Ginkgo biloba: A Comprehensive Review of Phytochemicals and Medicinal Applications
Summary
This review provides an extensive overview of Ginkgo biloba (G. biloba), a plant with a long history of medicinal use. It details the plant's diverse phytochemical constituents, including flavonoids, terpenoids, and phenolic acids, and explores their associated therapeutic properties. The paper examines G. biloba's nutraceutical value, pharmacological activities across various diseases like respiratory conditions, cancer, and neurological disorders, as well as its commercial uses, synergistic effects with other compounds, and potential adverse effects and toxicity. Clinical studies and future research perspectives are also discussed, highlighting G. biloba's potential as a natural therapeutic agent when used judiciously.
Key Insights
Ginkgo biloba possesses a rich array of bioactive compounds that contribute to its diverse medicinal applications.
Ginkgo biloba (G. biloba) is a chemically diversified plant containing numerous bioactive compounds, including flavonoids (e.g., quercetin, kaempferol), terpenoids (bilobalide, ginkgolides), bioflavonoids, organic acids, lignans, proanthocyanidins, polyprenols, and polysaccharides. These compounds are responsible for its wide range of medicinal and pharmacological properties, such as antioxidant, anti-inflammatory, anticancer, neuroprotective, and cardioprotective effects. The extract EGb 761, a standardized leaf extract, contains specific concentrations of these active components and is widely used for therapeutic benefits.
Ginkgo biloba demonstrates a broad spectrum of pharmacological activities beneficial for various health conditions.
G. biloba exhibits numerous pharmacological activities including, but not limited to, anticancer, antidementia, antidiabetic, antiobesity, antilipidemic, antimicrobial, antioxidant, anti-inflammatory, hepatoprotective, antidepressant, antiaging, immunomodulatory, antihypertensive, and neuroprotective effects. It is frequently used to treat neurological, cardiovascular, and respiratory diseases. Its ability to act as a free radical scavenger is particularly critical, and synergistic effects with other plant extracts can enhance antioxidant properties. Clinical and preclinical studies support its potential in managing various diseases, though further verification of safety and efficacy through ongoing research is recommended.
Despite its benefits, Ginkgo biloba has potential adverse effects and toxicities that require careful consideration.
While G. biloba offers many therapeutic advantages, it also presents potential drawbacks. The seeds contain the neurotoxic compound 4′-O-methylpyridoxine (MPN), also known as ginkgotoxin, which interferes with vitamin B6 metabolism and can cause seizures. Leaf extracts, while generally considered safe at therapeutic doses, may have associated risks like bleeding, especially when combined with anticoagulant medications like warfarin. Other reported adverse effects include allergic contact dermatitis and proarrhythmic activities. Long-term use or high doses can lead to toxicity, and careful monitoring is advised, particularly when co-administered with other medications or in specific patient populations like pregnant women.
Sections
Abstract
Ginkgo biloba is an ancient plant with diverse bioactive components and broad medicinal benefits.
Ginkgo biloba is an ancient plant species rich in bioactive components, offering a variety of health benefits. It possesses numerous medicinal and pharmacological properties including anticancer, antidementia, antidiabetic, antiobesity, antilipidemic, antimicrobial, antioxidant, anti-inflammatory, hepatoprotective, antidepressant, antiaging, immunomodulatory, antihypertensive, and neuroprotective effects. It is commonly used for neurological, cardiovascular, and respiratory diseases. This review covers therapeutic applications, chemical constituents, toxicity, adverse effects, synergistic effects, and clinical studies of G. biloba, highlighting its potential as a free radical scavenger and the synergistic enhancement of antioxidant properties when combined with other plant extracts. While long-term or high-dose use can lead to adverse effects and drug interactions, preclinical and clinical data confirm its potential in various diseases, though further research on safety and efficacy is warranted.
1. Introduction
Ginkgo biloba, a 'living fossil', has been used medicinally for over 2000 years.
Plant-based phytochemicals have been a source for novel drug discovery for millennia. Ginkgo biloba L. (Ginkgoaceae), known as the Maidenhair tree, is an ancient, tall, deciduous plant with fan-shaped leaves. It is considered a 'living fossil' due to its evolutionary significance as one of the oldest seed plants. Notably, it was the first plant to germinate after the atomic bomb in Hiroshima. G. biloba exhibits remarkable resilience to environmental factors. Its leaves and nuts have been used in traditional Chinese medicine for over 2000 years, with documented uses for asthma, tuberculosis, skin issues, digestive problems, bronchitis, hearing loss, nervousness, arteriosclerosis, thrombosis, ischemic heart disease, and diabetes mellitus. Extracts like EGb 761 show antioxidant properties by scavenging reactive oxygen and nitrogen species, and combinations with other extracts can enhance these effects. Key compounds include flavonoids, terpenoids, and organic acids. G. biloba is widely used for cardiovascular and neurological disorders. Marketed products include supplements like Nutricost, GreeNatr, Nature's Bounty, and VH Nutrition.
Herbal medicine research faces challenges in standardization and efficacy validation.
Recent years have seen increased attention on clinical studies of herbal medicines and their pharmacological functions. However, comprehensive profiling of biopharmaceutical characteristics, including both efficacy and safety, remains less common. Herbal medicinal products are expected to meet stringent standards for potency, purity, and biological content, comparable to synthetic medicines, which is often not achieved. This review aims to disseminate information on G. biloba, covering trade patterns, bioactive compounds, therapeutic effects, molecular pathways, nutritional value, toxicity, and drug interactions, to provide a thorough overview for researchers and practitioners.
2. Chemical Constituents
Ginkgo biloba contains a variety of chemical compounds, including flavonoids, terpenoids, and phenolic acids.
Ginkgo biloba yields diverse chemical compounds with therapeutic potential. Novel terpenoids and lignans have been identified. Flavonoids, such as kaempferol, quercetin, and isorhamnetin, are abundant, often found as glycoside derivatives, and exhibit antioxidant properties. Ten diterpenoid lactones (ginkgolides A-Q) and bilobalide (a sesquiterpene lactone) are key terpenoids. The plant also contains alkylphenols (cardols, cardanols), alkylphenolic acids (ginkgolic acids, known for some toxicity but also potential pharmacological effects), and various carboxylic acids like ferulic and caffeic acid. Lignans, proanthocyanidins (prodelphinidin and procyanidin), and polyprenols are also present. Toxic components like 4′-O-methylpyridoxine (MPN) have been identified, primarily in seeds.
Specific classes of compounds identified in G. biloba include flavonoids, terpenoids, alkylphenols, carboxylic acids, and lignans.
Key chemical constituents of G. biloba are categorized as follows: * **Flavonoids:** Over 110 identified, including flavonol glycosides like kaempferol 3-O-α-L-[6'''-p-coumaroyl-(β-D)-glucopyranosyl-(1,2)-rhamnopyranoside]-7-O-β-D-glucopyranoside and isorhamnetin 3-O-α-L-[6'''-p-coumaroyl-(α-D)-glucopyranosyl-(1,2)-rhamnopyranoside]. These exhibit antioxidant properties. Flavonoids are grouped into flavanones, isoflavones, flavones, biflavones, flavan-3-ols, flavonols, and biginkgosides. * **Terpenoids:** Includes ten diterpenoid lactones (ginkgolides A-Q) and bilobalide, a sesquiterpene lactone, with a new bilobalide isomer identified in 2020. Nor-terpenoids have also been found. * **Alkylphenols and Alkylphenolic Acids:** This group includes cardols, cardanols, α-hydroxycardanols, urushiols, isourushiols, and alkylphenolic acids like ginkgolic acids, which possess both toxicity and potential pharmacological effects. * **Carboxylic Acids:** Identified acids include ferulic acid, p-coumaric acid, protocatechuic acid, caffeic acid, p-hydroxybenzoic acid, m-hydroxybenzoic acid, vanillic acid, isovanillic acid, gallic acid, and sinapic acid, often existing in glycosidic or covalent bonds. * **Lignans:** Found in roots and seeds, exhibiting antioxidant properties. Five lignans were isolated from G. biloba. * **Proanthocyanidins:** Two types, prodelphinidin and procyanidin, have been identified. * **Polyprenols:** Long-chain isoprenoid alcohols with antibacterial properties. * **Polysaccharides:** Composed of glucose, rhamnose, mannose, arabinose, and galactose. * **Others:** Including the toxic component 4′-O-methylpyridoxine (MPN). Essential oil contains sesquiterpenes.
3. Nutraceutical Value of Ginkgo biloba
Ginkgo biloba nuts are nutritious and offer potential health benefits but contain toxic compounds.
Nutraceuticals, or phytochemicals, from plants like G. biloba offer health benefits. G. biloba seeds (nuts) are rich in vitamin C, carbohydrates, riboflavin, and proteins, and are traditionally used for cancer prevention and treating neurological diseases. They are incorporated into various foods and delicacies. However, seeds also contain toxic ginkgolic acids and 4′-O-methylpyridoxine (MPN), which can cause adverse effects like vitamin B6 deficiency and allergic reactions, limiting their widespread use as everyday foods. Processing methods are being explored to reduce these toxic substances.
Nutritional analysis shows G. biloba seeds are a source of essential vitamins, minerals, and macronutrients.
A 100g serving of G. biloba seeds provides essential nutrients. Key macronutrient profiles include Calories (182 Kcal), Carbohydrates (72.98 g), Protein (12.27 g), and Fats (4.75 g, with varying polyunsaturated, monounsaturated, and saturated fatty acid content). It also contains significant amounts of minerals like Potassium (510 mg), Magnesium (27 mg), and Phosphorus (124 mg), along with vitamins such as Vitamin C (15 mg), Vitamin B1 (0.22 mg), Vitamin B2 (0.09 mg), Vitamin B6 (0.328 mg), and Folate (54 µg). Sodium (7 mg) and Calcium (2 mg) are also present. While cholesterol is absent, ash and water content are noted.
4. Bioactive Compounds in Ginkgo biloba
G. biloba leaves are rich in flavonoids and terpenoids, contributing to various pharmacological activities.
The primary medicinal components of G. biloba are found in its leaves, primarily flavonoids and terpenoids. These extracts exhibit a wide range of pharmacological activities, including antibacterial, antioxidant, anti-inflammatory, antiallergic, and cytotoxic anticancer effects. Other identified compounds like biflavonoids, organic acids, and polyprenols also contribute to its bioactivity. Ginkgolides and bilobalide are notable terpenoids, while flavonoids, such as quercetin and kaempferol, exist as glycoside derivatives. A standardized extract, EGb 761, contains specific proportions of terpenoids, flavonoid glycosides, and organic acids, maximizing its health benefits.
Key bioactive compound classes in G. biloba include polyphenols, terpenoids, and organic acids with diverse actions.
G. biloba harbors several classes of bioactive compounds: * **Polyprenols:** Found in leaves, including di-trans-poly-cis-octadecaprenol, exhibiting antibacterial properties and safety against Aβ₂₅-₃₅. * **Flavonoids:** Present in leaves, such as quercetin, kaempferol, isorhamnetin, rutin, luteolin, delphinidinon, and myricetin, with noted antioxidant, anticancer, antibacterial, antiviral, anti-inflammatory, and neuroprotective effects. * **Organic acids:** Including benzoic acid derivatives (ginkgolic acid) and N-containing acids, showing inhibitory effects on xanthine oxidase (XOD) and antitumor properties. * **Biflavonoids:** Such as sciadopitysin, ginkgetin, isoginkgetin, amentoflavone, bilobetin, and 5′-methoxybilobetin, possessing antiadipogenesis, antiobesity, and antithrombin activities. * **Terpenoids:** Isolated from roots, leaves, and bark, including triterpenes (sterols), sesquiterpenes (bilobalide), and diterpenes (ginkgolides A, B, C, J, M). These compounds offer cerebral protection, antioxidant, anti-inflammatory, antiplatelet, antilipidemic, antiapoptotic effects, and enhance memory and learning. * **Others:** Including waxes, steroids, 2-hexenal, cardanols, sugars, catechins, phenols, aliphatic acids, and rhamnose, which confer antioxidant, anti-inflammatory, antidiabetic, antiapoptotic, antiradiation, antiviral, antitumor, hepatoprotective, and antiatherosclerosis properties.
5. Pharmacological Activities
G. biloba extract (GBE) is utilized for respiratory diseases, exhibiting anti-inflammatory and lung protective effects.
GBE is commonly used for asthma and bronchitis. In models of acute respiratory distress syndrome, asthma, and COPD, GBE components like ginkgolide M (GM) and ginkgolide B (GB) have shown effectiveness in reducing inflammatory cell aggregation (lymphocytes, neutrophils, macrophages) and improving lung damage. EGb 761 treatment in allergic mouse models also reduced pro-inflammatory cytokines (IL-4, IL-5, IL-6, IL-8, IL-13, TNF-α) and regulated leukocyte elastase activity, demonstrating anti-inflammatory effects in the lungs.
G. biloba shows anticancer effects by inhibiting cell proliferation and metastasis in various cancer models.
Research indicates G. biloba exhibits anticancer properties. In hepatocellular carcinoma (HCC) rats, GBE improved histological characteristics and reduced tumor markers (AFP, glypican-3, CEA) by modulating gene expression. Ginkgo biloba exocarp extracts (GBEE) demonstrated anti-Lewis lung cancer (LLC) efficacy by limiting cell growth and inhibiting tumor angiogenesis via Wnt/β-catenin and VEGF signaling pathways. In gastric cancer cells, GBE inhibited cell cycle progression by reducing cyclin D1 and c-Myc production, and through the KSR1-mediated ERK1/2 pathway.
G. biloba extract (EGb 761) shows promise for treating dementia, potentially by addressing multiple etiologies.
EGb 761 is frequently studied for cognitive enhancement and dementia treatment, including vascular, Lewy body, and frontotemporal dementia. Its potential mechanisms include preventing amyloid production and toxicity, controlling excitotoxic glutamatergic neurotransmission, and acting as a radical scavenger, suggesting a broad applicability across different dementia subtypes.
G. biloba demonstrates antidiabetic effects by improving insulin sensitivity and reducing inflammation.
In vivo studies show GBE possesses antidiabetic properties. Bilobalide protected lipid cells against hypoxia-induced insulin resistance and inflammation by increasing adiponectin secretion and modulating insulin signaling pathways. Ginkgolide B improved vascular function in diabetic rats by enhancing antioxidant activity (SOD, eNOS) and decreasing oxidative stress markers (MDA). GBE's impact on glucose metabolism and insulin sensitivity suggests its therapeutic potential in managing diabetes mellitus.
G. biloba exhibits antiobesity effects by influencing appetite regulation and lipid metabolism.
GBE administration has shown benefits in reducing body weight and improving metabolic parameters associated with obesity. It may stimulate the insulin signaling cascade and reduce inflammatory markers like TNF-α. Biflavones in GBE, such as ginkgetin and isoginkgetin, may act as pancreatic lipase inhibitors, potentially aiding in weight management. Ginkgolide B and C have also shown effects on reducing body weight, improving hepatic steatosis, and enhancing lipolysis in preclinical models.
G. biloba helps improve lipid profiles, showing antilipidemic effects relevant to cardiovascular health.
G. biloba treatment in animal models has demonstrated significant improvements in lipid profiles. In male rabbits, it decreased plasma cholesterol and triglyceride levels while increasing HDL-C. Aortic tissue showed reduced MDA levels and increased GSH. Ethanolic extracts of G. biloba seeds in high-fat diet-fed mice prevented fat accumulation and lowered body weight, suggesting a hypocholesterolemic impact through lipid synthesis reduction, beneficial for treating cardiovascular disorders.
G. biloba offers cardiovascular benefits, including hypocholesterolemic effects and potential protection against atherosclerosis.
Studies on G. biloba seeds suggest effects on cholesterol metabolism and cardiovascular disease prevention. The lipid-soluble fraction of seeds reduced hepatic cholesterol, while the water-soluble fraction increased serum cholesterol, indicating potential application in heart disease management. Ethanol extracts have shown efficacy in reducing body weight and fat accumulation in obese mice, potentially by lowering HDL cholesterol and reducing lipid synthesis. Detoxified nut powder improved lipid metabolism in obese mice, suggesting protective effects against cardiovascular disorders.
G. biloba possesses antimicrobial properties effective against various bacteria and fungi.
Several G. biloba components, including phenolic acids, polysaccharides, and proteins, exhibit antimicrobial activity. Ginkgolic acids show potent antibacterial activity against Gram-negative bacteria like E. coli and Gram-positive bacteria. Ginkgolides are bactericidal against certain bacteria and fungi. A protein isolated from G. biloba demonstrated broad-spectrum antibacterial activity. Polysaccharides from the seeds also possess antibacterial characteristics. These findings highlight G. biloba's potential as a source of natural antimicrobial agents.
The potent antioxidant capacity of G. biloba protects against oxidative stress and age-related damage.
G. biloba is recognized for its robust antioxidant properties, crucial for combating oxidative stress that contributes to aging and various diseases. Its antioxidant components, including terpenes, flavonoids, and bioflavonoids, effectively scavenge various free radicals. Studies show GBE protects cardiovascular systems, the brain, and the retina from age-related free radical damage, reduces ROS/RNS production, and mitigates oxidative stress in conditions like ischemic injury and cisplatin-induced neurotoxicity. It helps maintain cellular integrity by controlling oxidative stress.
G. biloba promotes wound healing and offers protection against radiation and frostbite injury.
G. biloba demonstrates benefits in wound healing and tissue repair. It has shown protective effects against radiation-induced cataract development in rats by enhancing antioxidant enzyme activities. Its antioxidant properties help alleviate reperfusion damage and minimize tissue peroxidation in frostbite injuries. GBE also reduced VEGF and CXCL8/IL-8 levels in keratinocytes, indicating roles in skin health and potentially wound healing processes.
Antiplatelet activity of G. biloba, particularly ginkgolides, is significant for cardiovascular health.
G. biloba components, especially ginkgolides A and B, exhibit antiplatelet activity. They inhibit platelet activation by blocking Syk and p38 MAPK phosphorylation and reduce the release of inflammatory mediators like CD40L and RANTES. Ginkgolide C acts as a PAF antagonist but is less potent than ginkgolide B. Bilobalide also contributes anti-inflammatory effects. These antiplatelet properties are relevant for preventing thrombosis and managing cardiovascular conditions.
G. biloba possesses significant anti-inflammatory effects through various molecular pathways.
Flavonoids and other phenolic compounds in G. biloba demonstrate potent anti-inflammatory properties. Extracts and specific compounds like ginkgetin and biflavones have been shown in vitro and in vivo to reduce pro-inflammatory cytokines (IL-4, IL-6, TNF-α), regulate signaling pathways (Akt, p38 MAPK), and inhibit enzymes involved in inflammation like leukocyte elastase and cyclooxygenase-2. These effects make G. biloba a potential candidate for treating inflammatory diseases.
The hepatoprotective effects of G. biloba are attributed to its antioxidant and anti-inflammatory actions.
G. biloba exerts hepatoprotective effects largely through its antioxidant capacity, restoring levels of antioxidant enzymes (SOD, GPX, CAT) and glutathione while reducing lipid peroxidation. It has shown benefits in protecting the liver from oxidative injury induced by substances like carbon tetrachloride and methotrexate. GBE also reduces pro-inflammatory markers (TNF-α, IL-6) and modulates signaling pathways involved in liver injury and fibrosis, contributing to its liver-protective role.
G. biloba exhibits antidepressant-like effects, potentially by modulating neurotransmission and gut microbiota.
G. biloba compounds, including polysaccharides and diterpene ginkgolides (DGs), show antidepressant effects. Polysaccharides may influence the gut-brain axis, increasing serotonin and dopamine levels in the brain. DGs have shown antidepressant but not anxiolytic effects in mice. GBE, when used as an adjunct therapy, can enhance antidepressant outcomes and modulate neurotransmission, suggesting its utility in managing depression and related neurological conditions.
G. biloba demonstrates antiaging effects, possibly by combating oxidative stress and improving skin health.
G. biloba exhibits antiaging properties, primarily by counteracting oxidative stress, a key factor in skin aging. Leaf extracts have shown protective effects against UV damage and improve skin elasticity. EGb 761 provided protection against frostbite injury, potentially through its antioxidant mechanisms. Total lactones of Ginkgo (TLG) have shown antiaging effects in aged mice by reducing lipid peroxidation and apoptosis. These effects suggest G. biloba contributes to maintaining cellular health and mitigating age-related decline.
G. biloba acts as an immunomodulator, enhancing immune responses at optimal doses.
G. biloba polysaccharides (GBPS) and exocarp polysaccharides (GBEP) have demonstrated immunomodulatory effects. They can enhance macrophage phagocytosis and stimulate the production of pro-inflammatory cytokines like NO, TNF-α, IL-1, and IL-6. In fish models, G. biloba at optimal dietary levels boosted immunity against pesticide toxicity. However, high doses can have immunosuppressive effects, emphasizing the importance of dosage optimization for beneficial immune modulation.
G. biloba extract shows promise in treating tardive dyskinesia (TD) via antioxidant mechanisms.
Tardive dyskinesia (TD), an adverse effect of antipsychotic drugs, is characterized by involuntary movements. Evidence suggests that EGb 761 may help reduce TD symptoms by increasing brain-derived neurotrophic factor (BDNF) levels through antioxidant mechanisms, offering neuroprotection. Clinical trials and meta-analyses indicate EGb 761 can be an effective and safe adjunctive therapy for improving TD symptoms in schizophrenia patients, likely mediated by its antioxidant properties.
G. biloba extract may alleviate generalized anxiety disorder (GAD) symptoms through neuroprotective and mood-stabilizing effects.
GBE is used globally for anxiety disorders. EGb 761 has shown beneficial effects in reducing anxiety symptoms and stabilizing mood in patients with cognitive impairment and GAD. Its neuroprotective effects are attributed to its antioxidant properties and regulation of neurotransmission, neuroendocrine signaling, and neurotrophic factors, leading to the alleviation of anxiety.
G. biloba exhibits antihypertensive effects, potentially through vasodilation and renal protection.
Studies in animal models indicate G. biloba possesses antihypertensive properties. EGb 761 demonstrated hypotensive and renoprotective effects in rats with impaired kidneys by inhibiting renal NO overproduction and reducing pro-inflammatory cytokines. Its vasodilatory action, possibly via enhanced eNOS expression and NO production, contributes to lowering blood pressure. GBE also increases endothelial intracellular Ca2+ levels, supporting endothelium-dependent vasodilation.
G. biloba offers neuroprotective benefits, potentially combating neurodegenerative diseases like Alzheimer's.
Due to the increasing prevalence of neurodegenerative diseases, G. biloba is being investigated for neuroprotection. It shows promise in preventing neurodegeneration by improving cerebral blood supply and combating excitotoxicity. Flavonoids and terpenoids in G. biloba are thought to enhance brain circulation. GBE has shown benefits in Alzheimer's disease and brain ischemia, possibly by modulating inflammation and oxidative stress, and preserving cognitive function.
6. Commercial Use
G. biloba leaves are widely used in traditional medicine and commercial products for various health benefits.
G. biloba leaves are recognized in traditional Chinese medicine for treating neurological issues, circulatory disorders, and respiratory diseases. Commercially, G. biloba leaf extracts are utilized as food additives due to their perceived medicinal benefits, influencing the global market aimed at improving well-being. Identified pharmaceutically active compounds include glycosides and ginkgolides. The extract EGb 761 is a prominent example, marketed in many countries for cardiovascular conditions and as a dietary supplement. The use of ginkgolides A, B, C, J, and M is also increasing.
By-products of G. biloba, such as shells and nuts, offer industrial and culinary applications.
Industrial by-products like Ginkgo shells are rich in lignin, ferulates, p-coumarates, and vanillin, making them suitable for food and drink flavoring agents with significant antioxidant functions. Ginkgo nuts have historical use in treating various ailments including coughs, sputum, fever, diarrhea, toothaches, skin diseases, gonorrhea, and overactive bladder. They are also consumed as a side dish. Furthermore, G. biloba seeds possess hypocholesterolemic effects that can benefit lipid metabolism, and EGb 761 has shown potential in preventing diabetic-induced cataracts.
7. Synergistic Effects
G. biloba exhibits synergistic effects when combined with other compounds, enhancing health outcomes.
Synergism occurs when combined treatments yield greater health benefits than the sum of individual effects. GBE combined with aspirin has shown synergistic effects in reducing oxidative stress in human endothelial cells. Combining G. biloba with other plant extracts, like green tea, has shown success in improving skin conditions, such as elasticity. Polyprenols from G. biloba lipids, when combined with other lipids like isophytol, exhibited synergistic antimicrobial activity against certain bacteria. These combinations highlight G. biloba's potential for enhanced therapeutic efficacy.
Combinations of G. biloba with other agents can enhance antioxidant, antimicrobial, and therapeutic outcomes.
Synergistic effects have been observed where G. biloba, particularly its extract (GBE), enhances the activity of other compounds. For instance, GBE and aspirin together attenuate oxidative stress in endothelial cells. Polyprenols isolated from G. biloba leaves, when combined with other lipids, show synergistic antimicrobial activity against specific bacterial strains. The formulation of green tea and GBE has demonstrated improved skin elasticity. Furthermore, combinations with isorhamnetin and caffeic acid can facilitate enzyme expression, suggesting synergistic interactions are a key aspect of G. biloba's therapeutic potential.
8. Adverse Effects
G. biloba seeds can cause neurotoxicity due to MPN, leading to seizures.
The seeds of G. biloba contain the neurotoxic chemical 4′-O-methylpyridoxine (MPN), also known as ginkgotoxin. Ingestion of sufficient quantities can lead to tonic-clonic convulsions, vomiting, and loss of consciousness. MPN inhibits vitamin B6 metabolism, potentially causing deficiency and decreased GABA synthesis. Cases of seizures have been reported in children and adults following ingestion of G. biloba seeds, with toxicity verified by monitoring MPN levels.
G. biloba leaf extracts may pose risks of bleeding and interactions, requiring careful monitoring.
While MPN levels in leaf extracts are typically below detection limits, contamination by seeds or fruits is possible. GBE consumption should be monitored in patients taking medications metabolized by CYP2C19 and CYP2C9. The potential for increasing bleeding risk has been noted, although evidence is debated; some studies suggest it may reduce bleeding risk when combined with warfarin. Other adverse effects include irregular palpitations and allergic contact dermatitis.
9. Toxicity
High doses or prolonged use of G. biloba can lead to toxicity, including liver effects and developmental abnormalities.
In vivo studies indicate that high doses and long-term administration of G. biloba can result in toxic effects. In rats and mice, treatment increased liver weights and hepatocytic hypertrophy, with male rats showing a higher frequency of hepatocellular adenomas. Prolonged use decreased survival rates. Studies in pregnant mice showed an increased incidence of fetal abnormalities. Generally, polyprenols from G. biloba show low toxicity, and standardized EGb 761 extract did not significantly affect embryo-fetal development in mice.
In vitro studies show G. biloba extract can induce genotoxicity and cytotoxicity.
In vitro genotoxicity tests revealed that G. biloba leaf extract was mutagenic in S. typhimurium and E. coli strains. It also increased intracellular ROS and decreased GSH levels. Specific flavonoids like kaempferol and quercetin were found to inhibit cellular growth in oral cancer cell lines. Ginkgolides share structural similarities with picrotoxin, a GABA receptor antagonist. Certain ginkgolic acids exhibited cytotoxicity in hamster lung fibroblast cells.
10. Clinical Studies
Clinical trials show G. biloba extract (EGb 761) offers benefits for dementia, anxiety, and diabetes management.
Clinical trials consistently show positive safety profiles and promising results for G. biloba extract (EGb 761). Studies in dementia patients indicate EGb 761 can stabilize or delay cognitive decline, especially those with neuropsychiatric symptoms. For generalized anxiety disorder (GAD), EGb 761 improved cognitive abilities and reduced anxiety. In type 2 diabetes mellitus (T2DM) patients, GBE combined with metformin significantly reduced glycemic levels and body weight markers. It also showed benefits in improving lipid profiles when used adjunctively with statins.
EGb 761 demonstrates efficacy in treating tardive dyskinesia and has antidepressant-like effects.
A randomized controlled trial indicated EGb 761 (240 mg/day) was effective in reducing tardive dyskinesia (TD) symptoms, outperforming placebo. Meta-analyses suggest EGb 761 is a safe and efficient adjunct therapy for TD in schizophrenia patients. Clinical studies also indicate EGb 761 has antidepressant effects, improving symptoms in elderly patients with depression through modulation of neurotransmission. GBE has also shown potential benefits in treating ADHD and vitiligo vulgaris.
Clinical studies explore G. biloba's effects on various conditions, including cancer, cardiovascular disease, and aging.
Clinical research has investigated G. biloba's role in cancer treatment, with GBE combined with sorafenib showing favorable safety profiles for advanced HCC. Its use in cardiovascular health is supported by studies showing improvement in lipid parameters. Furthermore, compounds within G. biloba have demonstrated antiaging effects in human dermal fibroblasts and clinical trials have explored its role in ADHD and vitiligo. The extract has also been linked to improved cognitive functions and mood stabilization.
11. Conclusion and Future Perspectives
G. biloba shows promise as a natural therapeutic agent, but requires standardized research methodologies.
G. biloba has consistently demonstrated positive safety profiles and promising therapeutic results across numerous studies. However, variations in research methodologies complicate cross-study comparisons. Future research should focus on developing standardized outcome measures, improving patient descriptions and diagnoses, and investigating dose-response relationships, optimal treatment durations, adjunct therapy roles, and specific conditions where G. biloba is most or least effective. The complex interactions of its components, pharmacokinetics, and long-term consequences warrant further investigation.
Further research is needed to explore G. biloba's potential in areas like mitochondrial function and drug interactions.
While G. biloba serves as a valuable natural substitute and complementary treatment, potential drug interactions and adverse effects require ongoing study. Future research should delve deeper into its effects on DNA protection, mitochondrial dysfunction, ROS inhibition, apoptosis regulation, mitochondrial respiratory chain function, and intramitochondrial calcium homeostasis. Understanding the precise mechanisms, optimal dosages, treatment durations, and identifying conditions where G. biloba is most or least beneficial are crucial for informed clinical practice and patient safety.
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Ginkgo biloba: A Comprehensive Review of Phytochemicals and Medicinal Applications
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