Botany: Cloves and Hibiscus

Cloves

• Botany: Cloves are the dried flower-buds of Eugenia aromatica (E.caryophyllata), belonging to the Myrtaceae family.
• Geographical source: Zanzibar, Indonesia, Madagascar, and Brazil.
• Active constituents:
  • 15-20% volatile oil (Eugenol 84-90%, acetyl eugenol 3%, sesquiterpene α-, β-, γ-caryophellen).
  • 10-13% tannin.
• Microscopy:
  • Triangular pollen grains.
  • Fragments of parenchymatous tissue showing entire or broken oil gland (Schizolysigenous oil gland).
• Therapeutic uses:
  • Treatment of teeth pain (dental analgesic).
  • Carminative and antispasmodic.
  • Preparation of vanillin.
  • Preparation of clove oil.
  • Antiseptic and antihistaminic.
  • Sesquiterpene has anticarcinogenic properties.
• Pharmaceutical preparations: Local anesthetic ointments.
• Tests:
  • Eugenol test: Forms needle-shaped crystals of potassium eugenate with 5% KOH.
  • Tannin test: Produces a deep blue color with FeCl3 solution.

Hibiscus

• Botany: Dried calyx and epicalyx of Hibiscus sabdariffa, family Malvaceae.
• Geographical source: South of Egypt, Sudan.
• Active constituents:
  • Organic acids (15%): Citric, Malic, Hibiscic.
  • Colouring matter of anthocyanins (Hibiscin).
  • Flavonoid: Hibiscetin.
  • Large amount of mucilage.
• Microscopy:
  • Calyx: petaloid, crimson, 5-united cup shape, triangular with acuminate apex.
  • Epicalyx: 8-10 linear segments, connate below the base of the calyx.
• Therapeutic uses:
  • Antihypertensive (decreases blood pressure in hypertensive individuals).
  • Sedative.
  • Digestive.
  • Soft drink.
  • Emollient.
  • Substitute for tea and coffee (for sensitive individuals).
  • Weight reducing agent.
• Tests:
  • Filtrate with 1% HCl: Dark red color.
  • Sodium acetate solution: Violet color.
  • Conc. NH4OH: Green color.

Important Note

Cloves

• Adulteration:
  • Clove stalk: Less pleasant odor, yields 5% volatile oil, detected by presence of thick-walled sclereids and prisms of calcium oxalate in powdered cloves.
  • Mother Clove: Presence of abundant starch, absent in clove.
  • Exhausted Cloves: Darker, much shrunken, floats in H2O, free from oil (removed by steam distillation).

This quiz covers the characteristics, constituents, and geographic sources of cloves, a spice derived from the dried flower-buds of Eugenia aromatica. It also touches on the related Hibiscus plant.