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PubMed2004

[Comparison study on inhibitory effect of extracts from leaves of Ginkgo biloba L. on the oxidation of human low density lipoproteins].

OBJECTIVE: To compare the effects of extracts from leaves of Ginkgo biloba L. (EGB761), ginkgo flavonoids (GF) and ginkgo terpenlactones (GT) on the oxidation of human plasma low density lipoproteins (LDL) induced by Fe2+ or Cu2+. METHOD: LDL was pretreated with EGB761, GF and GT, then was oxidized by CuSO4 or FeSO4 6 micromol/L for 4 h. Fluorescence Spectroscopy methods were adopted to determine the contents of lipofusion (LF), malondialdehyde (MDA) and vitamin E (VitE) of LDL oxidized by Fe2+ or Cu2+ and protected by EGB761, GF or GT. RESULT: After the oxidation of LDL induced by Fe2+ or Cu2+, VitE was exhausted, while MDA and LF were markedly increased. EGB761, GF and GT prevented the decrease of VitE and increases of MDA and LF in the ox-LDL. The inhibitory effect was GF > EGB761 > GT. CONCLUSION: GF played the main role in anti-oxidation.

Antioxidants↗
PubMed2002

Induction of heme oxygenase 1 by Ginkgo biloba in neuronal cultures and potential implications in ischemia.

Ginkgo biloba extract (EGb 761) is a standardized extract originating in traditional Chinese medicine. Ginkgo biloba dried leaves have been used for centuries to treat various neurological conditions. The constituents from the extract are likely to have synergistic effects that have been shown to be protective against oxidative stress injury. However, the cellular mechanisms of protection afforded by Ginkgo biloba are still unclear. The cascade leading to neuronal cell death in acute and chronic neurodegenerative conditions, such as cerebral ischemia and Alzheimer's disease, has been postulated to be mediated by free radical damage. We tested the hypothesis that the neuroprotective action of EGb 761 could be due partially to an induction of heme oxygenase I (HO1). We and others have previously reported that modulation of HO total activity may well have direct physiological implications in stroke and in Alzheimer's disease. Heme oxygenase acts as an antioxidant enzyme by degrading heme into iron, carbon monoxide, and biliverdin which is rapidly converted into bilirubin. Through the use of primary neuronal cultures, we demonstrated that EGb 761 induces HO1 in a dose-dependent manner (0, 10, 50, 100 and 500 microg/ml) and time-dependent manner with a maximal induction at 8 hr. We are proposing that several of the protective effects of EGb 761 in ischemia could be mediated through beneficial actions of heme degradation and its metabolites.

Animals↗
PubMed1996

The neuroprotective properties of the Ginkgo biloba leaf: a review of the possible relationship to platelet-activating factor (PAF).

Ginkgo biloba (Ginkgoaceae) is an ancient Chinese tree which has been cultivated and held sacred for its health-promoting properties. There is substantial experimental evidence to support the view that Ginkgo biloba extracts have neuroprotective properties under conditions such as hypoxia/ischemia, seizure activity and peripheral nerve damage. Research on the biochemical effects of Ginkgo biloba extracts is still at a very early stage. One of the components of Ginkgo biloba, ginkgolide B, is a potent platelet-activating factor (PAF) antagonist. Although the terpene fraction of Ginkgo biloba, which contains the ginkgolides, may contribute to the neuroprotective properties of the Ginkgo biloba leaf, it is also likely that the flavonoid fraction, containing free radical scavengers, is important in this respect. Taken together, the evidence suggests that Ginkgo biloba extracts are worthy of further investigation as potential neuroprotectant agents.

Animals↗
PubMed2002

[Expression of vascular endothelial growth factor in U937 foam cells and the inhibitory effect of drugs].

AIM: To study the expression of vascular endothelial growth factor (VEGF) in U937 foam cells and the inhibitory effect of salvianolic acid B and Ginkgo biloba extract in vitro. METHODS: U937 cells were incubated with 80 mg.L-1 oxidized low density lipoprotein (OX-LDL) for 48 h and a macrophage-derived foam cell model was established. The VEGF concentration in the media was determined by ELISA; the VEGF protein expression in cells was measured with immunohistochemistry; the VEGF mRNA level in cells was measured by in situ hybridization; the positive ratio detected by a morphometrical analysis system was used as the amount of the VEGF protein expression and the mRNA level. RESULTS: After U937 cells were incubated with OX-LDL, VEGF expression level increased greatly both in the cells and in the media. Salvianolic acid B and Ginkgo biloba extract were shown to remarkably inhibit the increase of VEGF. After treated with 10 micrograms/L-1 salvianolic acid B and Ginkgo biloba extract, the VEGF protein concentration in the media and positive ratio in the cells decreased compared with foam cells. After treated with 10 micrograms.L-1 salvianolic acid B and 100 micrograms.L-1 Ginkgo biloba extract, the VEGF mRNA level decreased measured by in situ hybridization. CONCLUSION: A high VEGF expression level was determined in U937 foam cells. Salvianolic acid B and Ginkgo biloba extract were found to inhibit VEGF expression significantly in U937 foam cells in vitro.

Benzofurans↗
PubMedDate not supplied

Improved extraction of ginkgotoxin (4'-O-methylpyridoxine) from Ginkgo biloba products.

A simple extraction procedure was applied to the analysis of canned/packaged white nuts and Ginkgo biloba extracts. Extraction by shaking with water at room temperature was more convenient to use than a previously published Soxhlet procedure for analysis of packaged Ginkgo biloba seeds (white nuts) for ginkgotoxin; recoveries from spiked dried seeds by the simple extraction procedure averaged 76%. Determination was by liquid chromatography with UV or fluorescence detection. Recoveries of ginkgotoxin from a spiked and unspiked natural health product (powder from Ginkgo biloba capsules) were equivalent by both procedures; recovery from spiked powder by the simple extraction procedure was 81%. Application of this extraction procedure in the analysis of 6 samples of white nuts (vacuum packaged and canned products) showed that free ginkgotoxin was present in 5 samples at concentrations up to 25 microg/g dry weight. Total ginkgotoxin was determined after hydrolysis with beta-glucosidase of sample extracts in which a peak corresponding to the 5'-O-glucoside was detected. Ginkgotoxin was determined in 10 Ginkgo biloba natural health products by the same method at levels up to 181 microg/g.

Chemistry Techniques, Analytical↗
PubMed2003

[Study on extraction process of flavone from Ginkgo biloba leaves by enzymic treatment].

The extraction technology of flavonoids from Ginkgo biloba leaves was studied in this paper. When the crude leaves used the cellulase enzyme pretreatment before extraction process, the extraction yield of total flavone was up to 2.01%. The extraction conditions were also determined experimentally as following: concentration of enzyme in the liquor being 0.125 g/L, mixture ratio between enzyme and substrate being 1:1200, treating 2 hours, at 45 degrees C, under natural pH value.

Cellulase↗
PubMed2004

Preventive effects of extract of leaves of ginkgo (Ginkgo biloba) and its component bilobalide on azoxymethane-induced colonic aberrant crypt foci in rats.

The modifying effects of dietary feeding of extract of leaves of ginkgo (Ginkgo biloba) (EGb) and bilobalide isolated from EGb on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were investigated in male F344 rats. We also assessed the effects of EGb and bilobalide on proliferating cell nuclear antigen (PCNA) index in 'normal-appearing' crypts and activities of detoxifying enzymes of cytochrome P450 (CYP), glutathione S-transferase (GST) and quinine reductase (QR) activity in the liver. To induce ACF, rats were given two weekly subcutaneous injections of AOM (20 mg/kg body wt). They also received the experimental diets containing EGb (50 or 500 ppm) and bilobalide (15 or 150 ppm) for 4 weeks, starting 1 week before the first dosing of AOM. AOM exposure produced a substantial number of ACF (106 +/- 10) at the end of the study (week 4). Dietary administration of EGb and bilobalide caused significant reduction in the frequency of ACF: 50 ppm EGb, 73 +/- 17 (31% reduction, P < 0.001); 500 ppm EGb, 56 +/- 13 (47% reduction, P < 0.001); 15 ppm bilobalide, 79 +/- 17 (25% reduction, P < 0.001); and 150 ppm bilobalide, 71 +/- 30 (33% reduction, P < 0.01). Immunohistochemically, EGb or bilobalide administration significantly lowered PCNA index in normal-appearing crypts. Feeding with EGb or bilobalide increased activities of CYP as well as GST and QR in the liver. These findings might suggest possible chemopreventive ability of EGb or bilobalide, through alterations in cryptal cell proliferation activity and drug metabolizing enzymes' activities, in colon tumorigenesis.

Administration, Oral↗
PubMed2000

Antimicrobial investigation of semipurified fractions of Ginkgo biloba leaves.

A total methanolic extract of Ginkgo biloba leaves was fractionated by solvent partition using ethyl acetate (fraction A), n-butanol (fraction B) and water (fraction C). The antimicrobial activity of the three fractions was evaluated using a number of Gram-positive and -negative bacteria and yeasts. The apolar fraction A appeared to be the most interesting because of its activity against several microorganisms; this fraction was further separated by high performance liquid chromatography, and shown to contain substances with strong inhibitory activity against Enterococcus faecalis 31, different from the major known chemical components of G. biloba leaves.

Anti-Bacterial Agents↗
PubMed2000

The efficacy of ginkgo for elderly people with dementia and age-associated memory impairment: new results of a randomized clinical trial.

OBJECTIVES: To evaluate the efficacy, the dose-dependence, and the durability of the effect of the ginkgo biloba special extract EGb 761 (ginkgo) in older people with dementia or age-associated memory impairment. DESIGN: A 24-week, randomized, double-blind, placebo-controlled, parallel-group, multicenter trial. SETTING: Homes for the elderly in the southern part of the Netherlands. PARTICIPANTS: Older persons with dementia (either Alzheimer's dementia or vascular dementia; mild to moderate degree) or age-associated memory impairment (AAMI). 214 Participants were recruited from 39 homes for the elderly. INTERVENTION: The participants were allocated randomly to treatment with EGb 761 (2 tablets per day, total dosage either 240 (high dose) or 160 (usual dose) mg/day) or placebo (0 mg/d). The total intervention period was 24 weeks. After 12 weeks of treatment, the initial ginkgo users were randomized once again to either continued ginkgo treatment or placebo treatment. Initial placebo use was prolonged after 12 weeks. MEASUREMENTS: Outcomes were assessed after 12 and 24 weeks of intervention. Outcome measures included neuropsychological testing (trail-making speed (NAI-ZVT-G), digit memory span (NAI-ZN-G), and verbal learning (NAI-WL)), clinical assessment (presence and severity of geriatric symptoms (SCAG), depressive mood (GDS), self-perceived health and memory status (report marks)), and behavioral assessment (self-reported level of instrumental daily life activities). RESULTS: An intention-to-treat analysis showed no effect on each of the outcome measures for participants who were assigned to ginkgo (n = 79) compared with placebo (n = 44) for the entire 24-week period. After 12 weeks of treatment, the combined high dose and usual dose ginkgo groups (n = 166) performed slightly better with regard to self-reported activities of daily life but slightly worse with regard to self-perceived health status compared with the placebo group (n = 48). No beneficial effects of a higher dose or a prolonged duration of ginkgo treatment were found. We could not detect any subgroup that benefited from ginkgo. Ginkgo use was also not associated with the occurrence of (serious) adverse events. CONCLUSIONS: The results of our trial suggest that ginkgo is not effective as a treatment for older people with mild to moderate dementia or age-associated memory impairment. Our results contrast sharply with those of previous ginkgo trials.

Activities of Daily Living↗
PubMedDate not supplied

Preliminary EEG study of protective effects of Tebonin in transient global cerebral ischemia in rats.

Free radicals and platelet activating factor (PAF) have been implicated as important mediators in neuronal injury after cerebral ischemia-reperfusion and, particularly, in postischemic hypoperfusion. The electroencephalography (EEG) is a real time reflection of changes in neuronal activity and metabolism. The objective of this study was to investigate the effects of preventive treatment with Ginkgo biloba extract (EGb 761--Tebonin) in cerebral global ischemia and reperfusion in rats using computerized EEG analysis. Ginkgo biloba extract, known to be, in vitro, a free radicals scavanger and a PAF--antagonist, was administrated in dose of 100 mg/kg over 24 hours, for 5 days before and 5 days after cerebral ischemia--reperfusion. The apparition of isoelectric EEG (flat-line) following 4-vessel occlusion was observed after a mean time of 25 sec. in Ginkgo biloba treated rats and after 18 sec. in control rats (p < 0.0015). Computerized spectral analysis of EEG has shown that the percentage of slow waves at 10 minutes after reperfusion was 117% higher in control group than in Ginkgo biloba group (p < 0.015) and the percentage of slow waves after 15 minutes of reperfusion was 100% higher in the control group than in the Ginkgo biloba group (p < 0.02). Five days after cerebral ischemia--reperfusion the percentage of slow waves was unsignificantly higher in the control group than in the Ginkgo biloba group (p > 0.05).

Animals↗
PubMed2000

Cholinesterase inhibitors and Gingko extracts--are they comparable in the treatment of dementia? Comparison of published placebo-controlled efficacy studies of at least six months' duration.

The efficacy of four cholinesterase inhibitors (tacrine, donepezil, rivastigmine, metrifonate) and Ginkgo special extract EGb 761 in Alzheimer's disease were compared. The differences in the effects of the active substance and placebo on cognition were measured on the ADAS-Cog scale, taking into account the different degrees of dementia in the various studies and the dropout rate due to adverse drug reactions. Efficacy, expressed as the delay in symptom progression or the difference in response rate between active substance and placebo, showed no major differences between the four cholinesterase inhibitors and the Ginkgo special extract. Only tacrine exhibited a high dropout rate due to adverse drug reactions. In view of this, the subject of new prescriptions should be critically reviewed. Second-generation cholinesterase inhibitors (donepezil, rivastigmine, metrifonate) and Ginkgo special extract EGb 761 should be considered equally effective in the treatment of mild to moderate Alzheimer's dementia.

Alzheimer Disease↗
PubMed1993

Ischaemia and reperfusion-induced injury in rat retina obtained from normotensive and spontaneously hypertensive rats: effects of free radical scavengers.

The authors have studied the effects of free radical scavengers, superoxide dismutase (SOD) and extract of Ginkgo biloba (EGb 761, flavone-rich extract) on ion shifts (Na, K and Ca) induced by ischaemia and reperfusion in rat retina obtained from normotensive and spontaneously hypertensive rats. Eyes were subjected to 90 min of ischaemia by occlusion of the retinal artery, followed by 4 and 24 hours of reperfusion. SOD (15,000 U/kg, i.v.) or EGb 761 (50 mg/kg, per os) was administered in a daily dose for 10 days. In the drug-free control groups, 90 min of ischaemia significantly increased tissue Na gains from their pre-ischaemic control values of 63 +/- 7 microM/g dry weight (in retina obtained from normotensive rats) and 76 microM/g dry weight (in retina obtained from hypertensive rats) to 89 +/- 9 microM/g dry weight and 101 +/- 7 microM/g dry weight, respectively. During reperfusion, a further elevation was found in retinal Na in both the normotensive and hypertensive groups. Probably, because of the ischaemia-induced inhibition of Na-K-ATPase, retinal K loss was detected after ischaemia and reperfusion, respectively. An accumulation of retinal Ca was measured after ischaemia and reperfusion in the normotensive and spontaneously hypertensive groups. Both free radical scavengers significantly reduced the maldistribution of ions induced by ischaemia and reperfusion, but the effectiveness of drugs was more evident in normotensive than hypertensive groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Free radical-mediated effects in reperfusion injury: a histologic study with superoxide dismutase and EGB 761 in rat retina.

In Sprague-Dawley rats, retinal ischemia was induced by occlusion of the central retinal artery, while reperfusion was initiated by unclamping and removing the occluder. Ninety minutes of regional ischemia followed by 24 h of reperfusion resulted in a development of retinal edema in the inner plexiform layer and a migration of neutrophils into the retinal tissue. Oxygen free radicals have been implicated as inducers of cell damage in different tissues. This finding has led us to speculate that, if oxygen free radicals play an important role in the development of reperfusion injury, superoxide dismutase (SOD) and EGB 761 (Tanakan, extract of Ginkgo biloba, IPSEN) should be protective against reperfusion-induced injury. Under our experimental conditions, SOD dose-dependently reduced the development of edema formation (which was expressed in micrometers, measuring the thickness of the inner plexiform layer). Thus, 3,750, 7,500 and 15,000 U/kg of SOD reduced the reperfusion-induced edema formation from its drug-free ischemic value of 112 +/- 4 to 107 +/- 7, 91 +/- 6 (p less than 0.05) and 85 + 4 microns (p less than 0.001), respectively. Furthermore, SOD significantly reduced the migration of neutrophils which can also contribute to the development of reperfusion-induced injury. The same protective effect was observed, concerning the edema formation and neutrophil migration, in the EGB 761-treated groups. Our results indicate that free radicals play an important role in the development of reperfusion-induced injury, and the treatment of ischemic and reperfused retina with free radical scavengers may reduce the severity of reperfusion damage.

Animals↗
PubMed2001

Evidence for toxic effects of alkylphenols from Ginkgo biloba in the hen's egg test (HET).

Extracts from the leaves of the Gingko tree (Ginkgo biloba L.) are therapeutically used for the treatment of peripheral and cerebral vascular disorders as well as multi-infarct or Alzheimer-type dementia. As constituents with potential contact allergenic and toxic properties in crude Ginkgo extracts a group of alkylphenols (e.g., ginkgolic acids, ginkgol, bilobol) has been described. Thus, for reasons of drug safety a maximal concentration (< or = 5 ppm) of ginkgolic acids is requested by the Monograph of the Commission E of the former German Federal Health Agency (Bundesgesundheitsamt, BGA). During production of the standardized Ginkgo extract EGb 761, alkylphenols are largely eliminated as water insoluble compounds (decanter sludge) from the primary acetone extract. To further assess the adverse properties of alkylphenols, different fractions derived from the decanter sludge were evaluated for their embryotoxic effects in the hen's egg test (HET). A fraction enriched for ginkgolic acids (16%) and biflavones (6.7%) was found to induce death of 50% of the chick embryos (LD50) at a dose of 1.8 mg/egg (approximately/= 33 ppm). A similar strong lethal effect (LD50: 3.5 mg/egg; 64 ppm) was oberserved for a fraction which contained 58% ginkgolic acids but less than 0.02% biflavones. In contrast, an extreme low toxic potential (LD50: 250 mg/egg or 4540 ppm) was established for a fraction containing 16% biflavones and 1% ginkgolic acids. Thus, the present investigations confirm the high toxic potential of ginkgolic acids, although it can not be excluded that biflavones or some other constituents in the different fractions may amplify the adverse effect of these substances. Since no contribution of alkylphenols to the therapeutic efficacy of Ginkgo extracts has been confirmed and their elimination during the manufacturing process does not cause technical problems, these results further support the requirement for the completest possible removal of these compounds under toxicological considerations.

Animals↗
PubMed2005

Treatment effects of EGb 761 and cholinesterase inhibitors--why available studies do not demonstrate superiority of the latter.

Based on simple comparisons of drug-placebo differences found in clinical trials, it has repeatedly been concluded that EGb 761 is less effective in the treatment of Alzheimer's disease than cholinesterase (ChE) inhibitors. However, the data of pivotal studies with both types of drugs show that drug-placebo differences in cognitive outcomes are more influenced by the degrees of deterioration of the placebo groups than by changes of the actively treated groups. Since the former are determined by characteristics of the patient samples and the therapeutic environment, but not by drug effects, it is concluded that direct comparisons of drug-placebo differences are inappropriate to assess the relative potencies of anti-dementia drugs. Comparisons have to take into account the different unspecific influences. The currently available data do not support the notion of superiority of ChE inhibitors over EGb 761.

Alzheimer Disease↗
PubMedDate not supplied

Gingko biloba extract diminishes stress-induced memory deficits in rats.

Exposure to chronic restraint stress in rats and psychosocial stress in humans has been shown to alter cognitive functions such as learning and memory and has been linked to the pathophysiology of mood and anxiety disorders. Antianxiety or sedative agents used in the management of stress have several disadvantages and undesired effects. Therefore, in this study, we investigated efficacy of a natural medicine, the extract of Ginkgo biloba (EGB 761), in prevention and treatment of the post-stress memory dysfunctions. The results showed that chronic restraint stress (2 h for 21 days) or an 'equivalent' dose of exogenous corticosterone (5 mg/kg) impaired nonspatial memory as measured by an object recognition test. In control rats, EGB 761 improved spatial and nonspatial memory in Morris water maze and object recognition tests. Preventive doses of EGB 761 (100 mg/kg) normalized cognitive deficits, seen in rats chronically stressed or treated with corticosterone in object recognition test, and improved memory processes in these rats measured by Morris water maze test. There was no influence of our treatments on locomotor exploratory activity and anxiety measured in open field and elevated 'plus' maze tests, making a contribution of unspecific motor and emotional effects of the used drugs to their performance in the memory tests improbable.

Animals↗