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Flowers are typically conical or funnelform with five petals, usually fused. The leaves are alternate, often with a hairy or clammy surface. Solanaceous plants produce a fruit that is either a berry, as in the case of the tomato, or a dehiscent (breaks open upon drying, or dehiscing, releasing the seeds) capsule as in the case of Datura. The seeds are usually round and flat, being 2-4 millimeters in diameter. The stamens are usually present in multiples of four (most commonly four or eight). The ovaries are inferior. The hypogynus gynoecium is a syncarp located obliquely in relation to the median.
The Solanaceae are known for possessing a diverse range of alkaloids. As far as humans are concerned, these alkaloids can be desirable, toxic, or both, though they presumably evolved because they reduced the tendency of animals to eat the plants.
One of the most important groups of these compounds is called the tropane alkaloids. The term "tropane" comes from a genus in which they are found, Atropa (the belladonna genus). The belladonna genus is so named after the Greek Fate, Atropos, who cut the thread of life. This nomenclature betrays the toxicity and lethality that has long been known to be characteristic of these compounds. Tropane alkaloids are also found in the Datura, Mandragora, and Brugmansia genera, as well as many others in the Solanaceae family. Chemically, the molecules of these compounds have a characteristic bicyclic structure and include atropine, scopolamine, and hyoscyamine. Pharmacologically, they are the most powerful known anticholinergics in existence, meaning they inhibit the neurological signals transmitted by the endogenous neurotransmitter, acetylcholine. Symptoms of overdose may include mouth dryness, dilated pupils, ataxia, urinary retention, hallucinations, convulsions, coma, and death. Despite the extreme toxicity of the tropanes, they are important drugs when administered in appropriate (and extremely small) dosages. They can reverse cholinergic poisoning, which can be caused by overexposure to pesticides and chemical warfare agents such as sarin and VX. More commonly, they can halt many types of allergic reactions. Scopolamine, a commonly used opthamalic agent, dilates the pupils and thus facilitates examination of the interior of the eye. They can also be used as antiemetics in people prone to motion sickness or receiving chemotherapy. Atropine has a stimulant effect on the central nervous system and heart, whereas scopolamine has a sedative effect.
Cocaine is also considered a tropane alkaloid due to its structural similarity to the aforementioned compounds. Its pharmacology, however, is radically different, and it does not occur in the Solanaceae family.
The most famous alkaloid from the Solanaceae family is nicotine. Like the tropanes, its pharmacology acts on cholinergic neurons, but with the opposite effect (it is an agonist as opposed to an antagonist). It has a higher specificity for nicotinic acetylcholine receptors than other ACh proteins. Its effects are well known. Nicotine occurs naturally in the Nicotiana or Tobacco genus.
Capsaicin is structurally unrelated to nicotine or the tropanes, and is found in the genus Capsicum, which includes chile peppers such as Tabasco peppers and habaneros. The compound is not appreciably toxic to animals. However, it stimulates specific pain receptors in most mammals, those which sense heat, in the oral mucosa as well as many other epithelial tissues. This causes a sensation of burning not unlike an actual heat or chemical burn. It is used in high concentration as a deterrent in pepper sprays, and sought after for many culinary dishes for its "spiciness". It is thought that the reason one would deliberately induce pain while eating is the rewarding release of endorphins it has been shown to induce. The "hotness" of capsaicin products and foods is expressed in Scoville units. A scoville unit is the factor by which the capsaicin-containing substance must be diluted to render the resulting solution imperceptible to a tester (for example, a teaspoon of a 5,000 Scoville unit hot sauce would have to be diluted with 4,999 teaspoons of a sugar water solution to negate its potential to cause a sensation on the palate).
The most important species of this family for the global diet is the potato or Solanum tuberosum, whose carbohydrate-rich tubers have been a staple food in many times and places, and which is one of the most grown crops today. In many genera, the fruits are the desirable item, for example, tomatoes, tomatillos, eggplants, uchuva, and peppers.
While very popular, some people experience sensitivity or allergy-like symptoms in response to nightshade plants.
D'Arcy, William G. (1986). Solanacea. Columbia University Press. ISBN 0-231-05780-6.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Solanaceae". A list of authors is available in Wikipedia.|