For more than half a century, cytotoxic agents have been investigated as a possible treatment for cancer. Research on animal venoms has revealed their high toxicity on tissues and cell cultures, both normal and tumoral. Snake venoms show the highest cytotoxic potential, since ophidian accidents cause a large amount of tissue damage, suggesting a promising utilization of these venoms or their components as antitumoral agents. Over the last few years, we have studied the effects of snake venoms and their isolated enzymes on tumor cell cultures. Some in vivo assays showed antineoplastic activity against induced tumors in mice. In human beings, both the crude venom and isolated enzymes revealed antitumor activities in preliminary assays, with measurable clinical responses in the advanced treatment phase. These enzymes include metalloproteases (MP), disintegrins, L-amino acid oxidases (LAAOs), C-type lectins, and phospholipases A2 (PLA2s). Their mechanisms of action include direct toxic action (PLA2s), free radical generation (LAAOs), apoptosis induction (PLA2s, MP, and LAAOs), and antiangiogenesis (disintegrins and lectins). Higher cytotoxic and cytostatic activities upon tumor cells than normal cells suggest the possibility for clinical applications. Further studies should be conducted to ensure the efficacy and safety of different snake venom compounds for cancer drug development.

L-amino acid oxidases are enzymes found in several organisms, including venoms of snakes, where they contribute to the toxicity of ophidian envenomation. Their toxicity is primarily due to enzymatic activity, but other mechanisms have been proposed recently which require further investigation. L-amino acid oxidases exert biological and pharmacological effects, including actions on platelet aggregation and the induction of apoptosis, hemorrhage, and cytotoxicity. These proteins present a high biotechnological potential for the development of antimicrobial, antitumor, and antiprotozoan agents. This review provides an overview of the biochemical properties and pharmacological effects of snake venom L-amino acid oxidases, their structure/activity relationship, and supposed mechanisms of action described so far.

Screening for new bioactive peptides in South American anurans has been pioneered in frogs of the genus Phyllomedusa. All frogs of this genus have venomous skin secretions, i.e., a complex mixture of bioactive peptides against potential predators and pathogens that presumably evolved in a scenario of predator-prey interaction and defense against microbial invasion. For every new anuran species studied new peptides are found, with homologies to hormones, neurotransmitters, antimicrobials, and several other peptides with unknown biological activity. From Vittorio Erspamer findings, this genus has been reported as a "treasure store" of bioactive peptides, and several groups focus their research on these species. From 1966 to 2009, more than 200 peptide sequences from different Phyllomedusa species were deposited in UniProt and other databases. During the last decade, the emergence of high-throughput molecular technologies involving de novo peptide sequencing via tandem mass spectrometry, cDNA cloning, pharmacological screening, and surface plasmon resonance applied to peptide discovery, led to fast structural data acquisition and the generation of peptide molecular libraries. Research groups on bioactive peptides in Brazil using these new technologies, accounted for the exponential increase of new molecules described in the last decade, much higher than in any previous decades. Recently, these secretions were also reported as a rich source of multiple antimicrobial peptides effective against multidrug resistant strains of bacteria, fungi, protozoa, and virus, providing instructive lessons for the development of new and more efficient nanotechnological-based therapies for infectious diseases treatment. Therefore, novel drugs arising from the identification and analysis of bioactive peptides from South American anuran biodiversity have a promising future role on nanobiotechnology.

Ophidian envenomation is an important health problem in Brazil and other South American countries. In folk medicine, especially in developing countries, several vegetal species are employed for the treatment of snakebites in communities that lack prompt access to serum therapy. However, the identification and characterization of the effects of several new plants or their isolated compounds, which are able to inhibit the activities of snake venom, are extremely important and such studies are imperative. Snake venom contains several organic and inorganic compounds; phospholipases A2 (PLA2s) are one of the principal toxic components of venom. PLA2s display a wide variety of pharmacological activities, such as neurotoxicity, myotoxicity, cardiotoxicity, anticoagulant, hemorrhagic, and edema-inducing effects. PLA2 inhibition is of pharmacological and therapeutic interests as these enzymes are involved in several inflammatory diseases. This review describes the results of several studies of plant extracts and their isolated active principles, when used against crude snake venoms or their toxic fractions. Isolated inhibitors, such as steroids, terpenoids, and phenolic compounds, are able to inhibit PLA2s from different snake venoms. The design of specific inhibitors of PLA2s might help in the development of new pharmaceutical drugs, more specific antivenom, or even as alternative approaches for treating snakebites.

In the present study, micronucleus with cytokinesis blocking and comet assays were used to evaluate the genotoxic potential of Bothrops jararacussu, Bothrops atrox, Bothrops moojeni, Bothrops alternatus (Rhinocerophis alternatus) and Bothrops brazili snake venoms, and also of some isolated toxins (MjTX-I, BthTX-I and II myotoxins, BjussuMP-II metalloprotease, and BatxLAAO l-amino acid oxidase) on human lymphocytes. Significant DNA damages were observed, indicating genotoxic potential after exposure of the lymphocytes to the toxins BthTX-I, II and BatxLAAO compared to untreated and Cisplatin-treated controls, which were able to induce greater formation of micronuclei. B. brazili, B. jararacussu and B. atrox crude venoms also presented genotoxic potential, and the latter two induced DNA breakage 5 times more often than in normal environmental conditions (control without treatment). B. jararacussu venom and its isolated toxins, as well as an LAAO from B. atrox, were able to cause lymphocyte DNA breakage in the comet test with more than 85% damage levels. The DNA damage evaluation allows a widening of the toxic-pharmacological characterization of snake venoms and their toxins and also contributes to the understanding of the mechanisms of action of these molecules in several human pathologies.

Antivenoms, produced using animal hyperimmune plasma, remains the standard therapy for snakebites. Although effective against systemic damages, conventional antivenoms have limited efficacy against local tissue damage. Additionally, the hypersensitivity reactions, often elicited by antivenoms, the high costs for animal maintenance, the difficulty of producing homogeneous lots, and the instability of biological products instigate the search for innovative products for antivenom therapy. In this study, camelid antibody fragments (VHH) with specificity to Bothropstoxin I and II (BthTX-I and BthTX-II), two myotoxic phospholipases from Bothrops jararacussu venom, were selected from an immune VHH phage display library. After biopanning, 28 and 6 clones recognized BthTX-I and BthTX-II by ELISA, respectively. Complementarity determining regions (CDRs) and immunoglobulin frameworks (FRs) of 13 VHH-deduced amino acid sequences were identified, as well as the camelid hallmark amino acid substitutions in FR2. Three VHH clones (KF498607, KF498608, and KC329718) were capable of recognizing BthTX-I by Western blot and showed affinity constants in the nanomolar range against both toxins. VHHs inhibited the BthTX-II phospholipase A2 activity, and when tested for cross-reactivity, presented specificity to the Bothrops genus in ELISA. Furthermore, two clones (KC329718 and KF498607) neutralized the myotoxic effects induced by B. jararacussu venom, BthTX-I, BthTX-II, and by a myotoxin from Bothrops brazili venom (MTX-I) in mice. Molecular docking revealed that VHH CDRs are expected to bind the C-terminal of both toxins, essential for myotoxic activity, and to epitopes in the BthTX-II enzymatic cleft. Identified VHHs could be a biotechnological tool to improve the treatment for snake envenomation, an important and neglected world public health problem.

Snake venoms are natural sources of biologically active molecules that are able to act selectively and specifically on different cellular targets, modulating physiological functions. Thus, these mixtures, composed mainly of proteins and peptides, provide ample and challenging opportunities and a diversified molecular architecture to design and develop tools and agents of scientific and therapeutic interest. Among these components, peptides and small proteins play diverse roles in numerous physiological processes, exerting a wide range of pharmacological activities, such as antimicrobial, antihypertensive, analgesic, antitumor, analgesic, among others. The pharmaceutical and cosmetic industries have recognized the huge potential of these privileged frameworks and believe them to be a promising alternative to contemporary drugs. A number of natural or synthetic peptides from snake venoms have already found preclinical or clinical applications for the treatment of pain, hypertension, cardiovascular diseases and aging skin. A well-known example is captopril, whose natural peptide precursor was isolated from Bothrops jararaca snake venom, which is a peptide-based drug that inhibits the angiotensin-converting enzyme, producing an anti-hypertensive effect. The present review looks at the main peptides (natriuretic peptides, bradykinin-potentiating peptides and sarafotoxins) and low mass proteins (crotamine, disintegrins and three-Finger toxins) from snake venoms, as well as synthetic peptides inspired by them, describing their biochemical, structural and physiological features, as well as their applications as research tools and therapeutic agents.

Bothrops mattogrossensis snake is widely distributed throughout eastern South America and is responsible for snakebites in this region. This paper reports the purification and biochemical characterization of three new phospholipases A2 (PLA2s), one of which is presumably an enzymatically active Asp49 and two are very likely enzymatically inactive Lys49 PLA2 homologues. The purification was obtained after two chromatographic steps on ion exchange and reverse phase column. The 2D SDS-PAGE analysis revealed that the proteins have pI values around 10, are each made of a single chain, and have molecular masses near 13 kDa, which was confirmed by MALDI-TOF mass spectrometry. The N-terminal similarity analysis of the sequences showed that the proteins are highly homologous with other Lys49 and Asp49 PLA2s from Bothrops species. The PLA2s isolated were named BmatTX-I (Lys49 PLA2-like), BmatTX-II (Lys49 PLA2-like), and BmatTX-III (Asp49 PLA2). The PLA2s induced cytokine release from mouse neutrophils and showed cytotoxicity towards JURKAT (leukemia T) and SK-BR-3 (breast adenocarcinoma) cell lines and promastigote forms of Leishmania amazonensis. The structural and functional elucidation of snake venoms components may contribute to a better understanding of the mechanism of action of these proteins during envenomation and their potential pharmacological and therapeutic applications.