Appearance A pile of<unk>  hydrochloride A piece of compressed<unk>  powder<unk>  in its purest form is a white, pearly product.<unk>  appearing in powder form is a salt, typically<unk>  hydrochloride. Street<unk>  is often adulterated or "cut" with talc, lactose, sucrose, glucose, mannitol, inositol, caffeine, procaine, phencyclidine, phenytoin, lignocaine, strychnine, amphetamine, or heroin. The color of "crack"<unk>  depends upon several factors including the origin of the<unk>  used, the method of preparation – with ammonia or baking soda – and the presence of impurities. It will generally range from white to a yellowish cream to a light brown. Its texture will also depend on the adulterants, origin, and processing of the powdered<unk> , and the method of converting the base. It ranges from a crumbly texture, sometimes extremely oily, to a hard, almost crystalline nature. Forms Salts<unk>  – a tropane alkaloid – is a weakly alkaline compound, and can therefore combine with acidic compounds to form salts. The hydrochloride (HCl) salt of<unk>  is by far the most commonly encountered, although the sulfate (SO42-) and the nitrate (NO3−) salts are occasionally seen. Different salts dissolve to a greater or lesser extent in various solvents – the hydrochloride salt is polar in character and is quite soluble in water. Base As the name implies, "freebase" is the base form of<unk> , as opposed to the salt form. It is practically insoluble in water whereas hydrochloride salt is water-soluble. Smoking freebase<unk>  has the additional effect of releasing methylecgonidine into the user's system due to the pyrolysis of the substance (a side effect which insufflating or injecting powder<unk>  does not create). Some research suggests that smoking freebase<unk>  can be even more cardiotoxic than other routes of administration because of methylecgonidine's effects on lung tissue and liver tissue. Pure<unk>  is prepared by neutralizing its compounding salt with an alkaline solution, which will precipitate non-polar basic<unk> . It is further refined through aqueous-solvent liquid–liquid extraction. Crack<unk>  A woman smoking crack<unk>  "Rocks" of crack<unk>  Smoking or vaporizing<unk>  and inhaling it into the lungs produces an almost immediate "high" that can be very powerful (and addicting) quite rapidly – this initial crescendo of stimulation is known as a "rush". While the stimulating effects may last for hours, the euphoric sensation is very brief, prompting the user to smoke more immediately. Powder<unk> <unk>  hydrochloride) must be heated to a high temperature (about 197 °C), and considerable decomposition/burning occurs at these high temperatures. This effectively destroys some of the<unk>  and yields a sharp, acrid, and foul-tasting smoke.<unk>  base/crack can be smoked because it vaporizes with little or no decomposition at , which is below the boiling point of water. Crack is a lower purity form of free-base<unk>  that is usually produced by neutralization of<unk>  hydrochloride with a solution of baking soda (sodium bicarbonate, NaHCO3) and water, producing a very hard/brittle, off-white-to-brown colored, amorphous material that contains sodium carbonate, entrapped water, and other by-products as the main impurities. The origin of the name "crack" comes from the "crackling" sound (and hence the onomatopoeic moniker "crack") that is produced when the<unk>  and its impurities (i.e. water, sodium bicarbonate) are heated past the point of vaporization.<unk> a leaf infusions<unk> a herbal infusion (also referred to as<unk> a tea) is used in<unk> a-leaf producing countries much as any herbal medicinal infusion would elsewhere in the world. The free and legal commercialization of dried<unk> a leaves under the form of filtration bags to be used as "coca tea" has been actively promoted by the governments of Peru and Bolivia for many years as a drink having medicinal powers. In Peru, the National<unk> a Company, a state-run corporation, sells<unk> -infused teas and other medicinal products and also exports leaves to the U.S. for medicinal use. Visitors to the city of Cuzco in Peru, and La Paz in Bolivia are greeted with the offering of<unk> a leaf infusions (prepared in teapots with whole<unk> a leaves) purportedly to help the newly arrived traveler overcome the malaise of high altitude sickness. The effects of drinking<unk> a tea are mild stimulation and mood lift. It does not produce any significant numbing of the mouth nor does it give a rush like snorting<unk> . To prevent the demonization of this product, its promoters publicize the unproven concept that much of the effect of the ingestion of<unk> a leaf infusion would come from the secondary alkaloids, as being not only quantitatively different from pure<unk>  but also qualitatively different. It has been promoted as an adjuvant for the treatment of<unk>  dependence. In one controversial study,<unk> a leaf infusion was used—in addition to counseling—to treat 23 addicted<unk> a-paste smokers in Lima, Peru. Relapses fell from an average of four times per month before treatment with<unk> a tea to one during the treatment. The duration of abstinence increased from an average of 32 days before treatment to 217 days during treatment. These results suggest that the administration of<unk> a leaf infusion plus counseling would be an effective method for preventing relapse during treatment for<unk>  addiction. Importantly, these results also suggest strongly that the primary pharmacologically active metabolite in<unk> a leaf infusions is actually<unk>  and not the secondary alkaloids. The<unk>  metabolite benzoylecgonine can be detected in the urine of people a few hours after drinking one cup of<unk> a leaf infusion. Biosynthesis Biological source of<unk>  molecule in the context of the tropane class of molecules. The biological source of each tropane alkaloid is indicated by species, and below that a phylogenetic map is provided. Biosynthesis of N-methyl-pyrrolinium cation Biosynthesis of<unk>  Robinson biosynthesis of tropane Reduction of tropinone The first synthesis and elucidation of the<unk>  molecule was by Richard Willstätter in 1898. Willstätter's synthesis derived<unk>  from tropinone. Since then, Robert Robinson and Edward Leete have made significant contributions to the mechanism of the synthesis. (-NO3) The additional carbon atoms required for the synthesis of<unk>  are derived from acetyl-CoA, by addition of two acetyl-CoA units to the N-methyl-Δ1-pyrrolinium cation. The first addition is a Mannich-like reaction with the enolate anion from acetyl-CoA acting as a nucleophile towards the pyrrolinium cation. The second addition occurs through a Claisen condensation. This produces a racemic mixture of the 2-substituted pyrrolidine, with the retention of the thioester from the Claisen condensation. In formation of tropinone from racemic ethyl 2,3-13C24(Nmethyl-2-pyrrolidinyl)-3-oxobutanoate there is no preference for either stereoisomer. In<unk>  biosynthesis, only the (S)-enantiomer can cyclize to form the tropane ring system of<unk> . The stereoselectivity of this reaction was further investigated through study of prochiral methylene hydrogen discrimination. This is due to the extra chiral center at C-2. This process occurs through an oxidation, which regenerates the pyrrolinium cation and formation of an enolate anion, and an intramolecular Mannich reaction. The tropane ring system undergoes hydrolysis, SAM-dependent methylation, and reduction via NADPH for the formation of methylecgonine. The benzoyl moiety required for the formation of the<unk>  diester is synthesized from phenylalanine via cinnamic acid. Benzoyl-CoA then combines the two units to form<unk> . N-methyl-pyrrolinium cation The biosynthesis begins with L-Glutamine, which is derived to L-ornithine in plants. The major contribution of L-ornithine and L-arginine as a precursor to the tropane ring was confirmed by Edward Leete. Ornithine then undergoes a pyridoxal phosphate-dependent decarboxylation to form putrescine. In some animals, the urea cycle derives putrescine from ornithine. L-ornithine is converted to L-arginine, which is then decarboxylated via PLP to form agmatine. Hydrolysis of the imine derives N-carbamoylputrescine followed with hydrolysis of the urea to form putrescine. The separate pathways of converting ornithine to putrescine in plants and animals have converged. A SAM-dependent N-methylation of putrescine gives the N-methylputrescine product, which then undergoes oxidative deamination by the action of diamine oxidase to yield the aminoaldehyde. Schiff base formation confirms the biosynthesis of the N-methyl-Δ1-pyrrolinium cation. Robert Robinson's acetonedicarboxylate The biosynthesis of the tropane alkaloid is still not understood. Hemscheidt proposes that Robinson's acetonedicarboxylate emerges as a potential intermediate for this reaction. Condensation of N-methylpyrrolinium and acetonedicarboxylate would generate the oxobutyrate. Decarboxylation leads to tropane alkaloid formation. Reduction of tropinone The reduction of tropinone is mediated by NADPH-dependent reductase enzymes, which have been characterized in multiple plant species. These plant species all contain two types of the reductase enzymes, tropinone reductase I and tropinone reductase II. TRI produces tropine and TRII produces pseudotropine. Due to differing kinetic and pH/activity characteristics of the enzymes and by the 25-fold higher activity of TRI over TRII, the majority of the tropinone reduction is from TRI to form tropine. Detection in body fluids<unk>  and its major metabolites may be quantified in blood, plasma, or urine to monitor for use, confirm a diagnosis of poisoning, or assist in the forensic investigation of a traffic or other criminal violation or sudden death. Most commercial<unk>  immunoassay screening tests cross-react appreciably with the major<unk>  metabolites, but chromatographic techniques can easily distinguish and separately measure each of these substances. When interpreting
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