Sinapis Albae Semina, B.P., White Mustard Seeds.
Related entries: Sinapis, B.P., Mustard. - Sinapis Albae Semina, B.P., White Mustard Seeds. - Sinapis Nigrae Semina, B.P., Black Mustard Seeds. - Oleum Sinapis Expressum, Expressed Oil of Mustard. - Oleum Sinapis Volatile, B.P., Volatile Oil of Mustard.
White mustard seeds are obtained from Brassica alba, Boiss. (N.O. Cruciferae), an annual herb, largely cultivated in temperate climates. They are also official in the U.S.P. The dried ripe seeds are yellow in colour, minutely pitted and nearly spherical, about 2 millimetres in diameter. Internally, they are yellow and oily, a transverse section showing two folded cotyledons embracing a small radicle. When soaked in water they become coated with mucilage. Odour, slight; taste, pungent, but the crushed seeds moistened with water exhale no pungent odour. The powdered seeds, after removal of the fixed oil by ether-alcohol, exhibit under the microscope the following characteristic cells and tissues:—Fragments of the sclerenchymatous layer appear in surface view as groups of small, yellow, strongly thickened, polygonal cells; epidermis, consisting of large, polygonal, thin-walled cells filled with colourless striated mucilage; hypodermis of large polygonal cells with moderately thick walls and intercellular spaces; cotyledons and radicle composed of small thin-walled cells containing minute, irregular, aleurone grains in which are a few, very minute globoids. Starch is either entirely absent or present only in the form of isolated groups of minute rounded grains derived from the occasional presence of an unripe seed. Oil incineration, the seeds yield front 4 to 5 per cent. of ash.
Constituents.—The seeds contain a crystalline glucoside, sinalbin, together with an enzyme, myrosin. The latter in the presence of water hydrolyses the sinalbin, producing acrinyl isothiocyanate, sinapine and sulphate, and dextrose. Acrinyl isothiocyanate is a yellow oily liquid with pungent taste and powerful, rubefacient action, but is it is not volatile it has no pungent odour. Sinapine is an alkaloid, but is. so unstable that it has not yet been isolated. White mustard seeds contain in addition fixed oil (about 30 per cent.), proteins (about 25 per cent.), and mucilage.
Uses.—White mustard seeds are used for the extraction of the fixed oil, and are mixed with black mustard seeds, in powder, for use as "round mustard" (see Sinapis).
PREPARATION.
- Charta Sinapis, B.P.—MUSTARD PLASTER.
- Black mustard seeds, 50; white mustard seeds, 50; benzol, a sufficient quantity; solution of indiarubber, a sufficient quantity. Remove the fixed oil from the bruised seeds by percolation with benzol, dry the residue by exposure to warm air, and reduce it to No. 60 powder. Mix 5 grammes (75 grains) of this with 18 mils (5 fluid drachms) of solution of indiarubber, spread the mixture with a suitable brush over about 2 square decimetres (30 square inches) of one side of a piece of cartridge paper, and dry by exposure to air. A mixture of white and black mustard seed, gives the best result, as the former contain an excess of ferment and the latter of glucoside. Mustard paper is used as a counter-irritant in lumbago, congestion of the lung, pneumonia bronchitis, phthisis, and wherever counter-irritation is indicated. Small pieces of suitable size and shape may be applied to the temple or behind the ear, and fixed in position by a strip of adhesive plaster. Mustard paper should be dipped in tepid water for about fifteen seconds before being applied. "Half-strength" mustard papers are prepared, or one or two layers of damped muslin may be placed next the skin, if the full-strength papers cause 100 much pain and irritation.
