Liquorice

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Chapter: Pharmacognosy and Phytochemistry : Drugs Containing Glycosides

Liquorice consists of subterranean peeled and unpeeled stolons, roots and subterranean stems of Glycyrrhiza glabra Linn, and other species of Glycytrhiza, belonging to family Leguminosae.


LIQUORICE

 

 

Synonyms

 

Radix Glycyrrhizae, Sweet liquorice.

 

Biological Source

 

Liquorice consists of subterranean peeled and unpeeled stolons, roots and subterranean stems of Glycyrrhiza glabra Linn, and other species of Glycytrhiza, belonging to family Leguminosae.

 

Geographical Source

 

It is mainly found in China, Europe, India, Iraq, Japan, Kurdistan, Spain, Turkey, and the United States.

 

Cultivation and Collection

 

Liquorice is often cultivated for its edible root which is widely used in medicine and as flavouring. The plant requires a deep well cultivated fertile moisture-retentive soil for good root production. Prefers a sandy soil with abundant moisture and does not flourish in clay. Slightly alkaline conditions produce the best plants. The plant thrives in a maritime climate. It is propagated using seeds and roots. The seeds are presoaked for 24 h in warm water and then sown in spring or autumn in a greenhouse. The seedlings are individually potted when they are large enough to handle, and grown them for their first winter in a green house. They are transplanted in late spring or early summer when in active growth. Plants are rather slow to grow from seed. The plant parts are procured from old plantations, being waste from the harvesting process, consisting of those side roots or runners which have eyes or buds, cut into sections about 6 inches long. They are dibbled in rows 3 or 4 feet apart, about 4 inches underneath the surface and about 18 inches apart in the rows. In the autumn, the ground is dressed with farmyard manure, about 40 tons to the acre. Plants are slow to settle in and do not produce much growth in their first two years after being moved. The young growth is also very susceptible to damage by slugs and so the plant will require some protection for its first few years. This species has a symbiotic relationship with certain soil bacteria; these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby.

 

 

Harvesting generally occurs in the autumn of the fourth year. The soil is carefully removed from the space between the rows to a depth of 2 or 3 feet as required, thus exposing the roots and rhizomes at the side, the whole being then removed bodily. The earth from the next space is then removed and thrown into the trench thus formed and these operations are repeated continuously. Every portion of the subterranean part of the plant is carefully saved; the drug consists of both runners and roots, the former constituting the major part. The roots are properly washed, trimmed and sorted, and either sold in their entire state or cut into shorter lengths and dried, in the latter case the cortical layer being sometimes removed by scraping. The older or ‘hard’ runners are sorted out and sold separately; the young, called ‘soft,’ are reserved for propagation.

 

Characteristics

 

Liquorice root is in long, straight, nearly cylindrical, unpeeled pieces, several feet in length, varying in thickness from 1/4 inch to about 1 inch, longitudinally wrinkled, externally greyish brown to dark brown, warty; internally tawny yellow; pliable, tough; texture coarsely fibrous; bark rather thick; wood porous, but dense, in narrow wedges; taste sweet, very slightly acrid. The underground stem which is often present has a similar appearance, but contains thin pith. When peeled, the pieces of root (including runners) are shorter, a pale yellow, slightly fibrous externally, and exhibit no trace of the small dark buds seen on the unpeeled runners here and there. Otherwise it resembles the unpeeled.

 


                 Root and twig of Glycyrrhiza glabra


Microscopy

 

Cork consists of several rows of radially arranged thin walled tubular cells. Phelloderm is composed of parenchymatous and sometimes collenchymatous cells. Starch grains and calcium oxalate crystals are seen in phelloderm. Pericyclic fibres are found in groups. Phloem consists of sieve tissue alternating with thick walled, lignified fibres surrounded by a sheath of parenchymatous cells containing prisms of calcium oxalate. Xylem vessels and xylem parenchyma are present. Medullary rays are radially elongated. Pith is present in rhizomes and absent in root.

 


           Transverse section of Liquorice stolon


Chemical Constituents

 

The chief constituent of liquorice root is Glycyrrhizin (6–8%), obtainable in the form of a sweet, which is 50 times sweeter than sucrose, white crystalline powder, con-sisting of the calcium and potassium salts of glycynhizic acid. Glycyrrhizic acid on hydrolysis yields glycyrrhetic or glycyrrhetinic acid.

Glycyrrhizinic acid is a triterpenoid saponin having α-amyrine structure. It shows especially in alkaline solu-tion frothing but it has very weak haemolytic property. The yellow colour of the drug is due to chalcone glycoside isoliquiritin. The drug also contains sugar, starch (29%), gum, protein, fat (0.8%), resin, asparagin (2–4%), a trace of tannin in the outer bark of the root, yellow colouring matter, and 0.03% of volatile oil.



 

Chemical Test

 

When 80% sulphuric acid is added to a section or powder of the drug orange yellow colour is produced due to transformation of flavone glycoside liquiritin to chalcone glycoside isoliquiritin.

 

Uses

 

Glycyrrhiza is widely used as a sweetening agent and in bronchial problems such as catarrah, bronchitis, cold, flu and coughs. It reduces irritation of the throat and yet has an expectorant action. It produces its demulcent and expectorant effects. It is used in relieving stress. It is a potent healing agent for tuberculosis, where its effects have been compared to hydrocortisone. Glycyrrhiza is also effective in helping to reduce fevers (glycyrretinic acid has an effect like aspirin), and it may have an antibacterial action as well. It is used in the treatment of chronic inflammations such as arthritis and rheumatic diseases, chronic skin conditions, and autoimmune diseases in general. It should be used in moderation and should not be prescribed for pregnant women or people with high blood pressure, kidney disease or taking digoxin-based medication. Prolonged usage raises the blood pressure and causes water retention. Externally, the root is used in the treatment of herpes, eczema and shingles.

 

Marketed Products

 

It is one of the ingredients of the preparations known as Herbolex, Koflet, Regurin (Himalaya Drug Company), Jeevani malt (Chirayu Pharma), Eladi Bati, Madhume-hari (Baidyanath), J.P. Nikhar oil, J.P. Kasantak (Jamuna Pharma), Respinova (Lupin Herbal Laboratory) and Yasti madhu (Zandu Pharmaceuticals Works Ltd.).

 

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