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The Solanaceae as Drugs and Medicine: A Natural History of the Potato Family
From: The Natural History Museum
| By:
Sandra Knapp |
EDITOR'S INTRODUCTION |
Potatoes, tomatoes and a host of other important fruit crops all belong to the Solanaceae plant family. But so do mandrakes, daturas and other poisonous and important medicinal plants. Sandra Knapp, of the department of botany at The Natural History Museum, explores the incredible diversity of this amazing plant family, focusing in part one on their use for food, and here for drugs and medicine in part two. Her study demonstrates the considerable contribution these species have made to humankind, in both positive and negative ways. |
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| Steroidal alkaloids. | |
 s well as being used for food, the Solanaceae are used widely for drugs and medicines. Many drugs are derived from solanaceous plants, including those used in shamanistic practices, for example, in the Peruvian Amazon. This is because they contain powerful alkaloids in their cells. There are two main kinds of alkaloids in members of the Solanaceae. The first are the steroidal alkaloids and one sort, the solanodine alkaloids, are found in particularly high concentrations in raw potatoes. The second main alkaloid type is the tropane alkaloids and these come in many different varieties in the Solanaceae. The tropanes are particularly interesting to alternative therapies, and occasionally their use has been quite controversial, for example, hyoscyamine or hyoscine (also called scopolamine) is known as a "truth" drug, and is rumoured to be administered to prisoners to encourage confessions. These alkaloids work by affecting the acetocholinesterase receptors in the brain, and the narcotic effect is achieved by blocking the release of normal brain chemicals. |
Tobacco
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| Flowers of tobacco, Nicotiana tabacum. | |
One of the most widely used drugs in the world today, besides alcohol, is tobacco. It is an important member of the Solanaceae and the plants from which we derive our tobaccos belong to the genus Nicotiana. Nicotiana tabacum is the most widely cultivated tobacco species, although much of the tobacco from Northern India and Afghanistan comes from the species Nicotiana rustica. These species are New World in origin, probably originating in the Andes, and there are no native Old World tobaccos, despite the fact that some people believe that they existed at the time of the Pharaohs. Both species are alloploid hybrids and have double the chromosome number of their parents, making them what is known as tetraploid, a combination of the genomes of two different progenitor species. The hybridisation event has been dated back to perhaps as long as five million years ago, which predates human occupation of South America. |
There are a great many sizes and shapes of tobacco leaves used for cigarettes and cigars, large and small. One reason Havana cigars are so prized is because they use a variety of tobacco with very big leaves in which the whole cigar can be wrapped in one go. Beyond Western civilisation, tobacco was used as an important narcotic and shamanistic drug in the Amazon and in the foothills of the Andes. Traditionally, the "tabaquero" cooked the leaves to produce a bitter, viscous mixture. Once taken, it produced hallucinatory effects. The drug was not solely for recreational use, but also to help identify people's problems. Unfortunately, such a tradition has long since died out. Despite being exclusively New World, tobacco has spread very quickly around the world; the tiny seeds will germinate just about anywhere and quickly grow into very tall, robust plants. |
The mandrake
Many of the drug plants from the Solanaceae are European in origin, which accounts for the initial huge suspicion surrounding introduced food species like tomatoes. There are several similar types that are highly toxic, the most famous being the mandrake, often thought to have a root in the form of a human being. In the Middle Ages there was a huge mythology surrounding mandrakes, including the suggestion that there were female and male mandrake plants. They are in fact perfectly hermaphroditic plants, with the flowers containing both male and female parts. Another myth that dates probably from the time of Theophrastus (the Greek so-called "father of botany") suggested that if a mandrake was pulled from the ground, it would scream so loudly that the person would die from the sound. Dogs were therefore used to pull mandrakes from the ground, by tying them to the plant then urging them to run to get pieces of meat, a ludicrous way to dig up a plant! |
The henbane
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| Hyoscyamus albus, the white henbane, from the Mediterranean region. | |
Widely used in Chinese medicine, henbane was historically a very important component in witches' balms and unguents. The effect of tropane alkaloids is to induce a feeling of flying. A seventeenth century Spanish physician wrote how he tried to convince members of the Inquisition that women who had been accused of being witches were really just drug users. He locked the women in a room and stood guard outside to watch to see whether the balm they had rubbed on their skin beforehand induced them to confess that they had been flying. If they suggested they had, but he had not seen them leave the room, he would know they were drug users rather than witches! The Inquisition was not interested and it was only later that the symptoms were induced by this hallucinogenic drug were shown to be the restult of the effects of tropane alkaloids. |
Fruits of the henbane were often mistaken for hazel nuts and were deadly if eaten. Sir Hans Sloane reportedly treated a case in which people had mistaken woody roots for parsnips in a time of famine, and had boiled them and eaten them, with catastrophic results, particularly in the children of the family. Hallucinations are often produced in adults, but the tropane alkaloids can be very toxic if body weight is low. Because of these experiences, it is easy to understand the suspicion surrounding the harmless tomato at the time of their introduction to Europe. |
Deadly nightshade
 Also related to henbanes is the European genus Atropa belladonna, the deadly nightshade. Atropa is named after the Greek Atropos, the muse of fate and death (despite being such a pretty plant with shiny black fruit), and has been associated with witchcraft in the past. The compound atropine, deriving from Atropa, is still widely used in medicine today. It is extracted from the plant itself and has the effect of making the eyes dilate, and therefore is used by opthamalogists to make the eyes easier to examine. The species name belladonna comes from the Italian "beautiful woman", and back in the time of Linnaeus (the eighteenth century), it was common for women to add drops of ground Atropa to their eyes to make the pupils dilate to give a deep, black appearance. |
Datura
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| Datura inoxia, the toxic jimsonweed. | |
Another important Solanaceous genus is Datura, named by Linnaeus after its common name in India, which was "dutra". Although common in India and China in the 1700s, it is again New World in origin, probably brought originally by the Portuguese (like peppers). Dutra was the drug used by the whirling dervishes to make them hallucinate and it is extremely toxic. In the United States "Datura" is known as jimsonweed, derived from Jamestown, because soldiers there decided that the seeds might be good for grinding up as flour for bread. The results were, of course, catastophic. Datura is also used as a hallucinogen in the southwestern United States. Though beautiful, these plants are the cause of many fatal accidents. |
Brugmansia
Tree daturas, Brugmansia species, also known as "floripondios", produce beautiful hanging flowers that smell particularly sweet at night. In Latin America, suspicion has it that if you sleep near to the plant it will induce terrible nightmares, perhaps as alkaloids are contained in the smell emitted at night. Brugmansia is also used in shamanistic healing and visionary practice, such as thate in the valley of Sibundoy in southern Colombia. Shamans here grow virally infected versions of a particular species that have an extremely high alkaloid content. The different varieties are used for divination practices and to cure a range of diseases. Another species, the Brugmansia sanguinea, was also used as a drug plant by the high Andean peoples. It grows at a much higher elevation and has bright red flowers that are hummingbird pollinated. |
Brunfelsia
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| Brunfelsia grandflora, commonly called San Juan in Central America and chiricsanango in South America, cultivated in Panama. | |
Brunfelsia species are beautiful plants that grow exclusively in the New World tropics. In South America the stems and bark are used widely amongst indigenous peoples as a cure for rheumatism. The genus was named after Otto Brunfels, a friend of Linnaeus. Brunfelsia is also a very important ingredient in ayahuasca or yajé, a hallucinogenic drug based on another plant called Banisteriopsis. Ayahuasca is an important New World hallucinogen, used widely in the Amazon for divination and curing. Another genus of New World hallucongens, Latua, grows in coastal Chile and an entire shamanistic cult is based on the use of this plant. |
Effects of steroidal alkaloids
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| Flowers and fruits of Solanum glaucophyllum, a native of Argentina and Paraguay. | |
All of the Solanaceae plants already discussed that are used as drugs and medicines contain tropane alkaloids, and have been seen to cause serious brain dysfunction and produce hallucinogenic and narcotic effects. Steroidal alkaloids found in other members of the family can also result in strong effects, for example, Solanum glaucophyllum, which has high concentrations of these compounds, is rooted out of pastures in southern Argentina and Paraguay because of the terrible birth defects it causes in cattle. |
The steroidal alkaloid solasodine was rumoured to have been implicated in the increased incidence of spina bifida in Irish children during famine years, as the result of eating potatoes that had been stored for some time and thus built up high concentrations of harmful alkaloids. It was only later discovered that vitamin C can negate the harmful effects of the steroidal alkaloids. This, however, is not the entire story--the real cause-and-effect relationship between the chemical and birth defect has never been adequately established. |
In the 1980s, Solanum marginatum was experimentally used by a pharmaceutical company to produce birth- control pills. The standard source for the hormones in oral contraceptives had been diosgenin, which is chemically very similar to progesterone and oestrogen, which was harvested from wild yams--dioscoreas--mostly in Mexico. It was thought to be becoming unsustainable and so alternatives were tried for the production of diosgenin analogues. A plantation was established in Ecuador and the fruits harvested to extract the solasodine, which was then chemically changed to diosgenin. However, this practice too proved unsustainable over time, and it became cheaper to produce diosgenin chemically rather than to harvest it from plants. |
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