Ginkgo biloba is an ancient and primitive larvae relic species. It has been growing on earth about 200 million years, as a "living fossil". China is the hometown of ginkgo, the current Chinese ginkgo resources accounted for 70% of the world. Dating back to "Daily Materia Medica" published in 14th century, Ginkgo have already been used a Chinese herbal medicine folk use, first appeared in the fourteenth century among folks, mainly used for treating cough, asthma and inflammation.
Ginkgo biloba, also known as duck feet, maidenhair tree, tree duck, is deciduous trees as high as 40m. It has a erecting trunk and gray bark. It has both short and long branches with leaves clustering on short branches and alternating in long branches. It has fan blades with length 4~8cm, width 5~10cm. Its seed is named “Baiguo”.
Ginkgo is mainly distributed in latitude 19° 40~43° 40, longitude 97° 00~126°30, with a average annual temperature of 14 °C~18 °C. It grows well in a cool but warm winter and spring, and a humid and warm summer and fall. It is susceptible to frost damage in the cold of winter ( the following-20°C). It also grows poorly in tropic areas with long-term summer but no winter. Ginkgo biloba is widely distributed in China, located from the middle of China to the west. You can also find it in north place such as Liaoning, south place such as Guangdong, east place such as Taiwan, west place Qinghai are planted. It is mainly planted at Jiangsu, Shandong, Zhejiang, Hubei provinces. Now it has also been introduced into Japan and United States.
Figure 1. Leaves and seeds of Ginkgo biloba (ginkgo)
Ginkgo biloba extract is the dried leaf extract of Ginkgo ginkgo species Ginkgo (GinkgobilobaL) Its main component is flavonoids and terpene lactones and has a variety of health functions. It is widely used in food and cosmetics.
The above information is edited by the Chemicalbook of Dai Xiongfeng.
1. Pharmacokinetics of Flavonoids
Ginkgo flavonoid is absorbed mainly in the form of aglycone. However, there is hardly any detectable glycoside or aglycone form of Ginkgo flavonoids in the plasma, urine. It is mainly in the form of aglycone glucuronide or sulfate conjugates. It also has been reported that some level of flavonoids aglycone can be detected after hydrolysis of plasma and urine. Different conclusions may be caused by the sensitivity of analytical instruments and methods, but it anyway reveals the low bioavailability of ginkgo flavonoids.
Ginkgo flavonoid glycosides has two main parts of in vivo metabolism: One is the liver, A series of reactions occur after the effect of liver CYP450, generating more water-soluble metabolites which are further excreted; The second is the gut where it was hydrolyzed into aglycone by gut microbes. Be contrary to the Ginkgo terpene lactones’ effect on activating CYP3A enzyme, ginkgo flavonoids on exhibit a inhibitory effect on CYP3A enzyme activity, which should be taken seriously in the future course of the experiment and in clinical tests. Quercetin and kaempferol could cause the activity decrease of rat and human liver microsomes, CYP1A1, CYP1A2, and CYP3A4 etc.
2. Pharmacokinetics of terpene lactones
In the phase I metabolism of ginkgolides, the effects of different lactone on CYP450 enzymes are tissue specificity. The impact of different compounds is also different. Ginkgolide A can induce the expression of CYP3A23. However, ginkgolide A, B has no induction on transcription of CYP3A4. Bilobalide can induce the expression of CYP3A4 and CYP2B1. Ginkgolides’ effect on CYP450 enzyme system may be the foundation for pharmacological activity. Compared to the phase I metabolism, similar as flavonoids, in vitro studies have shown that the metabolism of ginkgolides are also mainly phase II metabolism. Bilobalide and ginkgolide A has on significant induction effect on rat phase II metabolic enzymes (UGT) GSH-S-transferase and lipoamide dehydrogenase. However, ginkgolide B, C have no significant effect on the same doses.
Ginkgo biloba extract, a commonly used drug for treatment of cardiovascular diseases, is often combined with drugs of anti-platelet, sedation, and blood pressure, lipid-lowering. Ginkgo and its monomer flavonoids component such as quercetin, kaempferol and isorhmnetin etc can inhibit CYP3A4, CYP2C9, CYP2B6. Moreover, its monomer components ginkgolides A, B and bilobalide can induce the expression of CYP1A2, CYP2B1/2, CYP3A2, CYP2C19, UGT1A1, etc. It is also the substrate of the P-glycoprotein. Therefore combination with other drugs can easily lead to drug-drug interactions, whose processes are complex. Therefore this issue needs to be taken seriously.
In recent years, there have been individual cases of bleeding caused by taking ginkgo biloba and other anticoagulant drugs in combination. Ginkgo biloba cause bleeding through inhibiting PAF. Ginkgolide B is considered as the most important component during this process. But there is still no corresponding control study. Currently the components and the amount of ginkgo biloba commercialized products vary greatly with each other. The dose of Ginkgolide B associated with the amount of bleeding is still unknown. Moreover, other components in the products may also cause bleeding. Therefore, research in this area remains to be deepened. Therefore, according to the current studies, we needs to report to physicians about the cases in which Ginkgo biloba cause bleeding to attract enough attention. Also try to avoid the preparation of Ginkgo biloba extract together with anticoagulants such as aspirin, warfarin.
The leaf Ginkgo biloba has a complex chemical composition. People has isolated out more than 140 kinds of compounds from it. Flavonoids and terpene lactones compound are the two main functional components. Ginkgo flavonoid is also known as single flavonoids, mainly as glycosidase form of kaempferol, quercetin and isorhamnetin. Ginkgolides belongs to a terpene, consists of the times of abundant terpene lactones and diterpene lactone, further mainly as ginkgo esters and ginkgolide. Besides, it also contains Polyprenols, organic acids, polysaccharides, amino acids, phenols and trace elements.
1. food and health food industry
Flavonoids in Ginkgo biloba has antioxidant activity, thus can be added as an antioxidant into fats and sweets. Total flavonoids are mostly yellow, and have a wide solubility spectrum including both water-solubility and lipid solubility, so it can play a role of coloring agent. People can process Ginkgo biloba into ultrafine powder and add into food. Grinding ginkgo leaf ultra-finely and adding to cakes, biscuits, noodles, candy, ice cream as 5% to 10% can make Ginkgo biloba health food.
Ginkgo biloba extract is taken as a food additive in Canada. It has been approved in Germany and France as non-prescription drugs, Ginkgo biloba has been loaded into United States Pharmacopeia (24th edition). Ginkgo biloba extract can be used as a dietary supplement in the United States. There are more than 30 international Ginkgo products including: Ginkgo leaves, Ginkgo Oral Liquid, ginkgolide injection, gingko injection, Ginkgo Biloba pills, granules Compound Ginkgo biloba, Ginkgo biloba extract, etc. From 2009 to 2011, sales of ginkgo biloba preparation and DDDs list stably rank the top three among commonly used Chinese medicine for treating cardiovascular disease.
Ginkgo biloba leaves contains a small amount of proanthocyanidins and urushiol acid, which have certain toxicity to humans. Processing Ginkgo leaves as raw material for foods needs undergo a special treatment to reduce proanthocyanidins and urushiol acid. However, the current dose range applied has no acute, chronic toxicity, and teratogenic effects. In 1992, the Ministry of Health has approved ginkgo biloba extract as a new food additive. In recent years, total flavonoids of Ginkgo biloba leaves have been widely used in the food industry. Research and development of related products has broad prospects.
2. Daily chemical industry
The combination between Ginkgo biloba extract and skin absorption enhancer can also prevent irritation of the adhesives when using topical ointments and sticking agents, including creams, ointments, and plasters, etc. The skin care products containing GBE in current market include anti-aging facial cleanser, bath foam, lipstick, eye cream and so on. GBE can also be used to produce hair growth, hair care products. Chen Yan, et al., even adds Ginkgo biloba extract into toothpaste, which has a certain anti-caries effects according to their research.
In the early 1960s, foreign countries have been using the extract of Ginkgo biloba for treatment of cerebral vascular diseases and neurological diseases. It has high efficacy and no significant side effects. Ginkgo extract has strong antioxidant effect, which can eliminate excess free radicals in the body, prevent lipid peroxidation. It can also expand coronary vessels, increase cerebral blood flow, enhance the antagonism effect of platelet activating factor for treating vascular aging, cerebrovascular insufficiency and other neurological diseases. In addition, it can also improve immunity and have anti-aging effects.
1. The effect on the cardiovascular system
Ginkgo biloba extract can inhibit the activity of angiotensin-converting enzyme (ACE) in serum of normal body, thereby inhibiting the shrinking of small arteries, expanding blood vessels, and increasing the blood flow. Ginkgolides is a PAF receptor antagonist with a high degree of specificity. Ginkgo biloba extract or ginkgolides can inhibit platelet activating factor (PAF) and cyclooxygenase or lipoxygenase. Ginkgo biloba extract is well tolerated and can antagonize the platelet aggregation caused by PAF. However, it has no effect on the aggregation induced by ADP.
2. The effect on the central nervous system
Ginkgo biloba extract affect the endocrine system and affect the interaction of between the immune system and the central nervous system by inhibiting PAF. It can promote the circulation and metabolism of the brain, improve the memory, alleviating the memory defect resulted from NaNO2. Its anti-hypoxia effects may be related to its effect on increasing cerebral blood flow and improve cerebral energy metabolism during hypoxia. Ginkgolide B can be used in the clinical treatment of stroke.
3. The effect on the digestive system
Ginkgo biloba extract can significantly alleviate the rat gastric and gut ulcer caused by the PAF and endotoxin, and can partially inhibit the damage effect of ethanol on stomach. It also has potential therapeutic effect on Cirrhosis. Ginkgolides B may also have effect on the treatment of acute pancreatitis.
4. Role of the respiratory system
Ethanol extract of Ginkgo biloba has a direct relaxant effect on trachea smooth muscle. Inhalation of aerosolized Ginkgo biloba extract not only inhibits bronchoconstriction, but also inhibiting the decrease of white blood cells and eosinophils cells caused by PAF. Ginkgo biloba extract has great significance in the suppression and treatment of bronchial hyperresponsiveness.
5. The anti-aging effects
The ginkgo double flavonoids, iso ginkgo double flavonoids, quercetin and Ginkgo prime in Ginkgo biloba leaves, all can inhibit lipid peroxidation. Quercetin has a especially strong inhibitory activity.
6. Role in transplant rejection and other immune reactions
Ginkgo biloba extract may prolong the survival time of transplanted skin, heterotopic cardiac xenotransplantation, orthotopic liver xenograft. Ginkgo biloba extract can inhibit the body's natural killer cell activity to KC526 target cells. It can also prevent the natural killer cell activity induced by interferon.
7. The anti-tumor effect
Ginkgo biloba green leaf extract which is fat-soluble portion can inhibit the EB virus. Both heptadecene salicylic acid and ginkgo flavin (Bilo-betin) have a strong inhibitory activity; Ginkgo Biloba can increase the thymus weight and SOD activity of tumor-bearing mice, stimulating the body's inherent anti-tumor ability. Quercetin and myricetin can inhibit the occurrence of carcinogens.
8. Antioxidant effect
Ginkgo biloba extract can directly scavenge lipid radicals, alkyl radicals and lipid peroxidation free radicals, stopping free radical reaction chain. It can also participate in regulating and increase the activity of antioxidant enzymes such as superoxide dismutase and glutathione peroxidase. The antioxidant effects of flavonoids in EB even exceed vitamins, and also have anti-free radical attack properties in vitro.
According to incomplete statistics, the current international standard of Ginkgo biloba extract is product EGb761 produced by the Schwabe patented technology of the German. The appearance is brown powder with a slight smell of ginkgo biloba. Ginkgo biloba extract of Ginkgo biloba is extracted with GinkgobilobaL leaves as raw material. Commercially extracts are usually marked as containing 24% flavonoid glycosides, ginkgolides 6%.
There are many reports and literatures on productive technology of Ginkgo biloba extract, mainly including in the acetone extraction & lead salt precipitation, ethanol extraction & macroporous resin adsorption separation, supercritical carbon dioxide extraction, alcohol extraction& Extraction & chromatography, etc., Domestic production mainly apply ethanol extraction-resin separation.
Organic solvent extraction is the mostly widely used approach. Owing to the significant toxicity and volatility of other organic solvents, people generally take ethanol as the extraction agent. Zhang Yonghong et al, showed that a good extraction condition of Ginkgo biloba extract is using 70% ethanol as extraction agent with extraction temperature 90 °C, solid-liquid ratio 1:20, 3 times extraction with a 1.5 h reflux for each time.
1. Ethanol Extraction & macroporous resin separation
Remove Mildew leaves and impurities, wash, chopped and extract with 70% ethanol reflux, fractionate the extract, filtrate, decompress to recycle the ethanol, remove the debris by high-speed centrifugation, add certain amount water for dilatation and add into macroporous resin column. Elute the mixture with water until the eluents become clear. Further elute by a certain concentration of ethanol and collect the eluents. Concentrate it under reduced pressure and vacuum dry it to obtain the final extract.
2. The acetone extract-lead hydroxide precipitation
Extract the Ginkgo biloba leaves with 60% acetone. Filter after cooling, extract with carbon tetrachloride, then add ethyl ketone and mix to separate out the acetone-butanone phases, add solid ammonium sulfate to the phase and stir for filtering off solid substance. Decompress and evaporate the filtrate to a concentration that containing 20%-60% solid. Use 50% denatured ethanol to dilute it to a concentration of 10% solid. Add lead hydroxide suspension and filter off the precipitate. The filtrate was decompressed and concentrated to half volume and then added ammonia sulfate and methyl ethyl ketone under stirring, The butanone-ethanol phase comes out after stirring; Separate out butanone-ethanol from the aqueous phase, and then add butanone into the aqueous phase, stir to separate butanone-ethanol phase for the 2nd time. Combine the two times butanone-ethanol phase above, add ammonium sulfate under stirring, mix and collect the aqueous phase separated out, Further dry the butanone-ethanol phase using sodium sulfate, evaporated to dryness under reduced pressure. Dissolve the denatured viscous residue liquid with denatured ethanol residue. Place them for 12 hour after which precipitate separated was collected, subject to evaporation reduced pressure and vacuum drying for obtaining the final product.
Toxicity and Side Effect
LD50 of Ginkgo biloba extract, (1202.5 ± 141.3) μg/g for intravenously administration, equivalent to crude drug (7.8 ± 0.9) g/Kg; (17.9 ± 1.0) g/kg for intragastric administration, equivalent to crude drug (116.4 ± 6.5) g/kg. Injection dogs with a dose 10 to 40 times of the clinical doses for one week causing nausea, vomiting, diarrhea, loss of appetite. Histological section found hyper-secretion of small intestine tissue, increased intestinal peristalsis of anesthetized dogs and rabbits, local vascular hardening under injection.
Ginkgo phenol and ginkgo toxicity have hemolysis effect. Ginkgo poison has a narcotic effect on the central nervous system of frog. Injection intravenously 0.2g/kg of Ginkgo to Rabbit briefly elevating the blood pressure first, then blood pressure drops, animals have difficulty in breathing and finally die under convulsions. The typical doses of flavonol have no effect on the blood coagulation system. However, it interferes with hematopexis at larger doses. LD50 of Ginkgo iso-Biflavones is 242mg/kg upon mouse tail intravenous injection. The acute poisoning symptoms include shortness of breath, motionless, finally died of respiratory paralysis.
White acid has hemolysis effect. To guinea pigs, Ginkgo flavonoids with 100 to 1000 times of the therapeutic dose cause moderate decrease on blood pressure, increase the breathing rate but reduce the heart rate.
Cardiovascular disease treatment
Ginkgo biloba extract is a commonly used traditional Chinese medicine for the treatment of cardiovascular and cerebrovascular diseases. Its main functional ingredient is ginkgo flavonoids and ginkgo diterpenoid lipid compounds, wherein the flavonoids including quercetin glycosides, kaempferol, iso-buckthorn Su. Ginkgo diterpene lipid component includes ginkgolides A, B, C, J, M and bilobalide.
Ginkgo biloba extract has antioxidant activity, cardiovascular activity, anti-inflammatory activity and anti-tumor effect. It can not only expand cardiovascular and arteries, but also protect microvascular well, thus effectively preventing vascular blockage of blood vessels and having a good precaution effect against hyperlipaemia, hypertension, diabetes and so on. Moreover, it also indirectly reduce the common eye diseases (cataract, glaucoma, vitreous opacity, retinopathy, diabetes-concurrent eye diseases, etc.). On one hand, it effectively cleans the blood, strengthens the blood vessels, prevents and treats cardiovascular disease. On the other hand, it is also effective in treating brain mal-function, anti-aging, preventing cancer. For the last 10 years, American consumers have been taking the product of ginkgo biloba as health food for preventing stroke and coronary heart disease. According to recent reports the American Journal of Medicine, during a over 3-years clinic studies, researchers from Oregon State University, Department of Medicine found that, taking Ginkgo biloba is very effective in preventing memory recession and Alzheimer's disease for over 65-years old men.