... in which we learn about many beneficial (or harmful) compounds isolated from plants and animals.
"Molecules that affect the heart are not found only in plants. Toxic compounds that are similar in structure to the cardiac glycosides are found in animals. These molecules do not contain sugars, nor are they used as heart stimulants. Rather, they are convulsive poisons and of little medical value. The source of these venoms is amphibians; extracts from toads and frogs have been used as arrow poisons in many parts of the world. Interestingly, the toad is, after the cat, the most common animal attributed in folklore as a familiar to a witch. Many potions prepared by so-called witches were said to contain parts of toads. The molecule bufotoxin is the active component of the venom of the common European toad, Bufo vulgaris, and is one of the most toxic molecules known. "
"Alkaloids are often physiologically active in humans, usually affecting the central nervous system, and are generally highly toxic. Some of these naturally occurring compounds have been used as medicines for thousands of years. Derivatives made from alkaloids form the basis of a number of our modern pharmaceuticals, such as the pain-relieving molecule codeine, the local anesthetic benzocaine, and chloroquine, an antimalarial agent."
"Toxicity alone has been enough to ensure fame for some alkaloids. The poisonous component of the hemlock plant, Conium maculatum, responsible for the death of the philosopher Socrates in 399 B.C., is the alkaloid coniine. Socrates, convicted on charges of irreligion and the corruption of the young men of Athens, was sentenced to death by drinking a potion made from the fruit and seeds of hemlock. Coniine has one of the simplest structures of all the alkaloids, but it can be just as lethal a poison as more complicated alkaloid structures such as that of strychnine, from the seeds of the Asiatic tree Strychnos nux-vomica."
"As bizarre as it might seem, the poisonous compound atropine acts as an antidote for groups of even more toxic compounds. Nerve gases such as sarin—released by terrorists in the Tokyo subway in April of 1995—and organophosphate insecticides, such as parathion, act by preventing the normal removal of a messenger molecule that transmits a signal across a nerve junction. When this messenger molecule is not removed, nerve endings are continuously stimulated, which leads to convulsions and, if the heart or lungs are affected, to death. Atropine blocks the production of this messenger molecule, so provided the right dosage is given, it is an effective remedy for sarin or parathion."
"The effects of some of the alkaloid molecules from this group can be so devastating that whole communities, afflicted with horrendous suffering, assumed that the catastrophe was the result of an evil spell cast by local witches. This group of alkaloids is found in the ergot fungus, Claviceps purpurea, that infects many cereal grains but especially rye. Ergotism or ergot poisoning was until fairly recently the next-largest microbial killer after bacteria and viruses. One of these alkaloids, ergotamine, causes blood vessels to constrict; another, ergonovine, induces spontaneous abortions in humans and livestock; while others cause neurological disturbances. Symptoms of ergotism vary depending on the amount of the different ergot alkaloids present but can include convulsions, seizures, diarrhea, lethargy, manic behavior, hallucinations, distortion of the limbs, vomiting, twitching, a crawling sensation on the skin, numbness in the hands and feet, and a burning sensation becoming excruciatingly painful as gangrene from decreased circulation eventually sets in. "
"Like cocaine, ergot alkaloids, although toxic and dangerous, have had a long history of therapeutic use, and ergot derivatives still play a role in medicine. For centuries herbalists, midwives, and doctors used extracts of ergot to hasten childbirth or produce abortions. Today ergot alkaloids or chemical modifications of these compounds are used as vasoconstrictors for migraine headaches, to treat postpartum bleeding, and as stimulants for uterine contractions in childbirth."
"The alkaloids of ergot all have the same common chemical feature; they are derivatives of a molecule known as lysergic acid."