Plant of the Month: Squill

Squill (Drimia maritima (L.) )

Squill is a common name for a group of plants that are lily like and are members of the Asparagaceae family. The Squill of commerce comprises two main species namely Drimia maritima (L.) Stearn also known as Urginea maritima and commonly known as maritime squill, sea onion or red squill and Drimia indica (Roxb.) Jessop which is commonly known as Indian squill. Maritime squill is native to coastal areas of the Mediterranean and is found growing wild in France, Portugal, Spain, Italy, Greece, Turkey, Syria, Lebanon, Israel, Algeria and Morocco, at up to 300 m above sea level. It is also found in the Canary Islands and Southern Iran and Iraq. Drimia indica has a distribution from tropical and South Africa, the Indian subcontinent and eastwards to Vietnam.

Both plants are herbaceous perennials and contain large bulbs up to 20-30 cm in diameter with each bulb bearing dark green, leathery leaves, up to 100 cm long and 12 cm wide. The flowers of Indian squill are greenish brown to somewhat purple in colour whilst those of maritime squill are white but some varieties have red tinted flowers lending to the name Red squill.

Drimia maritima has a long history of use in traditional medicine. In fact the classical name of the plant, Scilla is derived from a Greek word meaning to excite or disturb. The Greek physician Dioscorides and the Greek philosopher Pythagoras used it as a protection against evil spirits and unwelcome visitors by hanging the bulb, with its leaves, outside the door in spring. It was also used in ancient Greece as a treatment for jaundice, convulsions and asthma. The Greek scholar Theophrastus recommended its use as a rat poison as unlike most other animals rats seem undeterred from eating it. This is because of its extremely bitter taste which induces vomiting. Historically, wild bulbs were dug up and chopped into small pieces and dried, then ground to produce ‘powdered squill’. The fresh bulb is slightly more medicinal than the dried bulb, but it also contains a viscous acrid juice that can cause skin inflammation. The plant has also been historically used as an insect repellent. In more recent times maritime squill has been used as an expectorant, emetic, diuretic and cardio tonic to regulate heart rhythm and it is a common ingredient of cough mixtures. For example Squill Oxymel and Squill Tincture are respective ingredients in the Herbal Mucus Cough Syrup and Chesty Cough Mixture (Mentholated) products from the Covonia range of liquid medicines marketed by Thornton & Ross.

Official liquid preparations include Squill Liquid Extract BPC 1973, Squill Tincture BPC 1973, Squill Vinegar BPC 1973, Ipecacuanha and Squill Linctus, Opiate (Paediatric) BPC 1973, Squil Oxymel BP and Squill Elixir BP 1980. Squill oxymel is basically a preparation containing honey and Vinegar of Squill with the latter prepared by macerating the plant material in aqueous acetic acid.

The active constituents of Squill are bufadienolides based mainly on the aglycone scillaridin A. The principal glycosides are scillarin A (1) and proscillaridn A (2). They contain a triterpenoid skeleton which is steroidal in structure. They function as cardiac glycosides by exhibiting positive inotropic and negative chronotropic effects on the cardiac muscle. This is believed to be accomplished by inhibition of Na+/K+ – ATPase in the cardiac muscle by the bufadienolides. The plant also has additional cardiovascular properties that include reducing left ventricular diastolic pressure, and reducing pathologically elevated venous pressure. However due to its cardiac glycoside content squill has a similar property to Digitalis including arrhythmia and atrioventricular block. Other common adverse effects include abdominal pains, vomiting, nausea and seizures. The plant is therefore toxic if taken in large amounts. Proscillaridin A is not a constituent in Drimia maritima but it is present in D. indica. Therefore Indian squill is of inferior quality to the European species as it is more toxic although it is occasionally substituted for D. maritima in trade. The latter is thus recognised as the true squill of commerce. In addition to the cardiac glycosides squill is also known to contain flavonoids such as apigenin, luteolin, vitexin, isovitexin, orientin, taxifolin and dihydroquercetin.

Ransom Naturals Ltd manufracture several herbal drug preparations containing squill. These are SQ/01 – Squill Aqueous Soft Extract (Indian squill), SQ/02 – Squill Aqueous Soft Extract (Italian squill), SQ/05 – Solution for Making Squill Elixir BP1980, SQ/11 – Squill Liquid Extract BP, SQ/14 – Squill 65% Alcoholic Soft Extract, SQ/15 – EFM Squill Liquid Extract BP, SQ/16 – EFM Squill Tincture BP, SQ/25 – Squill Vinegar for oxymel, SQ/27 – SFM Squill Oxymel BP, SQ/28 – Squill Oxymel BP