Bioactive Ingredients of the Leech Body and Saliva

Leeches are a class of segmented invertebrates, known for their blood-feeding habits and used in phlebotomy to treat various ailments since antiquity. In Europe, medicinal leeches have recently been rediscovered and are used by maxillofacial and other microsurgeons to aid salvage of compromised venous engorged tissue and amputations, such as digits, ears, and nasal tips. Because of their important salivary components, blood-sucking (sanguivorous) leeches, such as Hirudo medicinalis and related species, have engendered great interest from pharmaceutical companies searching for anticoagulants to prevent blood clotting during microsurgeries. Scienti!c research reveals that the bene!cial e"ects of leeching, in addition to decongestion, include injection of a cocktail of several medicinally useful bioactive molecules present in their saliva. Owing to its therapeutic potential, the research is continuing as many new salivary compounds are being isolated and synthesized. (Altern Med Rev 2011;16(1):59-65) Introduction Leeches are sanguivorous or blood-sucking annelid worms with ability to extend or contract their bodies. Table 1 describes leech taxonomy. Since antiquity, they have been known for their blood-feeding habits and use in the art of phlebotomy or bloodletting. Although this practice fell into disrepute by the end of the 19th century, it always occupied an important place in the Unani system of medicine to treat various ailments. Most leeches are permanent or temporary external parasites, attaching themselves to the host and sucking blood. Sucked blood is stored in lateral diverticula of the crop and, as the blood passes down the pharynx, it is mixed with a glandular secretion that prevents its coagulation. At a single meal a leech ingests several times its own weight of blood that may suffice for several months.1,2 Recent scientific research on salivary components has restored its lost reputation. Hirudo medicinalis is the most frequently used species of leech (Figure 1) that is not native to the Indian subcontinent. In India the species used traditionally for therapeutic purposes is Hirudinaria granulosa. Besides these, Macrobdella decora (American medicinal leech), Hirudo michaelseni, Hirudo nipponia, Hirudo verbena, and Hirudo orientalis5-9 are also being used for therapeutic purposes (Figure 2). Bioactive Ingredients of the Leech Body and Saliva As mentioned previously, scientific research reveals the beneficial effect of leeching occurs via blood decongestion and injection of a cocktail of several medicinally useful bioactive molecules present in their saliva.10-12 Hirudin In 1950, Fritz Marquardt of Germany isolated a protein from Hirudo medicinalis that he termed hirudin.13-15 He also demonstrated its thrombin inhibitor effect. As a heparin-like substance, it is the most potent known natural inhibitor of thrombin. Due to its high affinity for thrombin, hirudin inhibits almost all the physiological actions of thrombin. It does not cross-react in vitro with antibodies from patients with heparin-induced thrombocytopenia. In fact, its administration has exhibited no side effects, including effects on platelets. A thrombin inhibitor similar to hirudin, known as bufrudin, has been isolated from the leech Hirudo manillensis, which differs in its structural and S.M. Abbas Zaidi, MD – Lecturer, Department of Moalijat (Medicine), H.S.Z.H. Govt. Unani Medical College, Bhopal (M.P.), India Correspondence address: H.S.Z.H. Govt. Unani Medical College, Behind MANIT, Nehru Nagar-Kolar Bypass Road, Bhopal (M.P.), India Email: [email protected] S.S. Jameel MD (Unani) – Director General, Central Council for Research in Unani Medicine, New Delhi & Professor and Head, Department of Moalijat (Medicine); Faculty of Unani Medicine, Hamdard University, New Delhi, India 110062 F. Zaman, MD (Unani) – Senior Lecturer, Department of Moalijat (Medicine), Faculty of Unani Medicine, Hamdard University, New Delhi, India 110062 Shazia Jilani, MD (Unani) – Lecturer, Department of Taha!uzi wa Samaji Tibb (PSM); Faculty of Unani Medicine, Hamdard University, New Delhi, India 110062 A. Sultana M.D. (Unani) Senior Lecturer, Department of Moalijat (Medicine), Faculty of Unani Medicine, Hamdard University, New Delhi, India, 110062 Shariq A. Khan, MD (Unani) – Assistant Director & Incharge, Clinical Research Unit (Unani Medicine), CCRUM, Aligarh (U.P.), India A Systematic Overview of the Medicinal Importance of Sanguivorous Leeches S.M. Abbas Zaidi, MD; S.S. Jameel, MD; F. Zaman, MD; Shazia Jilani, MD; A. Sultana, MD; Shariq A. Khan, MD