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Biomedical subjects

H Chai

Publications and source records attributed to H Chai.

At least 19 recordsLinked to original sources
PubMed1999

Long-term effects of a single dose of brain-derived neurotrophic factor on motoneuron survival following spinal root avulsion in the adult rat.

The long-term effect of a single dose of Brain-derived neurotrophic factor (BDNF) treatment on adult motoneuron survival and on expression of nitric oxide synthase (NOS) following nerve injury (avulsion) was investigated and compared with that of continuous BDNF treatment. By 6 weeks post-injury, more than 80% of motoneurons survived in animals treated with either a single dose or continuous treatment of BDNF, while only 30% of motoneurons survived in control animals (avulsion only). There were no significant differences in motoneuron survival between animals receiving a single dose and those with continuous treatment of BDNF. Additionally, the expression of NOS in avulsed motoneurons was almost completely inhibited in all BDNF treatment groups regardless of the mode of administration (single vs. continuous). These data indicate that treatment with a single dose of BDNF at the time of injury can inhibit NOS expression and provide the first evidence that in this situation BDNF has a long-term rescue effect on adult motoneuron survival after root avulsion.

Age Factors↗
PubMed1999

Phenolic aporphine-benzylisoquinoline alkaloids from Thalictrum faberi.

From the roots of Thalictrum faberi, six new phenolic aporphine-benzylisoquinoline alkaloids, 3-hydroxy-6'-desmethyl-9-O-methylthalifaboramine (1), 3-hydroxythalifaboramine (2), 6'-desmethylthalifaboramine (3); 3,5'-dihydroxythalifaboramine (4), 5'-hydroxythalifaboramine (5) and 3-hydroxy-6'-desmethylthalifaboramine (6) were isolated. Their structures were established through the use of one- and two-dimensional NMR techniques. All of the tested alkaloids showed potent cytotoxic and antimalarial activities.

Alkaloids↗
PubMed1999

Quinoline alkaloids from Acronychia laurifolia.

Bioassay-directed fractionation of a root extract of Acronychia laurifolia (Rutaceae) using the KB-V1+ human tumor cell line led to the isolation of six quinoline alkaloids. One of these alkaloids is novel, namely, 2,3-methylenedioxy-4,7-dimethoxyquinoline and the other five were identified as the known compounds, evolitrine, gamma-fagarine, skimmianine, kokusaginine and maculosidine. Two known bis-tetrahydrofuran lignans, sesamolin and yangambin, were also identified. The structure of the new alkaloid was determined by spectroscopic methods. All of the isolates were evaluated against a panel of human cancer cell lines; four of the alkaloids showed weak cytotoxic activity.

Alkaloids↗
PubMed1999

Cytotoxic sesquiterpenoids from Ratibida columnifera.

Bioassay-directed fractionation of the flowers and leaves of Ratibida columnifera using a hormone-dependent human prostate (LNCaP) cancer cell line led to the isolation of 10 cytotoxic substances, composed of five novel xanthanolide derivatives (2-4, 7, and 8), a novel nerolidol derivative (9), and three known sesquiterpene lactones, 9alpha-hydroxy-seco-ratiferolide-5alpha-O-angelate+ ++ (1), 9alpha-hydroxy-seco-ratiferolide-5alpha-O-(2-methylbut yrate) (5), 9-oxo-seco-ratiferolide-5alpha-O-(2-methylbutyrate) (6), as well as a known flavonoid, hispidulin (10). On the basis of its cytotoxicity profile, compound 5 was selected for further biological evaluation, and was found to induce G1 arrest and slow S traverse time in parental wild type p53 A2780S cells, but only G2/M arrest in p53 mutant A2780R cells, with strong apoptosis shown for both cell lines. The activity of 5 was not mediated by the multidrug resistance (MDR) pump, and it was not active against several anticancer molecular targets (i.e., tubulin polymerization/depolymerization, topoisomerases, and DNA intercalation). While these results indicate that compound 5 acts as a cytotoxic agent via a novel mechanism, this substance was inactive in in vivo evaluations using the murine lung carcinoma (M109) and human colon carcinoma (HCT116) models.

Animals↗
PubMed1998

Limonoids from Azadirachta excelsa.

Activity-directed fractionation of a stem extract of Azadirachta excelsa using KB (human oral epidermoid carcinoma) cells led to the isolation of four meliacin-type limonoids. Two of these constituents were novel, namely, 2,3-dihydronimbolide and 3-deoxymethylnimbidate, and these were purified along with the known compounds, nimbolide and 28-deoxonimbolide. The structures of the new compounds were determined by spectroscopic methods. Nimbolide and 28-deoxonimbolide were broadly cytotoxic when evaluated against a panel of human cancer cell lines, while the two novel compounds were inactive in this regard. The defection of nimbolide and 28-deoxonimbolide as cytotoxic constituents was facilitated by an electrospray LC/MS dereplication procedure.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Novel cytotoxic acylated oligorhamnosides from Mezzettia leptopoda.

Activity-guided fractionation of a stem extract of Mezzettia leptopoda using human oral epidermoid carcinoma (KB) cells led to the isolation of seven highly acylated oligorhamnosides. Four of these constituents are novel, namely, n-octyl 2-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-2, 4-di-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-4-O-hexanoyl-alpha-L-rh amnopyranoside (mezzettiaside 8) (1); n-octyl 2, 3-di-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-4-O-hexanoyl-alpha-L-rh amnopyranoside (mezzettiaside 9) (2); n-octyl 2, 4-di-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-4-O-hexanoyl-alpha-L-rh amnopyranoside (mezzettiaside 10) (3); and n-octyl 2,3, 4-tri-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-4-O-hexanoyl-alpha-L-r hamnopyranoside (mezzettiaside 11) (4). Three known compounds were identified as mezzettiasides 2 (5), 3 (6), and 4 (7), respectively, previously isolated from this same plant. The structures of novel compounds 1-4 were determined by spectroscopic methods. All the isolates were evaluated against a panel of human cancer cell lines in this study, and compounds 1-2 and 4-7 were found to be weakly cytotoxic toward KB and/or human colon and lung cancer cell lines.

Animals↗
PubMed1998

Megathyrin B: a cytotoxic diterpene from Isodon megathyrsus.

From the leaves of Isodon megathyrsus, a novel ent-kaurene diterpene, megathyrin B, was isolated and its structure determined as 1 alpha,7 beta,11 beta,15 beta-tetrahydroxy-ent-7 alpha,20-epoxy-kaur-16-ene by 1D- and 2D-NMR spectral analysis. Additionally, its stereochemistry was unambiguously assigned by X-ray crystallography. This compound was cytotoxic to the KB and KB-V cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed1995

Cytotoxic biflavonoids from Selaginella willdenowii.

Bioactivity-guided fractionation of the leaves of Selaginella willdenowii afforded three known biflavones, 4',7"-di-O-methylamentoflavone, isocryptomerin and 7"-O-methylrobustaflavone, that were significantly cytotoxic against a panel of human cancer cell lines. Non-cytotoxic isolates were also obtained, namely, amentoflavone, bilobetin, robustaflavone and 2",3"-dihydroisocryptomerin, a new dihydrobiflavone. The structure for the new biflavonoid was unambiguously assigned by a combination of spectroscopic methods.

Antineoplastic Agents↗
PubMed1995

(-)-Roemerine, an aporphine alkaloid from Annona senegalensis that reverses the multidrug-resistance phenotype with cultured cells.

A known aporphine alkaloid, (-)-roemerine [1], isolated from the leaves of Annona senegalensis, was found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB-V1 cells. In the absence of vinblastine, no significant cytotoxicity was observed with KB-3 or KB-V1 cells (ED50 > 20 micrograms/ml), and several other human tumor cell lines were also relatively insensitive. As indicated by its ability to inhibit ATP-dependent [3H]vinblastine binding to multidrug-resistant KB-V1 cell membrane vesicles, (-)-roemerine appears to function by interacting with P-glycoprotein. In addition to alkaloid 1, three inactive compounds [the aporphine alkaloid(-)-isocorydine (reported in the levo-configuration for the first time), and the lignans (+/-)-8,8'-bisdihydrosiringenin [2] (a new natural product), and (+)-syringaresinol] were also isolated.

Africa↗
PubMed1995

Discovery of betulinic acid as a selective inhibitor of human melanoma that functions by induction of apoptosis.

As a result of bioassay-guided fractionation, betulinic acid, a pentacyclic triterpene, was identified as a melanoma-specific cytotoxic agent. In follow-up studies conducted with athymic mice carrying human melanomas, tumour growth was completely inhibited without toxicity. As judged by a variety of cellular responses, antitumour activity was mediated by the induction of apoptosis. Betulinic acid is inexpensive and available in abundant supply from common natural sources, notably the bark of white birch trees. The compound is currently undergoing preclinical development for the treatment or prevention of malignant melanoma.

Animals↗
PubMed1995

Cytotoxic constituents of Bursera permollis.

Four cytotoxic lignans were isolated from the stem bark of Bursera permollis (Burseraceae), namely, deoxypodophyllotoxin (1), beta-peltatin methyl ether (2), picro-beta-peltatin methyl ether (3), and dehydro-beta-peltatin methyl ether (4). Also isolated was the inactive lignan, nemerosin (5). Compounds 1 and 2 were potently cytotoxic when evaluated against a panel of human cancer cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed1995

[The effects of 2-chloro-4-bromo-alpha-methylcinnamic acid on the neuromuscular transmission of toad].

The effects of 2-chloro-4-bromo-alpha-methylcinnamic acid sodium (SC1001 Na) on neuromuscular transmission were tested by means of intracellular recordings in isolated sciatic nerve-sartorius preparations of toad. The results were: (1) at a concentration of 0.1mmol/L, SC1001 Na had no effect on end-plate potential (EPP); at a concentration of 1 mmol/L, SC1001 Na reduced the amplitude of the EPP significantly, and the paired-pulse facilitation was also decreased; at a concentration of 10mmol/L, SC1001 Na blocked the EPP completely; (2) the 0.1 mmol/L and 1mmol/L groups of drug had no effect on the resting potential of the toad muscle fibers; the resting potential was reduced significantly by SC1001Na at the concentration of 10mmol/L, the action of 10mmol/L drug was irreversible. These results suggest that SC1001 Na may block the neuromuscular transmission of toad, and the blocking effect might be mainly due to a presynaptic mechanism.

Animals↗
PubMed1995

[A potentially new sodium channel blocker: 2-chloro-4-bromo-alpha-methylcinnamic acid].

The effects of 2-Chloro-4-Bromo-alpha-Methylcinnamic acid sodium (SC1001 Na) and some channel antagonists on the action potential (AP) and the resting potential (RP) were tested intracellularly in the sartorius muscle of the toad (Bufo bufo gargarizans). TEA (10mmol/L) and MnCl2 (10 mmol/L) had no effect on the amplitude of the AP, otherwise, TTX (1 mumol/L) blocked the AP completely. SC1001 Na at the concentration of 2mmol/L largely decreased the amplitude of the AP and expanded the duration of the AP (measured at 1/2 peak amplitude), but it had no effect on the RP. The effects of ms group of drug were reversible. Under the pretreatment of the muscle preparation with TEA (10 mmol/L), SC1001 Na still increased the duration of the AP while decreased its amplitude. At the concentration of 10mmol/L, SC1001 Na completely blocked AP and depolarized the RP significantly. These effects were not reversible. As the structure of SC1001 Na is different from that of heterocycloguanidine Na channel blocker, such as TTX, or that of local anesthetics, we infer that SC1001 Na may be a new sodium channel blocker.

Action Potentials↗
PubMed1994

Cytotoxic diterpenoids from Isodon megathyrsus.

A new diterpenoid, megathyrin A, together with three known compounds, rabdocoetsins B, C, and D, were isolated from the leaves of Isodon megathyrsus, and their structures and nmr spectral data were assigned by a combination of one- and two-dimensional nmr techniques. These compounds displayed significant cytotoxic activity.

Antimalarials↗
PubMed1994

Thalifaberidine, a cytotoxic aporphine-benzylisoquinoline alkaloid from Thalictrum faberi.

From Thalictrum faberi, thalifaberidine [1], a new aporphine-benzylisoquinoline alkaloid, together with four known alkaloids, thalifaramine [2], thalifaricine [3], thalifarazine [4], and thalifaronine [5], were isolated. Thalifaberidine [1] was identified as 6',8-desmethylthalifaberine, and its 1H- and 13C-nmr data were completely assigned through the use of one- and two-dimensional nmr techniques. Thalifaberidine [1], thalifaberine [6], and thalifasine [7] showed cytotoxic activity against several human cancer cell lines, as well as antimalarial activity.

Alkaloids↗
PubMed1994

[Study on red blood cell immune adherence function in coriaria lactone-induced epileptic seizure rats].

The immune adherence function of red blood cells in 17 rats was studied. It was found that the rosette rate of red blood cell C3b receptor (RBC-C3bRR) was 7.45 +/- 1.36% in the epilepsy group (8 rats), and 10.84 +/- 1.77% in the control group (9 rats); and that the rosette rate of red blood cell immune complex (RBC-ICR) was 7.42 +/- 2.62% in the epilepsy, and 10.80 +/- 1.72% in the control. As compared with the control group, the rosette rate of red blood cell C3b receptor was remarkably decreased in the epilepsy group (P < 0.05). There was no significant difference between the two groups in RBC-ICR. The results from this study demonstrated that the CL-induced seizures might result in decrease in red blood cell immune adherence function of the epilepsy rats.

Animals↗
PubMed1993

1H- and 13C-nmr assignments of phyllanthin and hypophyllanthin: lignans that enhance cytotoxic responses with cultured multidrug-resistant cells.

Complete 1H-nmr data and unambiguous assignments of the 13C-nmr spectra of phyllanthin [1] and hypophyllanthin [2] were obtained through extensive nmr studies, including homonuclear COSY, homonuclear decoupling, APT, HETCOR, nOe difference, selective INEPT, and COLOC experiments. The absolute configuration of hypophyllanthin [2] was determined by cd. Neither of these lignans demonstrated significant cytotoxic activity when evaluated with a battery of cultured mammalian cells, but both were found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB cells. In addition, 1 was found to displace the binding of vinblastine with membrane vesicles derived from this cell line, suggesting an interaction with the P-glycoprotein.

Animals↗