Medicinal Plants Flashcards

Medicinal Plants

History of Medicinal Plants

  • Introduction
    • Plants are highly active chemists, more so than animals.
    • Some plants provide nutrition, while others are poisonous, hallucinogenic, or therapeutic.
    • Many secondary compounds in plants serve as a self-defense mechanism.
    • These chemicals can significantly affect animal and human physiology.
  • Egyptians: Possessed extensive knowledge of medicinal plants, including garlic for heart and circulatory disorders. The Ebers Papyrus (3500 years ago) documents this knowledge.
  • Ancient China: Thousands of herbal cures are described in the Pun-tsao.
  • India: Developed a healthcare system known as Ayurvedic medicine, documented in the Rig-Veda.
  • Arab Physicians: Published manuscripts in Moorish Spain.
  • The Americas: Aztec traditional knowledge of medicinal plants and treatments was recorded in the Badianus Manuscript by Martin de la Cruz, an Aztec healer. This manuscript was sent to King Charles I in 1592.
  • Greeks and Romans
    • Hippocrates (460-377 BC), known as the "Father of Medicine," initiated Western medicine.
    • He advocated for the use of herbal remedies for diseases.
    • Dioscorides, a Roman physician, compiled medicinal information on over 600 plants in De Materia Medica in 75 B.C.
    • This reference was authoritative for 1500 years, and many remedies are still in use today.
  • Age of Herbals
    • In the 1400s in Europe, the Renaissance spurred a revival of herbalism.
    • The invention of the printing press led to the publication of numerous herbals, such as Theatrum Botanicum and The Complete Herbal.
  • Doctrine of Signatures
    • Originated in the 1500s.
    • Belief that a plant's use could be determined by “signatures” visible on the plant that corresponded to human anatomy.
    • The idea was that if a part of a plant resembled a part of the human body, it could be used to treat ailments of that body part.
    • Examples:
      • Liverwort, resembling a liver, was used for liver ailments.
      • Bloodwort's red juice was used for blood disorders.
      • Walnuts, resembling brains, were used for treating brain disorders.
      • Mandrake root was believed to boost male virility and aid conception.
    • This doctrine lacked scientific basis.
  • Modern Prescription Drugs
    • In the 18th century, a dichotomy existed between herbal medicine and Western medicine.
    • Many herbal remedies persist in modern prescription drugs; aspirin is an example.
    • Approximately 25% of prescriptions contain plant-derived active ingredients.
    • Many synthetic prescription drugs were initially isolated from plants.
  • Herbal Medicine Today
    • Up to 90% of the rural population worldwide relies on herbal medicine for healthcare.
    • Herbal medicine continues to be prevalent in China, India, and many African and South American countries.
  • Traditional Chinese Medicine (TCM)
    • Preventive and holistic; aims to maintain balance and is individually tailored.
    • Components include:
      • Food
      • Exercise
      • Meditation
      • Massage
      • Acupuncture
      • Herbal formulations
  • TCM Herbal Formulations
    1. Mutual Accentuation: Combining two herbs with similar functions to enhance their therapeutic effect.
    2. Mutual Enhancement: Using two substances with different functions, where one enhances the function of the other.
    3. Mutual Counteraction: Using one substance to neutralize the toxicity or side effects of another.
    4. Mutual Suppression: One substance reduces the toxic effects of the other (converse of Mutual Counteraction).
    5. Mutual Antagonism: Each substance suppresses the function of the other.
    6. Mutual Incompatibility: The combination of substances is toxic, even if neither substance is toxic individually.
    7. Single Effect: Using a single herb for treatment.

Active Compounds in Medicinal Plants

  • Plants produce secondary plant products to defend against herbivores and discourage bacterial and fungal growth.
  • Active compounds in medicinal plants can be classified into:
    • Alkaloids
    • Glycosides
Alkaloids
  • A diverse group of over 3000 compounds, mostly found in herbaceous dicots.
  • Contain nitrogen and are usually alkaline (basic pH) with a bitter taste.
  • Affect the nervous system of animals.
  • Some are medicinally important, while others are hallucinogenic or poisonous.
  • The difference between medicinal and poisonous effects often lies in the dosage.
  • Common alkaloids include caffeine, nicotine, cocaine, morphine, quinine, and ephedrine (most end in -ine).
Glycosides
  • Named for containing a sugar molecule (glucose) attached to the active component.
  • Three Important Glycosides:
    • Cyanogenic glycosides: Contain cyanide (HCN); found in cassava and apricot pits.
    • Cardioactive glycosides: Contain a steroid molecule as the active component; affect heart muscle contraction and are used to treat forms of heart failure.
    • Saponins: Generally don’t have much medicinal value and can be toxic.

Medicinal Plants

  • Discussion of some of the most important medicinal plants:
    • Foxglove: Used for heart disease.
    • Willow bark: Used to derive aspirin for pain and fever relief.
    • Cinchona tree: Used to treat malaria.
    • Snakeroot: Used for schizophrenia and hypertension.
    • Aloe: Used for burns, cuts, and skin moisturizing.

Foxglove – Digitalis purpurea

  • Digitalis purpurea, known as foxglove, is a flowering plant – biennial, native to Europe, Africa, and Western Asia.
  • It features flower clusters that appear every two years and is insect-pollinated.
  • Produces compounds to deter grazing by mammals.
  • Originally used to treat dropsy (severe bloating) in England.
  • William Withering, an English doctor, determined the correct dosage for treatment in 1785.
  • Contains cardioactive glycosides in the leaves, which can be extracted.
    • Digoxin is the most widely used cardioactive glycoside, as it can be cleared by the kidneys.
    • Digitoxin has a longer life and is not cleared well by the kidneys.
  • Biological Effects
    • Treatment for congestive heart failure (CHF), where the heart doesn’t pump enough blood to the rest of the body.
    • The body tries to compensate by increasing blood pressure and decreasing blood flow to the kidneys, exacerbating the problem.
  • Biological Activity of Digitalis
    • Digitalis works by:
      • Slowing the heart rate
      • Increasing the strength of each heartbeat, improving circulation.
    • This leads to more blood supply to the heart.
    • More blood to the kidneys increases urine production and excretion.
  • Contraindications of Digitalis
    • Excessive dose can be fatal (never chew).
    • Effectiveness in CHF treatment today is about 80% (similar to Withering’s time) because the ideal dose varies by patient.
    • What is ideal for one patient may be subtherapeutic, or even lethal, to another.
    • Overdose/side effects include nausea, vomiting, headache, arrhythmia (rapid, irregular heartbeat), and death.

Willow Tree Bark: Aspirin

  • Bark from willow (Salix species) has been used by Greeks to treat gout, rheumatism, pain, and fever; Native Americans also discovered its healing powers.
  • Aspirin
    • Salicylic acid = aspirin.
    • Isolated by German chemists from the Bayer Co. in 1898.
    • A ‘wonder drug’ with three classic properties:
      • Anti-inflammatory
      • Antipyretic (fever-reducing)
      • Analgesic (pain-relieving)
  • Other Properties of Aspirin
    • Prevents heart attacks and strokes
    • May help prevent some cancers
    • Delays cataracts
    • Enhances the immune system
  • Drawbacks of Aspirin
    • May irritate the stomach (thus, pills are often coated).
    • Reye’s Syndrome: Children recovering from chicken pox or the flu may develop unusual symptoms (vomiting, affects brain, liver, and may be fatal) upon taking aspirin.
    • May be used as a plant pesticide in the future, as it stimulates the plant’s defense system, making them more resistant to pests.

Cinchona Tree: Malaria

  • Malaria is still the world’s most prevalent disease (3 million people die every year).
  • Endemic in tropical and subtropical countries.
  • Plasmodium vivax is carried by the Anopheles mosquito; symptoms include fever, chills, seizures, convulsions, coma, and death.
  • Alkaloid quinine in the cinchona tree bark (from Peru) is used to treat people infected with malaria – it has fever-reducing properties.
  • In 1638, the wife of the Spanish viceroy, Countess of Cinchon, recovered from Malaria using quinine.
  • Action of Quinine
    • Quinine kills the parasite in the bloodstream of the infected person.
    • It also helps prevent initial infection for people traveling to malaria-infested areas.
    • The British in India mixed quinine with tonic water and gin, creating the drink “gin and tonic.”

Snakeroot

  • Rauwolfia serpentina from India is the source of the drug reserpine and other alkaloids used to treat hypertension (chronic high blood pressure).
  • Also used as a tranquilizer (sedative) to treat schizophrenia.

Aloe

  • Also called the burn plant; Aloe species are native to Africa.
  • Aloe vera has been used for thousands of years to treat various skin ailments, including:
    • Rashes
    • Burns
    • Sunburns
    • Scalds
    • Wounds
  • Sap from the succulent leaves contains aloin and other compounds that heal skin.
  • Popular in cosmetic products due to moisturizing effects:
    • Soaps
    • Skin creams
    • Shampoos
    • Sunscreen lotions
    • Bath oils
  • Aloe Sap Medicinal Uses
    • As a purgative – relieves constipation
    • Treats skin/mouth ulcers, eczema, psoriasis, ringworm, athlete’s foot, poison ivy rashes
    • Diabetes treatment – lowers blood glucose levels.