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Alliin
Alliin is a sulfoxide that is a natural constituent of fresh garlic. It is a derivative of the amino acid cysteine. When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma of fresh garlic. Allicin and other thiosulfinates in garlic are unstable and form a number of other compounds, such as diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DAT), dithiins and ajoene. Garlic powder is not a source of alliin, nor is fresh garlic upon maceration, since the enzymatic conversion to allicin takes place in the order of seconds. Alliin was the first natural product found to have both carbon- and sulfur-centered stereochemistry. Chemical synthesis The first reported synthesis, by Stoll and Seebeck in 1951, begins the alkylation of -cysteine with allyl bromide to form deoxyalliin. Oxidation of this sulfide with hydrogen peroxide gives both diastereomers of -alliin, differing in the orientation o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alliinase
In enzymology, an alliin lyase () is an enzyme that catalyzes the chemical reaction :an ''S''-alkyl-L-cysteine ''S''-oxide \rightleftharpoons an alkyl sulfenate + 2-aminoacrylate Hence, this enzyme has one substrate, ''S''-alkyl-L-cysteine ''S''-oxide, and two products, alkyl sulfenate and 2-aminoacrylate. This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is ''S''-alkyl-L-cysteine ''S''-oxide alkyl-sulfenate-lyase (2-aminoacrylate-forming). Other names in common use include alliinase, cysteine sulfoxide lyase, alkylcysteine sulfoxide lyase, ''S''-alkylcysteine sulfoxide lyase, L-cysteine sulfoxide lyase, ''S''-alkyl-L-cysteine sulfoxide lyase, and alliin alkyl-sulfenate-lyase. It employs one cofactor, pyridoxal phosphate. Many alliinases contain a novel ''N''-terminal epidermal growth factor-like domain (EGF-like domain). Occurrence These enzymes are found in plants of the genus ''All ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Garlic
Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Allium fistulosum, Welsh onion and Allium chinense, Chinese onion. It is native to South Asia, Central Asia and northeastern Iran and has long been used as a seasoning worldwide, with a history of several thousand years of human consumption and use. It was known to ancient Egyptians and has been used as both a food flavoring and a traditional medicine. China produces 76% of the world's supply of garlic. Etymology The word ''garlic'' derives from Old English, ''garlēac'', meaning ''gar'' (spear) and leek, as a 'spear-shaped leek'. Description ''Allium sativum'' is a perennial flowering plant growing from a bulb. It has a tall, erect flowering stem that grows up to . The leaf blade is flat, linear, solid, and approximately wide, with an acute apex. The plant may produce pink to purple flowers from July to September in the Nort ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allicin
Allicin is an organosulfur compound obtained from garlic, a species in the family Alliaceae. It was first isolated and studied in the laboratory by Chester J. Cavallito and John Hays Bailey in 1944. When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma of fresh garlic. The allicin generated is unstable and quickly changes into a series of other sulfur-containing compounds such as diallyl disulfide. Allicin is part of a defense mechanism against attacks by pests on the garlic plant. Allicin is an oily, slightly yellow liquid that gives garlic its distinctive odor. It is a thioester of sulfenic acid and is also known as allyl thiosulfinate. Its biological activity can be attributed to both its antioxidant activity and its reaction with thiol-containing proteins. Produced in garlic cells, allicin is released upon disruption, producing a potent aroma when garlic is cut or cooked, and is among the chemicals res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfoxide
In organic chemistry, a sulfoxide, also called a sulphoxide, is an organosulfur compound containing a sulfinyl () functional group attached to two carbon atoms. It is a polar functional group. Sulfoxides are oxidized derivatives of sulfides. Examples of important sulfoxides are alliin, a precursor to the compound that gives freshly crushed garlic its aroma, and dimethyl sulfoxide (DMSO), a common solvent. Structure and bonding Sulfoxides feature relatively short S–O distances. In DMSO, the S–O distance is 1.531 Å. The sulfur center is pyramidal; the sum of the angles at sulfur is about 306°.. Sulfoxides are generally represented with the structural formula R−S(=O)−R', where R and R' are organic groups. The bond between the sulfur and oxygen atoms is intermediate of a dative bond and a polarized double bond. The double-bond resonance form implies 10 electrons around sulfur (10-S-3 in N-X-L notation). The double-bond character of the S−O bond may be accoun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stereocenter
In stereochemistry, a stereocenter of a molecule is an atom (center), axis or plane that is the focus of stereoisomerism; that is, when having at least three different groups bound to the stereocenter, interchanging any two different groups creates a new stereoisomer. Stereocenters are also referred to as stereogenic centers. A stereocenter is geometrically defined as a point (location) in a molecule; a stereocenter is usually but not always a specific atom, often carbon. Stereocenters can exist on chiral or achiral molecules; stereocenters can contain single bonds or double bonds. The number of hypothetical stereoisomers can be predicted by using 2''n'', with ''n'' being the number of tetrahedral stereocenters; however, exceptions such as meso compounds can reduce the prediction to below the expected 2''n''. Chirality centers are a type of stereocenter with four different substituent groups; chirality centers are a specific subset of stereocenters because they can only ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur Amino Acids
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Elemental sulfur is a bright yellow, crystalline solid at room temperature. Sulfur is the tenth most abundant element by mass in the universe and the fifth most on Earth. Though sometimes found in pure, native form, sulfur on Earth usually occurs as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, being mentioned for its uses in ancient India, ancient Greece, China, and ancient Egypt. Historically and in literature sulfur is also called brimstone, which means "burning stone". Today, almost all elemental sulfur is produced as a byproduct of removing sulfur-containing contaminants from natural gas and petroleum.. Downloahere The greatest commercial use of the element is the production of su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfoxides
In organic chemistry, a sulfoxide, also called a sulphoxide, is an organosulfur compound containing a sulfinyl () functional group attached to two carbon atoms. It is a polar functional group. Sulfoxides are oxidized derivatives of sulfides. Examples of important sulfoxides are alliin, a precursor to the compound that gives freshly crushed garlic its aroma, and dimethyl sulfoxide (DMSO), a common solvent. Structure and bonding Sulfoxides feature relatively short S–O distances. In DMSO, the S–O distance is 1.531 Å. The sulfur center is pyramidal; the sum of the angles at sulfur is about 306°.. Sulfoxides are generally represented with the structural formula R−S(=O)−R', where R and R' are organic groups. The bond between the sulfur and oxygen atoms is intermediate of a dative bond and a polarized double bond. The double-bond resonance form implies 10 electrons around sulfur (10-S-3 in N-X-L notation). The double-bond character of the S−O bond may be accounted ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Radical
A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing. Ageing Ailments of unknown cause Biogerontology Biological processes Causes of death Cellular processes Gerontology Life extension Metabolic disorders Metabolism Old age Time in life Wikipedia categories named after diseases and disorders {{CatAutoTOC ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroxyl
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy groups. Both the negatively charged anion , called hydroxide, and the neutral radical , known as the hydroxyl radical, consist of an unbonded hydroxy group. According to IUPAC definitions, the term ''hydroxyl'' refers to the hydroxyl radical () only, while the functional group is called a ''hydroxy group''. Properties Water, alcohols, carboxylic acids, and many other hydroxy-containing compounds can be readily deprotonated due to a large difference between the electronegativity of oxygen (3.5) and that of hydrogen (2.1). Hydroxy-containing compounds engage in intermolecular hydrogen bonding increasing the electrostatic attraction between molecules and thus to higher boiling and melting points than found for compounds that lack this f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antioxidant
Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricants, to prevent oxidation, and to foods to prevent spoilage, in particular the rancidification of oils and fats. In cells, antioxidants such as glutathione, mycothiol or bacillithiol, and enzyme systems like superoxide dismutase, can prevent damage from oxidative stress. The only dietary antioxidants are vitamins A, C, and E, but the term ''antioxidant'' has also been applied to numerous other dietary compounds that only have antioxidant properties in vitro, with little evidence for antioxidant properties in vivo. Dietary supplements marketed as antioxidants have not been shown to maintain health or prevent disease in humans. History As part of their adaptation from marine life, terrestrial plants began producing non-marine antioxi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanium Isopropoxide
Titanium isopropoxide, also commonly referred to as titanium tetraisopropoxide or TTIP, is a chemical compound with the formula . This alkoxide of titanium(IV) is used in organic synthesis and materials science. It is a diamagnetic tetrahedral molecule. Titanium isopropoxide is a component of the Sharpless epoxidation, a method for the synthesis of chiral epoxides. The structures of the titanium alkoxides are often complex. Crystalline titanium methoxide is tetrameric with the molecular formula . Alkoxides derived from bulkier alcohols such as isopropyl alcohol aggregate less. Titanium isopropoxide is mainly a monomer in nonpolar solvents. Preparation It is prepared by treating titanium tetrachloride with isopropanol. Hydrogen chloride is formed as a coproduct: : TiCl4 + 4 (CH3)2CHOH → Ti4 + 4 HCl Properties Titanium isopropoxide reacts with water to deposit titanium dioxide: :Ti4 + 2 H2O → TiO2 + 4 (CH3)2CHOH This reaction is employed in the sol-gel synthesis of TiO2-bas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diethyl Tartrate
Diethyl tartrate is an organic compound with the formula (HOCHCO2Et)2 (Et = ethyl). Three stereoisomers exist, R,R-, S,S-, and R,S (=S,R-). They are the ethyl esters of the respective R,R-, S,S-, and R,S-tartaric acids. The R,R- and S,S- isomers are enantiomeric, being mirror images. The meso stereoisomer is not chiral. The chiral isomer is far more common. In the Sharpless epoxidation, diethyl tartrate and titanium isopropoxide Titanium isopropoxide, also commonly referred to as titanium tetraisopropoxide or TTIP, is a chemical compound with the formula . This alkoxide of titanium(IV) is used in organic synthesis and materials science. It is a diamagnetic tetrahedral m ... form a chiral catalyst ''in situ''. The TADDOL ligand scaffold is produced from diethyl tartrate.{{cite journal , doi=10.1002/anie.200906550, title=Enantioselective Gold Catalysis: Opportunities Provided by Monodentate Phosphoramidite Ligands with an Acyclic TADDOL Backbone, author=Henrik Teller, Sus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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