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Biomedical subjects

Gao Li

Publications and source records attributed to Gao Li.

At least 19 recordsLinked to original sources
PubMed2006

Cytotoxicity and DNA topoisomerase inhibitory activity of constituents isolated from the fruits of Evodia officinalis.

Four alkaloids (1-4), three quinolone alkaloids (5-7), and three flavanoid glucosides (8-10) were isolated from the fruits of Evodia officinalis Dode, and their structures were determined from chemical and spectral data. Compounds, 3, 8, 9 and 10 were isolated from this plant for the first time. Of these compounds, 1-3 and 5-7 exhibited moderate cytotoxicities against cultured human colon carcinoma (HT-29), human breast carcinoma (MCF-7), and human hepatoblastoma (HepG-2). Compound 8 showed strong inhibitory effects on DNA topoisomerases I and II (70 and 96% inhibition at a concentration of 20 microM, respectively).

Alkaloids↗
PubMed2006

Optimization of the preparation of nalmefene-loaded sustained-release microspheres using central composite design.

Nalmefene-loaded poly(lactic-co-glycolic acid) microspheres were prepared by O/O emulsification/solvent evaporation method. The central composite design-response surface methodology was used to optimize and predict the preparation microspheres. Effects of three independent variable variables i.e., Span80 concentration in outer phase, poly(lactic-co-glycolic acid) concentration in inner phase and theoretical drug content were evaluated on a number of response variables. Response variables selected in this study were drug content, encapsulation efficiency, mean diameter, diameter span and the cumulative percentage of the drug released in the first day after incubation (marked as F1d, and it was also calculated as the initial burst). Multiple linear regression and second-order polynomial model were fitted to the data, and the resulting equations were used to produce five dimensional response graphs, by which optimal experimental conditions were selected. The results showed that all response variables were greatly dependent on three independent variables, and the optimal conditions were Span80 concentration 1.5%, poly(lactic-co-glycolic acid) concentration 17.5%, and theoretical drug content 6%. According to the optimal conditions, the drug content, encapsulation efficiency, mean diameter, diameter span and F1d of prepared microspheres were 4.37%, 72.8%, 64.1 microm, 1.36 and 8.93%, respectively.

Delayed-Action Preparations↗
PubMed2005

Neuroprotective and free radical scavenging activities of phenolic compounds from Hovenia dulcis.

The EtOAc-soluble fraction from a methanolic extract of Hovenia dulcis Thunb. exhibited neuroprotective activity against glutamate-induced neurotoxicity in mouse hippocampal HT22 cells. The neuroprotective activity-guided isolation resulted in 8 phenolic compounds (1-8), such as vanillic acid (1), ferulic acid (2), 3,5-dihydroxystilbene (3), (+)-aromadendrin (4), methyl vanillate (5), (-)-catechin (6), 2,3,4-trihydrobenzoic acid (7), and (+)-afzelechin (8). Among these, compounds 6 and 8 had a neuroprotective effect on the glutamate-induced neurotoxicity in HT22 cells. Furthermore, compound 6 had a DPPH free radical scavenging effect with an IC50 value of 57.7 microM, and a superoxide anion radical scavenging effect with an IC50 value of 8.0 microM. Both compounds 6 and 8 had ABTS cation radical scavenging effects with IC50 values of 7.8 microM and 23.7 microM, respectively. These results suggest that compounds 6 and 8 could be neuroprotectants owing to their free radical scavenging activities.

Animals↗
PubMed2005

Synthesis and anticonvulsant activity of 1-substituted-7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline.

Starting from 6-hydroxy-3,4-dihydro-1H-quinoline-2-one, a series of 1-substituted-7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolines was synthesized and their structures were characterized using IR, 1H-NMR, MS, and elemental analysis techniques. Anticonvulsant activity was evaluated in the maximal electroshock (MES) test, subcutaneous pentylenetetrazol (scMet) test, and rotarod neurotoxicity test. The most active compound was 7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline 4a. Its ED50 in the MES and scMet tests was 17.3 and 24 mg.kg-1, respectively. The safest compound was 4 g, 1-phenyl-7-benzyloxy-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline, with TD50 and protective index (PI) (PI=TD50/ED50) values of greater than 300 mg.kg-1 and 13, respectively. The PI value of compound 4 g was better than that of most marketed drugs. Structure-activity relationships are also described in this paper.

Animals↗
PubMed2005

Agents protecting against sepsis from the roots of Angelica dahurica.

In the course of isolating agents preventing sepsis from the EtOAc extract of the roots of Angelica dahurica, four known furanocoumarins, isoimperatorin (1), oxypeucedanin (2), (+/-)-byakangelicin (3), and (+)-oxypeucedanin hydrate (4), were isolated as active compounds based on the in vivo assay model of sepsis induced by lipopolysaccharide (LPS) and D-galactosamine (D-GalN). Among them, 3 showed the highest survival rate (100% with a dose of 30 mg/kg versus 20% for the control experiment) and decreased the plasma levels of tumor necrosis factor-alpha and alanine aminotransferase in mice adminstered LPS/D-GalN.

Angelica↗
PubMed2004

Inhibition of cell cycle progression on HepG2 cells by hypsiziprenol A9, isolated from Hypsizigus marmoreus.

Antiproliferative activities of fractions of Hypsizigus marmoreus were examined using HepG2 cells in vitro. The methanol extract of H. marmoreus markedly induced antiproliferative activity, and an active compound from this mushroom was identified as hypsiziprenol A9. Hypsiziprenol A9 inhibited cell proliferation in a time- and concentration-dependent manner by up to 80% on HepG2 cells by inducing arrest of the G1 phase. Further investigation revealed that hypsiziprenol A9 decreased expression of phosphorylated retinoblastoma protein (ppRb), cyclin D1, and cyclin E in a dose-dependent manner. These results suggest that hypsiziprenol A9 can inhibit the growth of HepG2 cells through inducing G1 phase cell cycle arrest due to the inhibition of pRb phosphorylation.

Agaricales↗
PubMed2004

Protective constituents against sepsis in mice from the root cortex of Paeonia suffruticosa.

The bioassay-guided fractionation of protective agents against sepsis-induced lethality from the root cortex of Paeonia suffruticosa ANDREWS (Ranunculaceae) led to the isolation of eight known compounds: paeonol (1), 2,5-dihydroxy-4-methoxyacetophenone (2), acetovanillone (3), paeonoside (4), paeoniflorin (5), oxypaeoniflorin (6), apiopaeonoside (7), and methyl 3-hydroxy-4-methoxybenzoate (8). Among them, 3 showed the highest survival rate (100% with a dose of 30 mg/kg versus 17% for the control experiment) and reduced alanine aminotransferase level to be a half of the control value on the sepsis model induced by lipopolysaccharide/D-galactosamine.

Alanine Transaminase↗
PubMed2004

Cytotoxicity and DNA topoisomerases inhibitory activity of constituents from the sclerotium of Poria cocos.

The bioactivity-guided fractionation of the methylene chloride extract of the sclerotium of Poria cocos led to the isolation of (S)-(+)-turmerone (1), ergosterol peroxide (2), polyporenic acid C (3), dehydropachymic acid (4), pachymic acid (5), and tumulosic acid (6). Compounds 4-6 exhibited moderate cytotoxicities, with IC50 values of 20.5, 29.1, and 10.4 microM, respectively, against a human colon carcinoma cell line. However, 3-6 not only showed inhibitory activities as potent as etoposide used as a positive control on DNA topoisomerase II (36.1, 36.2, 43.9 and 66.7% inhibition at a concentration of 20 microM, respectively), but also inhibition of DNA topoisomerase I (55.8, 60.7, 43.5, and 83.3% inhibition at a concentration of 100 microM, respectively).

Cell Line, Tumor↗
PubMed2004

New furofuran and butyrolactone lignans with antioxidant activity from the stem bark of Styrax japonica.

A new furofuran lignan, styraxlignolide B (1), and four new dibenzyl-gamma-butyrolactone lignans, styraxlignolides C-F (2-5), were isolated from the EtOAc-soluble fraction of stem bark of Styrax japonica. Known compounds, taraxerol (6), syringin (7), and (-)-pinoresinol glucoside (8), were also obtained. The structures of styraxligonolides B-F were determined as 2alpha-(4'-hydroxy-3'-methoxyphenyl)-6alpha-(3' ',4' '-methylenedioxyphenyl)-8-oxo-3,7-dioxabicyclo[3.3.0]octane 4'-O-(beta-D-glucopyranoside) (1), (2S,3S)-2alpha-(3' '-hydroxy-4' '-methoxybenzyl)-3beta-(4'-hydroxy-3'-methoxybenzyl)-gamma-butyrolactone 4'-O-(beta-D-glucopyranoside) (2), (2S,3S)-2alpha-(4' '-hydroxy-3' '-methoxybenzyl)-3beta-(4'-hydroxy-3'-methoxybenzyl)-gamma-butyrolactone 4'-O-(beta-D-glucopyranoside) (3), (2S,3S)-2alpha-(4' '-hydroxy-3' '-methoxybenzyl)-3beta-(4'-hydroxy-3'-methoxybenzyl)-gamma-butyrolactone 4' '-O-(beta-D-glucopyranoside) (4), and (2S,3S)-2alpha-(3' ',4' '-dimethoxybenzyl)-3beta-(4'-hydroxy-3'-methoxybenzyl)-gamma-butyrolactone 4'-O-(beta-D-glucopyranoside) (5) by spectroscopic means including 2D NMR. Compounds 1-8 were tested in vitro for antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Styraxlignolide C (2), styraxlignolide D (3), styraxlignolide E (4), and (-)-pinoresinol glucoside (8) exhibited weak radical-scavenging activity in the DPPH assay, with IC50 values of 380, 278, 194, and 260 microM, respectively.

4-Butyrolactone↗
PubMed2004

Preventive effects of Laminaria japonica aqueous extract on the oxidative stress and xanthine oxidase activity in streptozotocin-induced diabetic rat liver.

Increasing evidence in both experimental and clinical studies suggests that oxidative stress plays a major role in the pathogenesis of diabetes mellitus type 1 and type 2. Xanthine oxidase (XO) has been proposed as one of the sources of free radical formation in diabetes. We therefore investigated the preventive effects of Laminaria japonica aqueous extract (LJE) on alterations in the activity of hepatic XO and oxidative stress in the streptozotocin-induced experimental diabetes. We found that lipid peroxide levels and xanthine oxidase activity were increased, whereas glutathione (GSH), GSH reductase and GSH peroxidase were decreased in the liver of streptozotocin-induced diabetic rats. Pretreatment with LJE of 100 mg/kg orally for 5 d significantly reduced blood glucose levels and hepatic lipid peroxidation in the diabetic rats. In addition, the content of glutathione was restored to the control level by LJE pretreatment. Furthermore, LJE significantly suppressed the increased activity of XO and type conversion of the xanthine dehydrogenase to XO in diabetic rat liver. The results suggest that Laminaria japonica would be of great value in preventing hyperglycemia in diabetes mellitus as a dietary supplement possibly, through its antioxidant activity.

Animals↗
PubMed2004

Lignans from the bark of Machilus thunbergii and their DNA topoisomerases I and II inhibition and cytotoxicity.

Activity-guided fractionation based on topoisomerase I inhibitory activity lead to the isolation of ten lignans (1-10) from the methylene chloride extract of the bark of Machilus thunbergii SIEB. et ZUCC. (Lauraceae). These were identified as machilin A (1), erythro-austrobailignan-6 (2), meso-monomethyl dihydroguaiaretic acid (3), meso-dihydroguaiaretic acid (4), galbacin (5), machilin F (6), nectandrin A (7) nectandrin B (8), (-)-acuminatin (9) and (7S,8S)-7-(4-hydroxy-3-methoxyphenyl)-1'-formyl-3'-methoxy-8-methyldihydrobenzofuran (10) by spectral evidence. In DNA topoisomerase I and II assays in vitro at a concentration of 100 microM, 4 showed the most potent inhibitory activity, 93.6 and 82.1% inhibition, respectively, and 8 showed 79.1 and 34.3% inhibition, respectively. All of these compounds exhibited weak or no cytotoxicities against either the human colon carcinoma cell line (HT-29) or the human breast carcinoma cell line (MCF-7).

Cell Line, Tumor↗
PubMed2003

DNA topoisomerases I and II inhibitory activity of constituents isolated from Juglans mandshurica.

Nine diarylheptanoids (1-9), one triterpene (10), one sesquiterpenoid (11), one naphthoquinone (12), four tetralones (13-16), one naphthalene carboxylic acid glucoside (17) and six naphthalenyl glycosides (18-23) were isolated from the roots of Juglans mandshurica Maximowicz (Juglandaceae), and their structures determined from the chemical and spectral data. Here, we report the inhibitory effects, on the DNA topoisomerases I and II activities, of all these compounds. Compounds 10 and 23 showed more potent inhibitory effects, on the DNA topoisomerases I and II (94.0 and 86.0% inhibitions at the concentration of 5 microg/mL, respectively), than the positive control compounds, camptothecin and etoposide.

Animals↗
PubMed2003

Preventive agents against sepsis and new phenylpropanoid glucosides from the fruits of Illicium verum.

The bioassay-guided fractionation of preventive agents against lethality due to septic shock from the fruits of Illicium verum led to the isolation of two known racemic mixtures of phenylpropanoids, [1-(4'-methoxyphenyl)-(1 R,2 S and 1 S,2 R)-propanediol (1) and 1-(4'-methoxyphenyl)-(1 R,2 R and 1 S,2 S)-propanediol (2)], along with two known phenylpropanoid glucosides, [1-(4'-methoxyphenyl)-(1 S,2 R)-propan-1-ol 2-O-beta-D-glucopyranoside (3) and 1-(4'-methoxyphenyl)-(1 R,2 S)-propan-1-ol 2-O-beta-D-glucopyranoside ( 5)], and two new phenylpropanoid glucosides, [1-(4'-methoxyphenyl)-(1 S,2 S)-propan-1-ol 2- O-beta- D-glucopyranoside (4) and 1-(4'-methoxyphenyl)-(1 R,2 R)-propan-1-ol 2-O-beta-D-glucopyranoside (6)]. Their chemical structures were elucidated on the basis of spectroscopic studies. Among them, 1 exhibited the highest survival rate in a dose-dependent manner (100 % with a dose of 10 mg/kg against 40 % for the control experiment) and showed a reduction of the plasma alanine aminotransferase (ALT) value on the in vivo assay model of septic shock induced by tumor necrosis factor (TNF)-alpha.

Alanine Transaminase↗
PubMed2003

Melanin biosynthesis inhibitors from the bark of Machilus thunbergii.

The bioassay-guided fractionation of the methylene chloride soluble portion of a methanol extract of Machilus thunbergii bark led to the isolation of four known lignans, machilin A (1), meso-monomethyl dihydroguaiaretic acid (2), nectandrin A (3) and nectandrin B (4), which exhibited potent inhibitory activity on melanin biosynthesis in cultured B-16 mouse melanoma cells (IC(50): 39.9, 15.1, 19.4 and 37.8 microM, respectively).

Animals↗
PubMed2002

Cytotoxic diarylheptanoids from the roots of Juglans mandshurica.

A new (2) and three known diarylheptanoids (1, 3, and 4), along with one known sesquiterpenoid (5), were isolated from the roots of Juglans mandshurica, and their structures were elucidated on the basis of spectroscopic studies. Four of these compounds (2-5) exhibited moderate cytotoxicities against human colon carcinoma and human lung carcinoma cell lines with IC(50)'s ranging from 2 to 25 microg/mL.

Antineoplastic Agents, Phytogenic↗