Cardiac glycosides are a class of organic compounds that increase the output force of the heart and decrease its rate of contractions by inhibiting the cellular sodium-potassium ATPase pump. Their beneficial medical uses are as treatments for congestive heart failure and cardiac arrhythmias; however, their relative toxicity prevents them from being widely used. Most commonly found as secondary metabolites in several plants such as foxglove plants, these compounds nevertheless have a diverse range of biochemical effects regarding cardiac cell function and have also been suggested for use in cancer treatment.
The sodium–potassium pump is an enzyme found in the membrane of all animal cells. It performs several functions in cell physiology.
Ouabain or also known as g-strophanthin, is a plant derived toxic substance that was traditionally used as an arrow poison in eastern Africa for both hunting and warfare. Ouabain is a cardiac glycoside and in lower doses, can be used medically to treat hypotension and some arrhythmias. It acts by inhibiting the Na/K-ATPase, also known as the sodium–potassium ion pump. However, adaptations to the alpha-subunit of the Na+/K+-ATPase via amino acid substitutions, have been observed in certain species, namely some herbivore- insect species, that have resulted in toxin resistance.
Cerberin is a type of cardiac glycoside, a steroidal class found in the seeds of the dicotyledonous angiosperm genus Cerbera; including the suicide tree and the sea mango. This class includes digitalis-like agents, channel-blockers that as a group have found historic uses as cardiac treatments, but which at higher doses are extremely toxic; in the case of cerberin, consumption of the C. odollam results in poisoning with presenting nausea, vomiting, and abdominal pain, often leading to death. The natural product has been structurally characterized, its toxicity is clear—it is often used as an intentional human poison in third-world countries, and accidental poisonings with fatalities have resulted from individuals even indirectly consuming the agent—but its potentially therapeutic pharmacologic properties are very poorly described.
Bufotoxins are a family of toxic steroid lactones or substituted tryptamines of which some are toxic. They occur in the parotoid glands, skin, and poison of many toads and other amphibians, and in some plants and mushrooms. The exact composition varies greatly with the specific source of the toxin. It can contain 5-MeO-DMT, bufagins, bufalin, bufotalin, bufotenin, bufothionine, dehydrobufotenine, epinephrine, norepinephrine, and serotonin. Some authors have also used the term bufotoxin to describe the conjugate of a bufagin with suberylarginine.
Bufagin is a toxic steroid C24H34O5 obtained from toad's milk, the poisonous secretion of a skin gland on the back of the neck of a large toad (Rhinella marina, synonym Bufo marinus, the cane toad). The toad produces this secretion when it is injured, scared or provoked. Bufagin resembles chemical substances from digitalis in physiological activity and chemical structure.
Bufotalin is a cardiotoxic bufanolide steroid, cardiac glycoside analogue, secreted by a number of toad species. Bufotalin can be extracted from the skin parotoid glands of several types of toad.
Cardiotoxin III is a sixty amino-acid polypeptide toxin from the Taiwan Cobra Naja atra. CTX III is highly basic and hydrophobic protein. It is an example of a group of snake cardio/cytotoxins, which are made up of shorter snake venom three-finger toxins. Over 50 different cytotoxin polypeptides have been isolated and sequenced from venom samples. The difference in the CTX functionality may be due to the relatively small difference in the polypeptide's structure, allowing different CTXs to induce lysis in different cell types. The CTX III molecule contains multiple binding sites and is cytolytic for myocardial cells and human leukemic T cells.
Bufadienolide is a chemical compound with steroid structure. Its derivatives are collectively known as bufadienolides, including many in the form of bufadienolide glycosides. These are a type of cardiac glycoside, the other being the cardenolide glycosides. Both bufadienolides and their glycosides are toxic; specifically, they can cause an atrioventricular block, bradycardia, ventricular tachycardia, and possibly lethal cardiac arrest.
The Akt signaling pathway or PI3K-Akt signaling pathway is a signal transduction pathway that promotes survival and growth in response to extracellular signals. Key proteins involved are PI3K and Akt.
Cinobufagin is a cardiotoxic bufanolide steroid secreted by the Asiatic toad Bufo gargarizans. It has similar effects to digitalis and is used in traditional Chinese medicine.
The PI3K/AKT/mTOR pathway is an intracellular signaling pathway important in regulating the cell cycle. Therefore, it is directly related to cellular quiescence, proliferation, cancer, and longevity. PI3K activation phosphorylates and activates AKT, localizing it in the plasma membrane. AKT can have a number of downstream effects such as activating CREB, inhibiting p27, localizing FOXO in the cytoplasm, activating PtdIns-3ps, and activating mTOR which can affect transcription of p70 or 4EBP1. There are many known factors that enhance the PI3K/AKT pathway including EGF, shh, IGF-1, insulin, and CaM. Both leptin and insulin recruit PI3K signalling for metabolic regulation. The pathway is antagonized by various factors including PTEN, GSK3B, and HB9.
Convallatoxin is a glycoside extracted from Convallaria majalis.
Bufanolide is a C24 steroid and, indirectly, a parent structure of bufadienolide. Its derivatives was found in Bufo and Scilla, as an aglycone of cardiac glycosides and is usually toxic.
Bufothionine is a sulfur-containing compound which is present in the bufotoxins secreted by the parotoid gland of certain toads of the genera Bufo and Chaunus. This specific compound can be found in the skin of certain species of toad such as the Asiatic Toad, Chaunus arunco, Chaunus crucifer, Chaunus spinulosus, and Chaunus arenarum.
mTOR inhibitors are a class of drugs that inhibit the mammalian target of rapamycin (mTOR), which is a serine/threonine-specific protein kinase that belongs to the family of phosphatidylinositol-3 kinase (PI3K) related kinases (PIKKs). mTOR regulates cellular metabolism, growth, and proliferation by forming and signaling through two protein complexes, mTORC1 and mTORC2. The most established mTOR inhibitors are so-called rapalogs, which have shown tumor responses in clinical trials against various tumor types.
HuaChanSu is a traditional Chinese medicine extracted from the skin of toads from the genus Bufo that is believed by some to slow the spread of cancerous cells. The parotoid gland of toads of the Bufo genus secrete a venom, which is dried and dissolved in water. This solution, HuaChanSu, is injected into a cancerous area and targets specific cancer cells. HuaChanSu is undergoing further trials, and its effect is not completely understood.
Oxymatrine is one of many quinolizidine alkaloid compounds extracted from the root of Sophora flavescens, a Chinese herb. It is very similar in structure to matrine, which has one less oxygen atom. Oxymatrine has a variety of effects in vitro and in animal models, including protection against apoptosis, tumor and fibrotic tissue development, and inflammation. Furthermore, oxymatrine has been shown to decrease cardiac ischemia, myocardial injury, arrhythmias, and improve heart failure by increasing cardiac function.
Bufalin is a cardiotonic steroid toxin originally isolated from Chinese toad venom, which is a component of some traditional Chinese medicines.
