Greater celandine
The greater celandine (Chelidonium majus, aka. 'Tetterwort') is a yellow flowering plant in the poppy family, native to Europe and the Mediterranean basin. It is also widespread in North America, having been brought there by settlers as a herbal remedy for skin problems such as warts as early as 1672.
Greater celandine is plant of size may reach 30 to 120 cm high, with an erect stem.  The  leaves are deeply divided, 30-cm long. The flowers comprise four yellow petals, each about 1 cm long, with two sepals.  The flowers appear from May to July.  The seeds are small and black, and possess an elaiosome, which attracts ants to disperse the seeds (myrmecochory).  A double-flowered variety, a naturally occurring mutation, also exists.  It is considered an aggressive invasive plant in natural areas (both woods and fields). Control is mainly via pulling or spraying the plant before seed dispersal.
The greater celandine is the only species in the genus Chelidonium, and is not closely related to the lesser celandine, which is in a different family.

# Pharmacology
The whole plant is toxic in moderate doses as it contains a range of isoquinoline alkaloids but there are numerous therapeutic uses when used at the correct dosage. The main alkaloid present in the herb and root is coptisine. Other alkaloids present include berberine, chelidonine, sanguinarine and chelerythrine.   Sanguinarine is particularly toxic with a lethal dose of only 18mg per kg body weight Despite this acute toxicity, sangunarine is present in such small quantities that the LD50 dose would require >50g of raw herb to be ingested.  Caffeic acid derivatives are also present.
The effect of the fresh herb is of a mild analgesic, cholagogic, antimicrobial, oncostatic and central nervous system sedative.  In animal test, Celandine is shown to be cytostatic.  An immune stimulating effect has also been noted.  Some studies show that the alkaloid extraction can have the same effects.  The alkaloids are known to cause immobilization in mice after been taken orally or injected.  The alkaloids cause limpness and tone reduction of smooth muscle in rabbits.  The alkaloids are also noted to stimulate the heart and lungs of frogs, cats and dogs, raising the blood pressure and widening the arteries.
Early studies of Celandine showed that it causes contact dermatitis and eye irritation, particularly from contact with the red to yellow latex.  This effect has not been observed in animal studies; no inflammation was observed in rabbit eye tests.  The latex can leave a non-permanent stain.  Stains on skin of the fingers are sometimes reported to cause eye irritation after rubbing the eyes or handling contact lenses.  When any part of the plant causes eye irritation, wash it out with clear water and when needed seek medical help.  The latex is also known to stain clothes.

# Herbalism
The aerial parts and roots of Greater Celandine are used in herbalism.  The above ground parts are gathered during the flowering season and dried at high temperatures.  The root is harvested in Autumn between August and October and dried.  The fresh rhizome is also used.  Celandine has a hot and bitter taste.  The latex has a narcotic fragrance.
Preparations are made from alcoholic and hot aqueous extractions (tea).  The average daily dosage is 2 to 4 g, equivalent to 12 to 13 mg total alkaloids.  For fluid extracts, the daily dosage is 1 to 2 ml of 1:1 25% alcoholic extraction, up to 3 times per day.  For hot tea infusions, 1.5 desert spoonfuls left in boiling water for 10 minutes can be taken 3 times a day.
It was formerly used by gypsies as a foot refresher; modern herbalists use its purgative properties.  .
Greater celandine acts as a mild sedative which has been used historically to treat asthma, bronchitis, and whooping cough.  The herb's antispasmodic effect improves bile flow in the gallbladder and has been reputed to treat gallstones and gallbladder pain. As far back as Pliny the Elder and Dioscorides (1st century AD) this herb has been recognized as a useful detoxifying agent.  The root has been chewed to relieve toothache.