Glycosides
➢ Aloes
➢ Rhubarb
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Content
Glycosides
✓ Source, diagnostic characters, constituents and uses of
➢ Aloes
➢ Rhubarb
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Objectives
• At the end of this lecture, student will be able to
– Discuss the source, diagnostic characters, constituents
and uses of
» Aloes
» Rhubarb
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Aloes
Synonym
Aloe, Musabbar, Kumari
Source
Dried juice of the leaves of Aloe barbadensis (Curacao aloes), Aloe perry
(Socotrine aloes), Aloe ferox, and hybrid of this sps with Aloe Africana and
Aloe spicata (cape aloes)
Family
Liliaceae
Geographical source
Indigenous to eastern and southern Africa, grown in cape colony, Zanzibar
and islands of Socotra
✓ Also cultivated in many parts of India
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Aloes
Preparation
Barbados or curacao aloes (A. barbadensis)
✓ Islands of aruba and boniare in West Indies
✓ Transverse cut near the base
✓ Cut leaves kept along the sides of V shaped wooden troughs
✓ Collected juice- boiled, latex evaporates, juice thickens
✓ Thick juice poured into gourds or metal containers
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Aloes
Preparation
Cape aloes (A. ferox)
✓ Transversely cut leaves kept in circular manner in basin shaped
depression dug in ground, covered with goat skin or canvas
✓ Leaves placed so that cut ends overlaps
✓ Kept for 5-6 hrs, juice collected in goat skin
✓ Juice transferred to large iron kettle, boiled with continuous stirring
✓ Poured into wooden boxes
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Aloes
Preparation
Zanzibar aloes
✓ Variety origin – not known
✓ Regarded as variety of Socotrine
✓ Juice in skin of small carnivorous animals, solidifies then packed
✓ Monkey skin aloes – even though skin is not of monkey
Socotrine aloes (A. perryi)
✓ Island of Socotra and main land of East Africa
✓ Juice collected in goat skin, allowed to solidify
✓ Exported in pasty condition
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Aloes
Description
Curacao aloes
✓ Occurs as cape Barbados and livery variety
✓ Both varieties- strong odour, resemble iodoform
✓ Intensely bitter
✓ Brownish black
✓ Opaque mass
✓ Waxy, somewhat resinous
✓ Uneven fractured surface
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Aloes
Description
Cape aloes
✓ Dark brown or greenish brown to olive brown masses
✓ Nauseating and bitter taste
✓ Glassy fracture
✓ Distinct odour
Socotrine aloes
Zanzibar aloes
✓ Brownish yellow
✓ Liver brown colour
✓ Opaque mass
✓ Dull and waxy
✓ Pasty or semi solid consistency
✓ Conchoidal fracture ✓ Smooth and even fracture
✓ Extremely bitter ✓ Characteristic and
✓ Nauseating odour disagreeable odour
✓ Totally soluble in 60 % alcohol ✓ Bitter
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Aloes
Powder
✓ Studied in lactophenol (particles gradually solublises, crystals are
clearly seen)
Curacao
Fragments with large number of very small needles or slender prisms
Cape
Transparent, brown, angular or irregular fragments
Socotrine
Fragments with large prisms in groups are in dispersed form
Zanzibar
Irregular lumps
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Aloes
Constituents
Anthraquinone glycosides
✓ Principal component – Aloin – Mixture of glucosides, Barbaloin- chief
constituent
✓ Barbaloin – Aloe emodin anthrone C10 glucoside, water soluble
✓ Not hydrolysed by heat with dilute acid or alkali
✓ Decomposed by ferric chloride to aloe – emodin-anthrone, little
aloe-emodin, glucose (oxidative hydrolysis)
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Aloes
Constituents
Others
✓ Isobarbaloin, β Barbaloin, aloe emodin,
✓ Resin – Aloesin – purgative action
✓ Aloetic acid, saponins, mucopolysaccharides, glucosamines, hexuronic
acid, coniferyl alcohol etc
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Aloes
Tests
For specific variety
General test
1 g boiled in 10 ml water, fliter with kieselghur, filtrate used for
bromine and Schoenteten’s test
Bromine test
✓ Filtrate + freshly prepared bromine solution – pale yellow ppt
(tetrabromaloin)
Schoenteten’s test (Borax test):
✓ Filtrate + Borax, shaken till borax dissolves
Few drops added to test tube full of water – green fluorescence
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Aloes
Special tests
Nitrous acid test
Aq. Solution of aloes + sodium nitrite + Acetic acid
✓ Curacao aloes – sharp pink to carmine colour
✓ Cape aloes – faint pink
✓ Socotrine/Zanzibar aloes – very less change in colour
(isobarbaloin)
Nitric acid test
Aq. Solution or drug + nitric acid
✓ Curacao aloes – deep brownish red colour
✓ Cape aloes – Brownish colour to green
✓ Socotrine aloes – Pale brownish to yellow colour
✓ Zanzibar aloes – Yellowish brown colour
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Aloes
Special tests
Kupraloin test (klunge’s isobarbaloin test)
Dilute Aq. Solution + drop of saturated copper sulphate solution + little
of NaCl + excess of 90% alcohol
❖ Curacao aloes – wine red colour persistent for hours
❖ Cape aloes – Faint, rapidly changes to yellow
❖ Socotrine aloes – no colour
❖ Zanzibar aloes – no colour
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Aloes
Special tests
Modified anthraquinone test
For C glycosides- aloe emodin
Aq. Solution + FeCl3 + dil HCl – oxidative hydrolysis of aloe emodin
Add CCl4, Organic layer separated and ammonia added
Ammoniacal layer shows rose pink to cherry red colour
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Aloes
Uses
✓ Purgative – colon
✓ Aloin is used instead of aloes
✓ To counter effect gripping action, given along with carminatives
✓ Aloe gel- inner parenchyma of leaf
❖ Topical and cosmetic products – moisturizing property
✓ Anti-inflammatory property
❖ Increases the removal of dead tissues – Aloctine (stimulates
macrophage production)
✓ Pain, itching, slow down ulceration, keratosis
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Aloes
Adulterants/Substitutes
✓ Natal aloes – resemble cape aloe microscopically- as substitute
❖ Natalion, homonatalion, resin with nataloresinotannol
❖ Weak purgative
✓ Mocha aloes –brittle, black, glassy, strong odour
✓ Adulterated with black catechu, stones, iron pieces
➢ Aloe alcohol extract- deep brown colour under UV, black
catechu- black colour under UV
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Rhubarb
Synonyms
Radix rhei, Rheum, Revandchini
Source
Dried rhizome of Rheum emodii (Indian rhubarb), R. palmatum, R.
webbianum (Chinese rhubarb)
Family
Polygonaceae
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Rhubarb
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 spotwsww.DuloMix.com 20
Rhubarb
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
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Rhubarb
Other constituents
✓ Galic acid as glucogallin
✓ Tannin
✓ Catechin
✓ Epicatechin
✓ Pectin
✓ Starch
✓ Fat
✓ Calcium oxalate (3-40%)
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Rhubarb
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
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Rhubarb
Rhapontic rhubarb
✓ R. rhaponticum
✓ Rhein, emodin aloe emodin absent
✓ Rhaponticin – crystalline glycoside, derivative of diphenyl ethylene
✓ Blue fluorescence in UV
✓ Esterogenic activity
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Summary
✓ Aloes – Dried juice of the leaves of Aloe barbadensis (Curacao aloes), Aloe
perry (Socotrine aloes), Aloe ferox, and hybrid of this sps with Aloe Africana
and Aloe spicata (cape aloes), Anthraquinone glycosides – Aloin, Barbaloin-
chief constituent
✓ Bromine test (tetrabromaloin), Schoenteten’s test (Borax test), Modified
anthraquinone test, Purgative
✓ Rhubarb – Dried rhizome of Rheum emodii (Indian rhubarb), R. palmatum, R.
webbianum (Chinese rhubarb), Anthraquinone glycosides
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Thank You
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