Scientific Name(s): Urginea indica (Roxb.) Kunth. (Indian squill), Urginea maritima (L.) Baker (European or white squill), Urginea maritima var. pancratium Stein Baker (red squill)
Common Name(s): European squill, Indian squill, Mediterranean squill, Red squill, Scilla, Sea onion, Sea squill, White squill
White squill is a perennial herb that is native to the Mediterranean region. It often grows in sandy soil near the sea, and its onion-like appearance accounts for the common name sea onion or sea squil (and is synonymous with Drimia maritima). The bulbous portion of the base is harvested, and the dried inner scales of the bulb (not the central portion of the bulb) is used. White squill has sometimes been adulterated by the inclusion of Indian squill, which has comparable biological activity.1 Red squill is primarily used as a rodenticide.2
Some varieties of squill have been known to be effective rodenticides for more than a thousand years. In humans, extracts of the bulb were used as a cardiotonic by the Romans and ancient Egyptians for the treatment of edema, as an expectorant, and as an emetic. It continues to find use as an expectorant in some commercial cold preparations. Because of the popularity of the digitalis glycosides, squill components are rarely used in the United States as cardioactive agents, although squill was approved in 1985 by the German Comission E for cardiac insufficiency.
Squill contains a large number of related steroidal cardioactive glycosides. Those found in the greatest concentration in the bulb include scillaren A and proscillaridin A, the aglycone of both being scillarenin. In addition, glucoscillaren A, scillaridin A, and scilliroside have been characterized. In 1 study, the most common components identified in dried bulbs were scilliroside (approximately 45 ppm) and scillaren A (approximately 38 ppm)3; other studies have found proscillaridin A in the greatest concentration.4 Scillaren B refers to a mixture of squill glycosides.5 Components of squill tissue cultures appear to vary in quantitative composition from whole bulb extracts.6 Furthermore, extracts from fresh bulbs can vary based on the time of year they are collected. Many novel cardiac glycosides recently have been isolated and identified from squill.7, 8, 9, 10 Indian squill also contains proscillaridin A and scillaren A as major glycosides, with minor components differing from white squill.11 Red squill's glycosides also have been studied.3, 12 Other constituents found in squill include flavonoids,13, 14 the fructan sinistrin,15 and related carbohydrates16 and an antifungal glycoprotein.17
Uses and Pharmacology
Squill extracts cause peripheral vasodilation and bradycardia in anesthetized rabbits.6
Squill glycosides have cardiotonic properties similar to digitalis. However, squill components are generally poorly absorbed from the GI tract and are less potent than digitalis.18
A pilot study has evaluated the effect of squill in asthma, reporting improvement in spirometry parameters especially FEV1 over 6 weeks of supplementation.19
Squill induces vomiting through a central action and local gastric irritation. Vomiting may be preceded by a generalized increase in the flow of secretions, and therefore these compounds appear to exert an expectorant effect in sub-emetic or near-emetic doses.
In general, red squill is not used medicinally; the powdered dried bulbs of red squill are mainly used as rodenticides. Death is caused by the centrally induced convulsant action of scilliroside, rather than by direct cardiotoxicity. Rats lack a vomit reflex and are insensitive to the emetic action of these glycosides. Because squill-laced bait is vomited by domestic animals before a lethal dose can be absorbed, often it is considered to be a rat-specific agent.3
Methanolic extracts of red squill have been used as hair tonics in treating seborrhea and dandruff, the activity being ascribed to scilliroside.5
Squill has been used traditionally as a cancer remedy, and silliglaucosidin has shown activity in an experimental cancer cell line.18
Squill has been studied for its cardiovascular effects at an IV dose of methylproscillaridin 1 mg, a cardiac glycoside of the herb. Classical use of the dried bulb was at 100 mg doses. As with any cardiac glycoside-containing product, use squill with caution.20
Preparations for oral administration are enteric-coated to prevent degradation by gastric acid. Meproscillaren, a semisynthetic derivative of proscillaridin, is absorbed orally and may be effective in some patients.
The strength of squill preparations and extracts may vary, and therefore must be used with caution.21
Pregnancy / Lactation
Documented abortifacient effects; affects menstrual cycle.22 Avoid use.
Use caution when coadministered with calcium, laxatives, quinidine, saluretics, and extended glucocorticoid therapy.
Adverse reactions related to squill include vomiting and convulsions, which generally are observed in overdose situations. In general, red squill is not used medicinally and may induce convulsions.
A pilot study on the effect of squill in asthma, reported nausea and vomiting amongst some participants.19
Although white squill and its extracts have the potential to induce life-threatening cardiac effects in relatively low doses, they generally have not been associated with human toxicity. Vomiting often is induced as a reflex in cases of overdosage, minimizing the absorbed dose. The toxic dose of squill soft mass (a galenical extract form used to make certain squill preparations) in guinea pigs is 270 mg/kg; tinctures made from Indian squill caused death at a dose of 36 mg/kg.23 Fresh bulbs contain a vesicant.18
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