Rhubarb
Source, diagnostic
characters, constituents and uses
Content
• Source,
diagnostic characters, constituents and uses of Rhubarb
Rhubarb
Synonyms
• Radix rhei, Rheum, Revandchini
Source
• Dried rhizome of Rheum emodii (Indian rhubarb), R.
palmatum, R. webbianum (Chinese rhubarb)
Family
• Polygonaceae
Macroscopy
• Round – (small rhizomes), barrel, cylindrical, 8-10 cm L,
4 cm thick
• Flat – (large rhizome), plano convex, 7-10 cm L, 3-6 cm
thick
• Sharp odour
• Bitter astringent taste
• Irregular granular fracture (drug with pink fracture is of
superior quality)
• Star spots – abnormal vascular bundles, medullary ray
appear as star spots
Constituents
• Anthraquinone glycosides and astringent principles
• Anthraquinone with carboxyl group – Rhein, Glucorhein
• Anthraquinone without carboxyl group – Aloeemodin, Emodin,
Chrysophanol, Physcion
• Anthrones and dianthrones of aloe Emodin, Emodin,
Chrysophanol, Physcion
• Heterdianthrones like Palmidin A, Palmidin B, Palmidin C
Other constituents
• Galic acid as glucogallin
• Tannin
• Catechin
• Epicatechin
• Pectin
• Starch
• Fat
• Calcium oxalate (3-40%)
Tests
• Modified borntrager’s test
• Red colour with addition of alkali
• Indian Rhubarb – Deep violet fluorescence in UV
Uses
• Bitter stomachic
• In diarrhoea
• As purgative
Adulterants/Substitutes
Rhapontic rhubarb
• R. rhaponticum
• Rhein, emodin aloe emodin absent
• Rhaponticin – crystalline glycoside, derivative of
diphenyl ethylene
• Blue fluorescence in UV
• Esterogenic activity
Summary
• Rhubarb – Dried rhizome of Rheum emodii (Indian
rhubarb), R. palmatum, R. webbianum (Chinese rhubarb), Anthraquinone
glycosides