Ginkgo Leaf

Ginkgo leaf, also known as Bai Guo Ye, is a plant with high medicinal value. The ginkgo tree is an ancient species, considered a miraculous medicinal tree. It has existed for over 250 million years, thriving during the Jurassic period when dinosaurs dominated the Earth. Despite numerous changes in Earth's life forms over billions of years, particularly after the glaciation in the fourth century, the ginkgo remains in its most primitive form and is known as a "living fossil" in the history of biological evolution. The leaves, fruits, and seeds of the ginkgo have significant medicinal value, and its pharmacological effects are continually being studied, with clinical applications expanding.

Functions and Indications: Ginkgo leaves are used to:

• Astringe the lungs, relieve asthma, activate blood circulation, and alleviate pain.
• Treat lung deficiency coughs and asthma, coronary heart disease, angina pectoris, high blood lipids, and anticoagulation. There is some evidence that ginkgo leaves may improve memory.
• Although ginkgo leaves promote blood circulation and prevent cardiovascular diseases, they should not be used concurrently with other cardiovascular medications (e.g., aspirin). Ginkgo extract, in its concentrated granulated form, has strong free radical scavenging and antioxidant effects. The flavonoids, amino acids, and collagen-synthesizing components in ginkgo leaves significantly contribute to beauty, inhibit melanin growth, and maintain skin's luster and elasticity.

Plant Morphology: The ginkgo tree is a deciduous tree that can grow up to 40 meters tall. It has both long and short branches. The bark is light gray-brown when young, turning gray-brown with deep longitudinal cracks as it ages. Leaves are arranged in a spiral on long branches and clustered 3-5 (up to 8) on short branches; petioles are 3-10 cm long. The leaf blades are fan-shaped, pale green, hairless, with many bifurcated parallel veins, and measure 5-8 cm wide, with shallow undulations and sometimes shallow or deep central clefts. Ginkgo trees are dioecious with unisexual flowers; male flowers are arranged in catkin-like inflorescences and hang down, while female flowers have long peduncles that are often bifurcated with each bifurcation bearing a disc-like ovary, each containing a single ovule that develops into a seed. The seeds are fruit-like, oval to nearly spherical, 2.5-3.5 cm long, and about 2 cm in diameter; the outer seed coat is fleshy with a white powder, turning light yellow or orange when ripe; the middle seed coat is bony and white with 2-3 ridges; the inner seed coat is membranous with abundant endosperm. Flowering occurs from March to April, and seed maturity is from September to October.

Pharmacological Actions:

1. Effect on Platelet Aggregation and Hemostasis: Ginkgo extract BN52021 prevents platelet aggregation caused by PAF in rabbits, mice, and pigs, but does not interfere with aggregation induced by adrenaline.
2. Effect on Cardiac Function and Myocardial Infarction:BN52021 prevents myocardial degeneration caused by butylphthalide in rats, inhibits hypoxia-induced coronary artery constriction in humans and pigs, and alleviates PAF-induced cardiac arrhythmias in dogs. It significantly inhibits ventricular fibrosis and reduces the extent of myocardial infarction.
3. Effect on Blood Vessels:Flavonoids extracted from ginkgo leaves dilate blood vessels in guinea pigs and have a stronger effect on the heart. Quercetin, kaempferol, and isorhamnetin are compounds that have vasodilatory and spasmolytic effects. They also increase coronary blood flow.
4. Neuroprotective Effects: French researchers have reported that standardized ginkgo extract restores brain alertness in rats poisoned with triethyl tin. It also promotes recovery from traumatic brain injury in adult male rats. Ginkgo extract protects the brain and the blood-brain barrier and has some effect on brain metabolism and neurotransmitters.
5. Effects on Ear and Eye: BN52021 prevents changes in inner ear potentials caused by PAF, inhibits cochlear changes induced by furosemide, and reduces increased intraocular pressure in rabbits. It also decreases PGE2 and protein content in aqueous humor caused by iris laser irradiation. BN52021 has potential therapeutic effects on immune-related corneal inflammation and edema.
6. Anti-inflammatory Effects: BN52021 ointment can counteract irritation dermatitis induced by 1,8,9-thiocyanate, significantly suppressing capillary resistance reduction, skin temperature increase, and skin fold thickening. It also improves acute pancreatitis induced by cerulein in rats and alleviates inflammation.
7. Anti-allergic Effects: BN52021 inhibits bronchoconstriction and reactivity induced by PAF and ovalbumin, preventing antigen-induced bronchoconstriction but is ineffective against bronchial hyperreactivity caused by propanol or ibuprofen. It provides partial protection against normal bronchoconstriction.
8. Anti-shock Effects: Ginkgo leaf extract BN52021 effectively reverses various shock states and improves survival rates.
9. Anti-tumor Effects: Ginkgo lactone A, B, C, or just ginkgo lactone B can be used in the treatment of metastatic cancer. It enhances the effectiveness of anticancer chemotherapy agents, reduces side effects, and makes cancer cells resistant to cytotoxic drugs more sensitive to chemotherapy. Ginkgo extract has inhibitory effects on S180 and P388 lymphocytic leukemia.
10. Effects on Reproductive System: BN52021 can prevent follicular rupture and increases in ovarian collagen dissolution and vascular permeability induced by human gonadotropins during ovulation.
11. Protection Against Organ Transplant Rejection: BN52021 at 10 mg/kg improves protection for the lungs, aiding long-term preservation and transplantation. Ginkgo lactone can be used in lung donors and recipients, making distant lung transplants feasible.
12. Effects on Digestive System: Ginkgo lactone improves gastrointestinal ulcers caused by PAF and endotoxins and significantly alleviates mucosal damage from localized intestinal ischemia. It shows potential efficacy in treating liver cirrhosis and acute pancreatitis.
13. Effects on Urinary System: BN52021 inhibits reductions in glomerular filtration rate and renal blood flow caused by PAF, endotoxins, and intramuscular glycerol. It also prevents CSA-induced renal toxicity and changes in glomerular hemodynamics.
14. Other Effects: Ginkgo lactone has been studied for its effects on cellular toxicity and other immune responses. It inhibits natural killer cell activity against F562 target cells and has potential effects on arthritis. Additionally, ginkgo lactone has sporicidal effects against Pneumocystis carinii.

Toxicology:

• Ginkgo leaf extract administered intravenously in rabbits for 10 days at doses of 0.5-1 ml/kg showed no changes in blood parameters, liver, kidney functions, or pathology. Higher doses in dogs caused excessive salivation, nausea, vomiting, diarrhea, and appetite loss. Histological examination revealed mucosal hypersecretion, increased intestinal peristalsis, and localized vascular hardening. Higher doses of flavonoids may impair blood coagulation.

Identification of Herbal Medicine:

1. Macroscopic Identification: The leaves are often wrinkled or fragmented, typically fan-shaped, 4-8 cm long, and 5-10 cm wide. The margins are irregularly waved, sometimes with central depressions. The base is wedge-shaped with numerous parallel bifurcated veins. Petioles are 2-7 cm long, paper-like, and easily torn longitudinally. The aroma is faint, and the taste is slightly astringent. Preferred specimens are yellow-green and intact.
2. Microscopic Identification: The upper epidermis has a single layer of cells covered with a cuticle. Mesophyll cells are not well-differentiated, often elongated or oval, containing brownish substances or oil droplets. The vascular bundles are of the collateral type with secretory ducts between them. The lower epidermis also has a cuticle and sunken stomata. Older leaves have a vascular bundle sheath composed of 1-2 layers of thick-walled cells. Calcium oxalate clusters are found within the cells, measuring 8-106 μm in diameter.
3. Physicochemical Identification: 
   (1) Boil 10 g of the crushed sample in 10 ml of water for 15 minutes, filter while hot. Add a small amount of magnesium powder and 3-4 drops of hydrochloric acid to 2 ml of the filtrate, heat in a water bath for a few minutes, and observe a reddish-brown color (test for flavonoids).
   (2) Spot 2 ml of the filtrate on filter paper, spray with 2% aluminum chloride ethanol solution, dry, and observe under ultraviolet light (365 nm) for a yellow-green fluorescence (test for flavonoids).

Clinical Applications: Ginkgo leaf is used in the treatment of coronary arteriosclerotic heart disease. Its extract, containing ginkgo leaf flavonoids, is the primary component in pharmaceutical preparations. It has shown good effects on angina pectoris and may lower cholesterol and blood pressure. The extract can be made into tablets or injectable solutions. For tablets, the dosage is 2 tablets (each containing 2 mg of extract) 3 times a day. For injection, the dosage is 2-5 mg/kg, administered intravenously.

Cautions:

• Ginkgo leaf extract is generally well-tolerated, but potential side effects include nausea, headache, dizziness, and allergic reactions. It should be used with caution in individuals with bleeding disorders or those on anticoagulant therapy. Always consult with a healthcare provider before use.