Digitalis
Source, diagnostic characters, constituents, uses, adulterants and
substitutes
Content
Glycosides
• Source,
diagnostic characters, constituents, uses, adulterants and substitutes of
Digitalis
Digitalis
Synonym
• Digitalis leaf, foxglove leaf
Source
• Dried leaves of Digitalis purpurea, dried at temp
below 60oC, immediately after collection, should not contain more than 5% moisture
Family
• Scrophulariaceae
Geographical source
• England, Europe, US, India
Macroscopy
• Colour – Dark greyish green
• Odour – Slight
• Tatse – Bitter
• Size – 10-40 cm in length, 4-20 cm wide
• Shape- ovate- Lanceolate to broadly ovate
• Margin – Irregularly crenate or serrate or occasionally
dentate margin
• Venation – Pinnate
• Texture – Pubescent
• Veinlets prominent in the lower surface
Microscopy
• Dorsiventral
• Stomata – Anamocytic
• Trichomes
– Covering – uniseriate, multicellular (3-5 cells), blunt
apex, (collapsed cell covering trichomes)
– Glandular – Unicellular stalk, uni or bicellular head,
seen in veins
• Free from calcium oxalate and scelerenchyma
• Collenchyma – upper epidermis, lower epidermis, pericycle
Powder characters
Constituents
• Cardiac glycosides – cardenolides
• Pupurea glycosides A & B, Glucogitaloxin – primary
glycosides
• Purpurea glycoside A – Digitoxin + glucose –
digitoxigenin + 3 -digitoxose
• Purpurea glycoside B – Gitoxin + glucose –
Gitoxigenin + 3 –digitoxose
Other glycosides
• Odoroside H, Gitaloxin, verodoxin, glucoveradoxin
• Saponin glycosides
• Digitonin, gitonin
Tests
Keller KIliani test (For digitoxose)
1gm Drug + 10 ml 70%
alcohol, Boil
â
Filter, to the
filtrate add 5 ml water, 0.5 ml strong lead acetate solution
â
Shake and separate
the filtrate
â
Clear filtrate
treated with chloroform and evaporated to dryness
â
Extract dissolved in
glacial acetic acid
â
Cooled, 2 drops of
ferric chloride solution is added
â
Content transferred
to test tube with 2 ml conc, sulphuric acid
â
Reddish brown layer
acquiring bluish green colour after standing – Digitoxose
Legal test
• Extract dissolved I pyridine, sodium nitro prussiade
solution is added, made alkaline – pink or red colour
Baljet test
• Section of digitalis- sodium picrate – yellow to orange
Assay
• Bioassay – IP suggests pigeon or guinea pig
Use
• CHF – blocks the Na-K ATPase pump, hence
intracellular Na level increase- leads to increase in Ca ions – protein action
is enhanced (actin, myosin) – forceful contraction of myocardium
• Slows ventricular rate in atrial fibrillation, atrial
flutter, supraventricular tachycardia and premature extra systoles
Adulterants
• Verbascum Thapsus – Scrophulariaceae – Candelabra
trichomes
• Primrose leaves – Primula vulgaris –
Primulaceae – uniseriate covering trichomes (8-9 cells)
• Comfrey leaves – Symphytum officinale –
Boraginaceae – Multicellular trichome with hook in top
Allied drugs
Digitalis lanata – Scrophulariaceae – Wooly fox glove
Constituents: Primary
glycosides – Lanotoside A, B, C, D, E (glycone- digitoxose is acetylated)
Use: Commercial source for digoxin, lanatoside C, Lanatoside
A and mixture of lanatosides
Digitalis lutea – Scrophulariaceae – Straw
fox glove
• Sessile, oblanceolate with serrate or dentate margin
• As potent as D. purpurea
• Common substitute for official drug
Digitalis
thapsi –Scrophulariaceae – Spanish fox glove
• Small leaves, yellowish green, lanceolate with crenate
• Covering trichome absent
• Calcium oxalate present
Other species
• D. subalpine
• D. dubia
• D. grandiflora
• D. ferruginea
• D. mertonensis
Summary
• Digitalis – Digitalis purpurea, dried at temp below
60oC, immediately after collection, should not contain more than 5 %
moisture – Cardenolides – Purpurea glycoside A & B – Kellerkiliani test –
cardio tonic
• Allied drugs include D. lanata, D. lutea, D. thapsi etc