The Medicinal Value of Ginkgo Biloba Leaves
The ginkgo is a national botanical treasure of China, a rare relict species from the Mesozoic era. Wild ginkgo is found only on Tianmu Mountain in Zhejiang Province. But ginkgo is a highly pollution-resistant plant with an attractive appearance, especially in autumn when its leaves turn yellow and ginkgo-lined streets become a beautiful sight. So today many countries around the world have introduced ginkgo as an urban greening tree.
Both the ginkgo fruit (known in Chinese medicine as baiguo, Ginkgo Semen) and its leaves are used medicinally. I have already written about the effects of baiguo, so I will not repeat them here. This article focuses on the medicinal value of ginkgo leaves.
Ginkgo leaf preparations (GbE, aqueous or alcoholic extracts) can be given orally or intravenously. Whether orally or intravenously, they increase cerebral or regional cerebral blood flow in dogs, cats, rats, and humans, and reduce vascular resistance. Oral or intravenous GbE inhibits cerebral cortical vasospasm induced by autologous serum in rabbits, increases cerebral glucose transport and utilization in rats under hypoxia, and markedly improves cerebral circulation. It has a protective effect against cerebral ischemia, hypoxia, and edema; normalizes brain cell metabolism; increases cerebral blood flow; and reverses the tendency toward brain tissue damage. Ginkgo leaves protect the blood-brain barrier; the total flavonoids of ginkgo leaves stabilize biofilms, increasing the resistance of rat red blood cells by 54% and reducing blood-brain barrier permeability, thereby protecting the brain.
Ginkgo biloba extract also protects the central nervous system and can improve learning and memory. It also markedly improves tinnitus and deafness caused by ischemia or metabolic disorders, and improves vertigo and balance dysfunction. It has clear beneficial effects on aging, dementia, and cerebral dysfunction. Clinical trials have shown that ginkgo biloba extract significantly improves age-related cerebral dysfunction, cerebral insufficiency, insomnia, and memory impairment, and is relatively safe. Ginkgo biloba extract is effective for cerebrovascular accidents and various types of dementia.
In addition, ginkgo biloba extract can be used to treat depression. In Andrew Weil's bestselling book Spontaneous Healing, Andrew mentions a depressed patient who wrote him a letter of recommendation describing her and her mother's real experience of improvement in depression, pain, and tinnitus after persistently taking ginkgo biloba extract. Edmund Bourne's The Anxiety and Phobia Workbook (6th ed.) also mentions ginkgo leaves, noting that they can indirectly reduce anxiety by increasing blood flow, oxygen, and cerebral neurotrophic support.
Note: Many patients with the above conditions also take aspirin. Ginkgo leaves inhibit platelet function (what Chinese medicine calls activating blood and resolving stasis), so when used together with blood-activating and stasis-resolving drugs like aspirin, the dosage of both should be reduced accordingly to avoid coagulation side effects.
Ginkgo leaves also act on the cardiovascular system. Intravenous ginkgo biloba extract reduces myocardial oxygen consumption in anesthetized cats; in normal or hypertrophic hearts it protects ischemic myocardium and reduces arrhythmias. Ginkgo leaves inhibit angiotensin-converting enzyme (ACE), reduce capillary permeability, and have a good therapeutic effect on edema due to increased capillary permeability and on hypovolemic shock caused by monoclonal gammopathy. The flavonoids in ginkgo biloba extract dilate blood vessels in experimental animals and stimulate glucose transport and glycogen synthesis in aortic smooth muscle cells, increasing nutrients to the vessel walls.
Traditional Chinese medicine holds that ginkgo leaves activate blood and nourish the heart, and modern pharmacological experiments offer a reasonable explanation. Because ginkgo leaves improve cerebral function, they nourish the heart; because of their cardiovascular effects and antithrombotic action, they resolve stasis. Traditional Chinese medicine mostly uses ginkgo leaves to treat chest impediment (xiongbi) and wind-stroke, which in modern medicine correspond to hypertension, arteriosclerosis, aortitis, occlusive vasculitis, angina pectoris, myocardial infarction, and cerebral embolism. The main indication of current drugs such as ginkgo leaf dispersible tablets and Shuxuening (made from ginkgo leaves) is precisely these diseases. In addition, 707, made from ginkgo biloba extract, is also used to treat aplastic anemia.
Ginkgo leaves also scavenge free radicals, resist lipid peroxidation, and lower blood lipids. Intraperitoneal injection of total ginkgo flavonoids treats hypercholesterolemia and lowers serum triglycerides in rats, so ginkgo leaf dispersible tablets are also frequently used to treat hyperlipidemia.
Since the populations at highest risk for the above cardiovascular and cerebrovascular diseases and hyperlipidemia are the elderly, it is no surprise that ginkgo leaves are made into anti-aging health supplements.
Like the ginkgo fruit (baiguo), ginkgo leaves are also frequently used to treat asthma. Ginkgolide B (BN52021) in ginkgo leaves, given intravenously, inhibits ovalbumin-induced bronchoconstriction and thrombocytopenia and leukopenia in guinea pigs. Thus BN52021 and other PAF antagonists may become effective drugs for asthma prevention. Ginkgo biloba extract also directly relaxes tracheal smooth muscle and antagonizes contractions of isolated guinea pig organs caused by histamine phosphate and acetylcholine, arresting histamine-induced asthma in guinea pigs. These findings confirm the scientific basis of the classical materia medica records that ginkgo leaves and ginkgo fruit stop cough and calm wheezing.
Modern pharmacological research has also discovered antimicrobial effects of ginkgo leaves. A decoction of ginkgo leaves inhibits Staphylococcus aureus, Shigella, and Pseudomonas aeruginosa, and has a strong inhibitory effect on Epstein-Barr virus — even exceeding that of retinoic acid, a known potent anticarcinogenic initiator inhibitor. So ginkgo leaves are also used as a health supplement for preventing cancer and cancer recurrence.
Ginkgo leaves also have cosmetic uses. Folk medicine uses them to treat freckles (crushed and applied to the face), onychomycosis (decocted for washing), and corns (crushed and applied as a poultice). Pinhui Jingyao records ginkgo leaves for treating dysentery, and the Compendium of Chinese Herbal Medicine records them for pediatric enteritis.
Common Chinese patent medicines containing ginkgo leaves mainly include Shuxuening tablets, ginkgo leaf dispersible tablets, and ginkgo leaf flavonoid glycoside tablets; there is also ginkgo leaf injection.
Both ginkgo leaves and baiguo have some toxicity. In animal experiments, intravenous injection of ginkgo biloba extract at 10 or 40 times the human dose produced gastrointestinal symptoms such as salivation, nausea, vomiting, diarrhea, and anorexia. Therefore ginkgo leaves should not be used in excess; long-term users should keep doses low. Modern pharmaceutical companies generally remove the toxic components before making patent medicines, making them safer than using ginkgo leaves directly.