Digitalis - Source, diagnostic characters, constituents, uses, adulterants and substitutes

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

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Filter, to the filtrate add 5 ml water, 0.5 ml strong lead acetate solution

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Shake and separate the filtrate

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Clear filtrate treated with chloroform and evaporated to dryness

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Extract dissolved in glacial acetic acid

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Cooled, 2 drops of ferric chloride solution is added

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Content transferred to test tube with 2 ml conc, sulphuric acid

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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 60^oC, 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