Duboisia

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Chapter: Pharmacognosy and Phytochemistry : Drugs Containing Alkaloids

Duboisia consists of the dried leaves of Duboisia myoporoides R., Duboisia hopwoodii, D. leichhardtii, belonging to family Solanaceae.


DUBOISIA

 

 

Synonyms

 

Corkwood, cork tree.

 

Biological Source

 

Duboisia consists of the dried leaves of Duboisia myoporoides R., Duboisia hopwoodii, D. leichhardtii, belonging to family Solanaceae.

 

Geographical Source

 

It is mainly found in Australia and Ecuador.

 

Characteristics

 

Duboisia hopwoodii: Perennial shrub to 3 m, sometimes as small tree with brown to purplish bark on the young stems and corky older bark. Leaves are narrow, long and alternate to 15 cm, with recurved point and straight margins. Open clusters of white (with purple striped tube) flowers at the end of the branches. Black berry to 6 mm, containing one to two seeds in a dark pulp.

 

Duboisia myoporoides: Perennial shrub to small tree with corky bark with intensely bitter taste, Leaves alternate pale green 3–10 cm × 1–1.5 cm, tapered at both ends. Open clusters of small white flowers at the end of the branches and black juicy berry, containing a few seeds in a dark pulp.

 

Duboisia leichardtii: Perennial shrub to small tree with corky bark with intensely bitter taste, similar to D. myoporo-ides. Leaves narrowly elliptic pale green 4–10 cm × 1–2 cm, tapered at both ends. Open clusters of small white flowers, sometimes tinged with mauve, at the end of the branches. Flowers, late winter to spring. Black juicy berry, containing a few seeds in a dark pulp.

 

Microscopy (Duboisia myoporoides)

 

The upper epidermis consists of polygonal tabular cells covered with thick and striated cuticle. Stomata are very less with very few near the midrib. The mesophyll has cylindrical palisade cells and just next to it is a row of sub-rectangular collecting cells and 7 or 8 rows of spongy parenchyma with scattered idioblasts. Each scattered idioblasts consist of small micro-sphenoidal crystals of calcium oxalate. In the lower epidermis it has numerous stomata which are cruciferous in nature. Scattered glandular trichomes occur on both surfaces which are about 75–95 μ long and 15–25 μ wide at the head. The midrib has well developed ridge and contains a meristele with xylem and superior supernumerary phloem.


                Duboisia myoporoides



Chemical Constituents

 

Duboisia myoporoides is considered as the chief commercial source of scopolamine and atropine. It contains hyoscyamine which is converted to atropine during extraction. Along with it, the drug also contains norhyoscyamine, tigloidine, valtropine, tiglyoxytropine. The synthetic process for scopolamine and atropine is very costly and hence, much reliance is placed on its natural source. Atropine (C17H23O3N) occurs as colourless crystals, with a bitter taste and no odour. It is soluble in chloroform and alcohol. It is a racemic form of hyoscyamine.

 

The chief constituent of Duboisia hopwoodii was found to be nicotine and nonnicotine, with content reportedly up to 25% of the dried weight of the plant material.

 


 

Chemical Tests

 

1. The addition of gold chloride solution to atropine in water and hydrochloric acid gives lemon yellow precipitate.

 

2. It gives positive Vitali Morin reaction.

 

Uses

 

Duboisia leaves are the main source of atropine and scopolamine. Atropine is the parasympatholytic drug. It also causes stimulant action on central, medullary and higher nerve centres. Atropine has many different therapeutic uses. It is used as an antidote for pilocarpine, physostigmine and other choline esters. It relieves bronchial spasms in asthma. As it suppresses the gastric secretions, it is used in peptic ulcer. It has applications in ophthalmic practice, because of its dilatory effects on pupil of the eye. It is also used to reduce tremor and rigidity in Parkinsonism. Scopolamine is used as treatment for air and sea sickness and in the treatment of stomach ulcers. Sedative, hypnotic and mydriatic (of variable strength), which augments the activity of the respiratory system. Its alkaloid, Sulphate of Duboisia, is sometimes used as a substitute for atropine. The homoeopaths use the tincture and the alkaloid for paralysis and eye infections; a red spot interfering with vision is an indication for its use. It is antidoted by coffee and lemon juice.

 

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