10- Medicinal plants

Early History of Medicinal Plants

  • Plants served dual purposes as a source of food and medicine for early peoples.

  • Ebers Papyrus (1550 B.C.): Document detailing over 700 medicinal formulas, showcasing early pharmaceutical knowledge.

  • Golden Age of Greece: Significant advancements in biological and medical knowledge; various influential figures contributed to the field of pharmacology.

  • Pharmacology: The study of drugs concerning their composition, uses, and effects.

Doctrine of Signatures - Paracelsus

  • The Doctrine of Signatures suggests that the characteristics of plants (e.g., color, shape) indicate their medicinal uses as intended in a divine plan.

    • Plants with red sap used for blood disorders.

    • Walnuts (brain-shaped cotyledons) beneficial for mental health.

    • Heart-shaped leaves indicated remedies for heart conditions.

Modern Medicines

  • The contemporary approach focuses on:

    • Analyzing the chemical composition of plant medicines.

    • Testing their actual effectiveness.

    • Synthesizing the functional compounds for large-scale production.

  • The intricate nature of plant secondary compounds plays a vital role in their medicinal value.

Plant Secondary Metabolites

  • Secondary Metabolites: Compounds not necessary for basic growth and development, but derived from primary metabolites.

    • Found primarily in specific families of plants.

    • Functions include pollination attraction, environmental adaptation, and protection.

Major Groups of Secondary Metabolites

  • Secondary metabolites are categorized based on structure, biosynthesis, or plant origin:

    • Alkaloids: Nitrogen-containing compounds which can be toxic.

    • Terpenoids: Compounds often associated with fragrances.

    • Phenolics: Diverse compounds with beneficial properties.

Functions of Secondary Compounds

  • Plant secondary compounds have ecological roles influencing interactions with organisms:

    • Bright pigments (e.g., anthocyanins) attract pollinators.

    • Toxic compounds (e.g., nicotine) provide protection from herbivores and microbes.

    • Some compounds (e.g., THC, rubber) do not have known functions in plants.

Medicinal Value of Certain Secondary Compounds

  • Some secondary compounds possess medicinal properties:

    • Opium Poppy and Fever Bark Tree: Used historically for their pain-relieving or curative properties.

    • Example: Quinine as an anti-malarial treatment.

Alkaloids

  • Alkaloids represent a vast class of compounds; over 12,000 types have been identified across 4,000 plant species.

  • Potently toxic examples include:

    • Locoweed

    • Deadly Nightshade

    • Poison Hemlock

    • Yew shrub

Saponins

  • Found in various plants (e.g., wild yam, ginseng, quinoa).

  • Functions as steroid glycosides with potential medicinal properties.

  • Diosgenin: Used as a precursor for progesterone synthesis in medicine.

Cardiac Glycosides

  • Cardiac glycosides: Key in treating heart failures, found in:

    • Digitoxin (Purple Foxglove)

    • Milkweed (high in cardiac glycosides)

Anthocyanins

  • Pigments (blue, purple, and red) beneficial for vascular health.

  • Found in:

    • Red apple peels

    • Saskatoon berries

  • These compounds are biologically active in humans.

Phenols and Tannins

  • Phenols: Antioxidant effects; present in oils of clove, thyme, fennel, and olive.

  • Tannins: High concentrations in plant leaves and tree barks; found in grape berries, often exhibiting astringent properties.

Salicylates

  • Found in willow bark (Salix alba); the natural source of aspirin, used for headache relief.

Cyanogenic Glycosides

  • Found in cassava and seeds of apples and almonds; can convert to cyanide, a poisonous compound.

Echinacea: Overview

  • Echinacea: Comprising nine species, three main ones used medicinally:

    • Echinacea pallida

    • Echinacea angustifolia

    • Echinacea purpurea

  • Known for immune-boosting properties; roots harvested at age four for medicinal use.

Echinacea: Historical Significance

  • Historically used by Comanche and Sioux tribes for throat infections and snake bites since the 17th century.

  • By the late 19th century, marketed as an anti-infective agent, became popular in North America.

Echinacea: Medicinal Properties

  • Exhibits antibacterial and antifungal properties.

  • Considered preventative against viral infections; active ingredients still undiscovered.

Echinacea's Decline and Modern Use

  • Decline in popularity with the advent of penicillin in the mid-20th century.

  • Despite this, it continues to be a common herbal remedy, especially in North America, for flu and skin disorders.

Hydrastis canadensis – Goldenseal

  • A member of the buttercup family (Ranunculaceae); has antiseptic, anti-inflammatory, and antibiotic properties.

  • Traditionally used by Native Americans for various ailments.

  • The active compounds include berberine and hydrastine, effective for digestion and infections.

Medicinal Compounds from Trees

  • Pacific Yew (Taxus brevifolia):

    • Contains paclitaxel (Taxol), used in cancer treatment.

  • The issue of overharvesting; significant reduction in wild populations due to demand.

Fever Bark Tree (Cinchona officinalis)

  • Source of quinine; significant for malaria treatment.

  • Harvesting process detailed; requires a substantial volume for extraction.

Malaria Overview

  • Caused by Plasmodium genus, transmitted via Anopheles mosquito.

  • Global impact: infects millions and results in significant mortality, largely affecting children.

Discovery of Quinine

  • Isolated in 1820 by French chemists; quinine serves as an antimalarial and flavoring agent.

  • Supply challenges during WWII due to high demand; synthesis of alternatives began.

Plant Medicines: Below Ground

  • Plants like bloodroot and ginseng utilized for medicinal compounds from roots and rhizomes.

Bloodroot (Sanguinaria canadensis)

  • Commonly used by indigenous cultures for respiratory issues.

  • Contains sanguinarine, which has beneficial properties but can be toxic at high doses.

Common Dandelion (Taraxacum spp.)

  • Utilized for detoxification and as a diuretic.

  • Active ingredients include taraxacin and taraxasterol.

Ginseng Overview

  • Various types include Panax ginseng (Korean) and Panax quinquefolius (American).

  • Valued in traditional medicine; significant historical roots in Asia.

Ginseng's Medicinal Properties

  • Active chemicals possess anti-tumor effects, cholesterol-lowering properties, and immune system benefits.

St. John's Wort (Hypericum perforatum)

  • Traditionally used in herbal medicine; prescribed for depression in Europe.

  • Interaction with other medications; can affect efficacy.