8. Medicinal plants of the Rutaceae and Solanaceae families

The Rutaceae or rue family is a small family that consists of cultivated fruit trees and medicinal herbs. Plants in this family include the wall and garden rues (Ruta chalepensis and graveolens), orange (Citrus aurantium), lemon (Citrus limon), tangerine (Citrus paradisi) and grapefruit (Citrus paradisi).

The rues are two related species that have different medicinal uses. Both species are native to the Mediterranean region. They thrive on arid places that are usually rocky, and are in bloom between March and April. In Maltese folk medicine, the rues were used for the treatment of rheumatic pain and arthritis, that are two characteristic diseases of the Maltese. The fresh aerial parts were immersed in cooking oil and heated gently for about 20 minutes. The mixture was placed in an air-tight container and then the oil applied on the aching areas. This was used twice daily. The garden rue has been used internally as a sedative, antispasmodic, stomachic and anthelminthic. Caution should be practised when these are used internally as they are toxic in high doses. A volatile oil obtained from the rues has abortifacient properties. Today, an alkaloid called rutin is extracted in high quantities from these rues on an industrial scale.

A citrus tree with great medicinal value is the bitter orange tree (Citrus aurantium). The orange-flavoured water and Neroli oil is prepared from the fresh flowers of the bitter orange tree. It was used as a stomachic and sedative. It was also used in cases of vitamin C deficiency (scurvy). The bitter orange water has been used for culinary purposes, especially in confectionary items. The oil has important uses in aromatherapy and the perfumery industry. Although other citrus species have similar uses, the long-term use of the orange-flavoured water and Neroli oil have made the orange tree an important medicinal plant.

A family with several poisonous, but medicinally-important herbs is the Solanaceae or potato family. A species in this family that is widely cultivated and is a cash-crop for the Maltese farmer is the potato (Solanum tuberosum). Other cultivated edible crops are the tomato (Lycopersicum esculentum) and the aubergine (Solanum melongena). The potato is only edible when ripe, as green potatoes were found to be poisonous. Also although these three crops come from this poisonous family, through cultivation and experimentation, the genetic material that codes for the toxic compounds has been phased out, resulting in safer and non-toxic cultivars. Mediterranean natives in this family include the white henbane (Hyoscyamus albus), the Mediterranean withania (Withania somnifera) and garden thorn apple (Datura metel). Other important species include glaucous tobacco (Nicotiana glauca) and black nightshade (Solanum nigrum).

The white henbane (Hyoscyamus albus) is a native of the Mediterranean region that locally grows in arid waste places. Its yellow flowers, with white or purple anthers, bloom all the year round. The most important constituents with medicinal virtues are the alkaloids. These are obtained through a long process of extraction, although they can be recovered easily by preparing a crude extract. Although, these alkaloids are toxic, they have various pharmacological properties, so much so that some of them are included in modern medicine. These reduce the spasms in the intestine and in muscles and are effective against motion sickness. An overdose with these alkaloids may lead to death. An essential oil from the plant has antirheumatic properties.

The Mediterranean withania (Withania somnifera) is a shrub with yellow-green flowers that bloom between May and September. Although, it is native to the Mediterranean, it has been cultivated and naturalised in Maltese gardens. It has been used extensively in the treatment of inflammation and rheumatism, wounds and stomach conditions. This plant contains phytosterols, termed withanolides that have anti-cancer properties.

The garden thorn apple (Datura metel) has an unknown origin but it has been growing in the Mediterranean region for quite a long time. It has characteristic white, yellow or purple flowers, that appear between May and December. In folk medicine it has been used as a sedative, antispasmodic, insomnia and asthma. It is another poisonous plant that produces toxic alkaloids, too. In spite of this, the alkaloids are the constituents that give the plant, its medicinal virtues. Scientifically, it has been proved to be effective in asthma as it decreases the glandular secretions and dilates the airways. It has also prevents intestinal spasms and motion sickness.

Although glaucous tobacco (Nicotiana glauca) is a native of South America it has been cultivated and widely naturalised in the Mediterranean region. It has tubulular yellow flowers that appear between April and October. This is similar to the tobacco plant. It has a different group of alkaloids that the other plants mentioned. One of the most important alkaloids is nicotine. In fact the plant is liable to produce lung disease rather than curing it. Nicotine increases the blood pressure and pulse rate and decreases apetite. It contains also flavonoids with anti-inflammatory and anti-cancer properties.

The black nightshade (Solanum nigrum) is a poisonous plant with very attractive black berries, that have caused unintentional poisoning especially amongst children. Locally, it is found in waste places and road margins and flowers all the year round. Although poisonous, the Maltese used it in the treatment of haemorrhoids and wounds. The toxic alkaloid is solanine that induces coma at very low doses. Other alkaloids, like solanidine and solasodine although toxic have been used to reduce pain and today the industry is using them for the production of steroids for contraception and as anti-inflammatory agents.

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Last Update: 11th February 2010