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S-(+)-Carvone is the principal constituent (60–70%) of the oil from caraway seeds (Carum carvi), [8] which is produced on a scale of about 10 tonnes per year. [3] It also occurs to the extent of about 40–60% in dill seed oil (from Anethum graveolens), and also in mandarin orange peel oil.
Only the dextro-isomer (dextropropoxyphene) has an analgesic effect; the levo-isomer appears to exert only an antitussive effect. It was formerly marketed in the U.S. by Eli Lilly under the tradename Novrad (a reversal of Darvon) as an antitussive. [1] [2] Unlike many antitussives, it binds poorly to the sigma-1 receptor. [3]
In chemistry, racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic (optically inactive) form. This creates a 1:1 molar ratio of enantiomers and is referred to as a racemic mixture (i.e. contain equal amount of (+) and (−) forms).
[1] [2] It is also used in chemical synthesis as a precursor to carvone and as a renewables-based solvent in cleaning products. [1] The less common (-)-isomer has a piny, turpentine-like odor, and is found in the edible parts of such plants as caraway, dill, and bergamot orange plants. [3] Limonene takes its name from Italian limone ("lemon"). [4]
Carvacrol is present in the essential oil of Origanum vulgare (oregano), oil of thyme, oil obtained from pepperwort, and wild bergamot. [5] The essential oil of thyme subspecies contains between 5% and 75% of carvacrol, while Satureja (savory) subspecies have a content between 1% and 45%. [6]
Levmetamfetamine is excreted in urine 40.8 to 49.0% as unchanged levmetamfetamine and 2.1 to 3.3% as levoamphetamine. [2] [4] [3] The mean elimination half-life of levmetamfetamine ranges between 10.2 and 15.0 hours. [2] [4] For comparison, the elimination half-life of dextromethamphetamine was around 10.2 to 10.7 hours in the same studies.
Dextropropoxyphene [5] is an analgesic in the opioid category, patented in 1955 [6] and manufactured by Eli Lilly and Company.It is an optical isomer of levopropoxyphene.It is intended to treat mild pain and also has antitussive (cough suppressant) and local anaesthetic effects.
The most notable examples of mass-independent fractionation in nature are found in the isotopes of oxygen and sulfur.The first example was discovered by Robert N. Clayton, Toshiko Mayeda, and Lawrence Grossman in 1973, [2] in the oxygen isotopic composition of refractory calcium–aluminium-rich inclusions in the Allende meteorite.