Culture and Sustainable Utilization of Hirudos

Jinhua LIU, Shuang PAN*, Qiaoqiao SUN, Shulan CUI, Jinbo ZHANG

1. Jining Institute of Food and Drug Control, Jining 272004, China; 2. Baoji Vocational & Technical College, Baoji 721000, China; 3. Yantai Traditional Chinese Medicine Hospital, Yantai 264013, China

Abstract In this paper, the resource distribution, pharmacological action and culture status of hirudos were reviewed. Hirudo resources are widely distributed and have a variety of pharmacological effects, but culture is difficult, so the scientific development of hirudos culture and solving the problem of hirudos breeding can alleviate the contradiction in the medicine market and contribute to the sustainable development of hirudo medicine.

Key words Hirudo, Resource, Culture, Pharmacological action

1 Introduction

Hirudos, also known as blood suckers, are annelid phylum, vermiculite animals. The hirudo was first written in theClassicofShennongMateriaMedica: "The hirudo tastes salty and is neutral in nature." It was recorded in theCompendiumofMateriaMedica: "Its very bitter salty taste can damage blood."[2]Through comprehensive description of various medical works, hirudoses taste salty, bitter, and are neutral in nature; it’s a little toxic. It plays a major or special role in the treatment of liver lesions. It has the effect of removing blood stasis and stimulating the menstrual flow, eliminating dysmenorrhea, and can mainly treat blood stasis menstrual block, abdominal mass, apoplectic hemiplegia, and fall injury[3]. This paper summarizes the resources, pharmacological effects and culture status of hirudos, in order to provide a theoretical basis for the scientific development of breeding of hirudos to alleviate the contradictions in the medicinal material market and realize the sustainable development of hirudos.

2 Resource distribution

Hirudos generally live in fresh water, but there are also species that live in salt water, brackish water and on land. The species on land often live in a dark and humid environment all the year round. There are two kinds of feeding habits: blood-sucking and non-blood-sucking. In China, the aquatic blood-sucking hirudos includeH.nipponicaWhitman,H.pulchra,P.javanicaWahlberg,P.similis,D.feroxandP.manillensisLesson; the aquatic non-blood-sucking hirudos includeW.pigraWhitman,W.laevisBaird andW.acranulataWhitman; the terrestrial blood-sucking hirudos includeH.hainanaSong, Zhang et Tan andH.hainanaSong, Zhang et Tan. The hirudos in Family Haemopidae are distributed all over China, and the most abundant hirudos areW.pigraWhitman, especially in the areas around the main freshwater lakes in China. The wild resources ofW.pigraWhitman are rich, which account for about 70% of the output of hirudos in the country. The wild resources of hirudo in Family Hirudinidae are mainly distributed in South China, including Fujian, Guangdong, Guangxi, Yunnan, Hainan and other places.

3 Pharmacological action

3.1 Anticoagulant effectThe researchers have found that hirudin plays an anticoagulant role by specifically binding to thrombin to prevent the conversion of fibrinogen to fibrin. Zhai Xinyan’s research showed that hirudos extract could prolong the time of clotting and bleeding in mice to indicate that hirudo extract had anticoagulant effect. The anticoagulant experiments by Li Yanlingetal.[5]showed that the ethyl acetate layer of hirudos had the best anticoagulant effect, and n-butanol layer and n-hexane layer also had different degrees of anticoagulant effect. Compared with heparin, as the most widely used anticoagulant in clinic, hirudin has a stronger specificity of binding with thrombin, which does not depend on coagulation factor, does not induce thrombocytopenia and does not increase vascular permeability. It has a good application prospect[6]. With the development of genetic engineering and molecular biology technology, synthetic hirudin has come out[7]. In addition, the researchers also found components with better anticoagulant activity fromP.manillensisand hirudos. Zhong Shanetal.[8]extracted a hirudo polypeptide with a relative molecular weight of 8 608 from hirudos, and Xiao Lingetal.isolated a glycopeptide compound with a molecular weight of 9 374 fromW.pigraWhitman. At present, the material basis of anticoagulant activity in hirudos andW.acranulataWhitman is not clear and needs to be further studied.

3.2 Anti-thrombosisHirudin is considered to be the most specific thrombin preparation at present. Hirudin plays an anticoagulant effect by binding to thrombin. The combination of hirudin and thrombin inhibits the activation of thrombin on platelets in the process of thrombosis, thus inhibiting the formation of thrombus. Tan Yuzhietal.[9]found that the alcohol extract ofW.pigraWhitman could significantly inhibit the thrombosis induced by collagen-epinephrine in mice and arteriovenous bypass thrombosis in rats.

3.3 Anti-inflammation and improvement of cerebral hemorrhageCerebral hemorrhage is seriously harmful to people’s health and has a high fatality rate. But at present, there is still no special method for the treatment of cerebral hemorrhage. Studies have shown that hirudin extract contains anti-inflammatory enzymes and has anti-inflammatory effects. Studies of Bao Zonglinetal.[10]showed that hirudos could also play a certain role in the treatment of chronic viral hepatitis. Wu Yingetal.[11]confirmed that the use of hirudin in the early stage of cerebral hemorrhage on the basis of controlling cerebral hemorrhage could reduce the brain tissue injury in the acute stage.

3.4 Anti-tumorStudies have shown that hirudin can inhibit the growth of tumor cells by inhibiting the effect of thrombin. Cui Meiyueetal.[12]found that the active factor of hirudin had obvious inhibitory effect on S180 tumor. Yu Ruifaetal.[13]found that the extract of hirudos had a strong inhibitory effect on transplanted tumor in mice. In addition, Li Xiaojuetal.[14]found that hirudos could improve the anoxic microenvironment of tumor, thus inhibiting tumor angiogenesis and playing an anti-tumor effect.

4 Culture

4.1 Status of cultureDue to the deterioration of the environment in recent years, the wild resources of hirudos have decreased sharply, so many areas begin to carry out breeding and achieved success.

At present, the hirudos cultivated artificially and used as medicine in China are mainlyW.pigraWhitman andP.manillensisLesson, but the breeding time is short, the scale is small, the technology is poor, and the yield is low.

At present, the culture models include cage culture, cement pond culture and box culture. Nowadays, through soilless three-dimensional high-density culture of hirudos, the problem that hirudos can not be cultured in the north has been greatly solved. And it has three advantages: first, the management is convenient; second, the water exchange system is automated; third, the breeding cost is low, and one investment can bring year-on-year benefits. However, the current hirudos culture still has the problem of less cocoon production and low cocoon quality after overwintering, so efforts should be made to break through the problem of hirudos cocoon production over the winter. Only in this way can the closed-loop production of hirudos be realized.

4.2 Selection of culture conditionsHirudos come up in March or April in the Yangtze River Basin, and the mating period is generally from late April to early May. The temperature in this area is 20-25 ℃ during the day and 10 ℃ at night in April and May. The results of Liu Fei’s research found that the optimum spawning temperature of hirudo was 25 ℃, which was basically consistent with its biological habits. Temperature plays a very important role in the process of hirudos hatching. When the temperature is lower than 15 ℃, the hirudos hatching rate is very low, the hirudos can not hatch above 35 ℃, the hatching rate is the highest at about 25 ℃, and the hatching time of eggs at 25 ℃ is about one week earlier than that at room temperature. At the same temperature, there are significant differences in the number of eggs laid by hirudos with different body weight. The results showed that the number of eggs laid by hirudos with body weight of about 20 g was the highest, while the number of eggs laid by hirudos with body weight of over 30 g decreased, which may be related to their reproductive development. The egg weight was positively correlated with the hatching amount in the range of 0.1-2.0 g, and the hatching amount decreased when the egg weight was more than 2.0 g, so the eggs of about 2.0 g should be selected in artificial reproduction.

5 Conclusions

Hirudo is an aquatic animal used as traditional Chinese special medicinal. In history, wild hirudos were mainly caught naturally. In recent years, due to environmental pollution, deterioration of water quality and abuse of chemical fertilizers and pesticides, the living conditions of hirudos have deteriorated and the natural population has gradually decreased. In addition, overfishing makes hirudos wild resources face depletion. With the increase of cardiovascular and cerebrovascular diseases in recent years, and the continuous development of hirudo-containing proprietary Chinese medicine, its market demand is increasing, and it has become one of the most popular traditional Chinese medicines. Therefore, the importance of maintaining the sustainable utilization of hirudo resources should be fully recognized and the sustainable development system of hirudo resources should be established. In view of this, the species of medicinal hirudos should be further expanded and the research work on the species outside the Pharmacopoeia should be strengthened in order to supplement the species of hirudos in theChinesePharmacopoeia. In addition, we should dynamically monitor the distribution and resource status of hirudos, strengthen the research on hirudo population ecology, improve the consciousness of hirudo resource protection, establish hirudos reserves, and study the artificial culture technology of hirudos, vigorously develop artificial hirudo culture industry to ensure the sustainable development of traditional Chinese medicine resources of hirudos.