitory activity (IC₅₀ = 260 M) on 5-HT uptake. The pronounced toxicitiy of TaClo and 6-OH-TaClo against serotonergic cells became also evident from morphological findings: Dose-dependently, the survival of JAR cells was significantly impaired, while human dopaminergic IMR-32 cells were only moderately affected at similar toxin concentrations.     

β-N-acetylglucosaminidase from Phycomyces blakesleeanus

β-N-Acetylglucosaminidase was partially purified from sporanghiophores of Phycomyces blakesleeanus NRRL1555(−). The enzyme has a K_m for p-nitrophenyl-β-N-acetylglucosaminide of 0.30 mM at its pH optimum of 5.0. The same preparation had activity with p-nitrophenyl-β-N-acetylgalactosaminide and N,N′-diacetylchitobiose as substrates with K_m-values of 2.3. mM and 0.33 mM, respectively. The preparation can thus discriminate among N-acetylhexosamines and can act as a chitobiase. β-N-Acetylglucosaminidase (2-acetamido-2-deoxy-β-d-glucoside acetamidodeoxy-glucohydrolase, EC 3.2.1.30) is not sensitive to EDTA, high salt, reducing agents, or low concentrations of lecithin or Triton X-100. Diacetylchitobiose causes significant inhibition of β-N-acetylglucosaminidase in the submillimolar range while product inhibition by N-acetylglucosamine sets in only well above 2 mM. An apparent molecular mass of 72 000 was determined on Sephacryl S-200. An Arrhenius plot (ln rate vs. 1/T) and a temperature inactivation plot (ln rate vs. time held at 60°C) both showed breaks. Sporangiophores had high activities while the mycelium had less than one-fifth the activity. β-N-Acetylglucosaminidase was not secreted into the medium.     

2β-hydroxyteucvidin from teucrium webbianum

A new 19-nor-neo-clerodane diterpenoid, 2β-hydroxyteucvidin, has been isolated from the aerial parts of Teucrium webbianum, besides the previously known diterpenoids teuflidin and teucrin A. The structure of 2β- hydroxyteucvidin, (12S)-15,16-epoxy-2β-hydroxy-19-nor-10α-neo-clerodane-4,13(16),14-triene-18,6β;20,12-diolide, was established mainly by spectroscopic means.     

Endo-β-N-acetylglucosaminidase from fig latex

Commercially available fig latex contains several endo-β-N-acetylglucosaminidases which catalyze the reaction: (Man)_nG1cNAcβ₁→4G1cNAcAsn → (Man)_nG1cNAc + G1cNAcAsn. Using (NH₄)₂SO₄ fractionation followed by chromatography on Sephadex G-100 and DEAE-Sephadex A-50, two distinct types of endo-β-N-acetylglucosaminidases have been partially purified and characterized. One, called F-I, hydrolyzes the di-N-acetylchitobiosyl linkage in the glycopeptide, (Man)₃(G1cNAc)₂Asn prepared from human IgG, much faster than that linkage in the glycopeptides, (Man)₅(G1cNAc)₂Asn and (Man)₆(G1cNAc)₂Asn both from ovalbumin. The other, called F-II, hydrolyzes the same linkage in (Man)₅(G1cNAc)₂-Asn and (Man)₆(G1cNAc)₂Asn, but not that in (Man)₃(G1cNAc)₂Asn.     

6β-lactonized xanthanolides from Ratibida species

The aerial parts of two Ratibida species gave, in addition to two known ones, eight new xanthanolides, a nerolidol and a phenylpropane derivative as well as a tetrayne thioenol ether. The structures and the stereochemistry were elucidated by high-field NMR spectroscopy. The chemotaxonomy of the genus Ratibida is discussed briefly.     

4β-substituted flavans from Tephrosia hildebrandtii

A flav-3-ene and four 4β-substituted flavans were isolated from the roots of Tephrosia hildbrandtu and their structures established from spectral data.     

6-O-β-d-Xylopyranosylaucubin from Verbascum sinuatum

Verbascum sinuatum contains, in addition to aucubin and harpagide, four new highly polar iridoid glycosides one of which has been identified as 6-O-β-d-xylopyranosylaucubin on the basis of spectral data and chemical modifications.     

β-d-glucosidase in fractions from rat brain

-Glucosidase activity has been determined in homogenate and in centrifugation fractions of 7-day-old and adult rat brain; maximum activity was found at pH 4 and pH 5. Of the adult brain, more than 50% of the activity was concentrated in the 800-g sediment fraction (P₁), while in the brain of 7-day-old rat about 20% was found in the corresponding fraction. The activity maximum in all fractions after a 2% Triton X-100 treatment occurs at pH 5. Addition of Triton to adult brain homogenate enhances the activity, but this stimulation is less than the sum of the activities observed at pH 4 and pH 5 in the absence of Triton. Triton addition to brain homogenate of 7-day-old rat results in a fall in activity at pH 4 and in a maximum at pH 5. In rat brain homogenate subjected to sonication, a loss of activity is observed at pH 4, scarcely at pH 5; the activity loss is completely abolished and turned into an increase under the influence of Triton. This increase equals the level obtained when Triton is added to an untreated brain homogenate. Sonication of rat brain homogenate leads to changes in the distribution pattern; about 25% of the activity of the adult brain is found in the P₁ fraction compared to 50% in the corresponding fraction of the untreated brain. Fractionation of a sonicated brain homogenate from adult rat reveals that at pH 4 most activity (52%) is concentrated in the 20,000-g pellet (P₂), 23% in supernatant fluid (S₂); at pH 5 the opposite is observed: most activity (49%) is found in the 20,000-g supernatant (S₂) and 23% in the 20,000-g pellet (P₂). In the presence of Triton the activity of the sonicated brain homogenate of adult rat increases; this stimulation roughly equals the sum of the corresponding activities measured at pH 4 and pH 5 in the absence of Triton.     

4-Hydroxy-β-damascone and 4-Hydroxy-dihydro-β-damascone from Cigar Tobacco

The cDNA encoding a putative xylose reductase (xyrA) from Aspergillus oryzae was cloned and coexpressed in the yeast Saccharomyces cerevisiae with A. oryzae xylitol dehydrogenase cDNA (xdhA). XyrA exhibited NADPH-dependent xylose reductase activity. The S. cerevisiae strain, overexpressing the xyrA, xdhA, endogenous XKS1, and TAL1 genes, grew on xylose as sole carbon source, and produced ethanol.     

3β-Hydroxyhexanordammaran-20-one from Euphorbia supina

A new tetracyclic hexanortriterpene ketol, 3β-hydroxy-22,23,24,25,26,27-hexanordammaran-20-one, has been isolated from the whole herb of Euphorbia supina.     

Semi-β-carotenone from leaves of two cycads

A rare secocarotenoid, semi-β-carotenone, has been isolated from young leaves of Ceratozamia fuscoviridis (a form of C. mexicana Brongn.) and of C. kuesteriana. This is the first time that this carotenoid has been obtained from photosynthetic tissue. New data on the chromatographic behaviour and on the spectroscopic properties of the carotenoid are presented.