Sinapis Nigrae Semina, B.P., Black 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.
Black mustard seeds are obtained from Brassica sinapioides, Roth. (N.O. Cruciferae), an annual herbaceous plant, largely cultivated in temperate climates. They are also official in the U.S.P. The dried, ripe seeds are minute, about 1 millimetre in diameter, nearly dark or greyish-brown in colour. Outer surface distinctly pitted, internally yellowish and oily, the section exhibiting two folded cotyledons embracing a small radicle. When soaked in water the seeds become surrounded by mucilage. The entire seeds are odourless; when powdered they have a slight, characteristic odour, but when the powder is moistened the odour becomes strong and pungent, attacking the mucous membrane of both eyes and nostrils. Taste, at first bitter, but rapidly becoming pungent. The powdered seeds exhibit under the microscope characters similar to those described for white mustard, but differing chiefly in the following particulars:—The fragments of the sclerenchymatous layer are dark yellowish-brown in colour, and exhibit distinct, large, dark reticulations; the cells of the hypodermis have thinner walls; the mucilage in the epidermal cells exhibits no striations. On incineration, black mustard seeds yield front 4.2 to 5.7 per cent. of ash.
Constituents.—The seeds contain a crystalline glucoside, sinigrin (potassium myronate), and an enzyme, myrosin. In the presence of water these bodies give rise to allyl isothiocyanate, potassium acid sulphate, and dextrose. Allyl isothiocyanate (essential oil of mustard) is a mobile, volatile liquid, with an extremely pungent odour and taste. The drug yields from 0.7 to 1.3 per cent. of this volatile oil, Dutch seed being the best. In the oil, allyl isothiocyanate is generally accompanied by other bodies, such as allyl cyanide. Black mustard seeds also contain fixed oil (about 27 per cent.), proteins (about 29 per cent.), and mucilage.
Uses.—Black mustard seeds are used in the preparation of the volatile and fixed oils, and mixed with white mustard seeds, as "ground mustard." "Mustard bran" consists of the integuments of white and black mustard seeds. It has properties similar to those of ground mustard, but is much weaker in its action.