Medicinal Plants - Mentha (Peppermint)

• These are study notes on several medicinal plants and their properties

Mentha (Peppermint)

• Originates from the dried leaves and flowering tops of Mentha piperita, belonging to the family Labiatae
• Has volatile oil as a key active constituent, obtained through steam distillation
• The main components of the volatile oil are menthol (35-55%) and menthone (10-40%)
• Contains flavonoids, phenolic acids, tannins, and triterpenes
• Flavonoids are a dominant constituent
• Tannins are a poly phenolic compound and are antiseptic

Confirmatory Chemical Tests for Mentha

• Sudan III test: detects any volatile oil, producing a red color with Sudan III
• Vanillin/H2SO4 test: used for menthol, forms orange-yellow crystals that turn violet upon adding water
• KOH test: detects flavonoids, producing a yellow color with KOH
• Ferric chloride test: confirms tannins, resulting in a green color

Medicinal Uses of Mentha

• Used for its gastrointestinal (GIT) benefits
• Due to the presence of volatile oils (menthol) and flavonoids.
• Cholagogue: increases the flow of digestive juices and bile
• Antispasmodic: relaxes gut muscles, reducing colic and cramps, works on the GIT and the liver
• Carminative: relieves gas
• Irritable bowel syndrome (IBS) relief by alleviating spastic colon, diarrhea, and constipation
• Used for pain relief
• Effective in pain relief when applied to the skin
• Helpful in relieving headaches and migraines
• Treats infections, acts as antibacterial, and antifungal
• Cooling and anesthetic properties when applied to the skin in diluted oil, used as an inhalant and chest rub for respiratory infections
• Used as a flavoring agent in oral preparations like toothpaste and mouthwashes

Side Effects of Mentha

• Can cause heartburn due to relaxation of the lower esophageal sphincter
• Enteric-coated capsules can be used to deliver the medicine to the intestines and prevent heartburn

Morphology of Mentha

• Stem: erect and quadrangular-shaped
• Leaves: light to dark green with a purplish tinge
• Petiole: shortly petiolate
• Lamina (leaf blade):
• Apex: acute
• Surface: nearly glabrous (smooth)
• Margin: serrate (toothed)
• Form: simple
• Phyllotaxis: opposite decussate (pairs of leaves at right angles to the pair above and below)
• Flowers: occur as spikes of sessile flowers (without stalks) on the axis

Key Elements of Mentha (Microscopic)

• Epidermal cells: exhibit diacytic stomata with wavy anticlinal walls
• Labiaceous glandular hair: characteristic of Mentha, involved in volatile oil secretion
• Capitate hair: shares similarities with digitalis
• Non-glandular hair: multicellular and uniseriate
• Hexagonal pollen grain: characteristic pollen shape

Ephedra

• Originates from the dried stem of Ephedra species (Family Ephedraceae)
• Active constituents are alkaloids and flavonoid glycosides
• Alkaloids present include Ephedrine (50-90%), Norephedrine, and Pseudoephedrine

Confirmatory Chemical Tests for Ephedra

• Mayer's test: detects alkaloids, producing a creamy white precipitate
• KOH test: detects flavonoids, producing a yellow color

Medicinal Uses of Ephedra

• Due to alkaloids
• Treats nasal congestion from hay fever, allergic rhinitis, acute rhinitis, and common cold (local vasoconstrictor)
• Treats mild bronchospasms in respiratory tract in adults and children over 6 as a bronchodilator (treating bronchial asthma)
• Suppresses appetite (weight loss)

Contraindications for Ephedra

• Contraindicated in patients with high blood pressure and glaucoma
• Patients with hypertension should not use the drug

Vinca (Catharanthus)

• Originates from the dried whole plant of Catharanthus roseus, belonging to the family Apocynaceae
• Active constituents: Chemotherapy
• 150 alkaloids, e.g. Vinblastine (higher percentage) and Vincristine (lower percentage)
• Vinblastine is very harmful
• Vincristine can be produced from vinblastine through chemical or microbiological biotransformation

Confirmatory Chemical Tests for Vinca

• Mayer's test: produces a creamy white precipitate, indicating the presence of alkaloids

Medicinal Uses of Vinca

• Alkaloids have oncolytic (anti-cancer) activity
• Antimitotic (spindle poison), inhibiting cell division
• Vinblastine sulfate: Treats neoplasm, choriocarcinoma, and Hodgkin's disease.
• Vincristine sulfate: Treats acute leukemia in children and Hodgkin's disease.

Side effects of Vinca

• More common with Vinblastine
• Nausea and vomiting
• Constipation
• Headaches
• Depression
• Alopecia

Ergot (Fungi)

• The poisoning comes from contamination of rye grain by fungi (Claviceps purpura)
• Highly poisonous
• Active constituents: Alkaloids, e.g. Ergometrine and Ergotamine

Confirmatory Chemical Tests for Ergot

• Mayer's test: Alkaloids produce a creamy white precipate

Medicinal Uses of Ergot

• Due to presence of Ergometrine
• Oxytocic effect to expel the placenta after childbirth or to increase contractions
• Due to presence of Ergotamine
• Used to treat migraine by reducing vasodilation

Solanaceous Herbs

• Includes Belladonna (Deadly Nightshade), Datura (Thorn Apple), Hyoscyamus (Egyptian Henbane)
• Belladonna: Dried leaves with and without flowering tops of Atropa belladonna (Family Solanaceae)
• Datura: Dried leaves with or without flowering tops of Datura stramonium (Family Solanaceae)
• Hyoscyamus: Dried leaves and flowering tops of Hyoscyamus muticus and Hyoscyamus niger (Family Solanaceae) Tropane alkaloids (Atropine, Hyoscine, Hyoscyamine)
• The greater portion of the alkaloid of belladonna consists of Atropine
• The greater portion of the alkaloid of Datura consists of Hyoscine
• The greater portion of the alkaloid of Hyoscyamus consists of Hyoscine & Hyoscyamine

Confirmatory chemical tests for Solanaceous Herbs

• Mayer's test: gives a creamy white precipitate
• Vitalis' test: gives a violet color that fades over time

Medicinal uses for Solanaceous Herbs

• Acts as a sedative and pain killer and relax distended organs, relieving intestinal colic and abdominal cramping (antispasmodic)
• Reduces secretions and acts as a preoperative anesthetic
• Reduces digestive juices and secretions to treat peptic ulcers
• Used in motion sickness formulations (antiemetic)
• Decrease symptoms of Parkinson's disease, reducing tremors & rigidity
• Act as mydriatic to dilate the pupil for eye examination
• Used in the treatment of asthma, whooping cough and bronchitis

Precautions

• Can cause hallucinations so low doses are recommended