User:Jdanner22/sandbox/chem275

This is the sandbox for my Chem 275 Class Project!

Here is the page for my first toxin - Cicutoxin - where I added information to the Chembox.

The content for my other toxins will follow this.

Cicutoxin is a naturally-occurring poisonous chemical compound produced by several plants from the family Apiaceae including water hemlock (Cicuta species) and water dropwort (Oenanthe crocata). The compound contains polyene, polyyne, and alcohol functional groups and is a structural isomer of oenanthotoxin, also found in water dropwort. Both of these belong to the C17-polyacetylenes chemical class.

It causes death by respiratory paralysis resulting from disruption of the central nervous system. It is a potent, noncompetitive antagonist of the gamma-aminobutyric acid (GABA) receptor. In humans, cicutoxin rapidly produces symptoms of nausea, emesis and abdominal pain, typically within 60 minutes of ingestion. This can lead to tremors, seizures, and death. LD50(mouse; i.p.) ~9 mg/kg

History
Johann Jakob Wepfer's book Cicutae Aquaticae Historia Et Noxae Commentario Illustrata was published in 1679; it contains the earliest published report of toxicity associated with Cicuta plants. The name cicutoxin was coined by Boehm in 1876 for the toxic compound arising from the plant Cicuta virosa, and he also extracted and named the isomeric toxin oenanthotoxin from Oenanthe crocata. A review published in 1911 examined 27 cases of cicutoxin poisoning, 21 of which had resulted in death – though some of these cases involved deliberate poisoning. This review included a case where a family of five used Cicuta extracts as a topical treatment for itching, resulting in the deaths of two children, a report that suggests that cicutoxin may be absorbed through the skin. A review from 1962 examined 78 cases, 33 of which resulted in death, and cases of cicutoxin poisoning continue to occur:


 * A child used the stem of a plant as a toy whistle and died of cicutoxin poisoning
 * A 14-year-old boy died 20 hours after consuming a 'wild carrot' in 2001
 * In 1992, two brothers were foraging for wild ginseng and found a hemlock root. One of them ate three bites of the supposed ginseng root and the other one ingested one bite. The first brother died three hours later while the second made a full recovery with supportive medical care after experiencing seizures and delirium.

All plants from the genus Cicuta contain cicutoxin. These plants are found in swampy, wet habitats in North America and parts of Europe. The Cicuta plants are often mistaken for edible roots such as parsnip, wild carrot or wild ginseng. All parts of the Cicuta plants are poisonous, though the root is the most toxic part of the plant and toxin levels are highest in spring – ingestion of a 2–3 cm portion of root can be fatal to adults. In one reported incident, 17 boys ingested parts of the plant, with only those who consumed the root experiencing seizures whilst those who consumed only leaves and flowers merely became unwell. The toxicity of the plants depends on various factors, such as seasonal variation, temperature, geographical location and soil conditions. The roots remain toxic even after drying.

Plants containing cicutoxin
Cicutoxin is found in five species of water hemlock, all belonging to the family Apiaceae. These include all four species in the genus Cicuta and one species from the genus Oenanthe: the bulblet-bearing water hemlock, C. bulbifera; the Douglas water hemlock, C. douglasii; the spotted water hemlock or spotted cowbane, C. maculata; Mackenzie's water hemlock, C. virosa; and, the water dropwort, O. crocata. Cicutoxin is found in all parts of these plants, along with several other C17 polyacetylenes. C. virosa, for example, produces isocicutoxin, a geometric isomer of cicutoxin, while O. crocata contains the toxin oenanthotoxin, a structural isomer of cicutoxin. Cicuta plants also produce multiple congeners of cicutoxin, such as Virol A and Virol C.

Chemistry
Building on Boehm's work, Jacobsen reported the first isolation of pure cicutoxin as a yellowish oil in 1915. Its chemical structure was not determined until 1953, however, when it was shown that it has a molecular formula of C17H22O2 and it is an aliphatic, highly unsaturated alcohol with two triple bonds conjugated with three double bonds, and two hydroxyl groups. The first synthesis of cicutoxin was reported in 1955. Though the overall yield was only 4% and the product was the racemic mixture, the synthesis has been described as "a significant accomplishment" given that it was achieved "without the benefit of modern coupling reactions." The absolute configuration of the naturally-occurring form of cicutoxin was reported in 1999 to be (R)-(−)-cicutoxin, systematically named as (8E,10E,12E,14R)-heptadeca-8,10,12-triene-4,6-diyne-1,14-diol. Outside of a plant, cicutoxin breaks down when exposed to air, light, or heat, making it difficult to handle.

Cicutoxin has a long carbon structure and few hydrophilic substituents which gives it hydrophobic characteristics. Hydrophobic and/or small molecules can be absorbed through the skin. Research has shown that cicutoxin will pass through the skin of frogs and the experience of the family who used a Cicuta plant as a topical antipruritic strongly suggests that the compound is able to pass through human skin.

Laboratory synthesis
The first total synthesis of racemic cicutoxin was published in 1955 and reported that this racemate was about twice as active as the naturally-occurring enantiomer. A complete synthesis of the natural product, (R)-(–)-cicutoxin, in four linear steps was reported in 1999, from three key fragments: (R)-(–)-1-hexyn-3-ol (8), 1,4-diiodo-1,3-butadiene (9), and THP-protected 4,6-heptadiyn-1-ol (6). (R)-(–)-1-hexyn-3-ol (8) is a known compound and was obtained by Corey-Bakshi-Shibata reduction of 1-hexyn-3-one. 1,4-diiodo-1,3-butadiene (9) is also a known compound and it is readily available by dimerization of acetylene accompanied by addition of iodine in the presence of platinum (IV) catalyst and sodium iodide. The last key fragment, THP-protected 4,6-heptadiyn-1-ol (6) is a known compound.

The first step is the Sonogashira coupling of compound 8 and 9. This step gave dienynol (10) with 63 percent yield. The second step is a palladium -catalyzed coupling reaction. The coupling of compound 6 and 10 leads to the 17-carbon frame (11) with 74 percent yield. Compound 11 already has the stereo center in place and only needs a few structural changes: the third and fourth step. The third step is the reduction of the C5 triple bond in compound 11, this was accomplished by using a compound called Red-Al. The last step is the removal of the THP protection group. When THP is removed and a hydrogen is bound to the oxygen, then (R)-(–)-cicutoxin is formed. These four steps are the full synthesis of cicutoxin and gives an overall yield of 18 percent.

Biochemistry
Cicutoxin is known to interact with the GABAA receptor and it also has been shown to block the potassium channel in T lymphocytes. A similar effect where potassium channels in neurons are blocked could account for the toxic effect on the nervous system. The interactions are explained in Mechanism of action.

Mechanism of action
The exact mechanism of action is not known for cicutoxin, even though it is well-known to be a violent toxin. The mechanism is not known because of the chemical instability of cicutoxin, but there have been studies that delivered some evidence for a mechanism of action.

Cicutoxin is a noncompetitive gamma-aminobutyric acid (GABA) antagonist in the central nervous system (CNS). GABA normally binds to the beta domain of the GABAA receptor and activates the receptor which causes a flow of chloride across the membrane. Cicutoxin binds to the same place as GABA, because of this the receptor is not activated by GABA. The pore of the receptor won't open and chloride can't flow across the membrane. Binding of cicutoxin to the beta domain also blocks the chloride channel. Both effects of cicutoxin on the GABAA-receptor cause a constant depolarization. This causes hyperactivity in cells, which leads to seizures.

There also have been some studies that suggest that cicutoxin increases the duration of the neuronal repolarization in a dose-dependent manner. The toxin could increase the duration of the repolarization up to sixfold at 100 µmol L&minus;1. The prolonged action potentials may cause higher excitatory activity.

It has been demonstrated that cicutoxin also blocks potassium channels in T-lymphocytes. The toxin inhibits the proliferation of the lymphocytes. This has made it a substance of interest in research for a medicine against leukemia.

Metabolism
It is unknown how the body gets rid of cicutoxin. There is evidence that it has a long half-life in the body, because of a patient who was submitted in a hospital after eating a root of a Cicuta plant. The man was in the hospital for two days and still had a fuzzy feeling in his head two days after leaving the hospital. There is also the case of a sheep (discussed in Effects on animals) where the sheep fully recovered after seven days.

Symptoms
First signs of cicutoxin poisoning start 15–60 minutes after ingestion and are vomiting, convulsions, widened pupils, salivation, excess sweating and the patient may go into a coma. Other described symptoms are cyanosis, amnesia, absence of muscle reflexes, metabolic acidosis and cardiovascular changes which may cause heart problems and central nervous system problems which manifest themselves as convulsions and either an overactive or underactive heart. Due to an overactive nervous system respiratory failure occurs which may cause suffocation and accounts for most of the deaths. Dehydration from water loss due to vomiting can also occur. If untreated, the kidneys can also fail, causing death.

Treatment
The adverse effects from cicutoxin poisoning are gastrointestinal or cardiac nature. With no antidote known, only symptomatic treatments are available, though supportive treatments do substantially improve survival rates. Treatments used include the administration of activated charcoal within 30 minutes of ingestion to reduce the uptake of poison, maintaining open airways to prevent suffocation, rehydration to address the dehydration caused by vomiting, and administration of benzodiazepines that enhance the effect of GABA on the GABAA receptor or barbiturates to reduce seizures.

Effects on animals
The LD50 of cicutoxin for mice is 2.8 mg kg&minus;1 (10.8 μmol kg&minus;1). In comparison, the LD50 of virol A is 28.0 mg kg&minus;1 (109 μmol kg&minus;1) and of isocicutoxin is 38.5 mg kg&minus;1 (149 μmol kg&minus;1).

Cattle usually ingest parts of Cicuta plants in Spring, while grazing on new growth around ditches and rivers where these plants grow. Animals display similar effects of cicutoxin poisoning as do humans, but without vomiting (which can lead to increased lethality) – recorded symptoms include salivation, seizures, frequent urination and defecation, and degeneration of skeletal and cardiac muscles. Seizures are usually short, less than a minute per seizure, and occur at intervals of 15 to 30 minutes for around two hours. Ewes recover more slowly after eating cicutoxin-containing tubers, taking up to seven days to recover fully.

Research studies on ewes has shown that skeletal and cardiac myodegeneration (damage of muscle tissues) only occur after a dose sufficient to induce symptoms of intoxication is administered. Analysis of the animal's blood showed elevated serum enzymes that indicate muscle damage (LDH, AST and CK values). At necropsy, the ewe's heart had multifocal pale areas and pallor of the long digital extensor muscle groups; by contrast, a ewe given a lethal dose of cicutoxin-containing tubers had only microscopic lesions. The number and duration of seizures had a direct effect on the skeletal and cardiac myodegeneration and amount of serum change.

Ewes given up to 2.5 times the lethal dose along with medications to treat symptoms of cicutoxin poisoning recovered, demonstrating that symptomatic treatment can be life-saving. Medications administered included sodium pentobarbital (at 20–77 mg kg&minus;1 intravenously) at the first seizure to control seizure activity, atropine (75–150 mg) to reduce salivary excretion during anesthesia, and Ringer's lactate solution until the ewes recovered.

Medical use
Cicutoxin has been shown to have anti-leukemia properties as it inhibits the proliferation of the lymphocytes. It has also been investigated for antitumor activity, where it was shown that a methanolic extract of C. maculata demonstrated significant cytotoxicity in the 9 KB (human nasopharyngeal carcinoma) cell structure assay.

Additional References


Here is the page for my second toxin - Oenanthotoxin - in which I add a section about laboratory synthesis and include my own original graphic depicting the steps of lab synthesis.

The content for my final toxin will follow this.

Oenanthotoxin is a toxin extracted from hemlock water-dropwort (Oenanthe crocata) and other plants of the genus Oenanthe. It is a central nervous system poison, and acts as a noncompetitive antagonist of the neurotransmitter gamma-aminobutyric acid. A case has been made for the presence of this toxin in local Oenanthe species playing a causative role in euthanasia in ancient Sardinia. It was crystallized in 1949 by Clarke and co-workers. It is structurally closely related to the toxins cicutoxin and carotatoxin. Oenanthotoxin is a C17 polyacetylene isomer of cicutoxin.

Occurrence
Oenanthotoxin concentration in plants is dependent on seasonal changes and geographical location, the most is present during late winter and early spring. Contrary to most poisonous plants that contain bitter tastes or burning sensations, the water dropwort has a rather sweet and pleasant taste and odor. Water dropwort is characterized by a yellow liquid that changes color due to air exposure. The roots are the most toxic part, although the entire plant contains poisonous properties.

History and culture
The discovery and use of plants containing oenanthotoxin predates Socrates and Homer and its first use as a poison is thought to have been implemented between 1800 BC and 800 BC in Pre-Roman Sardinia. In Ancient Sardinia, it was considered to be a humane form of euthanasia. Elderly people who were unable to care for themselves were given water dropwort and dropped from a high rock to ensure death. It is also believed that Socrates ingested the plant when executed.

A common symptom of oenanthotoxin is risus sardonicus, better known as the Sardonic Grin, coined by Homer in the 8th century BC, due to the victim's rigid smile after ingestion.

Furthermore, as a muscle relaxant, it is believed to have cosmetic botox-like properties in small amounts.

Mechanism of action
Although oenanthotoxin is a relatively well known poison, its mechanism of action is not entirely understood. However, there is evidence that its mechanism of action is similar to that of cicutoxin.

Oenanthotoxin is part of a group of C17 conjugated polyacetylenes that act as noncompetitive gamma-aminobutyric acid (GABA) inhibitors in the central nervous system (CNS). GABA binds to the beta-domain of the GABAA receptor in the central nervous system and activates the receptor increasing chloride ion flow across the membrane and inhibiting the neuron. When oenanthotoxin is introduced to the body, it non-competitively binds to the same beta-domain receptor as GABA and prevents normal inhibitory function. Binding to the same receptor, oenanthotoxin blocks the chloride channel, allowing excessive excitation to occur. This, blocking GABAergic responses, causes hyperactivity in the neurons, resulting in convulsions, and seizures.

Symptoms
While oenanthotoxin is extremely dangerous and toxic (LD50 = 0.58 mg/kg for mice), there have been numerous case studies documenting the common symptoms including: convulsions, seizures, nausea, diarrhea, tachycardia, mydriasis, rhabdomyolysis, renal failure, respiratory impairment, and cardiac dysrhythmias.

Below is a comprehensive table listing the recorded symptoms caused oenanthotoxin within each system in the body Oenanthe crocata:

Laboratory Synthesis
Starting with 3,4-dihydro-2H-pyran (1), whose treatment with NBS in MeOH followed by the addition of KOH in a “one-pot reaction”, results in the majority product of 2-mehtoxy-5,6-dihydropyran (2). The reaction of (2) with phosphoric acid produced (2E)penta-2,4-dienal (3). The treatment of (3) with ethynylmagnesium bromide in the presence of lithium chloride produced the alkyne (4) and further reaction with PBr3 resulted in (5). This compound was fully purified by chromatography using basic Al2O3 followed by crystallization at 0C. (5) was then reacted with ethyl 3-oxo-hexanoate which formed a sodium hydride compound (6). The de-esterification and following decarboxylation produced (7). When commercial (2E)pent-2-en-4-ynol reacts with NBS, (2E)5-bromopent-2-en-4-yn-1-ol (8) is formed which is then reacted with (7) to form (9). The reaction of (9) with LiAlH4 formed a racemic mixture with 83% (racemic 1) which could not be successfully enantiomerically purified. Therefore, (racemic 1) was treated with vinyl acetate in the presence of the enzyme novozyme 435, which produced an enantiomerically pure monoacetate (10) along with a diacetate (11). Further reduction of (10) with LiAlH4 provided optically pure (14R)-oenanthotoxin.

History
Carrots are believed to have originated as a root crop in Central Asia nearly 1,100 years ago, although there is some evidence that they were being grown in the Roman Empire several hundred years earlier. While earlier research had been done on the components of carrot seed oil, it was not until the 1960s that scientists starting looking into the other kind of oil that can be harvested from the carrot root that was known to be volatile. In 1968, R.G. Buttery identified and started characterizing some of the physical and chemical properties of Falcarinol, or Carotatoxin as it was original referred to. Falcarinol has a relatively low toxicity compared to similar molecules like cicutoxin or Oenanthotoxin. There have been no reported deaths linked to falcarinol poisoning.

Chemistry
Falcarinol is a polyyne with two carbon-carbon triple bonds and two double bonds. The double bond at the carbon 9 position has cis stereochemistry was introduced by the desaturation, which requires oxygen and NADPH (or NADH) cofactors, creates a bend in the molecule that prevent fatty acid from solidifying in oils and cellular membranes.

It is structurally related to the oenanthotoxin and cicutoxin.

Biological effects
Falcarinol is an irritant that can cause allergic reactions and contact dermatitis. It was shown that falcarinol acts as a covalent cannabinoid receptor type 1 inverse agonist and blocks the effect of anandamide in keratinocytes, leading to pro-allergic effects in human skin. Normal consumption of carrots has no toxic effect in humans.

Biosynthesis
Starting with oleic acid (1), which possesses a cis double bond at the carbon 9 position from desaturation and a bound of phospholipids (-PL), a bifunctional desaturase/acetylnase system occurred with oxygen (a) to introduce the second cis double bond at the carbon 12 position to form linoleic acid (2). This step was then repeated to turn the cis double bond at the carbon 12 position into a triple bond (also called acetylenic bond) to form crepenynic acid (3). Crepenynic acid was reacted with oxygen (b) to form a second cis double bond at the carbon 14 position (conjugated position) leading to the formation of dehydrocrepenynic acid (4). Allylic isomerization (c) was responsible for the changes from the cis double bond at the carbon 14 position into the triple bond (5) and formation of the more favored trans (E) double bond at the carbon 17 position (6). Finally, after forming the intermediate (7) by decarboxylation (d), falcarinol (8) was produced by hydroxylation (e) at the carbon 16 position that introduced the R conformation to the system.