It is a biennial herb growing to a maximum height of 6 feet. The erect stem, springing from a brown tap-root, is smooth and pale green, sometimes spotted with purple. There are a few prickles on the lower part and short horizontal branches above. The numerous, large, radical leaves are from 6 to 18 inches long, entire, and obovate-oblong. The stem leaves are scanty, alternate, and small, clasping the stem with two small lobes. The heads are numerous and shortly-stalked, the pale-yellow corolla being strap-shaped. The rough, black fruit is oval, with a broad wing along the edge, and prolonged above into a long, white beak carrying silvery tufts of hair. The whole plant is rich in a milky juice that flows freely from any wound. This has a bitter taste and a narcotic odour. When dry, it hardens, turns brown, and is known as lactucarium.
Lactuca virosa L. (Asteraceae/Compositae).
Synonyms and Part Used
Bitter Lettuce, Lettuce Opium.
Related Lactuca species include Lactuca sativa (Garden Lettuce), Lactuca scariola (Prickly Lettuce), Lactuca altissima and Lactuca canadensis (Wild Lettuce of America).
All parts of the plant contain a milky, white latex (sap) which, when collected and dried, forms the drug known as lactucarium.
Citric, malic and oxalic (up to 1%) acids; cichoric acid (phenolic).
Hyoscyamine, later disputed. N-methyl-β-phenethylamine, also disputed.
Flavones (e.g. apigenin, luteolin), flavonols (e.g. quercetin) and their glycosides.
Bitter principles including the sesquiterpene lactones lactucin and lactupicrin (lactucopicrin); β-amyrin,germanicol, and lactucone (lactucerin). Lactucone is a mixture of α- and β-lactucerol acetates, β-lactucerol being identical to taraxasterol.
Mannitol, proteins, resins and sugars.
Wild lettuce is not used in foods, although the related species L. sativa is commonly used as a salad ingredient.
Wild lettuce is stated to possess mild sedative, anodyne and hypnotic properties. Traditionally, it has been used for insomnia, restlessness and excitability in children, pertussis, irritable cough, priapism, dysmenorrhoea, nymphomania, muscular or articular pains, and specifically for irritable cough and insomnia.
Dried leaves :
0.5–3.0 g or by infusion three times daily.
0.5–3.0 mL (1 : 1 in 25% alcohol) three times daily.
Lactucarium (dried latex extract):
(BPC 1934) 0.3–1.0 g three times daily.
(BPC 1934) 0.3–1.0 g three times daily.
In vitro and animal studies
Lactucarium has been noted to induce mydriasis.This effect may be attributable to hyoscyamine, although the dried sap is reportedly devoid of this alkaloid.
An alcoholic extract of a related species, L. sativa, has exhibited a sedative effect in toads, causing a reduction in motor activity and behaviour.Higher doses resulted in flaccid paralysis. In addition, an antispasmodic action on isolated smooth and striated muscle, and in vitro negative chronotropic and inotropic effects on normal and stressed (tachycardic) hearts were observed. The antispasmodic action was noted to be antagonised by calcium.
Lactucin, lactupicrin and hyoscyamine have all been proposed as the sedative components in wild lettuce. However in the above study,the active component was uncharacterised and acted mainly peripherally, not readily crossing the blood–brain barrier. The suggested mode of action was via interference with basic excitatory processes common to neural and muscular functions, and not via a neuromuscular block.
Low amounts (nanograms) of morphine have been detected in Lactuca species, although the concentrations involved are considered too low to exert any obvious pharmacological effect.
None documented for L. virosa. Wild lettuce contains sesquiterpene lactones which are potentially allergenic.
Occupational dermatitis has been documented for L. sativa together with an urticarial eruption after ingestion of the leaves.
The milky sap of L. sativa is reported to be irritant.
The toxicity of wild lettuce is stated to be low.
Consumption of large amounts of L. scariola has caused poisoning in cattle, who developed pulmonary emphysema,severe dyspnoea, and weakness.Only the immature plants were reported to be toxic.
L. sativa has been reported to produce only negative responses when tested for mutagenicity using the Ames test.
Overdosage may produce poisoning involving stupor, depressed respiration, coma and even death. Wild lettuce may cause an allergic reaction in sensitive individuals, in particular those with an existing sensitivity to other members of the Asteraceae/Compositae family.
Pregnancy and lactation
The safety of wild lettuce has not been established. In view of the lack of toxicity data and the possibility of allergic reactions, excessive use of wild lettuce during pregnancy and lactation should be avoided.
The chemistry of wild lettuce is well documented although it is not clear which constituents represent the active components. Early reports of hyoscyamine as a constituent have not been substantiated by subsequent study. No published information was found to support the traditional herbal uses of wild lettuce, although a sedative
action in toads has been reported for a related species L. sativa. In view of the potential allergenicity of wild lettuce and the lack of toxicity data, excessive use should be avoided.