Medicinal Plants

History of Medicinal Plants

  • Introduction

    • Plants are active and ingenious chemists, even more so than animals.

    • Some plants have nutritional value, while others can be poisonous, hallucinogenic, or therapeutic.

    • Many secondary compounds in plants originally serve as a self-defense mechanism.

    • These chemicals can affect animal and human physiology.

  • Egyptians: Had extensive knowledge of medicinal plants like garlic for heart and circulatory disorders. The Ebers Papyrus (3500 years ago) documents this.

  • Ancient China: Thousands of herbal cures are described in the Pun-tsao.

  • India: Features a system of healthcare known as Ayurvedic medicine, documented in the Rig-Veda.

  • Arab Physicians: Published manuscripts in Moorish Spain.

  • Americas: Aztec Knowledge: The Badianus Manuscript, written by Aztec healer Martin de la Cruz, detailed traditional medicinal plant knowledge and treatments. It was sent to King Charles I in 1592.

  • Greeks and Romans

    • Hippocrates (460-377 BC), known as the "Father of Medicine," initiated Western medicine with the use of herbal remedies.

    • Dioscorides, a Roman physician, compiled 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: The Renaissance in 1400s Europe saw a revival of herbalism, with many herbals published due to the invention of the printing press, such as Theatrum Botanicum and The Complete Herbal.

  • Doctrine of Signatures: Originated in the 1500s; the belief that a plant's use can be determined by "signatures" visible on the plant that correspond to human anatomy.

    • The idea was that if a part of the 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 to treat liver ailments.

      • Bloodwort's red juice was used for blood disorders.

      • Walnuts, resembling brains, were used for treating brain disorders.

      • Mandrake root was thought to promote male virility and ensure conception.

    • This doctrine had no scientific basis.

Modern Prescription Drugs

  • There was a dichotomy between herbal medicine and Western medicine in the 18th century.

  • Many herbal remedies still exist in modern prescription drugs; for example, aspirin.

  • 25% of prescriptions contain plant-derived active ingredients.

  • Many synthetic prescription drugs were originally isolated from plants.

  • Currently, up to 90% of the rural population in the world still relies on herbal medicine for healthcare.

  • Herbal medicine continues in China, India, and many African and South American countries.

Traditional Chinese Medicine (TCM)

  • A preventive and holistic type of medicine; aiming to maintain balance and is individually tailored through:

    • 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: Neutralizing the toxicity or side effects of one herb with another.

    4. Mutual Suppression: Similar to Mutual Counteraction, where one herb reduces the toxic effects of another.

    5. Mutual Antagonism: Each herb suppresses the function of the other.

    6. Mutual Incompatibility: The combination is toxic, even if neither herb is individually toxic.

    7. Single Effect: Using a single herb.

Active Compounds in Medicinal Plants

  • Plants produce chemical compounds called secondary plant products to defend against herbivores and discourage bacterial and fungal growth.

  • Active compounds can be classified into:

    • Alkaloids

    • Glycosides

  • Alkaloids

    • A diverse group of over 3000 compounds, mostly found in herbaceous dicots.

    • Contain nitrogen, are usually alkaline (basic pH), and have a bitter taste.

    • Affect the nervous system of animals.

    • Some alkaloids are medicinally important, while others are hallucinogenic or poisonous.

    • The difference between medicinal and poisonous effects often depends on the dosage.

    • Common alkaloids include caffeine, nicotine, cocaine, morphine, quinine, and ephedrine (most end in -ine).

  • Glycosides

    • Named glycosides because they contain a sugar molecule (glucose) attached to the active component.

    • Three important types:

      • Cyanogenic glycosides: Contain cyanide (HCN), like in cassava and apricot pits.

      • Cardioactive glycosides: Contain a steroid molecule as the active component and affect heart muscle contraction; used to treat forms of heart failure.

      • Saponins: Don’t have much medicinal value; some may be toxic.

Medicinal Plants

  • Out of hundreds of plant extracts used today, some of the most important medicinal plants discussed are:

    • Foxglove – heart disease

    • Willow bark – aspirin to relieve pain, fever

    • Cinchona tree – to treat malaria

    • Snakeroot – schizophrenia, hypertension

    • Aloe – burns, cuts, skin moisturizing

  • Foxglove – Digitalis purpurea

    • Digitalis purpurea is a flowering plant known as foxglove; it is biennial and native to Europe, Africa, and Western Asia.

    • It features flower clusters every two years and is insect-pollinated.

    • Produces compounds to discourage grazing by mammals.

    • Originally used to treat dropsy (severe bloating) in England.

    • William Withering, an English doctor, found the correct dosage for treatment in 1785.

  • Digitalis: Contains cardioactive glycosides

    • Contains cardioactive glycosides in the leaves, which can be extracted.

      • Digoxin – most widely used, because it can be cleared by the kidneys.

      • Digitoxin – has a longer life, and is not cleared very well by kidneys.

  • Biological Effects

    • Treatment for congestive heart failure (CHF), which is when the heart fails to pump enough blood to the rest of the body.

    • The body attempts to compensate by increasing blood pressure and decreasing blood to the kidneys, which worsens the problem.

  • Biological activity of Digitalis

    • Digitalis works in two ways:

      • Slowing the heart rate.

      • Increasing the strength of each heartbeat, improving circulation.

    • More blood supply to the heart.

    • More blood to the kidneys, leading to increased urine production and excretion.

  • Contraindications of Digitalis

    • Excessive dose can be fatal (never chew) – it can be a poison.

    • Today’s effectiveness in CHF treatment is about 80% (same as in Withering’s time).

    • Effectiveness varies depending on the patient: a dose ideal for one may be subtherapeutic for another or even lethal, depending on circumstances.

    • Overdose/side effects: Nausea, vomiting, headache, arrhythmia (rapid, irregular beating of the heart), and even 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 Bayer Co. in 1898.

    • A 'wonder drug' because it has three classic properties:

      • Anti-inflammatory

      • Antipyretic (fever-reducing)

      • Analgesic (pain relieving)

  • Other properties of aspirin

    • Also prevents heart attacks, strokes, some cancers, delays cataracts, and enhances the immune system.

  • Drawbacks of aspirin

    • May irritate the stomach (thus, coating of pills helps).

    • Reye’s Syndrome: Children recovering from chicken pox or the flu, can develop unusual symptoms (vomiting, affects brain, liver and may be fatal) upon taking aspirin.

    • May be used as a pesticide on agricultural crops one day, since 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: fever, chills, seizures, convulsions, coma, and even death.

    • Alkaloid quinine in the cinchona tree bark (from Peru) is used to treat malaria, as it has fever-reducing properties.

    • In 1638, the wife of the Spanish viceroy, Countess of Cinchon, recuperated from malaria by using quinine.

  • Action of quinine

    • Quinine kills the parasite in the bloodstream of the infected person.

    • Also acts to prevent the initial infection for people traveling to malaria-infested areas.

    • The British in India added tonic water and gin to make quinine more palatable, creating the drink “gin and tonic.”

  • Snakeroot

    • Rauwolfia serpentina from India is the source of the drug reserpine and other alkaloids used in the treatment of 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 as a treatment for various skin ailments, including rashes, burns, sunburns, scalds, and wounds.

    • Sap of 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 purgative – relieves constipation

    • Skin/mouth ulcers, eczema, psoriasis, ringworm, athlete’s foot, poison ivy rashes

    • Diabetes treatment – lowers blood glucose levels. Video on extracting aloe gel: https://www.youtube.com/watch?v=cD4Zjcd2jrs