Functional properties and toxicity

Nigella seed and oil are known to possess several pharmacological properties such as detergent, sedative, anti-inflammatory and expectorant. From ancient times, Nigella, because of its insect repellent properties, has been used as a seed spread in woollens and silk clothes to protect them from insects and used like moth balls. The presence of the carboxyl compound nigellone and non-carboxyl fractions are reported to protect guinea pigs against histamine-induced broncho-spasm and phenolic fractions obtained from seeds have been reported to be antibacterial. In Vitilago, Nigella powder is used as vinegar and applied on spots followed by exposure to sunlight. A decoction of seeds mixed with sesame oil is used externally in various skin eruptions. They are also used against scorpion sting. Preliminary clinical trials indicate Nigella's possible therapeutic use in some conditions of cough and bronchial-asthma. Alcoholic extracts of the seeds show antibacterial activity against Micrococcus pyogenes var. aureus and Escherichia coli (Pruthi, 2001).

Nigella sativa L. has not shown the specific inhibitory activity against tyrosinase (Mukherjee et al., 2001). The oil has microbial activity and has been investigated as antimicrobial (Minakshi and Banerjee, 1999), antiococeptive (Abdel-Fattah et al., 2000) and carminative (El-Dakhakhny, 2000). Nigella oils have played a significant role for altering the liver damage induced by Schistosoma mansoni infection in mice and helped in improving the immunological host system and to some extent with its antioxidant effect (Mahmoud et al., 2002). Recent studies had revealed that extract of Nigella sativa L. has a strong immunomodulatory and interferon-like activity (Medenica et al., 2000). It inhibits cancer and endothelial cell progression, and decreases the production of the angiogenic protein fibroblastic growth factor made by tumour cells.

Nigella is used in Indian medicine as a carminative and stimulant and is used against indigestion and bowel complaints. It is also used to induce post-natal uterine contraction and to promote lactation (Barbara, 2000). Nigella seeds are known from ancient Greece as a remedy for headaches, toothaches and intestinal parasites. Prajapati et al. (2003) have reviewed Nigella with many medicinal properties such as thermogenic, aromatic, carminative, diuretic, emmenagogue, anodyne, antibacterial, anti-inflammatory, deodorant, appetizing, digestive, anthelmintic, constipating, sudorific, febrifuge, stimulant, galacta-gogue and expectorant. It is also useful in skin diseases, haemorrhoids, cephalalgia, jaundice, inflammation, fever, paralysis, ophthalmia, halitosis, anorexia, dyspepsia, flatulence, diarrhoea, dysentery, cough, amenorrhoea, dysmenorrhoea, helminthiasis especially tapeworm, strangury, intermittent fevers, agalaetia and vitiated conditions of vata and kapha in the Indian Ayurvedic system of medicines.

The seeds are found to contain melanthin, a substance allied to helleborin and, like saponin, possessing emulsifying powers. The seeds are employed as a corrective of purgatives and other medicines and are believed to possess diuretic, anthelmintic and emmenagogue properties, useful in indigestion, loss of appetite, fever, diarrhoea, dropsy, puerperal diseases, etc. They have a definite action as a galactagogue and are therefore given to recently delivered women in combination with other medicines. The use of the seeds to protect clothing from insect damage is common all over India. For this purpose the seeds are mixed with powdered camphor as a preservative. The seeds have also antibilious property and are administered internally to arrest vomiting. The seeds are fried, bruised, tied in a muslin bag and smelt to give relief from cold and catarrh of the nose by constant inhalation.

Some of the native Indian medical preparations as reviewed by Nadkarni (2001) are given below:

• In intermittent fever Nigella seeds slightly roasted are recommended to be given in two-drachm doses with the addition of an equal quantity of treacle.

• In doses of 10-20 grains, Nigella seeds have a well-marked emmenagogue effect, useful in dysmenorrhoea and in large doses may induce abortion.

• In loss of appetite and distaste for food, a confection made of Nigella seeds, cumin seeds, black pepper, raisins, tamarind pulp, pomegranate juice and sonchal salt with treacle and honey is said to be very useful.

• In the after-pains of puerperal women, the administration of Nigella seeds with the addition of long-pepper, sonchal salt and wine have proved useful.

• In puerperal diseases such as fever, loss of appetite and disordered secretions after delivery, the following preparation called pancha jiraka paka is used. It consists of seeds of Nigella, cumin, anise, ajowain, carum, Anethum sowa, fenugreek, coriander, ginger, long pepper, long pepper root, plumbago root, habusha (an aromatic substance), dried pulp of Ziziphus jujuba, root of Aplotaxis auriculate and Kamala powder. To each 10 g, add treacle 1000 g, milk one seer (about 1 litre), butter 40 g. Boil them together and prepare a confection. Dose is about a drachm every morning.

Other uses as reviewed by Weiss (2002) are as follows:

• Crushed seeds in vinegar are applied to skin disorders such as ringworm, eczema and baldness.

• In Egypt, a tea made from powdered Nigella seeds fenugreek, garden cress, Commiphora spp. and dried leaves of Cleome spp., Abrosia maritina L. and Centaurium pulchellum (SW) Druce is used to treat diabetes.

The Nigella seed yields a volatile oil containing melanthin, nigelline, damascene and tannin. Melanthin is toxic in large dosages and nigelline is paralytic, so this spice must be used in moderation. The traditional use of Nigella seeds have been supported by Zaoui et al. (2002a) for treatment of dyslipidaemia; the hyperglycaemia and related abnormities, however, indicate a relative toxicity of this plant. In another report, Zaoui et al. (2002b) have reported acute and chronic toxicity of Nigella sativa fixed oil. The methanol extract from related species Nigella damascene seeds showed a high oestrogenic activity. Among the purified phenolic compounds tested, the phenolic ester 1-o-(2,4-dihydroxy) benzolglycerol showed the strongest oestrogenic activity owing to the presence of flavonoid compounds (Agardi et al., 2000). It has been said that love-in-the-mist (Nigella damascene) should never be used as a substitute for Nigella sativa (Chevallier, 2001).

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