Brassica juncea foliosa

• Leaf Mustard

Leaves - raw or cooked^{[1][2][3][4][5]}. A peppery flavour that can range from mild to hot, this is one of the most highly prized cooked vegetables in the Orient^[6]. The leaves can also be finely shredded and added to mixed salads^[6]. The protein extracted from the leaves mixes well with banana pulp and is well adapted as a pie filling^[7].

Flowers and young flowering stems - raw or cooked^[4]. Sweet and succulent^[8]. An edible semi-drying oil is obtained from the seed^{[9][10][11][12][7]}. The seed contains 25 - 30% oil^[13]. The seed is used as a mustard flavouring^[14]. It is the source of 'brown mustard'^[7], a prepared mustard that is milder than that produced from other species^[15]. Pungency of mustard develops when cold water is added to the ground-up seed - an enzyme (myrosin) acts on a glycoside (sinigrin) to produce a sulphur compound. The reaction takes 10 - 15 minutes. Mixing with hot water or vinegar, or adding salt, inhibits the enzyme and produces a mild bitter mustard^[15]. Black mustard comes from B. nigra and white mustard from Sinapis alba. The seed is also used whole in curries and pickles^[15]. They are often heated in oil to destroy their pungency and give them a nutty flavour^[15].

Sprouted seeds can be added to salads.

There is some evidence that if this plant is grown as a green manure it is effective in reducing soil-borne root rots in pea crops^[6]. This is attributed to chemicals that are given off as the plants decay^[6].

Reported to be anodyne, aperitif, diuretic, emetic, rubefacient, and stimulant, the plant is a folk remedy for arthritis, foot ache, lumbago, and rheumatism^[16].

The seed is used in the treatment of tumours in China^[16]. In Korea, the seeds are used in the treatment of abscesses, colds, lumbago, rheumatism, and stomach disorders^[16]. The root is used as a galactagogue in Africa^[16]. Ingestion may impart a body odour repellent to mosquitoes^[16]. Mustard oil is used in the treatment of skin eruptions and ulcers^[16]. Believed to be aperient and tonic, the volatile oil is used as a counterirritant and stimulant^[16]. In Java the plant is used as an antisyphilitic emmenagogue^[16]. Leaves applied to the forehead are said to relieve headache^[16].

The Chinese eat the leaves in soups for bladder, inflammation or haemorrhage^[16].