In vitro activities of two antimitotic compounds, pancratistatin and 7-deoxynarciclasine, against Encephalitozoon intestinalis, a microsporidium causing infections in humans.
The antiparasitic effect of a collection of compounds with antimitotic activity has been tested on a mammalian cell line infected with Encephalitozoon intestinalis, a microsporidian causing intestinal and systemic infection in immunocompromised patients. The antiparasitic effect was evaluated by counting the number of parasitophorous vacuoles detected by immunofluorescence. Out of 526 compounds tested, 2 (pancratistatin and 7-deoxynarciclasine) inhibited the infection without affecting the host cell. The 50% inhibitory concentrations (IC(50)s) of pancratistatin and 7-deoxynarciclasine for E. intestinalis were 0.18 microM and 0.2 microM, respectively, approximately eightfold lower than the IC(50)s of these same compounds against the host cells. Electron microscopy confirmed the gradual decrease in the number of parasitophorous vacuoles and showed that of the two life cycle phases, sporogony was more sensitive to the inhibitors than merogony. Furthermore, the persistence of meronts in some cells apparently devoid of sporonts and spores indicated that the inhibitors block development rather than entry of the parasite into the host cell. The occurrence of binucleate sporoblasts and spores suggests that these inhibitors blocked a specific phase of cell division. (+info)
Lycobetaine acts as a selective topoisomerase II beta poison and inhibits the growth of human tumour cells.
The phenanthridine alkaloid lycobetaine is a minor constituent of Amaryllidaceae. Inhibition of cell growth was studied in the clonogenic assay on 21 human tumour xenografts (mean IC(50) = 0.8 microM). The growth of human leukaemia cell lines was also potently inhibited (mean IC(50) = 1.3 microM). Athymic nude mice, carrying s.c. implanted human gastric tumour xenograft GXF251, were treated i.p. with lycobetaine for 4 weeks, resulting in a marked tumour growth delay. Lycobetaine was found to act as a specific topoisomerase II beta poison. In the presence of calf thymus DNA, pure recombinant human topoisomerase II beta protein was selectively depleted from SDS-gels, whereas no depletion of topoisomerase II alpha protein was observed. In A431 cells immunoband-depletion of topoisomerase II beta was induced, suggesting stabilization of the covalent catalytic DNA-intermediate in living cells. It is reasonable to assume that this mechanism will cause or at least contribute significantly to the antitumour activity. (+info)
Inhibition of cell cycle progression through specific phase by pancratistatin derivatives.
Pancratistatin derivatives, 1-O-(3-hydroxybutyryl)pancratistatin (HBP) and 1-O-(3-O-beta-D-glucopyranosylbutyryl)pancratistatin (GBP), showed strong cytostatic activity against rat embryo fibroblast 3Y1 at concentrations less than 1 microM. When the effect on cell cycle progression was examined in 3Y1 fibroblasts arrested at G0/G1 phase by serum deprivation, HBP, GBP, and pancratistatin inhibited the progression of 3Y1 fibroblasts from G0/G1 to S phase. In addition, when the effect on cell cycle progression was studied in 3Y1 fibroblasts synchronized at late G1/early S phases by treating with hydroxyurea, HBP blocked further progression through S phase, while GBP and pancratistatin did not affect the progression, but retarded it. On the other hand, when the effect of HBP and GBP on the progression was evaluated in promyelocytic leukemia HL-60RG cells synchronized at G0/G1 phase, the cells did not progress into S phase and accumulated in sub G0/G1 phase, which indicated apoptotic cells. These findings suggest that of Amaryllidaceae alkaloids, HBP blocks the progression of cell cycle at least at G0/G1 and S phases and GBP does at least at G0/G1 phase, resulting in apoptosis induction in tumor cells. (+info)
Isolation of the acetylcholinesterase inhibitor ungeremine from Nerine bowdenii by preparative HPLC coupled on-line to a flow assay system.
In an attempt to isolate the active compound while detecting acetylcholinesterase inhibitory activity, we applied a fluorometric flow assay system to an on-line coupled preparative HPLC. The MeOH extract of Nerine bowdenii showed a strong inhibitory peak in the on-line assay, and the active compound was isolated by CPC and HPLC. It was identified as ungeremine by analysis of its (1)H-NMR, 2D-NMR, and NOESY spectra. The assignment of the active N. bowdenii constituent was also confirmed by co-TLC, co-HPLC, and co-(1)H-NMR experiments using an authentic sample of synthetic ungeremine. The IC(50) value of ungeremine was 0.35 microM, showing stronger activity than galanthamine (2.2 microM). (+info)
Localization of ascorbic acid, ascorbic acid oxidase, and glutathione in roots of Cucurbita maxima L.
To understand the function of ascorbic acid (ASC) in root development, the distribution of ASC, ASC oxidase, and glutathione (GSH) were investigated in cells and tissues of the root apex of Cucubita maxima. ASC was regularly distributed in the cytosol of almost all root cells, with the exception of quiescent centre (QC) cells. ASC also occurred at the surface of the nuclear membrane and correspondingly in the nucleoli. No ASC could be observed in vacuoles. ASC oxidase was detected by immunolocalization mainly in cell walls and vacuoles. This enzyme was particularly abundant in the QC and in differentiating vascular tissues and was absent in lateral root primordia. Administration of the ASC precursor L-galactono-gamma-lactone markedly increased ASC content in all root cells, including the QC. Root treatment with the ASC oxidized product, dehydroascorbic acid (DHA), also increased ASC content, but caused ASC accumulation only in peripheral tissues, where DHA was apparently reduced at the expense of GSH. The different pattern of distribution of ASC in different tissues and cell compartments reflects its possible role in cell metabolism and root morphogenesis. (+info)
Effects of lycorine on HL-60 cells via arresting cell cycle and inducing apoptosis.
As a natural anti-cancer alkaloid extracted from Amaryllidaceae, lycorine shows various biological effects on tumor cells. The survival rate of HL-60 cells exposed to lycorine was decreased in a dose-dependent manner with 1 microM as the 50% inhibitory concentration (IC50), cell growth was slowed down by arresting cell cycle at G2/M phase, and cell regeneration potential was inhibited. HL-60 cells exhibited typical apoptotic morphological changes, apoptotic DNA "ladder" pattern, and sub-G1 peak in cell phase distribution, showing apoptosis of HL-60 cells. To further understand the apoptotic molecular mechanism of lycorine on HL-60 cells, caspase activity was tested by colorimetric assay, and the expression of Bcl-2 and Bax proteins was examined by Western blotting. The increase of caspase-8, -9, -3 activities demonstrated that caspase was a key mediator of apoptotic pathways induced by lycorine. Under-expression of Bcl-2 and increase of Bax:Bcl-2 ratio showed that Bcl-2 family proteins were involved in apoptosis. Our finding suggests that lycorine can suppress leukemia growth and reduce cell survival via arresting cell cycle and inducing apoptosis of tumor cells. (+info)
Antineoplastic agents. 553. The Texas grasshopper Brachystola magna.
Bioassay (P388 lymphocytic leukemia cell line and human cancer cell lines) guided separation of an extract prepared from the previously chemically uninvestigated Texas grasshopper Brachystola magna led to isolation of the cancer cell growth inhibitory pancratistatin (1), narciclasine (2), and ungeremine (3). Pancratistatin (1) was first isolated from the bulbs of Hymenocallis littoralis), and the original crystal structure was deduced by X-ray analysis of a monomethyl ether derivative. In the present study pancratistatin (1) was isolated from an extract of B. magna, which led to the X-ray crystal structure of this anticancer drug. Since isoquinoline derivatives 1-3 are previously known only as constituents of amaryllidaceous plants, some of the interesting implications of their rediscovery in the grasshopper B. magna that does not appear to utilize amaryllis family plants were discussed. (+info)
An efficient synthesis of (+/-)-Lycoricidine featuring a Stille-IMDAF cycloaddition cascade.
[reaction: see text] A highly efficient total synthesis of (+/-)-Lycoricidine is described. The synthesis features the ready preparation of the Lycoricidine skeleton by a Stille-IMDAF cycloaddition cascade. The resulting cycloadduct is then used for the stereocontrolled installation of the other functionality present in the C-ring of the target molecule. (+info)