This blog post explores how the complex structure and diverse functions of alkaloids have influenced medicine and society from the Middle Ages to the modern era.
According to modern chemical knowledge, the drug that put Juliet to sleep was an extract from belladonna. This drug was used in the Middle Ages to dilate pupils, but in large doses, it was a so-called poison that could induce a coma. To medieval people, lacking modern chemical knowledge, it likely seemed like nothing more than a witch’s magic potion. Belladonna itself means ‘beautiful woman,’ a name derived from its use by women of the time to make their eyes appear more captivating. However, this beauty came at a deadly price, and many people in the Middle Ages likely used it unaware of its dark side.
And mandrake wasn’t the only plant with such magical-seeming properties; there were various others. Mandrake, which appears in Harry Potter, and henbane, which killed Hamlet’s father in the play Hamlet, were among them. These plants were notorious for their toxicity and frequently featured in legends and folklore due to their potent effects. The common thread among these plants is their alkaloid content. Now, let’s explore what alkaloids are, their characteristics, which herbs contain which alkaloids, and how they work.
What are alkaloids? Alkaloids are a group of organic nitrogen compounds encompassing about 250 types of organic substances, including well-known compounds like caffeine, morphine, and nicotine, also called plant bases. Most are extracted from natural plants, though some are artificially synthesized in laboratories. As complex and diverse in structure as they are, their functions are also extremely wide-ranging. While there is no universal method for classifying these alkaloids, they are often grouped into categories such as true alkaloids and primitive alkaloids based on their chemical structure. Because they influence various physiological processes in the human body, they are used in medicines, poisons, and narcotics. Some alkaloids alter human senses or psychological states.
The precise role alkaloids play within the plants that produce them remains unclear. However, one undeniable fact is that alkaloids exert unique effects on animal physiology, particularly the central nervous system. For instance, alkaloids can either inhibit or amplify nerve signal transmission. This explains why they provide analgesic effects in small doses but exhibit severe toxicity when ingested in excess. Thus, while they are generally toxic substances dangerous in large quantities, they are also compounds commonly used in pharmaceuticals. As medicines, alkaloids have a long history. Records indicate they were used medicinally in Mesopotamian civilization around 2000 BCE. Since then, many alkaloids have been utilized in shamanistic rituals or folk remedies. Some of these effects caused hallucinations, which became a root cause of witch hunts during the Middle Ages. In modern times, they form the basis of numerous pharmaceuticals, such as the analgesic codeine, the local anesthetic benzocaine, and the effective malaria drug chloroquine.
During the Middle Ages, when medical knowledge was limited, people relied on folk remedies and ritualistic practices to treat the sick. Many herbs were used for disease treatment and pain relief. Notable examples include wild celery (to prevent muscle spasms) and ivy (to alleviate asthma). Digitalis, a highly effective cardiac glycoside, was extracted from foxglove. Cardiac glycosides like digoxin, extracted from foxglove, remain crucial components widely used in treating heart disease today. Similarly, salicylic acid, used before aspirin was developed, was derived from willow bark. Thus, many modern pharmaceuticals originated from medicinal herbs; unfortunately, some also became the source of illegal narcotics. Datura plants are widely distributed throughout the world’s temperate regions. It has long been known that mixing their seeds with tobacco induces hallucinations. This hallucinogenic component is atropine, a compound with a structure very similar to cocaine. Cocaine is also an alkaloid, extracted and purified from the leaves of the coca plant in South America. Another narcotic is morphine, used to alleviate severe pain. Morphine is still used as an analgesic due to its exceptional efficacy; it is an extract from the opium poppy.
What causes the physiological effects of alkaloids? Although the role of alkaloids is unclear, the prevailing view is that they likely evolved to protect plants. This is because alkaloids produce beneficial effects when ingested in small quantities but become lethal toxins when consumed in excess. This characteristic suggests they may have developed as part of a defense mechanism for plants to protect themselves in nature. Furthermore, the fact that important neurotransmitters in the central nervous system—such as serotonin, dopamine, and histamine—are linked to alkaloids provides a crucial clue to understanding their complex roles. Of course, the precise action principles and mechanisms differ for each alkaloid molecule, making this one of the important challenges modern chemistry must solve.
No matter how advanced modern technology becomes, the source of human life remains rooted in the great outdoors. Alkaloids vividly illustrate this deep connection between nature and humanity. For thousands of years, alkaloids have been used by humankind as medicinal herbs, and they remain the source of many pharmaceuticals today. Their applications extend far beyond medicine; they are also widely used as beverage ingredients and food additives. However, the numerous disasters caused by the misuse of these alkaloids underscore the critical importance of their wise use. Modern society must harness the full potential of alkaloids while clearly recognizing their risks and possessing the wisdom to manage them effectively.
