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Salicin is prepared from a decoction o~ the bark by first precipitating the tannin by milk of lime, then evaporating the filtrate to a soft extract, and dissolving out the salicin by alcohol. As met with in commerce it is usually in the form of glossy white scales or needles. It is neutral, odourless, unaltered by exposure to the air, and has a bitter taste. It is soluble in about 30 parts of water and 80 parts of alcohol at the ordinary temperature, and in 0.7 of boiling water or in 2 parts of boiling alcohol, and more freely in alkaline liquids. It is also soluble in acetic acid without alteration, but is insoluble in chloroform and benzol. From phloridzin it is distinguished by its ammoniacal solution not becoming colored when exposed to the air. Chemically, it is a glucoside derived from glucose and saligenin (o-oxy-benzyl alcohol), into which it is decomposed by the enzymes ptyaline and emulsin. Oxidation converts it into helicin (salicylaldehyde-glucose). Populin, a benzoyl salicin, is a glucoside found in the leaves and bark of Populus tremula.
Salicin is used in medicine for the same purposes as salicylic acid and the salicylates. It is also used as a bitter tonic, i.e. a gastric stimulant, in doses of five grains. The ordinary dose may go up to forty grains or more with perfect safety, though the British Pharmacopoeia limits it to twenty. The remote action of the drug is that of salicylic acid or the numerous compounds that contain it (see SALIcYLiC Acm).
Salicin is a glycoside, which acts as a precursor compound for the synthesis of acetyl salicylic acid. Glycoside consists of a carbohydrate molecule (sugar) and a non-sugar component (aglycone). Majorities of them have been isolated from plants and have considerable medicinal value. Salicylic acid is a colorless, crystalline organic carboxylic acid. It is usually prepared by Kolbe synthesis (aka Kolbe-Schmitt reaction), which works by heating sodium phenolate (the sodium salt of phenol) with carbon dioxide under pressure (100 atm, 125°C), then treating it with sulfuric acid.
Salicin is helpful for mild feverish colds and infections (influenza), acute and chronic rheumatic disorders, mild headaches, and pain caused by inflammation. Does not have the dangerous side effects associated with Aspirin.
Salicin is used in medicine for the same purposes as salicylic acid and the salicylates. It is also used as a bitter tonic, i.e. a gastric stimulant, in doses of five grains. The ordinary dose may go up to forty grains or more with perfect safety, though the British Pharmacopoeia limits it to twenty. The remote action of the drug is that of salicylic acid or the numerous compounds that contain it.
Salicylic acid is also found in plants, especially in fruit, in the form of methyl salicylate. It is toxic if digested in large quantities, but in small quantities used as a food preservative and antiseptic in toothpaste. The carboxyl group (-COOH) can react with alcohols, forming several useful esters. The hydroxyl group (-OH) can react with acetic acid to acetylsalicylic acid.
Salicylic acid is the active ingredient in many skin-care products for the treatment of acne. It helps acne by causing skin cells to slough off more readily, preventing pores from clogging up.
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