What is the medicinal effect of leeches?

Many countries in the world used the blood-sucking habit of medical leeches to bleed patients in ancient times, especially in Europe. Many places collect medical leeches and even cultivate them artificially in ponds. Medical leeches were used earlier in China, and it was recorded in ancient books that hungry leeches were put into bamboo tubes and buckled on washed skin to suck blood to cure red, white and lead swelling. However, it is more important to use leeches as medicine. Leech was first found in Shennong's Classic of Materia Medica in China, then in Compendium of Materia Medica and China Animal Medicine, among which Compendium of Materia Medica comprehensively recorded the pharmacological action and usage of leech. With the summary of Li Shizhen's Compendium of Materia Medica in Ming Dynasty, it was mainly used to treat traumatic injury, hemorrhage and postpartum dizziness. At present, it is recorded in the Pharmacopoeia that leeches have the functions of breaking blood, dredging menstruation, resolving food stagnation, reducing swelling and detoxifying. Dried leech is used as medicine, and contains hirudin and protein. It has the effects of anticoagulation and blood stasis, and is mainly used to treat hematological diseases, vascular diseases, blood stasis, innominate swelling, lymphoid tuberculosis and other diseases. In recent years, medical workers have tried to make water and injections for external use with live leeches and pure honey to treat the trigger period and swelling period of corneal macula and senile cataract, which can make the turbid body gradually transparent. Hirudin can also relieve arterial spasm and reduce blood pressure adhesion, so it can significantly relieve the symptoms of hypertension. Some people use leeches in combination with other blood-activating and antidotes to treat tumors. At present, cardiovascular and cerebrovascular diseases have become common and frequently-occurring diseases at home and abroad, so the demand for leeches is increasing year by year. 1. Hirudin is an anticoagulant protein extracted from leech. In 1884, Haycraft first discovered that European leech extract has anticoagulant properties and effects. 1904, Jacoby et al. isolated anticoagulant from leech for the first time, and officially named it hirudin; 1954, Mark wardt and others isolated pure hirudin from the salivary gland of leech head, and began to study its composition, structure and physical and chemical properties. In 1955, he pointed out that this anticoagulant is protein; In 1970s, hirudin was identified as a natural polypeptide compound, and its primary structure was analyzed. Hirudin is a polypeptide isolated from hirudin, which has anticoagulant activity similar to hirudin and inhibits thrombin. It is also composed of more than 60 amino acids with a molecular weight of more than 7000. Sequence analysis showed that 50% ~ 60% amino acid residues were the same as hirudin. Its three-dimensional structure and configuration need further study. Its immunosuppressive activity is different from hirudin. Fibrinolytic enzyme is a neutral metalloprotease, isolated from giant leech in South America, and its molecular weight is 120000. Degrade fibrinogen and fibrin, destroy the peptide bond between them, and coagulate without interacting with thrombin, thus playing an anticoagulant role. Its function is similar to that of some snake venom, but its mechanism is different. Fibrinolytic enzyme isolated from bloodsucking leeches in Brazil has an anticoagulant effect similar to that of streptokinase, and the fibrinogen preactivator is the activator of fibrinolytic preactivator. Dacorson, a leech isolated from North America, antagonizes fibrinogen receptor on platelet membrane and inhibits platelet aggregation. When its concentration reached 1mmol, platelet aggregation was completely inhibited. It is composed of 39 amino acids with a molecular weight of more than 4,000. Coagulation factor Xa inhibitor, isolated from European medical leech, only inhibits Xa, but not thrombin. Mild effect, regulating blood coagulation. In this paper, several effective components of leech for promoting blood circulation are briefly introduced, and the discovered components such as hirudin are undergoing large-scale clinical trials. Many leech scientists and biochemical experts continue to explore new components from various leeches. The salivary glands of bloodsucking leeches all contain anticoagulant substances, which prevent the blood of the host from clotting, which is beneficial to blood sucking and prevents the inhaled blood from clotting in the intestine. Through extensive study of anticoagulant substances in leeches, it is possible to obtain new components with blood circulation promoting effect. China has done a lot of work in pharmacological experiments and clinical application of leech, but the research on its effective components is far from the international level. 2. Structure and anticoagulant mechanism of hirudin Many active components, such as hirudin, Egelin and hirudin, have been extracted from medical hirudin and its saliva. Hirudin is a polypeptide composed of more than 60 amino acids, most of which contain 65 amino acids, and some isomers contain 64 to 69 amino acids. Natural hirudin contains many isomers. The n-terminal of hirudin peptide chain is surrounded by three disulfide bonds, forming a dense region, and the c-terminal is hydrophobic, rich in acidic amino acids, hydrophilic and extending on the molecular surface. More than 10 isomers have been isolated and identified. The secondary and tertiary structure of hirudin plays a decisive role in its anticoagulant activity, and disulfide bond is the key to determine its molecular configuration stability and maintain high anticoagulant activity. When disulfide bonds are oxidized or reduced, or molecules are degraded by protein, they lose anticoagulant activity. If the carboxyl group of hirudin is esterified, or the acidic C-terminal amino acid is lost, the ability to bind thrombin will also be lost. Natural hirudin has anticoagulant effect. Different sources and structures of hirudin have different anticoagulant mechanisms. Natural hirudin can affect coagulation and thrombosis in many ways. 1) antithrombin effect The antithrombin effect of hirudin can be found in European medical leeches, Asian buffalo leeches and Indian leeches. These hirudins contain six cysteine residues with similar distribution. This structure can make hirudin and thrombin form a stable complex in the ratio of 1: 1, which has a highly specific inhibitory effect on thrombin and plays an anticoagulant role in inhibiting thrombin. 2) Other Anticoagulant Effects In 1988, a polypeptide consisting of 1 19 amino acid residues was extracted from the salivary gland of leech in Mexico. Containing cysteine residue, it can specifically and reversibly combine with factor XA to form a complex, which plays an anticoagulant role. Recently, an anti-factor XIII, a substance containing 66 amino acid residues, was found in giant leeches in Amazon. It is the strongest factor XIII specific inhibitor found so far, and also inhibits other transglutaminase, which can completely inhibit the cross-linking reaction of fibrin monomer and play an anticoagulant role. 3) Antiplatelet Effect 1992 An antiplatelet protein called leech was extracted from Mexican leech. It can specifically inhibit platelet aggregation induced by collagen. From 65438 to 0994, a polypeptide containing 39 amino acid residues was extracted from leech in North America. Its three-dimensional conformation is very similar to hirudin, which can inhibit fibrinogen-mediated platelet aggregation. 4) Degradation of fibrinogen 1984 A substance extracted from the giant leech of Amazon can degrade the specific peptide chain of fibrinogen, thus preventing thrombosis and dissolving the formed thrombus.