Ginkgo biloba

Overview

• Ginkgo biloba is a living fossil tree whose leaves have been used for centuries in traditional Asian medicine.
• Modern supplements are standardized extracts of the leaf, primarily studied for their ability to modulate blood flow and oxidative stress, which underpins many of its reported health effects.

Benefits

• Extensive randomized‑controlled trials (RCTs) and meta‑analyses show that standardized Ginkgo extracts (24‑% flavonoid glycosides, 6‑% terpene lactones) modestly improve cognitive function in healthy adults and those with mild cognitive impairment, particularly in memory and processing speed.
• There is consistent evidence for vascular health, including reduced peripheral arterial symptoms and improved microcirculation in the retina and extremities.
• Ginkgo may modestly reduce symptoms of anxiety and tinnitus in some individuals, though effects are modest.
• In patients with vascular dementia or post‑stroke cognitive decline, Ginkgo has shown small but statistically significant benefits in global cognition scores.
• Evidence for metabolic effects (e.g., glucose regulation) is limited and inconsistent; current data do not support a strong therapeutic claim.

How It Works

• Ginkgo’s bioactivity derives mainly from flavonoid glycosides (quercetin, kaempferol) and terpene lactones (ginkgolides A–C, bilobalide).
• These compounds scavenge reactive oxygen species and up‑regulate endogenous antioxidant enzymes (e.g., superoxide dismutase) via activation of the Nrf2 pathway.
• Ginkgolides act as platelet‑activating factor (PAF) antagonists, reducing platelet aggregation and improving microvascular flow.
• Bilobalide enhances mitochondrial respiration, increasing ATP production and protecting neuronal cells from excitotoxicity.
• Together, these actions improve cerebral and peripheral perfusion, reduce inflammation (via NF‑κB inhibition), and support synaptic plasticity through modulation of the dopaminergic and cholinergic systems, thereby underpinning cognitive and vascular benefits.

Dosage

• The most widely studied formulation is EGb 761®, a 24 % flavonoid/6 % terpene lactone extract.
• Typical daily doses range 120–240 mg, taken in two divided doses (e.g., 120 mg in the morning and 120 mg in the afternoon).
• For acute cognitive tasks, a single 120 mg dose 1–2 h before the activity is commonly used.
• In studies of vascular or cognitive outcomes, 240 mg/day for 8–12 weeks is standard.
• In older adults with mild cognitive impairment, 240 mg/day is recommended, whereas lower doses (80–120 mg) may be sufficient for occasional “brain‑boost” use.
• Take with food to reduce gastrointestinal upset; avoid exceeding 300 mg/day unless supervised, as higher doses increase bleeding risk.

Safety & Side Effects

• Ginkgo is generally well‑tolerated.
• Common mild side effects include gastrointestinal upset, headache, and mild dizziness.
• Because ginkgolides inhibit platelet‑activating factor, bleeding risk is elevated, especially when combined with anticoagulants (warfarin, clopidogrel), antiplatelet agents (aspirin, NSAIDs), or thrombolytics.
• Contraindicated in pregnancy, lactation, and in patients with bleeding disorders.
• Caution is warranted in patients undergoing surgery ( discontinue ≥ 7 days pre‑op) and in individuals with seizure disorders because high‑dose extracts have occasionally been linked to seizures.
• Individuals with hypersensitivity to plant extracts should avoid use.
• Routine monitoring of coagulation parameters is advised for patients on anticoagulant therapy.

Chemistry

• Ginkgo leaf extract contains a complex mixture of flavonoid glycosides (e.g., quercetin‑3‑O‑glucoside, kaempferol‑3‑O‑rhamnoside) and terpene lactones (ginkgolides A‑C, bilobalide).
• The primary terpene lactone, ginkgolide B, has the molecular formula C₂₁H₂₄O₅, IUPAC name 5,7-dimethyl-3‑[2‑(4‑hydroxy‑3‑methoxy‑phenyl)‑2‑propyl]‑1‑[2‑(2‑hydroxy‑4‑methoxy‑phenyl)‑propyl]‑2‑hydroxy-7‑methoxy‑2‑[2‑(hydroxymethyl)‑4‑methoxy‑phenyl]‑2‑hydroxy‑1‑[2‑(hydroxy‑phenyl)‑2‑hydroxy‑3‑methoxy‑phenyl]‑1‑hydroxy‑1‑[2‑hydroxy‑4‑methoxy‑phenyl]‑2‑hydroxy‑1‑hydroxy‑2‑hydro‑* (simplified).
• Ginkgolides possess a unique cage‑like diterpene skeleton with multiple lactone rings, conferring high affinity for the platelet‑activating factor receptor.
• The flavonoids are polyphenolic, contributing antioxidant capacity.
• The standardized extract typically contains 24 % flavonoid glycosides (as quercetin equivalents) and 6 % terpene lactones (ginkgolides A, B, C, and bilobalide).

Sources & Quality

• Commercial Ginkgo biloba is sourced from mature leaves of the Ginkgo tree (Ginkgo biloba L.), cultivated primarily in China, Japan, and South Korea where the tree is cultivated under controlled agronomic conditions to ensure consistent phytochemical profiles.
• Leaves are harvested in late summer when flavonoid and terpene concentrations peak, then air‑dried and milled.
• Extraction typically uses 70 % ethanol or water‑ethanol mixtures under controlled temperature to preserve thermolabile ginkgolides.
• The extract is standardized to 24 % flavonoids and 6 % terpene lactones (e.g., EGb 761®).
• High‑quality supplements undergo HPLC fingerprinting to confirm the presence and ratio of key constituents, and heavy‑metal, pesticide, and microbial testing for safety.
• Look for products with third‑party certification (USP, NSF, or GMP) to ensure purity and consistent potency.