Effective Use of Mild Acting Herbs IV. Pueraria (Ge Gen)
Background: the herb and its constituents
Pueraria (gegen), the root of Pueraria lobata, is a commonly used herb in Chinese medicine. It is perhaps better known by its Japanese name: kudzu, from the Japanese word for vine. It is a fast growing plant that can extend a foot in length each day during the warm season. Its root are also fast growing, typically reaching 50 pounds or more, and can attain a weight of 400 pounds (about 2/3 of it is water). In Japan, aside from the use of pueraria as an ingredient in traditional Chinese medicine formulas, mainly those from the ancient Shanghan Lun, it is the source of a widely used food ingredient: starch. Kudzu starch has a mild taste that doesn’t conflict with delicate and subtle flavours; it creates a smooth consistency; it has an alkaline quality that blends well with acidic foods; and it crisps well when used as a coating for deep fried foods. Before isolating the starch (which is 99.6% starch with water), the roots also have a small amount of protein and are a reasonably good source of calcium, magnesium, iron, potassium and zinc, when compared to starchy foods such as wheat and sorghum.
As a medicinal herb, pueraria provides one major active component: a group of isoflavones often designated as puerarin, which is its main ingredient. Although several isoflavones have been isolated and characterized, there are five principal ones: puerarin, methylpuerarin, daidzein, daidzin, and daidzein glucopyranoside. Both daidzein and daidzin are also found in soy beans, which are known for their content of two other isoflavones, genistein and genistin (these isoflavones appear to be primarily responsible for soy’s benefit of alleviating menopausal symptoms). The total isoflavone content of the dried pueraria root slices generally does not exceed 2%, but is typically around 1%. By contrast, the main dietary source of isoflavones, soybeans, usually do not exceed 0.6% isoflavones and more typically contain about 0.3% of this component. Isoflavones are produced almost exclusively within the Fabaceae Family (Legumes), which includes the Chinese herbs pueraria, soja (soybeans), astragalus, licorice, sophora, and millettia.
The pueraria isoflavones were intensively researched in China during the 1970’s, and developed into a drug-like product that is used for circulatory disorders. The tablet or injection (usually given as an IV drip) of concentrated pueraria isoflavones is used to treat dizziness, headaches, neck pain, sudden deafness, glaucoma, diabetic retinopathy and hearing loss, angina, heart attack, myocarditis, and symptoms of hypertension (Yue and Hu 1987; Lai and Tang 1989). Its uses are similar to those of ginkgo leaf flavonoids, crataegus flavonoids, and hippophae (sea buckthorn) flavonoids; the first is known for promoting circulation to the brain and the latter two are used for promoting cardiac circulation.
Dosage and Effect
Using the appropriate dosage of the crude herb, as indicated in traditional texts, can be elaborated from work done with isolated active components in a standard dosage form. As examples of clinical applications (Chang and But 1986), pueraria flavones were given in tablets at a dose of 30–40 mg each time, three times daily (total daily dose is 90–120 mg) to 191 cases of coronary heart disease and angina pectoris; in the treatment of hypertension, 50 mg of pueraria flavones given twice per day (total daily dose is 100 mg) for several weeks; similarly, hypertensive patients suffering from angina were given a daily dose of pueraria flavones at 150 mg/day. From a survey of such applications for the tablets, the maximum daily dose recommended appears to be 300 mg/day. However, this upper level is apparently not because of toxicity, but simply an amount that was indicated as effective for the particular applications. Recently, work done with puerarin injection has involved 400 mg for a single injection whilst treating diabetic retinopathy (Ren, Hu, and Zhang 2000) and 500 mg in a single injection for heart attack patients (Xiao et.al. 2004).
At a maximum level of 2% isoflavones in the dried roots, to get a dosage in the range of about 100–500 mg, one would use 5–25 grams in a decoction. However, the level of isoflavones is more typically only about 1%, so that a dose of 10–50 grams would be more suitable (10–30 grams in decoction; the higher levels extracted and prepared in tablets or by injection). In the Materia Medica guides published in China, dosage recommendations range from 5–24 grams in decoction, so that mid-range value of about 15–18 grams appears consistent with what is known about the traditional use, the root constituents, and the modern clinical applications. For example, in Oriental Materia Medica (Hsu et.al., 1986), the recommended dosage range for pueraria roots in decoction is 6–24 grams, and the recommended dosage of the pueraria flavonoid is 100–300 mg/day; these quantities represent a good summary of the data that was presented above, with higher dosages of the pueraria isoflavones given in recent years (by injection), after the publication of that book.
The herb fits the model of being mild in nature because of the low toxicity and the relatively large dosage that is used, especially in modern practice. The low toxicity is also demonstrated by the fact that the isoflavone extract of pueraria has even been used as an IV drip without reported adverse effects. For example, the authors of a report (Zhao, et. al, 1999) on use of puerarin IV drip for heart disease patients concluded: “Puerarin is a safe and effective drug in treating patients with unstable angina and worth spreading in clinical usage.” The authors of a review of pueraria flavonoids (Du et.al. 2000), collaborating among several institutes in Beijing and Chengdu, stated that they “recently prepared [puerarin] in an 80+% concentration that showed little toxicity, benefited cardio-cerebro vascular disease, and had good absorption when taken orally. It has passed pre-clinical examination for new drugs in accordance with criteria established by the Health Ministry of the People’s Republic of China, and is presently in clinical trials.”
Pueraria isoflavones are rapidly absorbed from the GI tract, but are also rapidly eliminated (Penetar 2006). This is consistent with having low toxicity, but also indicates the need for frequent dosing when using the oral form at moderate dosage, such as three times a day, to maintain significant blood levels for the desired effects on circulation.
Conditions determining what form to use
A limiting factor in the use of high dosage pueraria in decoctions is that the starch turns the decoction quite thick, especially if it is allowed to cool. In China, because of the availability of puerarin in pill form, this herb is not often included in decoctions, as evidenced by infrequent inclusion of it in published modern formulas. The change in practice may have come also as a result of recognizing the need for higher dosage and the shift of applications from alleviating symptoms of the common cold to treating serious cardiovascular diseases. In a report on the treatment of diabetic hearing loss (Li et.al. 2000), the treatment group received a decoction for which the basic recipe included pueraria at 30 grams per day. In several modern applications, the injection (IV drip) form is used to obtain rapid effects, but because of the easy absorption of puerarin by the oral route, similar action may be attained by using a high dose of pueraria or its extract taken several times per day.
Low doses of pueraria root (e.g., 3-9 grams), as used in some large traditional formulas, may have limited effect. It is possible that when combined with liquorice root (Gan Cao, which is common in these formulations), the isoflavone components of these two herbs work together to alleviate inflammation, thus allowing the low dose of pueraria to contribute to the action of the formula.
In sum, China’s use of pueraria in recent years is tending towards less frequent administration in traditional style decoction formulas (or dried decoctions), relying more heavily on the form of concentrated extracts of the isoflavone fraction taken in daily doses of 100–300 mg puerarin per day orally or by IV drip with doses up to 500 mg. The herb can still be utilized in traditional decoction formulas with good effects especially if incorporated at a dose of about 15–18 grams/day (about 3.0-3.6 grams of dried decoction). The isoflavones are the key ingredient of pueraria roots that influences the determination of proper dosage.
Chang, M and But, P (1986). Pharmacology and Applications of Chinese Materia Medica, World Scientific, Singapore.
Du LJ, et al. (2000), 'Drug properties of pueraria flavonoid based on pharmacological action', International Journal of Oriental Medicine'; 25(2): 95–100.
Hsu HY, et al. (1986), Oriental Materia Medica: A Concise Guide, Oriental Healing Arts Institute, Long Beach, CA.
Lai, X and Tang, B. (1989). 'Recent advances in the experimental study and clinical application of Pueraria lobata', China Journal of Chinese Materia Medica; 14(5): 308-311, 277.
Li, R. et.al. (2000). 'TCM Treatment of diabetic hearing loss, Journal of Traditional Chinese Medicine' 20(3): 176–179.
Penetar DM, et. al. (2006), 'Pharmacokinetic profile of the isoflavone puerarin after acute and repeated administration of a novel kudzu extract to human volunteers,' Journal of Alternative and Complementary Medicine; 12(6): 543–548.
Ren P, Hu H, and Zhang R (2000), 'Observation on efficacy of puerarin in treating diabetic retinopathy, Chinese Journal of Integrated Chinese and Western Medicine, 20(8): 574–576.
Xiao LZ, et.al. (2004), 'Study on the effect and mechanism of puerarin on the size of infarction in patients with acute myocardial infarction,' Chinese Journal of Integrated Chinese and Western Medicine; 24(9): 790–792.