A Systematic Review on the Chemical Constituents of the Ginkgo Biloba L. and their Biological Activities

Abstract

Ginkgo biloba, often called a "living fossil" due to its long history, displays singular botanical traits and remarkable hardiness, rendering it advantageous across decorative, environmental, and health-related contexts. Its complex composition, encompassing flavonoids, terpenoids, and other active substances like alkylphenols and proanthocyanidins, gives rise to numerous medicinal benefits, including antioxidant, brain-protective, inflammation-reducing, anticancer, and antiviral effects. Consistent extracts, such as EGb 761, have shown potential in managing various ailments, like Alzheimer's, heart conditions, and cancer. Yet, possible hazards like poisoning, sensitivities, and medication clashes necessitate careful and professionally guided administration. Continuous studies into Ginkgo biloba's genetic makeup, environmental flexibility, and healing qualities are essential to optimise its advantages while guaranteeing its protection and secure utilisation.

Keywords

Introduction

Figure No.1: Ginkgo biloba L. Leaves ⁵

Geographical Distribution

Ginkgo biloba, a tree species of notable antiquity and cultural importance, exhibits a multifaceted distributional narrative shaped by both natural phenomena and human activity. Initially indigenous to China, it was brought to Korea and Japan within the last two thousand years, probably via dispersal facilitated by humans.⁷ The present-day dispersion of sizable, aged Ginkgo biloba trees throughout China extends from subtropical to temperate regions, with yearly rainfall levels and winter temperatures acting as significant determinants.⁸ Anticipated shifts in climate patterns are projected to influence its future dispersion, possibly leading to diminished and disjointed habitats. Nevertheless, certain predictive models suggest a potential broadening of favourable zones, notably across southern and northeastern China.⁹ Internally, lignans and lignan glucosides manifest dispersion patterns within the tree, with olivil 4,4'-di-O-β-d-glucopyranoside appearing as the most profuse and predominantly located within phloem, ray parenchyma cells, and pith tissues.¹⁰

Botanical Characteristics and Morphology of The Ginkgo Biloba L.

The ginkgo tree exhibits a pyramidal form with a columnar trunk that features sparse branching, potentially reaching 30 meters in height and 2.5 meters in diameter, often surviving for more than 1,000 years. Its bark is greyish, deeply furrowed, and develops a corky texture as the tree ages.¹¹ The wood, light in colour, is soft and not particularly strong, rendering it of limited commercial use. The leaves of a ginkgo are fan-shaped, reminiscent of maidenhair fern leaflets.¹² These leaves develop on notably expanded, short, spur-like branches. The leaves, which have a leathery texture, can reach lengths of up to 8 cm and widths that are twice as large.² Each leaf blade is entered by two parallel veins at the point where the long leafstalk connects; these veins then branch out toward the edges of the leaf. Typically, a central notch divides the majority of leaves into a pair of lobes. Their colour ranges from a muted grey-green to a yellow-green during the summer, transitioning to a golden yellow shade in the autumn. The leaves remain on the tree until the late season, when they abscise rapidly. Arranged alternately on extended shoots and in clusters on abbreviated spur shoots, the leaves undergo a striking colour change to yellow during autumn before they fall. This tree has distinct sexes, with male and female reproductive structures located on separate individuals. The male trees yield petite, hanging, catkin-like strobili, which discharge pollen dispersed by wind. Female trees produce paired ovules that ripen into seeds encased in a fleshy outer layer known as the sarcotesta, which gives off an offensive odour attributable to butyric acid.¹³ Internally, the wood predominantly consists of tracheids, and the reproductive components share similarities with those of cycads and conifers, highlighting its ancient lineage.¹⁴ The hardiness of the Ginkgo is remarkable, showing resistance to contaminants, pests, and illnesses, and it notably endured the atomic blast in Hiroshima. These characteristics, together with their therapeutic importance, notably in brain and circulatory well-being, have spurred in-depth pharmacognostic and ecological research.¹⁵

Sexual Reproduction in Ginkgo Biloba

The ginkgo tree is a dioecious species, indicating that male and female plants coexist in roughly a 1:1 proportion, although there are occasional accounts of monoecious specimens.¹⁶ Ginkgo biloba, the only surviving member of an ancient plant lineage, exhibits distinctive reproductive traits. Its short shoots generate both male (microsporangiate) and female (megasporangiate) strobili, displaying different distribution patterns along the shoot.¹⁷ Wind-driven pollination in plants, specifically in Ginkgo biloba and other species, demonstrates specific timing and adaptations. Male cones of G. biloba ripen and release pollen around mid-April, with the cones hanging perpendicularly to leaves during the pollination process.¹⁸ Determining the furthest distance at which pollen can effectively disperse remains challenging, as pollination eventually ceases; however, observations in the Boston area suggest that seed germination proceeds without delay even when male and female trees are separated by 400 meters.¹⁹ Its ovules, which are 2 to 3 mm in length, produce paired clusters at the ends of stalks measuring 1.5 to 2.0 cm long. During its receptive phase, the micropyle emits a somewhat mucilaginous fluid that assists in capturing airborne pollen. As the alternate ovules remain on the tree, the male gametophyte commences a four-month developmental period that culminates in the creation of a pair of multi-flagellated spermatozoids, one of which fertilises a waiting egg cell.²⁰ The mature seed of the ginkgo is relatively large (ranging from 20–30 mm or 16–24 mm) and houses an embryo embedded within the female gametophyte's tissue, all encased in a thick seed coat. This seed coat comprises a thin, membranous inner layer, a sturdy, stony middle layer, and a soft, fleshy outer layer referred to as the sarcotesta (or endotesta). The seed, absent of the fleshy sarcotesta, is commonly termed the "nut" and spans in size from 19 to 30 millimetres (or 11 to 14 millimetres). Ginkgo ovules maintain a green colouration until maturation, at which point they transition to a yellow hue, resembling the colour of the leaves, in response to colder temperatures. Seeds begin detaching from the tree approximately one-month post-fertilisation. The characteristic foul odour of Ginkgo seeds only emerges upon complete development, attributed to volatile substances such as butanoic and hexanoic acids present in the sarcotesta. These seeds also possess phenolic compounds that can induce contact dermatitis in humans.²¹

Chemical Components of Ginkgo Biloba L. And Their Bioactivities

Flavonoids

The flavonoids present in Ginkgo biloba can be classified into several distinct types, each contributing unique properties. The major classes include flavonols, biflavones, flavones, and flavan-3-ols. Flavonols are the most abundant flavonoids identified in Ginkgo biloba. Typically, these compounds are glycosylated, meaning they are linked to a sugar molecule, which improves their solubility and bioavailability. Examples include Kaempferol, Quercetin, and Isorhamnetin; these flavanols primarily function as antioxidants, effectively neutralising free radicals like reactive oxygen species (ROS) and hydroxyl radicals. This antioxidant capacity is essential for preventing oxidative damage, which is associated with ageing and various diseases, such as Alzheimer's disease (AD), cardiovascular diseases, and cancer.²² Biflavonoids, consisting of two flavonoid units connected, provide distinct bioactivities, including anti-inflammatory and antithrombotic effects. Their methoxylation patterns differ; for example, bilobetin has a methoxy group at the C-4′ position, while ginkgetin and isoginkgetin have two methoxy groups in different positions.²³ Catechins represent a smaller, yet significant category contributing to ginkgo's overall flavonoid profile and bioactivities.²⁴ Liquid chromatography-mass spectrometry (LC-MS) has been widely applied to identify and separate flavonoids in Ginkgo biloba. Over 70 flavonoids have been detected in this plant, including kaempferol, quercetin, isorhamnetin, myricetin, apigenin glycosides, and biflavonoids like ginkgetin.²⁵ Additionally, MALDI Mass Spectrometric Imaging is a technique that enables the visualisation of flavonoid distribution within plant tissues. One study utilised MALDI mass spectrometric imaging to map the localisation of flavonoid glycosides and biflavonoids in Ginkgo biloba leaves.²⁶

Terpenoids

Ten diterpenoid lactones, known as Ginkgolides A, B, C, J, K, L, M, N, P, and Q, have been documented in Ginkgo biloba. Before 2020, bilobalide was regarded as the only sesquiterpene lactone present. However, in 2020, Dong et al. identified a new bilobalide isomer, which broadened the understanding of Ginkgo biloba's sesquiterpene lactone composition.²⁷ In addition to terpenoids, G. biloba also contains non-terpenoid compounds, including three nor-sesquiterpenoids discovered by Shu et al. in G. biloba L. According to Chen, Ginkgo terpene tri lactones, such as ginkgolides A, B, C, and bilobalide, exhibit medicinal properties. These compounds protect cerebral hippocampus neurons from epilepsy, enhance memory and learning capabilities, and reduce neuronal damage. Moreover, ginkgolides A, B, and K have been shown to significantly reduce anxiety-like behaviour in mice. Ginkgolide B stands out as the most selective and competitive platelet-activating factor receptor antagonist, possessing antioxidant, anti-inflammatory, and anti-apoptotic properties. Nevertheless, some minor adverse effects associated with ginkgolide B, such as headache, drowsiness, hiccups, and general weakness, have been reported. Ginkgolide C demonstrates the potential to decrease fat accumulation and significantly inhibit human carboxylesterase 2 (hCE2). Bilobalide, a sesquiterpene lactone characterised by three γ-lactone rings and a tert-butyl group, was for a long time considered the only sesquiterpene lactone in Ginkgo. Its structure bears a close resemblance to ginkgolides, sharing similarities in NMR and mass spectra. This isomer, like bilobalide, features two lactone ring groups. The presence of tert-butyl groups in both bilobalide and ginkgolides is particularly noteworthy, as these structures had not been previously observed in other natural products. These terpene lactones have undergone comprehensive structural elucidation through various spectroscopic techniques.²⁸

Alkylphenols And Alkylphenolic Acids

Alkylphenols and alkyl phenolic acids are important bioactive compounds detected in different parts of Ginkgo biloba, such as leaves, seeds, sarcotesta, and fruits. These compounds are chemically identified as 2-hydroxy-6-alkylbenzoic acids and are grouped into five main categories: cardanols, α-hydroxycardanols, cardols, urushiols, isourushiols, and alkylphenolic acids, with ginkgolic acids being the most recognised among the alkylphenolic acids.²⁹ Ginkgolic acids are toxic constituents of ginkgo; however, there have been indications of additional pharmacological activities associated with these compounds. ³⁰ By altering molecular targets in tumour cells, ginkgolide C17:1 exhibits various anticancer effects, including the inhibition of the STAT3 signalling pathway against multiple myeloma cells.³¹ Moreover, new derivatives of ginkgolic acid continue to be isolated, and ongoing research is investigating their promising pharmacological properties, including antiviral activities against various viruses by inhibiting viral fusion processes. ³²

Carboxylic Acids

Carboxylic acids are a notable category of bioactive compounds in Ginkgo biloba, making up about 13% of its preparations. These acids identified in G. biloba 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. Besides existing in free form in GBL, phenolic acids can also form glycosidic or covalent bonds. Functionally, organic acids in Ginkgo biloba display significant free radical scavenging activity, adding to the plant's antioxidant characteristics. Specific acids, such as protocatechuic acid, have been shown to cause hepatocellular carcinoma cell death via kinase-dependent pathways and boost macrophage antioxidant potential, while gallic acid has been reported to have antitumor activity. Other acids like ferulic, p-coumaric, and caffeic acids also contribute diverse antioxidant, anti-inflammatory, and protective effects to different organs and tissues. Ascorbic acid, recognised for its antioxidant function, further enhances immune cell activation. This wide array of carboxylic acids substantially supports the therapeutic and health-promoting qualities associated with Ginkgo biloba preparations. ³³ Protocatechuic acid possesses certain pharmacological properties, including the ability to enhance the endogenous antioxidant capacity of macrophages and induce JNK-dependent hepatocellular carcinoma cell death. Gallic acid also exhibits anti-tumour properties.³⁴

Lignans

Lignans in Ginkgo biloba represents a notable group of non-flavonoid polyphenols that demonstrate phytoestrogenic activity through binding to estrogen receptors, alongside significant pharmacological properties, including antioxidant and anti-tumour effects. These compounds were initially identified in Ginkgo biloba roots around 2015 and later found in the seeds by 2018. The most abundant source of lignans within the plant is the shells around the seeds, where their concentration can reach up to 40%. Several lignans have been isolated from various parts of Ginkgo biloba, including a newly discovered lignan named ginkgol found in the roots, along with established lignans such as isolariciresinol and cycloolivil. Lignans present in the seeds often occur in glycosylated forms, such as diglucosides, with quantified amounts ranging from 0.012 to 0.020 mg/mL for diglucosides, and total lignan glycosides reaching 1.05 to 1.87 mg/mL.^10,35

Proanthocyanidins

Proanthocyanidins (PACs), also known as condensed tannins, are polyphenolic compounds present in Ginkgo biloba leaves. Although Ginkgo is mainly recognised for its flavonoids and terpenoids, PACs significantly contribute to its antioxidant properties.³⁶ PACs from Ginkgo biloba exhibit strong antioxidant activities, primarily through radical scavenging. In one study, the dimeric prodelphinidin epigallocatechin-(4β→8)-epigallocatechin showed an IC?? of 1.7 μg/ml in DPPH radical scavenging, surpassing butylated hydroxytoluene (BHT) as a positive control. Likewise, a purified proanthocyanidin polymer accounted for 37.7% of the total antioxidant activity in a Ginkgo leaf extract.³⁷ PACs in Ginkgo biloba have demonstrated the ability to inhibit β-amyloid peptide aggregation and destabilise preformed fibrils, which are implicated in neurodegenerative diseases like Alzheimer's. Catechins and procyanidins, including (+)-catechin, (-)-epicatechin, (-)-gallocatechin, (-)-epigallocatechin, and procyanidins B1 and B3, were identified as active constituents in this context.³⁸

Polyprenols

Polyprenols sourced from Ginkgo biloba leaves (GBP) are long-chain polyisoprenoid alcohols typically composed of 15 to 21 unsaturated isoprene units, structurally classified as betulaprenols featuring an E, E-farnesyl residue at the ω-end and a terminal isoprene unit carrying a primary hydroxyl group. These compounds predominantly exist as acetic esters, known as prenylacetic esters, which are free from adverse effects and have attracted interest due to their broad range of bioactivities. GBP exhibits diverse medicinal functions, including antiviral, antitumor, hepatoprotective, anti-Alzheimer, and synergistic antibacterial effects.³⁹ They consist of 14–24 isopentenyl units, containing homologs of long-chain lipids, and possess structures that are highly comparable to those of S-polyterpene alcohol (Dolichols) found in mammals and humans. Polyprenols have demonstrated antibacterial properties and protected Aβ25-35.⁴⁰

Pharmacological Activities of Ginkgo Biloba

Alzheimer’s And Dementia

Alzheimer's disease (AD) is characterised by the accumulation of amyloid-beta (Aβ) plaques and neurofibrillary tangles, composed of hyperphosphorylated tau protein, in the brain. These pathological hallmarks lead to synaptic loss and neuronal atrophy, particularly in the hippocampus and cerebral cortex. The amyloid hypothesis posits that abnormal processing of amyloid precursor protein (APP) by β-secretases and γ-secretases results in the production of Aβ peptides, which aggregate into plaques. Furthermore, microglial activation in response to Aβ deposition contributes to neuroinflammation and the progression of the disease. ⁴¹ Dementia is an overarching term for a decline in cognitive function that exceeds expectations for normal ageing. AD constitutes 60–70% of dementia cases. Other prevalent types include vascular dementia, resulting from cerebrovascular events like strokes; Lewy body dementia, characterised by abnormal protein deposits in neurons; and frontotemporal dementia, involving progressive damage to the frontal and temporal lobes.⁴² Ginkgo biloba, especially its standardised extract EGb 761®, has been widely investigated for its potential benefits in managing Alzheimer's disease (AD) and other forms of dementia. Although results vary, systematic reviews and clinical trials offer insights into its efficacy. EGb 761® affects neurotransmitter systems, including acetylcholine and glutamate, which are involved in cognitive processes.⁴³ Ginkgo biloba extract (GBE) has shown consistent neuroprotective and anti-Alzheimer effects in animal studies and may improve symptoms in early-stage AD patients, particularly with higher doses and longer treatment durations.⁴⁴ Clinical trials indicate small but significant cognitive improvements with GBE treatment, ranging from 120 to 240 mg daily over 3 to 6 months.⁴⁵

Treatment of Respiratory Diseases

Inflammatory processes are believed to influence the development, progression, and outcomes of various diseases, including acute respiratory distress syndrome (ARDS), asthma, and chronic obstructive pulmonary disease (COPD), all of which are associated with airway inflammation. Neutrophils and other inflammatory cells exacerbate airway inflammation. Neutrophils are crucial in the two fundamental metabolic processes of chemotaxis and respiratory burst during inflammatory conditions.⁴⁶ According to Wu et al., ginkgolide M (GM) and ginkgolide B (GB) both decreased the accumulation of inflammatory cells, including lymphocytes, neutrophils, and macrophages, and ameliorated cytological lung damage.⁴⁷ Ginkgo biloba extract (GBE), especially EGb 761, has exhibited anti-inflammatory and antioxidant effects in respiratory ailments. For instance, in lipopolysaccharide (LPS)-induced acute lung injury models, GBE inhibited the activation of NF-κB and COX-2 pathways, decreased oxidative stress markers, and improved lung histopathology.⁴⁸ In allergic asthma models, Ginkgo biloba biflavones, such as ginkgetin, diminished the activation of the Akt and p38 pathways in lung cells, reduced the expression of MUC5AC, and lessened inflammatory cytokines like IL-8, implying a role in modulating airway inflammation.⁴⁶ Studies suggest that Ginkgo biloba seeds can alleviate oxidative stress and inflammation in COPD models. By enhancing the Nrf2/HO-1 pathway and decreasing inflammatory cytokines, Ginkgo biloba may provide therapeutic advantages in COPD management.⁴⁹ During the COVID-19 pandemic, EGb was explored for its potential to lessen pulmonary inflammation. It was observed to reduce neutrophil elastase activity, proinflammatory cytokine release, platelet aggregation, and thrombosis, indicating its potential as an adjunctive therapy in managing COVID-19-related respiratory complications. ⁵⁰

Antidiabetic Activity

Diabetes mellitus, a widespread endocrine metabolic disorder, has been linked to significant morbidity and mortality due to complications in the micro- and macrovascular systems (heart attack, stroke, and peripheral vascular disease). Antioxidative systems in human bodies, both enzymatic and non-enzymatic, mitigate the production of reactive oxygen species, which are associated with several degenerative disorders, including diabetes. This disease is rapidly spreading worldwide and is found ubiquitously. Individuals with diabetes typically have high blood glucose levels because of insulin insufficiency. ⁵¹ A systematic review and meta-analysis of randomised controlled trials (RCTs) evaluated the effects of Ginkgo biloba extract (GBE) on blood metabolism in type 2 diabetes mellitus (T2DM) patients. The analysis, including 13 studies with 1,573 participants, found that GBE supplementation did not significantly alter haemoglobin A1c (HbA1c) or fasting serum glucose levels compared to placebo. However, GBE was associated with significant improvements in plasma viscosity, hematocrit, and ankle-brachial index, suggesting potential benefits in microvascular health and blood flow. ⁵² In a double-blind, placebo-controlled trial, GBE extract was administered as an adjunct to metformin in T2DM patients. The study observed improvements in fasting serum glucose, serum insulin levels, and HbA1c in the GBE group compared to placebo. Additionally, reductions in body mass index (BMI), waist circumference, and visceral adiposity index (VAI) were noted, indicating enhanced insulin sensitivity and metabolic health.⁵³ Animal studies have provided further insights into GBE's antidiabetic potential. In streptozotocin-induced diabetic rats, GBE administration led to significant reductions in blood glucose levels, improvements in lipid profiles, and enhanced antioxidant enzyme activities in hepatic and pancreatic tissues. These findings support the use of GBE as a supplementary treatment to manage hyperglycemia and associated metabolic disturbances. ⁵⁴

Antitumour Activity

Tumour/Cancer is a condition in which certain types of cells in the body begin to multiply uncontrollably and eventually spread to other areas of the body. Tumors can be classified as Benign Tumors, which are non-cancerous growths that do not spread to other parts of the body; Malignant Tumors, which are cancerous growths that can invade nearby tissues and spread to other parts of the body (metastasize); and Premalignant Tumors, which are abnormal growths that have the potential to become cancerous.⁵⁵ The National Institutes of Health report that EGb761 has been widely used as a complementary and alternative medicine for treating various cancers, including lung cancer, gastric cancer, adrenocortical carcinoma, breast cancer, colon cancer progression, and hepatocellular carcinoma. The primary bioactive compounds in Ginkgo biloba include flavonoids (e.g., quercetin, kaempferol, isorhamnetin) and terpenoids (e.g., ginkgolides, bilobalide). These constituents exhibit antitumor effects through several mechanisms, including Apoptosis Induction, where Ginkgo extracts can activate caspase pathways, leading to programmed cell death in cancer cells; Cell Cycle Arrest, where they modulate cyclin-dependent kinases, causing cell cycle arrest at various phases, particularly G2/M; Autophagy Modulation, where Ginkgo compounds influence autophagic processes, impacting cancer cell survival; Inhibition of Invasion and Metastasis, where they regulate epithelial-mesenchymal transition markers and matrix metalloproteinases, hindering cancer cell migration and invasion; and Angiogenesis Suppression, where they reduce vascular endothelial growth factor (VEGF) expression, limiting tumor blood supply.⁵⁶ In vivo studies have demonstrated that Ginkgo biloba extracts inhibit tumour growth and metastasis in models of melanoma, gastric, and liver cancers.⁵⁷

Antioxidant Activity

As tissues mature, they undergo oxidative stress that damages their DNA, proteins, lipids, and other molecules. This can impact the circulatory system, sensory tissues, and neurological function, with these defects significantly influencing the progression of degenerative diseases.⁵⁸ Research suggests that Ginkgo biloba extracts (GBE), especially EGb 761, exhibit substantial free radical scavenging activity, as evidenced by assays such as DPPH and ABTS. For instance, ethanol and methanol extracts of Ginkgo biloba has demonstrated high inhibition percentages in these tests, highlighting their potent antioxidant capacity. Additionally, GBE has been observed to regulate the expression of antioxidant enzymes, enhance mitochondrial function, and reduce lipid peroxidation, thereby protecting cellular components from oxidative damage associated with ageing and neurodegenerative diseases.⁵⁹ In vivo studies further corroborate these findings, with Ginkgo biloba demonstrating protective effects against oxidative damage in various organs, including the brain, liver, and cardiovascular system. These protective actions are believed to contribute to the therapeutic efficacy of Ginkgo biloba in managing conditions related to oxidative stress, such as neurodegenerative diseases, cardiovascular disorders, and metabolic syndromes. In a study involving rats treated with Ginkgo biloba phytosomes (50 and 100 mg/kg for 7 and 14 days), followed by induction of chemical hypoxia, there was a significant increase in the activities of antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase in various brain regions. This suggests that Ginkgo biloba phytosomes can enhance the brain's antioxidant defences under oxidative stress conditions.⁶⁰

Antilipidemic Activity

Elevated triglyceride (TG) levels, diminished high-density lipoprotein cholesterol (HDL-C) levels, and increased low-density lipoprotein cholesterol (LDL-C) levels are indicative of dyslipidemia. Hyperlipidemia has also been associated with insulin resistance and obesity. The plant's flavonoid content, estimated at 24%, is believed to be responsible for its hypolipidemic activity.  A study examined the lipid-regulating effects of GBE in rats on a high-fat diet.⁶¹ Oral administration of GBE at 40 mg/kg/day led to reduced total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels, increased high-density lipoprotein cholesterol (HDL-C) levels, enhanced activities of lipoprotein lipase and hepatic lipase, and elevated faecal bile acid excretion.⁶² In hyperlipidemic rats, a combination of GBE and atorvastatin resulted in superior improvements in lipid profiles compared to atorvastatin alone. This combination reduced liver fat content and adipocyte size, provided additional liver protection against potential statin-induced liver injury, and modulated liver lipid metabolism, enhancing the therapeutic effects of statins, as indicated by lipidomic analysis.⁶³

Antibacterial Activity

Ginkgo biloba, a plant celebrated for its therapeutic attributes, has shown notable antibacterial activity in multiple investigations. Studies suggest that different extracts of Ginkgo biloba, including methanol, ethanol, chloroform, and hexane, display varying levels of antibacterial effects against a spectrum of bacterial pathogens. For example, methanol extracts have demonstrated the highest antibacterial activity, with minimum inhibitory concentrations (MICs) as low as 7.8 µg/ml against several bacterial strains, such as Escherichia coli, Bacillus subtilis, and Xanthomonas phaseoli.⁶⁴ Specific compounds isolated from Ginkgo biloba, like ginkgolic acids, have also been recognised for their significant antibacterial properties. Ginkgolic acid (15:1), for example, has exhibited strong bactericidal activity against Staphylococcus aureus, including methicillin-resistant strains (MRSA), by disrupting biofilm formation and modulating iron homeostasis, which is essential for bacterial survival.⁶⁵

Antiplatelet Activity

A phospholipid-derived messenger known as platelet-activating factor (PAF) contributes to the immune response against infection, as well as neuronal damage resulting from ischemia and excitotoxic stress. During inflammatory damage, PAF is produced and can function as a paracrine, endocrine, or autocrine messenger by activating the PAF receptor (PAFR), which subsequently triggers inflammatory proteins.⁶⁶ GBE has demonstrated the ability to inhibit platelet aggregation induced by various agonists, including adenosine diphosphate (ADP) and collagen, in platelet-rich plasma (PRP), gel-filtered platelets (GFP), and whole blood. This inhibition is dose-dependent and involves the modulation of intracellular signalling pathways.⁶⁷ GBE inhibits the phosphorylation of Akt, a downstream molecule of the phosphoinositide 3-kinase (PI3K) pathway, which is implicated in platelet activation. This suggests that GBE's antiplatelet effects may be mediated through the PI3K/Akt signalling pathway.⁶⁸ Investigations have indicated that GBE can enhance the antiplatelet effects of medications such as cilostazol and aspirin, without significantly extending bleeding time. This suggests that GBE might amplify the effects of traditional antiplatelet therapies, potentially enhancing therapeutic results.⁶⁹

Glaucoma Treatment

Glaucoma encompasses a collection of eye diseases distinguished by progressive optic nerve damage, frequently linked to elevated intraocular pressure (IOP). It stands as a primary cause of irreversible blindness globally. The condition typically advances without noticeable symptoms, affecting the visual field until it reaches an advanced stage.⁷⁰ Glaucoma involves intricate mechanisms, including elevated IOP, ageing, genetic factors, and impaired regulation of ocular blood flow. These elements contribute to optic nerve damage, compromised circulation, and structural changes in glial and connective tissues. Contributing factors include extracellular matrix remodelling, excitotoxicity, nitric oxide, oxidative stress, and neuroinflammation.⁷¹ Research has indicated that GBE (EGb 761) shields retinal ganglion cells (RGCs) from damage induced by oxidative stress. Treatment with EGb 761 at concentrations of 1 or 5 μg/ml notably increased RGC survival compared to control groups. In a rat model of hypoxic optic nerve injury, EGb 761 administered intraperitoneally at doses of 100 and 250 mg/kg led to higher RGC densities compared to controls treated with a vehicle, which implies neuroprotective effects against hypoxic damage. ⁷²

Adverse Effects of Ginkgo Biloba L.

High doses of Ginkgo biloba, particularly from raw or roasted seeds containing ginkgotoxin, have been associated with seizures. A fatal case was reported involving a 55-year-old male who experienced a breakthrough seizure after beginning herbal supplements, including Ginkgo biloba. The autopsy revealed subtherapeutic levels of anticonvulsants, suggesting a potential interaction with Ginkgo biloba. Clinical trials and anecdotal reports indicate that some users report an exacerbation of tinnitus symptoms (persistent ringing in the ears) when using Ginkgo biloba.⁷³ The primary toxins are the neurotoxic chemical MPN, also known as ginkgo toxin, and its derivative MPN glucoside. MPN levels in Ginkgo biloba seeds range between 170 and 404 ppm. MPN is structurally similar to vitamin B6 and inhibits its synthesis, metabolism, and activities. MPN inhibits pyridoxal kinase's enzymatic activation of vitamin B6, resulting in vitamin B6 deficiency and decreased c-aminobutyric acid (GABA) synthesis.⁷⁴ G. biloba seed poisoning is characterised by tonic and clonic convulsions, vomiting, and loss of consciousness.⁷⁵ A 23-month-old child in Switzerland experienced two afebrile tonic-clonic seizures after ingesting an unknown amount of G. biloba seeds, and the toxicity was confirmed by measuring MPN levels in both blood and urine.⁷⁶ A 51-year-old Korean woman who consumed 1 kg of Ginkgo biloba nuts in 1 hour experienced tonic-clonic seizures 12 hours later, along with postictal confusion and a serum vitamin B6 level of 2.2 g/L.⁷⁷ MPN found in G. biloba leaf extract is below the detection limit (9 ppm). A 35-year-old woman experienced irregular nocturnal palpitations that were linked to Ginkgo Biloba’s proarrhythmic activities, and a 66-year-old woman developed allergic contact dermatitis after encountering Ginkgo tree fruit among Ginkgo leaves. ⁷⁸

CONCLUSION

Ginkgo biloba stands out as a remarkable "living fossil" with a deep evolutionary lineage, unique botanical features, and exceptional resilience, making it valuable both ecologically and medicinally. Its diverse chemical composition, including flavonoids, terpenoids, and other bioactive compounds, underpins a wide range of pharmacological effects such as neuroprotection, antioxidant, anti-inflammatory, and antitumor activities. Standardised extracts like EGb 761 have demonstrated therapeutic promise in managing various conditions, including neurological disorders, cardiovascular diseases, and metabolic ailments. However, despite its benefits, careful use is necessary due to potential toxicities and interactions. Continued research into its genetics, ecological adaptability, and bioactive compounds is essential to optimise its medicinal applications and ensure its conservation for future generations.

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