Chantui: Use of Chitin in Chinese Herb Formulas
Chantui (literally: the molt, tui, from the cicada insect, chan) is a commonly used ingredient in Chinese medicine formulations. It may at first seem like an odd material to use, but the large insects (Cryptotympana pustulata; aka C. atrata) tend to populate certain trees and leave behind in the natural settings a substantial collection of molted skins which look something like yellow-brown flower petals on the ground. One of the alternate names for this material is chanhua, the "flower" of the cicada (it is also called chanyi, the "husk" of the cicada). Thus, the ancient herbalists were interested in collecting this fallen material, not the insects themselves, which apparently held little interest to them, in contrast to other insects for which the whole body is used in the practice of Chinese medicine (such as eupolyphaga beetle, dibiechong).
The cicada skins are predominantly chitin, a polysaccharide that is a structural component also found in the cell walls of fungi (as well as yeasts and algae) and in the exoskeletons of insects and other arthropods. Chitin is comprised of glucosamine and acetylglucosamine (see structure, below), often in chains of several hundred units. The material is essentially a fiber and is similar to cellulose (which lacks the amine groups) in plants, and which is second only to cellulose as the most common structural component of the world's flora and fauna.
The molted skin of cicada consists of about 50% chitin and about 50% proteins; it has small amounts of minerals, amino acids, lipids, and wax, but no significant amount of known active components. The color of the skin is conferred by tiny amounts of phenols and quinones which also serve as cross-linking agents for the polysaccharide strands. The proteins, including arthropodin, resilin, and sclerotin, give chitin its shape and structural integrity-flexibility or hardness-the latter assisted by the cross-linking quinones and minerals (mainly calcium carbonate). When cicada slough is ingested in Chinese medicine preparations, the protein provides a miniscule nutritional component to what is otherwise an essentially inert polysaccharide. Obtaining chitin from cicada molt is relatively efficient. By contrast, fungal wall chitin would need to be extracted by modern techniques to get an adequate amount, while chitin from arthropods like crabs and shellfish provides a complex material with only 15-30% chitin.
A modern preparation of chitin used in large quantities is obtained from the discarded shells of edible crustaceans (mainly crab and shrimp). The processing, which involves use of potent acids and bases, results in removing the calcium (present in substantial amounts in these thick, hardened shells) and protein, yielding a purified chitin. This chitin is then deacetylated to make the product called "chitosan," which has the same basic properties as chitin but has only 25% or fewer acetylglucosamine molecules left in the chain (1), with the rest converted to glucosamine. Chitosan has a wide range of applications, including oral use as a dietary supplement (e.g., to bind cholesterol and fats) and as a medicinal to treat renal disease. It is being utilized as a delivery system for medicines, based on its qualities as a polysaccharide fiber. Over 2,000 patents have been issued for products and processes using chitosan. There are two basic qualities that make chitosan more desirable than plain chitin in modern applications: it is more soluble (readily solubilized in weak acid solutions) and it has more reactive groups (generated by removing acetyl groups) that help it to bind cholesterol, fats, and other substances. Chitin is more inert, but does possess some of the same binding properties. When ingested, most of the chitin or chitosan remains in the intestinal tract and is eliminated by that route; thus, their principal actions appear to be related to substances that may be bound and immobilized by them. There has been considerable interest in using chitin degrading enzymes (chitinases) to produce additional materials of value for the pharmaceutical and health foods industries. Further work has been done on combining chitosan with other polymers, such as beta-glucans, to adjust the solubility properties.
In contrast to this massive investment in research and development for chitosan and other derivatives of chitin, the study of ordinary chitin has been very limited, with most of the work carried out before chitosan became available in 1980. Based on the traditional Chinese uses of cicada, the raw material was subjected to some pharmacological investigations and clinical evaluations (usually in compound prescriptions as is typical of traditional medicine methods). A review of its traditional use and of the topics selected for these follow-up studies will be presented here.
The first mention of use of chantui is in the Mingyi Bielu, a Materia Medica published around 500 A.D. by the renowned physician Tao Hongjing. This book was the result of his effort to revise and expand the Materia Medica classic Shennong Bencao Jing (ca. 100 A.D.). Chantui has been included in the subsequent Materia Medica books of China and is an official component listed in the modern Pharmacopoeia of the PRC. A good rendition of its two primary traditional indications for use is found in the Advanced Textbook of Traditional Chinese Medicine and Pharmacology (2):
The yellow wine mentioned here is the ancient Chinese product made from glutinous rice and wheat; this wine is also specified elsewhere to accompany ingestion of cicada. Yellow wine-or other alcohol-is thought to make the remedy more quickly relieve the symptoms. It is also noted in the text that: "Cicada relieves itching by eliminating wind, and is indicated for urticaria and pruritis. Moreover it relieves optic nebulae and congestion of the eyes." These latter indications are sometimes incorporated into the first listing for alleviating wind-heat.
The term "wind-heat" is a broad indicator of pathogenic influence that affects mainly the upper respiratory tract and the skin or other parts of the body surface, such as the eyes. The "heat" aspect may be revealed in a burning sensation, in the presence of fever, and in the presence of inflammation. The "wind" aspect may be revealed by acute onset and limitation to-or primary effect on-the skin and upper body. Among wind-heat ailments are those that produce rashes, whether by infection (as in measles) or by allergic reaction. Spasms and convulsions are also attributed to the presence of "wind," so the secondary indication for cicada is related to the first in this regard. In modern Chinese medicine (but not in the ancient model, such as when this material was first described), spasms and convulsions are often attributed to the syndrome called "internal wind," which is distinguished from "external wind." Cases of internal wind tend to be chronic rather than acute. The Chinese uses of cicada for spasms and convulsions are primarily for acute syndromes, such as those that occur with certain feverish diseases. Indeed, uncontrolled fever in infants may be responsible for the convulsions described in the Chinese literature. The main use of cicada in this case is to reduce feverish conditions and calm the body. An example of an acute spastic ailment is Bell's palsy.
Another traditional application of chantui was recorded in the text Yizong Jinjian by Wu Qian, published in 1742. The instruction is to powder the material and to administer 0.25 to 0.5 grams each time, two or three times per day, swallowed down with some mentha tea (3). It is used as a calming agent to alleviate night crying in young children (presumed to be due to interior heat stirring up the mind). In his Ten Lectures on the Use of Medicinals (4), Jiao Shude points to this use of cicada and states: "I frequently add 1.5-6 grams [of cicada] to formulas that harmonize the stomach, disperse food, and clear heat, and it is invariably effective for incessant night crying in infants." Based on his presentation, this larger dosage appears to be indicated for making decoctions. Many of the Chinese clinical uses of cicada are for pediatric disorders.
Cicada is an ingredient in several formulations recorded in ancient texts and brought forward to modern times, but most practitioners today use cicada in formulas of modern design (those from the 20th Century until the present) instead. This may be because there are fewer cases of diseases treated by traditional formulas with cicada slough, such as measles, infantile convulsions, or tetanus. There is a well-known small formula including cicada, Qingjie Tang (3); it is from a book published around 1935, Yixue Zhongzhong Canxi Lu by Zhang Xichu. The ingredients are 9 grams cicada, 12 grams mentha, 18 grams gypsum, and 4.5 grams licorice. Qingjie means to "cleanse" the surface, meaning to alleviate wind-heat in the exterior of the body (tang refers to the preparation, being a decoction). Mentha and cicada are both classified as medicinals that dispel wind-heat and are frequently used together; gypsum [shigao] is a natural source of calcium that is used to alleviate fever, and licorice is considered a harmonizing ingredient (improves the taste, moderates the action) as well as an anti-inflammatory. This formulation is indicated for the initial stage of a febrile disease (e.g., a viral or bacterial infection) that yields symptoms such as soreness of the body, headache, and high fever. Such conditions might occur with influenza and meningitis.
An example of modern use of the ingredient is in a formula for treating vocal polyps. The formula was relayed in the book by Hou Jinglun, Traditional Chinese Treatment for Otolaryngologic Diseases (5), and includes 4.5 grams cicada slough in a decoction with 107 grams of other ingredients, including hoelen, alisma, coix, scrophularia, sterculia, ginseng, and licorice. Other formulas that can be found in modern guides to traditional Chinese medicine practice are directed at treatment of various skin diseases.
A summary of the work done with cicada was presented in Pharmacology and Applications of Chinese Materia Medica (6). That text includes brief summaries of original Chinese publications. The purpose of presenting this information below is not to demonstrate the effectiveness of cicada, for which more rigorous and repeated studies would be necessary, but rather to illustrate the areas of research that were pursued. Therefore, few details are to be presented. The majority of these studies were carried out from 1959-1979; a few of the clinical reports come from publications as late as 1984. Laboratory animal studies of cicada were aimed at confirming the traditional uses of the substance, and the claimed benefits observed in these experiments were anticonvulsive and sedative effects and antipyretic effects. In clinical studies, carried out during the same period and for several years after, the following benefits were described:
Of the above applications, only acute nephritis may appear to be distinct from the traditional applications; however, some of its symptoms include facial swelling, headache, and seizures, which would suggest cicada as part of the treatment. Chitosan, the modified chitin mentioned previously, has been indicated as potentially useful for renal disease, as indicated in this summary of the study (7):
The effects of chitosan have been investigated on eighty patients with renal failure undergoing long-term stable haemodialysis treatment. The patients were tested after a control treatment period of 1 week. Half were fed 30 chitosan tablets (45 mg chitosan/tablet), three times a day. Ingestion of chitosan effectively reduced total serum cholesterol levels (from 10.14 +/- 4.40 to 5.82 +/- 2.19 mM) and increased serum hemoglobin levels (from 58.2 +/- 12.1 to 68 +/- 9.0 g L-1). Significant reductions in urea and creatinine levels in serum were observed after 4 weeks of chitosan ingestion. The feeling of physical strength, the appetite and the sleep of patients in the treatment group had improved significantly after 12 weeks of ingestion, compared with those of patients in the control group. During the treatment period, no clinically problematic symptoms were observed. These data suggest that chitosan might be effective treatment for renal failure patients, although the mechanism of the effect should be investigated further.
In this study, the amount of chitosan ingested was 4 grams per day (the pills involved are very small, as is common for many Japanese preparations). When chitosan is sold as a dietary product for binding cholesterol and fats, it is labeled for ingestion of 2-3 grams per day (clinical studies with 2-3 grams per day have shown no significant effect of chitosan on blood lipids or body weight, which is understandable in that this amount can only bind a relatively small percentage of the consumed fats). In the Chinese literature, ingestion of 3 grams of cicada powder, which contains about 1.5 grams of chitin, is mentioned (with considerably higher doses for some applications). When used in decoction form, the dosage may be as high as 30 grams, though routine prescribing is 9-15 grams in decoction. Decocting cicada slough will release some of the chitin into solution by boiling for 45-60 minutes as is common practice; the low solubility of chitin means that it will come out of solution if the liquid is not poured off promptly. Since chitin may be less medicinally active than chitosan, the use of the latter as a supplement to Chinese herb formulas could be a reasonable approach.
It is not easy to understand how a fiber like chitin might successfully treat the conditions indicated in the Chinese literature. There can be a definite value to binding of substances that might be causing adverse responses in the individual and this is likely its function in renal disease. It is possible that immune system components entering the intestinal lining may generate broader, systemic responses in the presence of chitin. There is no doubt that the matter will be pursued further, though the focus of research will remain on the modified products, such as chitosan. At this time, there is no evidence of toxicity or adverse reactions to ingesting the amounts of chitin or chitosan that have been recommended.
November 2005