Tea, Digitalis & Senna: Origins, Uses & Tests

• These notes cover the topics of tea, digitalis (foxglove), and senna
• They include information on their origins, active constituents, confirmatory tests, medicinal uses, precautions, morphology, and key elements for identification

Tea

• Tea originates from the prepared leaves and leaf bud of Thea sinensis L. (Camellia thea Link) and belongs to the family Theaceae
• The part used is the two adjacent young leaves together with the stem and bud
• It is geographically found in India, Serilanka, China, and Japan

Types of Tea

• Green tea undergoes rapid drying and high temperatures
• Green tea uses methods to stop/destroy the oxidase enzyme, preventing fermentation
• In the production of green tea, oxidation of tannins does not take place, and there is no change in chlorophyll color
• Black tea undergoes slow drying and doesn't use high temperature
• Black tea uses methods to facilitate complete oxidation by the oxidase enzyme to allow complete fermentation
• The oxidation of tannins takes place in black tea production, which changes the color of the chlorophyll to dark

Active Constituents in Tea

• Both types of tea contain caffeine and tannins

Green Tea Active Constituents

• Green tea has soluble caffeine-phlobatannins complex, where no fermentation occurs because the oxidase enzyme is destroyed by high temperature
• Tannins are in the form of a complex with caffeine and are soluble
• Green tea has less caffeine and increased tannins compared to black tea

Black Tea Active Constituents

• Black tea has soluble caffeine-phlobatannins and insoluble phlobaphenes (tannins) + free caffeine
• This is due to complete hydrolysis of complex by fermentation by the oxidase enzyme
• Tannins are in the form of phlobaphenes after hydrolysis and become insoluble.
• Black tea has more caffeine than green tea due to complete hydrolysis of complex, and it possesses less tannins

Additional Constituents in Tea

• Both green and black tea contain traces of theobromine and theophylline alkaloids, volatile oil, and saponin glycosides
• Flavonoids glycosides are active constituents
• Green tea is used as an antioxidant and antitumor agent due to its high flavonoid content

Confirmatory Tests for Tea

Murexide test

• Used for caffeine detection
• Aqueous decoction is evaporated, and the residue is treated with concentrated HCl + H2O
• The solution is evaporated until dry, giving a yellow color, which turns crimson red
• Exposure to vapors of ammonia results in a violet color

Ferric chloride test

• Used for tannins detection
• Aqueous extract is treated with FeCl3 to produce a green color

KOH test

• Used for flavonoids glycosides
• Acidic extract is treated with KOH to produce a yellow color

Froth test

• Used for saponin glycosides detection
• Powdered drug is shaken with water to give a persistent froth that remains for 5 minutes

Medicinal Uses of Tea

• Due to the presence of caffeine, tea acts as a CNS stimulant, diuretic, and weak smooth muscle relaxant
• Due to the presence of tannins, tea is used as an antidiarrheal drug (constipating agent)
• Green tea is an antioxidant and anticancer agent

Precautions of Taking Large Doses of Tea

• Can cause gastritis, nervous irritability, anemia, constipation, a habituation syndrome, and an increase in heart rate

Digitalis (Foxglove)

Characteristics

• Digitalis is also known as Foxglove
• The Digitalis purpurea and Digitalis lanata belong to the family Scrophulariaceae
• The dried leaves of the plant are used

Active Constituents

• Active consistuents include cardiac glycosides such as Digoxin, Digitoxin, Lanatoside A, and Lanatoside C
• It also contains saponin glycosides

Confirmatory Chemical Tests for Digitalis

Baljet test

• Used for cardiac glycosides
• An alcoholic extract is treated with Baljet reagent (Picric acid + 10% NaOH = Sodium picrate)
• An orange to yellow color develops compared with a blank

Keller-Killiani test

• Used for deoxy sugar in the glycone part
• An acetic acid extract is treated with FeCl3 + Conc H2SO4
• A reddish-brown ring forms at the junction of the two layers, and the upper layer turns bluish-green

Froth Test

• Used for saponin glycosides
• Powdered drug is shaken with water to create a persistent froth that remains for 5 minutes

Medicinal Uses of Digitalis

• Digitalis has a cardiotonic action on a diseased heart; it strengthens the heartbeat, increases the force of contraction, and enables the heart to beat more strongly, slowly, and regularly without requiring more oxygen

Precautions when using Digitalis

• Cardiac glycosides in Digitalis are excreted very slowly
• The drug has a cumulative effect that may be fatal
• Because of this, it is best used as a long-term medication

Morphology of Digitalis

• Petiole: The petiole of Digitalis is petiolate
• Lamina (leaf blade).
  • Apex: Acute
  • Shape: Lanceolate and decurrent
  • Form (Type): Simple
  • Venation: Reticulate anastomosing

Key Elements of Digitalis

• Fragments of epidermal cells with beaded anticlinal walls and anomocytic stomata with striated cuticle
• Three types of glandular hairs: bicellular biserriate head unicellular stalk, unicellular head unicellular stalk (capitate hair), unicellular head multicellular uniserriate stalk
• Two types of non-glandular hairs: collapsed hair (characteristic), multicellular uniserriate
• Digitalis does not contain any type of calcium oxalate

Senna (Alexandrian & Indian Senna)

• Senna (Alexandrian & Indian Senna) is a compound

Origin

• Senna consists of dried leaflets of Cassia acutifolia (Alexandrian Senna) and Cassia angustifolia (Indian Senna), which belong to the family Leguminosae

Active Constituents

• Anthraquinones glycosides, including Sennoside A, B, C, and D
• These produce Sennidin A, B, C, and D upon hydrolysis
• It also contains mucilage (carbohydrates)

Confirmatory Chemical Tests for Senna

Borntrager's test

• This confirmatory test tests for free anthraquinones
• A chloroformic extract is mixed with NH4OH to produce a rose (pink) to intense red color in the aqueous layer

Modified borntrager's test

• This confirmatory test tests for combined anthraquinones
• A chloroformic extract gives with NH4OH a rose (pink) to intense red in the aqueous layer

Medicinal Uses of Senna

• Senna is used as a laxative and powerful cathartic in the treatment of constipation

Precautions for using Senna

• It includes anthraquinones glycosides
• Senna should not be taken for more than 10 days
• Prolonged use can lead to weakening of the large bowel muscles

Side effects of Senna

• Due to presence of anthraquinones glycosides, it can cause a slightly bitter taste and nausea
• It can act as a very strong laxative which may cause gripping and colic if not mixed with aromatic carminative herbs that relax the intestinal muscles such as mentha, cardamon, clove

Contraindications for Senna

• Should not be taken during pregnancy, since it causes muscle contraction which may lead to abortion because of the presence of anthraquinones glycosides

Morphology of Senna

• Has petiolate petioles
• Leaf blade
  • Shape: Obovate, lanceolate
  • Margin: Entire
  • Form: Compound, pinnate, paripinnate (even number)
  • Venation: Reticulate (netted) and pinnately reticulate
• Phyllotaxis is alternate

Key Elements to Identify Senna

• Palisade cells (leaf organ) shown in longitudinal colenchyma