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Biomedical subjects

X Z Feng

Publications and source records attributed to X Z Feng.

At least 19 recordsLinked to original sources
PubMed2004

Steroidal saponins from Dioscorea panthaica and their cytotoxic activity.

A new steroidal saponin, dioscoreside E (1), and a known compound, protodioscin (2), were isolated from an ethanol extract of the rhizomes of Dioscorea panthaica. The structure of 1 was established as 3-O-[bis-alpha-L-rhamnopyranosyl-(1 --> 2 and 1 --> 4)-beta-D-glucopyranosyl]-26-O-beta-D-glucopyranosyl-20(R)-methoxy-25(R)-furosta-5,22(23)-diene-3beta,26-diol, on the basis of spectral and chemical evidence. Compounds 1 and 2 showed cytotoxic activity against a panel of tumor cell lines.

Animals↗
PubMed2001

Conformation and rigidity of DNA microcircles containing waf1 response element for p53 regulatory protein.

The tumor-suppressor activity of p53 is closely related to its DNA-binding properties. It binds a number of DNA response-elements and it is likely that these share a common structural feature. Here, we present a new, general method to determine the absolute twist of flexible DNA promoter sequences based on direct imaging of the topology of microcircles containing the sequences. We have used magnetically driven dynamic force microscopy ("MacMode" AFM) to observe, in solution, the conformation of 168 base-pair DNA microcircles, each containing four equally spaced copies of the waf1/cip1/p21 p53 response-element. Analysis of the images showed that the microcircles are markedly puckered with a small excess of negatively writhed molecules. The average measured values of writhe are 0.109+/-0.013 (for 60 positively writhed molecules) and -0.098+/-0.011 (for 65 negatively writhed molecules). These values lead directly to a difference in linking number for the positively and negatively writhed molecules prior to ligation, from which we derive a twist mismatch of 178 degrees (overtwist). This is 44.5 degrees for each 42-mer precursor containing a single waf1/cip1/p21 p53 response-element, in good agreement with the range of values deduced by indirect biochemical techniques. The two values of writhe may also be used to determine the ratio of the bending (B) to twisting (C) rigidity, yielding B/C=0.23. This is about one-third of the value for long, random-sequence DNA, suggesting that the waf1/cip1/p21 p53 response-element is extremely flexible, a result that is also consistent with indirect biochemical experiments. These results support the idea, proposed by us earlier, that torsional stress may play a role in the regulation of p53 binding through modulation of twist at the binding site.

Aluminum Silicates↗
PubMed2001

Differential mercury volatilization by tobacco organs expressing a modified bacterial merA gene.

Mercury pollution is a major environmental problem accompanying industrial activities. Most of the mercury released ends up and retained in the soil as complexes of the toxic ionic mercury (Hg2+), which then can be converted by microbes into the even more toxic methylmercury which tends to bioaccumulate. Mercury detoxification of the soil can also occur by microbes converting the ionic mercury into the least toxic metallic mercury (Hg0) form, which then evaporates. The remediation potential of transgenic plants carrying the MerA gene from E. coli encoding mercuric ion reductase could be evaluated. A modified version of the gene, optimized for plant codon preferences (merApe9, Rugh et al. 1996), was introduced into tobacco by Agrobacterium-mediated leaf disk transformation. Transgenic seeds were resistant to HgCl2 at 50 microM, and some of them (10-20% ) could germinate on media containing as much as 350 microM HgCl2, while the control plants were fully inhibited or died on 50 microM HgCl2. The rate of elemental mercury evolution from Hg2+ (added as HgCl2) was 5-8 times higher for transgenic plants than the control. Mercury volatilization by isolated organs standardized for fresh weight was higher (up to 5 times) in the roots than in shoots or the leaves. The data suggest that it is the root system of the transgenic plants that volatilizes most of the reduced mercury (Hg0). It also suggests that much of the mercury need not enter the vascular system to be transported to the leaves for volatilization. Transgenic plants with the merApe9 gene may be used to mercury detoxification for environmental improvement in mercury-contaminated regions more efficiently than it had been predicted based on data on volatilization of whole plants via the upper parts only (Rugh et al. 1996).

Bacterial Proteins↗
PubMed2001

Two new steroidal saponins from the rhizomes of Dioscorea panthaica and their cytotoxic activity.

Two new steroidal saponins, dioscoresides C (1) and D (2), along with a new natural product, pregnadienolone 3-O-beta-gracillimatriose (3), and two known compounds, pregnadienolone 3-O-beta-chacotrioside (4) and pseudoprotodioscin (5), were isolated from the rhizomes of Dioscorea panthaica Prain et Burkill. On the basis of extensive NMR studies and chemical evidence, dioscoresides C and D were determined to be 26-O-beta-D-glucopyranosyl-3 beta,26-dihydroxy-23(S)-methoxy-25(R)-furosta-5,20(22)-dien-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside and 26-O-beta-D-glucopyranosyl-3 beta,26-dihydroxy-20,22-seco-25(R)-furosta-5-en-20,22-dine-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1--> 4)]-beta-D-glucopyranoside. These compounds showed mild cytotoxicity against the cancer cell lines, A375, L929, and HeLa, in a dose-dependent manner.

Animals↗
PubMed2001

A new sesquiterpene lactone glucoside from Ixeris sonchifolia.

A new sesquiterpene lactone glucoside, Ixerin Z1 (1), was isolated from the whole plants of Ixeris sonchifolia (Bge.) Hance, along with 15 known compounds. The structure of 1 was elucidated as 1(10),3,11(13)-guaiatriene-12,6-olide-2-one-3-O-[6'-(p-hydroxyphenylacetyl)]-glucopyranoside by spectroscopic methods including 2D-NMR techniques.

Asteraceae↗
PubMed2001

Three new triterpenoids from Fuscoporia obliqua.

Three new lanostane triterpenoids, fuscoporianol A (1), B (2), and C (3) were isolated from the petroleum ether extracts of Fuscoporia obliqua and their structures have been determined on the basis of chemical, spectroscopic methods and X-ray crystallographic analysis as 25-methoxy-21, 22-cyclolanosta-8-ene-3beta, 21alpha-diol(1), 3beta, 22alpha-dihydroxy-lanosta-8, 23E-diene-25-peroxide (2), 3beta, 22alpha, 25-trihydroxy-lanosta-8, 23E-diene (3).

Basidiomycota↗
PubMed2001

A new triterpenoidal saponin from Ixeris sonchifolia and its cytotoxic activity.

A new triterpenoidal saponin, echinocystic acid 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinopyranoside (1), was isolated from Ixeris sonchifolia. Its structure was elucidated on the basis of full spectral data analysis and chemical methods. The cytotoxic activity of compound 1 was evaluated using the tumor cell lines of A375, Hela, and L929 in vitro.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Conformational transition in DNA on a cold surface.

The contour length of DNA fragments, deposited and imaged on mica under buffer, was measured as a function of deposition temperature. Extended DNA molecules (on Ni- and silane-treated surfaces) contract rapidly with falling temperature, approaching the contour length of A-DNA at 2 degrees C. The contraction is not unique to a specific sequence and does not occur in solution at 2 degrees C or on a surface at 25 degrees C, indicating that it arises from a combination of low temperature and surface contact. It is probably a consequence of reduced water activity at a cold surface.

Aluminum Silicates↗
PubMed2000

Feigrisolides A, B, C and D, new lactones with antibacterial activities from Streptomyces griseus.

Four new lactone compounds, named feigrisolides A to D (1 to 4), have been isolated from Streptomyces griseus. The chemical structures were determined by detail analysis of their spectroscopic data and chemical transformations. Structurally, the feigrisolides A (1) and B (2) are hepta-lactones, feigrisolide C (3) and D (4) are 16-membered macrodiolides. Biological studies showed that feigrisolide B (2) exhibited strong antibacterial, as well as medium cyctotoxic, and antiviral activities. Feigrisolides A (1), C (3) and D (4) are medium inhibitors of 3alpha-hydroxysteroid-dehydrogenase (3alpha-HSD) inhibiting activity.

Anti-Bacterial Agents↗
PubMed2000

New 1-O-acyl alpha-L-rhamnopyranosides and rhamnosylated lactones from Streptomyces sp., inhibitors of 3 alpha-hydroxysteroid-dehydrogenase (3alpha-HSD).

Chemical screening with extracts of Streptomyces sp. (strain GT 61150) resulted in the detection, isolation, and structure elucidation of two new acyl alpha-L-rhamnopyranosides (1 and 2) and three new rhamnosyllactones A, B1 and B2 (3 approximately 5). Rhamnosyllactones B1 and B2 were obtained as a 5:1 mixture. The structures were confirmed by spectroscopic analysis, especially 2D-NMR techniques. The rhamnosyltransferase of our strain is able to connect the sugar moiety to heteroaromatic carboxylic acids and enols. The metabolites 1 and 4/5 as well as previously reported acylrhamnosides 6 approximately 11 inhibit the enzyme 3alpha-hydroxysteroid-dehydrogenase (3alpha-HSD).

Enzyme Inhibitors↗
PubMed1999

New guaianolides from Artemisia selengensis.

A new guaianolide artselenin (1) and a new dimeric guaianolide artselenoid (2), along with 10 known compounds, were isolated from the aerial parts of Artemisia selengensis. Their structures were elucidated by spectroscopic methods. Two-dimensional NMR techniques were used to make complete assignments for the 1H- and 13C-NMR chemical shifts of the two new guaianolides.

Artemisia↗
PubMed1997

[Chemical investigation of genus Hedyotis. II. Isolation and identification of iridoids from Hedyotis chrysotricha].

Many species of genus Hedyotis (Rubiaceae) were used as folk medicine for treatment of cold, inflammation, cancer and etc. in China. The alcoholic extract of the whole plant of H. chrysotricha showed good hepatoprotective effects. From the alcoholic extract ten iridoids were isolated and their structures were elucidated as: asperuloside (1), scandoside methyl ester (2), asperulosidic acid (3), deacetyl asperulosidic acid (4), loganin (5), deacetyl asperuloside (6), acetyl scandoside methyl ester (7), 6 beta-hydroxy-genipin (8) and two new compounds named hedyoside (9) and 6'-acetylasperuloside (10), by means of chemical and spectral methods.

Drugs, Chinese Herbal↗
PubMed1993

[New oxindole alkaloid glycosides from Uncaria sinensis].

Two 16-carboxy derivatives of pentacyclic oxindole alkaloids and its glucopyranosyl esters have been isolated from the ethanolic extract of the leaves of Uncaria sinensis (Olive.) Havil. These structures were deduced on the basis of spectroscopic evidences and chemical correlations, and named mitraphyllic acid (I), isomitraphyllic acid (II), isomitraphyllic acid (16-1)-beta-D-glucopyranosyl ester (III) and mitraphyllic acid (16-1)-beta-D-glucopyranosyl ester (IV).

Drugs, Chinese Herbal↗
PubMed1992

The in vivo systemic effect of human recombinant interleukin-1 beta on fibronectin in rats.

The in vivo systemic effect of interleukin (IL)-1 beta on plasma and cartilage fibronectin was studied in arthritic rats, as well as alpha 1-acid glycoprotein and albumin. Plasma fibronectin showed a 27% increase in the arthritic group, while alpha 1-acid glycoprotein increased 22-fold and albumin decreased by 46%. IL-1 effect depended on the administered dose. 2 micrograms injection significantly increased plasma fibronectin and alpha 1-acid glycoprotein. In cartilage, fibronectin was significantly modified in arthritic animals but increased in a dose-related manner after IL-1 treatment. As IL-1 increases fibronectin-degrading enzyme production and as some of these fragments can develop properties that do not possess the intact molecule, one can postulate a vicious circle in matrix degradation in the inflammatory process of the joint.

Animals↗
PubMed1991

New Indole Alkaloids from Amsonia sinensis.

Fourteen indole alkaloids, Delta (14)-isoeburnamine ( 1), amsosinine ( 2), tabersonine, vincadifformine, lochnericine, tetrahydroalstonine, beta-yohimbine, isoeburnamine, minovicinine, picrinine, strictamine, rhazimine, vincanidine, and decarbomethoxytetrahydrosecamine, were isolated from AMSONIA SINENSIS. Delta (14)-isoeburnamine ( 1) and amsosinine ( 2) are new compounds, their structures have been established by spectral and chemical methods. A known sterol glycoside, daucosterol, has also been obtained. The structures of compounds 1 and 2 were finally confirmed by X-ray diffraction of single crystals.

Journal Article↗
PubMed1991

[Chemical constituents of Armillaria mellea mycelium. VII. Isolation and characterization of chemical constituents of the acetone extract].

Eight compounds were isolated from the acetone extract of artificially cultured mycelium of Armillaria mellea (Vahl. ex Fr.)Quel.(Tricholomataceae). Three of them are protoilludane sesquiterpenoid aromatic esters. Their structures were elucidated by spectral data analysis as the known 4'-methylmelledonal (I)and two new compounds named armillaritin (II) and armillarivin (III). In addition, five known compounds were identified as D-erythritol, D-mannitol, azelaic acid, orsellinic acid and glycerin-alpha-monooleate.

Agaricales↗