Fecal medicines used in traditional medical system of China: a systematic review of their names, original species, traditional uses, and modern investigations

In China, the medical use of fecal matter (fresh fecal suspension or dry feces) can be dated back to the fourth century, approximately 1700 years ago. In long-term clinical practice, Chinese doctors have accumulated unique and invaluable medical experience in the use of fecal materials. In view of their good curative effect and medicinal potential, fecal medicines should be paid much attention. This study aimed to provide the first comprehensive data compilation of fecal medicines used in various Chinese traditional medical systems by bibliographic investigation of 31 medicine monographs and standards. A total of 54 fecal medicines were found to be used in 14 traditional Chinese medical systems. Their names, original species, medicinal forms, and traditional uses were described in detail. These fecal medicines were commonly used to treat gastrointestinal, nervous system, skin, and gynecological diseases. Commonly used fecal medicines include Wu-Ling-Zhi, Jiu-Fen and Hei-Bing-Pian. The information summarized in this study can provide a good reference for the development and utilization of fecal medicines. Further studies are necessary to prove their medicinal value, identify their active ingredients, and elucidate their mechanisms of action so that more people can accept these special medicines.


Background
Traditional medicines have been used for prevention and treatment of diseases for thousands of years in China. In recent decades, they have attracted worldwide attention due to their reliable therapeutic efficacy and low side effects. During the long-term struggle against diseases, ancient Chinese doctors found that some unexpected materials, such as human or animal feces, could also effectively treat diseases. In China, the medical use of fecal matter (fresh fecal suspension or dry feces) has a long history. During the Eastern Jin dynasty (ad 300-400 years), "Zhou Hou Bei Ji Fang", a well-known monograph of traditional Chinese medicine (TCM) written by Hong Ge, recorded a case of treating patients with food poisoning or severe diarrhea by ingesting human fecal suspension (known as yellow soup or Huang-Long decoction) [1]. During the Tang dynasty, Yutuo Ningma Yundan Gongbu compiled a world-famous book of Tibetan medicine called "The Four Medical Tantras", which recorded that digestive diseases can be treated with the processed product of the feces of Sus scrofa (Hei-Bing-Pian in Chinese) [2]. Later, the "Compendium of Materia Medica" (a masterpiece of herbalism written by Shizhen Li during the Ming dynasty) described a series of prescriptions for treating diarrhea, rheumatism, jaundice, fever, and pain using fresh fecal suspension or dry feces [3]. In addition, "Jing Zhu Materia Medica" written by Danzeng Pengcuo Dimaer in the nineteenth century recorded that Hei-Bing-Pian and the dry feces of Gypaetus barbatus or Aegypius monachus (Jiu-Fen in Chinese) are commonly used to treat dyspepsia and gastric ulcer [4]. These records indicate that fecal medicines are widely used and occupy an important position in Chinese traditional medical systems.
In long-term clinical practice, Chinese doctors have accumulated unique experience in the use of fecal medicines. For example, the dry feces of Trogopterus xanthipes (Wu-Ling-Zhi in Chinese) is often used to treat blood stasis, swelling and aching due to traumatic injury [5]. Jiu-Fen is good at treating gastrointestinal diseases, such as dyspepsia, weak gastrointestinal function and gastric ulcer. Hei-Bing-Pian can treat diseases, such as indigestion, diarrhea and distending pain in the stomach [6]. These traditional medication experiences are undoubtedly valuable assets and can provide a reference for modern drug development. However, documents on the traditional use of fecal medicines are scattered and lack systematic collation.
In this review, we comprehensively collect and summarize the names, origins, and treated diseases of fecal medicines that have been used in some Chinese traditional medical systems, including TCM, Tibetan ethnic medicine (EM), Oroqen EM, Kazak EM, Uygur EM, Mongolian EM, Nu EM, Yao EM, Wa EM, Tujia EM, Korean EM, Jino EM, Hani EM, and Dai EM. In addition, we review the most frequently used fecal medicines in terms of their origins, traditional uses, chemical constituents, and pharmacological activities. Such information can provide a good reference for their development and utilization. These fecal medicines may be a valuable gift from Chinese traditional medicine to the world and has potential as drug candidates for the treatment of some chronic diseases, such as gastrointestinal diseases.

Methods
We have manually searched 31 related medicine monographs and drug standards, such as "Zhou Hou Bei Ji Fang", "Compendium of Materia Medica", "Jing Zhu Materia Medica", "Dictionary of Chinese Ethnic Medicine", "Drug Standards of Tibetan Medicine", "Lan Liu Li", "Pharmacopoeia of the People's Republic of China", and "Chinese Tibetan Materia Medica", to obtain the information about the names, origins, traditional uses, and treated diseases of fecal medicines. In addition, we have searched the online Chinese literature databases (i.e., Wan fang and CNKI) and international English databases (i.e., PubMed, ISI Web of Science and Google Scholar), using their vernacular or Latin names as keywords, to obtain their chemical constituents and biological effects.

Results
This review recorded 54 fecal medicines that have been used in 14 Chinese traditional medical systems. Their names, original species, medicinal forms, and treated diseases are presented in Tables 1 and 2. These 54 medicines mainly originate from the feces of 56 animals. Among medicinal forms used, dry feces is the most frequently used (66.67%), followed by processed feces (29.63%) and fresh fecal juice (3.70%). In addition, we found that these 54 fecal medicines are mainly used to treat gastrointestinal (37.04%), nervous system (22.22%), skin (22.22%), ophthalmic (18.52%), and gynecological diseases (16.67%).

Fecal medicines used in the TCM system
Traditional Chinese medicine is the most representative traditional medical system in China. It has a long history of more than 2500 years. In recent decades, TCM has attracted global attention due to its reliable therapeutic efficacy. Generally, TCM uses herbs, animals or minerals to treat diseases. In long-term clinical practices, animal feces have been found to be effective in treating some specific diseases under the guidance of TCM theory. As early as the Eastern Jin dynasty, human fecal juice (i.e., yellow soup) has been used by TCM practitioners to treat severe diarrhea [1]. At present, some fecal medicines are still used in the clinical practice of TCM. In the 2015 edition of Chinese Pharmacopoeia [7], 18 preparations have been found to contain fecal medicines (Table 5). For example, "Shi-Xiang-Zhi-Tong Powder" and "Tong-Jing Pills" contain Wu-Ling-Zhi, and "Huang-Lian-Yang-Gan Pills" contains Ye-Ming-Sha (dry feces of some kinds of bats).
In the present study, a bibliographic investigation of TCM monographs and drug standards revealed 14 kinds of fecal medicines that are commonly used in the TCM system. They mainly come from the feces of 22 animals and are widely used to treat dysmenorrhea, amenorrhea, abdominal mass, diarrhea, and blurred vision. Additional information on these 14 medicines is provided in Table 1. Wu-Ling-Zhi is the most representative fecal medicine in the TCM system (Fig. 1). Therefore, its traditional uses, chemical constituents and pharmacological activities are described in detail in the subsequent sections.

The dry feces of Trogopterus xanthipes (Wu-Ling-Zhi in Chinese)
Wu-Ling-Zhi (Fig. 1b), also named as Goreishi or Trogopterorum faeces, is one of the commonly used fecal medicines. It derives from the dry feces of Trogopterus xanthipes. Wu-Ling-Zhi was first recorded in the classic Chinese medicinal book "Kai Bao Ben Cao" compiled in the Song Dynasty [8]. Its traditional uses were described in several TCM monographs and drug standards. For example, "Ben Cao Jing Shu" recorded that Wu-Ling-Zhi had a good therapeutic effect on stabbing pain caused by blood stasis [9]. In addition, the Chinese Pharmacopoeia 1990 edition recorded that Wu-Ling-Zhi had good effects of promoting blood circulation, removing blood stasis and relieving pain, and was usually used to treat the stabbing pain in the chest and hypochondrium, dysmenorrhea, amenorrhea, swelling and aching due to traumatic injury, postpartum blood stasis, and snake bites.
Moreover, it is worth pointing out that extracts or chemical constituents obtained from the Wu-Ling-Zhi have been proved to possess a wide spectrum of pharmacological activities, such as anti-inflammatory, anticerebral ischemia, anti-gastric ulcer, and antithrombin effects. The basic pharmacological data of Wu-Ling-Zhi extracts and some isolated compounds are shown in Tables 3 and 4. Kim et al. [24] reported that Wu-Ling-Zhi extract could reduce lipopolysaccharide-induced NO and cytokines production. Wang et al. [25] found that the ethyl acetate extract of Wu-Ling-Zhi showed obvious inhibitory effects on xylene-induced ear swelling in mice and carrageenan-induced paw swelling in rats (400 mg/kg, ip), and it could also significantly inhibit the proliferation of granulation tissue in mice (800 mg/kg, ip). These findings indicated that Wu-Ling-Zhi has obvious anti-inflammatory effect. Furthermore, the ethyl acetate extract of Wu-Ling-Zhi was also found to be able to protect gastric mucosa and prevent experimental gastric ulcer by inhibiting gastric acid secretion [26]. It was reported that the aqueous extract of Wu-Ling-Zhi could significantly prolong the survival time of mice with incomplete cerebral ischemia, reduce the brain water content, brain index and malondialdehyde (MDA) level, and increase superoxide dismutase (SOD) activity in rats, indicating that Wu-Ling-Zhi has good protective effect against cerebral ischemia [27]. Moreover, the aqueous extract of Wu-Ling-Zhi could down-regulate the expression of intercellular adhesion molecule-1 in experimental atherosclerotic rats and reduce the degree of vascular endothelial lesions, which may account for the anti-arteriosclerosis inflammatory effects of Wu-Ling-Zhi [28].

Fecal medicines used in other traditional ethnic medicine systems in China
In addition to the TCM system, there are other traditional medical systems in China, such as Tibetan, Mongolian, Uygur, Tujia, Kazak, Yao, Korean, and Dai ethnic medicines. These ethnic medical systems have their own unique theories in the use of natural medicines. Therefore, it is also important to collect information about fecal medicines from these ethnic medical systems.
Traditional Tibetan medicine (TTM) is a representative ethnic medicine in China, and it has a unique fundamental theory, namely three elements theory consisting of "rLung", "mKhris-pa" and "Badkan" [30]. In TTM system, the use of fecal medicines has a long history. The earliest Tibetan medicine monograph that recorded fecal medicines is "The Four Medical Tantras" [2]. Later, in the seventeenth century, famous "Tibetan Medical Thangka of The Four Medical Tantras" [31] was published by Sdesrid-sangs-rgyas-rgya-mtsho, which vividly depicted some commonly used fecal medicines in the form of wall chart (Fig. 3).
In this study, we found that the feces of 41 animals were used as medicines for the treatment of various diseases in 13 ethnic medical systems. More information on these medicines is provided in Table 2. Among them, the dry feces of Gypaetus barbatus or Aegypius monachus and the processed product of the feces of Sus scrofa are representative fecal medicines in Chinese ethnic medicine systems. Their traditional uses, chemical constituents and pharmacological activities have been described in detail in the following sections.

The dry feces of Gypaetus barbatus or Aegypius monachus (Jiu-Fen in Chinese)
The dry feces of G. barbatus or A. monachus, known as Jiu-Fen in Chinese, is a commonly used Tibetan medicine (Fig. 1d). It has the functions of strengthening stomach and promoting digestion. Jiu-Fen is used in the traditional Tibetan system of medicine for the treatment of dyspepsia, gastrointestinal dysfunction, gastric ulcer, and intestinal cancer in the past few decades [4,6]. In addition, the "Jing Zhu Materia Medica" recorded that Jiu-Fen can be used to treat mental illness [4]. Nowadays, Jiu-Fen is frequently used in the clinical practice of TTM by combining other herbs. According to our statistics, there are 32 preparations containing Jiu-Fen in some monographs and drug standards of Tibetan medicine [6,[32][33][34][35]. The representative prescriptions include "Shi-Wei-Jiu-Fen Powder", "Er-Shi-Jiu-Wei-Neng-Xiao Powder" and "Jian-Hua-Mu-Xiang Pills" ( Table 5). The "Tibetan Medicine Standards" recorded that "Shi-Wei-Jiu-Fen Powder" can strengthen stomach and promote digestion [6]. Consequently, it is usually used to treat gastrointestinal diseases such as dyspepsia.
The use of Jiu-Fen in the traditional Tibetan system of medicine has a long history, but modern research on the chemical composition, quality control and pharmacodynamic evaluation of Jiu-Fen has not yet been carried out. Therefore, further studies are needed to prove its medicinal values in gastrointestinal diseases treatment, identify active compounds and elucidate the underlying mechanisms with the help of modern chemistry and pharmacology methods.

The processed product of the feces of Sus scrofa (Hei-Bing-Pian in Chinese)
The processed product of the feces of Sus scrofa (wild boar), known as Hei-Bing-Pian (Chinese name), is a widely used Tibetan and Mongolian medicine in China (Fig. 1e). Its processing method was recorded in the "Chinese Materia Medica for Tibetan Medicine": firstly, the  dry feces of Sus scrofa is put into a ceramic jar, and yellow mud (adding a small amount of salt) is used to seal the ceramic jar. Secondly, the ceramic jar is calcined with fire until it turns gray outside. Then, the black matter is taken out from the ceramic jar, which is Hei-Bing-Pian [36]. In traditional Tibetan system of medicine, Hei-Bing-Pian is described as pungent in flavor and hot in nature. It is commonly used for the treatment of dyspepsia, gallbladder diseases, stomachache, and plague [6]. According to our statistics, there are 14 Tibetan medicine preparations containing Hei-Bing-Pian in official drug standards. The representative prescriptions include "Shi-Wei-Hei-Bing-Pian Powder", "Shi-Yi-Wei-Jin-Se Pills" and "Shi-Wu-Wei-Zhi-Xie-Mu Powder" ( Table 5). The "Drug Standards of Tibetan Medicines" recorded that "Shi-Wei-Hei-Bing-Pian Pills" is usually used to treat stomach and gallbladder diseases, such as dyspepsia, anorexia, jaundice, gallstones and nausea [35].
It has been reported that Hei-Bing-Pian contains a variety of inorganic elements, such as Fe, Ca, Zn, K, Cu, Mn, Co, Ti, and Mg. At present, the contents of these elements in Hei-Bing-Pian have been determined by using atomic absorption spectrometry or spectrophotometry [37,38]. The elements with high levels are Ca (18,570 μg/g), K (11,625 μg/g), Mg (9975 μg/g), and Fe (7800 μg/g). Furthermore, two bile acids (i.e., cholic acid and taurocholic acid) were detected and quantified in Hei-Bing-Pian by using ultra high-performance liquid chromatographymass spectrometry method [21]. Besides, Chang et al. [39] developed a spectrophotometric method to determine the absorption force of Hei-Bing-Pian on tartrazine, and used this adsorption force as an indicator to control the quality of Hei-Bing-Pian.
Modern pharmacological study has demonstrated that Hei-Bing-Pian can prevent mucosal damage caused by experimental colitis in rats. Compared with the model group, the high and low doses of Hei-Bing-Pian can significantly reduce the damage of colonic mucosa congestion, hyperplasia and ulcer (p < 0.05), and significantly increase the levels of superoxide dismutase (SOD) and glutathione (GSH) [40]. Cai et al. [41] reported the effect of Hei-Bing-Pian on the intestinal smooth muscle function of animals. It was found that Hei-Bing-Pian had no obvious effect on normal isolated ileum, and could not antagonize the inhibitory effect of atropine, adrenaline and promethazine Table 5 Representative prescriptions containing fecal medicines recorded in official drug standards  on isolated ileum smooth muscle. However, it could significantly inhibit histamine-induced ileal smooth muscle excitation, and the inhibition rate was 25%. Moreover, in vivo studies showed that Hei-Bing-Pian could inhibit the contraction effect of pilocarpine on ileal smooth muscle. These results indicate that the effect of Hei-Bing-Pian on intestinal smooth muscle is related to the cholinergic M receptor and histamine receptor. Bai et al. [42] found that Hei-Bing-Pian could significantly accelerate gastric emptying in rats and promote the propulsive speed of activated carbon in the small intestine of mice. Moreover, the high dose of Hei-Bing-Pian could significantly promote the healing of chronic gastritis caused by acetic acid, and had obvious protective effect on gastric mucosal injury induced by cold stress. Besides, in order to make better use of Hei-Bing-Pian, its long-term toxic effects have been studied by Li et al. The results showed that, after 12 weeks of administration of Hei-Bing-Pian, there were no significant changes in body weight, blood biochemical parameters, histopathology, and several organ indexes (e.g., heart, liver, spleen, kidney, and thymus) in rats, compared with the control group, which indicated that Hei-Bing-Pian has no potential toxicity [43]. The basic pharmacological data of Hei-Bing-Pian and its ingredients are shown in Tables 3  and 4.

Similarities and differences of fecal medicines related to treated diseases in Chinese traditional medical systems
Every traditional medical system in China has its own unique theory or medication experience. Therefore, the same fecal medicines are used in different medical systems, and their therapeutic uses may be different. A detailed comparison of these differences would help researchers and traditional medical practitioners to better understand the indications of fecal medicines and promote their development and utilization. In this study, we compared the similarities and differences of therapeutic uses of Wu-Ling-Zhi and Hei-Bing-Pian in different traditional medical systems, including TCM, Tibetan EM, Korean EM, Dai EM, Yao EM, Tujia EM, Nu EM, and Mongolian EM. Additional details are provided in Table 6. The results indicate that Wu-Ling-Zhi is commonly used to treat amenorrhea and dysmenorrhea in most traditional medical systems. However, its therapeutic uses also have some obvious differences in different medical systems. For example, in the Tibetan EM, Wu-Ling-Zhi can be used to treat stomachache, whereas in the Mongolian EM, it is mainly used to treat diarrhea, gout and itching. Moreover, Wu-Ling-Zhi can treat cold, whooping cough and fever in the Nu EM. Hei-Bing-Pian has the same therapeutic use in TCM and Tibetan EM systems. It is widely used in both systems to treat dyspepsia, biliary diseases, plague and distending pain in the stomach. There is no difference in the therapeutic use of Hei-Bing-Pian in the two medical systems.

Conclusion and future perspectives
Chinese traditional medicine is an important part of the world's medical system. In long-term clinical practice, ancient Chinese doctors have accumulated invaluable experience in the use of fecal medicines. As shown in Tables 1 and 2, some fecal medicines have been found to be effective in treating amenorrhea, dysmenorrhea dyspepsia, diarrhea, fever, and stomachache. These traditional medication knowledge are valuable assets. Currently, some fecal medicines (e.g., Wu-Ling-Zhi, Jiu-Fen and Hei-Bing-Pian) are still used in clinical practice. A total of 76 preparations containing fecal medicines were Amenorrhea and dysmenorrhea Stabbing pain in the chest and abdomen, swelling and aching due to traumatic injury, and snake bites (external use) [5,8,52] Tibetan EM Stomachache [59,60] Korean EM Stabbing pain in chest and abdomen [60] Dai EM Snake bites (external use) [60] Yao EM Epilepsy [63] Tujia EM Swelling and aching due to traumatic injury, and snake bites (external use) [60] Nu EM -Cold, whooping cough and fever [60] Mongolian EM -Diarrhea, gout and itching [62] Hei-Bing-Pian Tibetan EM Sus scrofa L. Dyspepsia, biliary diseases, plague and distending pain in the stomach - [6,36,59] Mongolian EM recorded in the latest official drug standards (Table 5).
Extensive clinical application demonstrates the role and value of fecal medicines in Chinese medical systems. Moreover, Wu-Ling-Zhi extracts and its chemical constituents have been proved to possess a wide spectrum of biological activities, such as anti-inflammatory, anticoagulative and antioxidant effects (Tables 3 and 4). Some possible molecular mechanisms have also been revealed. The results of these modern pharmacological studies provide some evidences to prove the scientific nature of fecal medicines. However, most fecal medicines still lack experimental evidences. For example, Jiu-Fen is a commonly used Tibetan medicine. However, so far, no biological activities or active ingredients have been reported for this drug. Therefore, in order to better develop and utilize these fecal medicines, more in vivo pharmacological studies and even clinical evaluations should be performed to prove their scientific and medicinal value. Fortunately, an in-depth study of gut microbiota has provided an opportunity to interpret the scientific connotation of some traditional fecal medicines, such as the yellow soup. This soup is a fresh fecal suspension of Homo sapiens commonly used to treat food poisoning, severe diarrhea, heat toxins, and unconsciousness due to high fever. Zhang et al. [44,45] believe that the efficacy of yellow soup is mainly caused by the gut microbiota from fresh fecal water, and its principle for treating diseases is similar to the fecal microbiota transplantation method of modern medicine. Therefore, reconstructing the gut microbiota of patients may be the mechanism of action of fresh fecal medicines for treating diseases.
However, most fecal medicines are derived from dry feces (e.g., Wu-Ling-Zhi) or processed products (e.g., Hei-Bing-Pian). During drying and processing, these fecal medicines lose the living microbiota. Therefore, their mechanisms for treating diseases may be different from fresh feces. Feces are intestinal excretions of humans or animals. The chemical constituents in feces are mainly derived from the host or dietary metabolites. These metabolites may be the key active constituents of fecal medicinal materials. For example, the terpenoids, flavonoids and lignans contained in Wu-Ling-Zhi are closely related to the foods eaten by Trogopterus xanthipes (e.g., Platycladus orientalis leaves, Pinus tabulaeformis bark, and peach kernels). These diet-derived metabolites may be the pharmacologically active ingredients of Wu-Ling-Zhi. Moreover, some bile acids (e.g., deoxycholic acid, lithocholic acid and taurocholic acid) have been found in Wu-Ling-Zhi and Hei-Bing-Pian [21]. These bile acids are the final metabolites of cholesterol under the common metabolism of liver and gut microbiota. Bile acids are endocrine-signaling molecules that regulate metabolic processes, including glucose, lipid and energy homeostasis, by regulating gut microbiota or activating bile acid receptors, such as the farnesoid X receptor (FXR) and G protein-coupled bile acid receptor 1 [46][47][48]. Distrutti et al. [49] reported that bile acidsactivated receptors are targets for maintaining intestinal integrity. Gadaleta et al. [50] found that FXR activation could prevent chemically induced intestinal inflammation with an improvement of colitis symptoms and inhibition of epithelial permeability. In addition, bile acids can also regulate cardiovascular functions via receptordependent and -independent mechanisms [51]. These findings provide a rationale to explore the mechanisms of Hei-Bing-Pian and Wu-Ling-Zhi in the treatment of gastrointestinal and cardiovascular diseases, respectively.
With the continuous development of science and technology, some unique but sometimes incomprehensible drugs in traditional medical systems will gradually be recognized. In this study, we provide the first comprehensive data compilation of fecal medicines used in Chinese traditional medical systems. The information recorded in ancient monographs and drug standards, such as original species, traditional uses and indications, can provide a good reference for the development and utilization of fecal medicines. In view of the current research status of fecal medicines, future research may focus on the following aspects: (1) applying multidisciplinary methods to further prove their effectiveness and medicinal value, (2) revealing their active ingredients associated with clinical efficacy using phytochemical and pharmacodynamic methods, and (3) elucidating the mechanisms of action of fecal medicines based on gut microbiota or receptormediated signaling pathways.