A Protein from Aloe vera that Inhibits the Cleavage of Human Fibrin(ogen) by Plasmin

Plant-Derived Compounds and Extracts as Modulators of Plasmin Activity-A Review

Functionality of the fibrinolytic system is based on activity of its central enzyme, plasmin, responsible for the removal of fibrin clots. Besides the hemostasis, fibrinolytic proteins are also involved in many other physiological and pathological processes, including immune response, extracellular matrix degradation, cell migration, and tissue remodeling. Both the impaired and enhanced activity of fibrinolytic proteins may result in serious physiological consequences: prothrombotic state or excessive bleeding, respectively. However, current medicine offers very few options for treating fibrinolytic disorders, particularly in the case of plasmin inhibition. Although numerous attempts have been undertaken to identify natural or to develop engineered fibrinolytic system modulators, structural similarities within serine proteases of the hemostatic system and pleiotropic activity of fibrinolytic proteins constitute a serious problem in discovering anti- or profibrinolytic agents that could precisely affect the target molecules and reduce the risk of side effects. Therefore, this review aims to present a current knowledge of various classes of natural inhibitors and stimulators of the fibrinolytic system being well-defined low-molecular plant secondary metabolites or constituents of plant extracts as well as plant peptides. This work also discusses obstacles caused by low specificity of most of natural compounds and, hence, outlines recent trends in studies aimed at finding more efficient modulators of plasmin activity, including investigation of modifications of natural pharmacophore templates.

Therapeutic effects of Aloe spp. in traditional and modern medicine: A review

Traditional medicine is a useful guide in medical sciences. In the Islamic Iranian traditional medicine, the medicinal properties of many plants have been mentioned that could be exploited in drug discovery. We aimed to explore the nature and properties of Aloe spp. As described in some major Islamic traditional texts including Ferdows al-Hekmah fi'l-Tibbe (The Paradise of Wisdom in Medicine), Al-Hawi fi'l-Tibb (Comprehensive Book of Medicine), Kamel al-Sanaat al-Tibbyyah (Complete Book of the Medical Art), Al-Qanun fi'l-Tibb (Canon of Medicine), Zakhireh Kharazmshahi (Treasure of Kharazmshah), and Makhzan al-Adwiah (Drug Treasure), and assess the conformity of traditional medicine instructions with the findings of modern pharmacological studies. Gastrointestinal activities, hepato-protective properties, beneficial effects against skin problems such as wounds, injuries, and infective diseases are among the most frequently mentioned properties of Aloe spp. Several activities of Aloe spp. described in traditional medicine have been the subject of recent in vitro and in vivo studies as well as clinical trials. Owing to the positive findings, different preparations of Aloe spp. are now present in pharmaceutical markets such as Aloe cosmetic products. On the other hand, there are many traditional therapeutic effects of Aloe spp. which have not been studied and require confirmatory experimental or clinical investigations. It is hoped that the present study could stimulate further research on the unexplored aspects of the medicinal properties of Aloe spp.

Protein-rich fraction of Cnidoscolus urens (L.) Arthur leaves: enzymatic characterization and procoagulant and fibrinogenolytic activities

Proteolytic enzymes are important macromolecules in the regulation of biochemical processes in living organisms. Additionally, these versatile biomolecules have numerous applications in the industrial segment. In this study we have characterized a protein-rich fraction of Cnidoscolus urens (L.) Arthur leaves, rich in proteolytic enzymes, and evaluated its effects on the coagulation cascade. Three protein-rich fractions were obtained from the crude extract of C. urens leaves by precipitation with acetone. Fraction F1.0 showed higher proteolytic activity upon azocasein, and thus, was chosen for subsequent tests. The proteolytic activity of F1.0 on fibrinogen was dose-dependent and time-dependent. The extract demonstrated procoagulant activity on citrated plasma and reduced the APTT, not exerting effects on PT. Despite the fibrin(ogen)olytic activity, F1.0 showed no defibrinogenating activity in vivo. The fraction F1.0 did not express hemorrhagic nor hemolytic activities. The proteolytic activity was inhibited by E-64, EDTA and in the presence of metal ions, and increased when pretreated with reducing agents, suggesting that the observed activity was mostly due to cysteine proteases. Several bands with proteolytic activity were detected by zymography with gelatin, albumin and fibrinogen. The optimal enzymatic activity was observed in temperature of 60 °C and pH 5.0, demonstrating the presence of acidic proteases. In conclusion, these results could provide basis for the pharmacological application of C. urens proteases as a new source of bioactive molecules to treat bleeding and thrombotic disorders.