TO BE UPDATED SLIGHTLY Plant Toxins and the Heart (3) (3)

HEART TOXINS

  • Aconite Alkaloids - Ranunculaceae

  • Taxus Alkaloids - Taxaceae

  • Cardiac Glycosides - Many families

BACKGROUND

  • Sodium-Potassium Pump: A mechanism vital for maintaining gradients of sodium and potassium in cellular environments.

  • The sodium potassium pump uses (what) to pump (what) out of the cell ...

  • Action Potential: A sudden change in electrical charge that occurs in excitable cells such as neurons and muscles, especially within the heart.

  • Electrical Conduction System of Human Heart: The key location affected by plant toxins, crucial for heart functionality.

Sodium-Potassium Pump

  • Location: Plasma membrane

  • Processes:

    • Controls gradients of sodium (Na+) and potassium (K+)

    • Uses ATP to function (ADP + Phosphate)

Action Potential in Excitable Cells

  • Typical Characteristics:

    • At -70mV, resting state;

    • Na+ ions flow in, K+ ions flow out, generating a positive action potential up to +40mV.

    • Key stages: Threshold (-55mV), Resting state, Stimulus, Hyperpolarization.

Electrical Conduction System of the Heart

  • Components:

    • Sinoatrial Node

    • Atrioventricular Node

    • His Bundle

    • Right and Left Bundle Branches

    • Purkinje Fibers

Nerves Controlling the Heart

  • Sympathetic Nervous System:

    • Releases: Norepinephrine (noradrenaline)

    • Effects: Increased heart rate and contraction force via beta-1 adrenergic receptors

  • Parasympathetic System:

    • Releases: Acetylcholine

    • Effects: Decreased heart rate by opening K+ channels causing hyperpolarization

  • Fight or Flight: Activation leads to increased heart rate by sympathetic nerves.

  • Concept Check: Tropane alkaloids may mimic norepinephrine action, increasing heart rate.

Ranunculaceae- Buttercup family (Ranunculaceae is a family of over 2,000 known species of flowering plants)

Aconite Alkaloids

A. Aconitine

B. Atisine

C.Veatchinine

Ranunculaceae (Ranunculaceae is a family of over 2,000 known species of flowering plants)

-aconitine- arrhythmias

  -atisine- numbness and tingling

  -veatchine-scant knowledge;  starting compounds of other   alkaloids

ACONITUM SPP. (Monkshood)[350 species worldwide]

Aconite Alkaloids

  • Types:

    • Aconitine: Known for arrhythmias

    • Atisine: Causes numbness and tingling

    • Veatchinine: Limited understanding; may be precursor for other alkaloids

**250 SPECIES FOUND IN WILD N.HEMISPHERE; IN GARDENS AND CUT FLOWERS

Toxicity and Usage

**Toxicity may be due to ability to pass through fat-containing barriers (cell membranes and skin).

  • Cultural Importance:

    • Used globally in various practices, known as poison (arrow),with notable toxicity due to roots contamination, large doses, and misidentification as edibles.

  • Effects of Aconitines:

    *Aconitine is an alkaloid toxin produced by various plant species belonging to the genus Aconitum (family Ranunculaceae), commonly known by the names wolfsbane and monkshood.

    • Act as agonists for voltage-gated Na+ channels, leading to delayed repolarization and severe symptoms (numbness, coma, death,weakness,vomitting,dizziness,arrtythmia).

Spirea japonica (toxin from veatchine group-least toxic)

***Used in Traditional Chinese medicine

***“pao zhi “ technique importan

HEART TOXINS

Taxus Alkaloids - Taxaceae(yew family)

YEW:

  • Commonly found in ornamental shrubs, with all but the aril being toxic.

  • nonflowering conifer

    Taxus baccata is a species of evergreen tree in the family Taxaceae,

  • Find fruit,  seed, aril, male cone; all but one structure is toxic

    Aril

  • Aril, accessory covering of certain seeds that commonly develops from the seed stalk, found in both angiosperms and gymnosperms.

    What is difference between Juniper and Yew?

    A juniper berry is the female seed cone produced by the various species of junipers. It is not a true berry but a cone with unusually fleshy and merged scales, which gives it a berry-like appearance. The cones from a handful of species, especially Juniperus communis, are used as a spice, particularly in European cuisine, and also give gin its distinctive flavour. Juniper berries may be the only spice derived from conifers.[1]

Who do you think “L.” stands for?

Every  plant species must have a Latin description.

The person who does this is acknowledged by name or abbreviation. In this case it was  Carl Linnaeus.

History of yew trees

* Slow growing

*Oldest in Europe in a Wales church yard; 5,000 yr old?

*All parts  are toxic except aril even after drying

*Some deer can browse on it, not live stock

Taxine B

  • Characteristics:

    • Found in leaves/seeds

    • Antagonist of calcium and sodium channels, causing hypotension and cardiac issues

••Some Taxus alkaloids are useful

     ANTI-CANCER AGENTS

•

•Present in low concentrations in yew

     trees (6 trees per patient)

•

•They work in relatively lower doses against

cancers so toxicity minor concern. 

•Semisynthetic approaches

Paclitaxel

•binds tubulin

•prevents breakdown

•induces apoptosis

•often used in combination with other drugs

Cardiac Glycosides

*****There are two flavors of Cardiac glycosides same mechanism of toxicity (Cardenolide and Bufadienolides)

  • Mechanism:

  • Bind and disable cardiac Na+/K+ pump, leading to Na+ accumulation, increased Ca2+ triggering cardiac contractions.

  • Major families: Apocynaceae, Plantaginaceae, Asparagaceae, Ranunculaceae.

Glycosides=sugar+ non sugar(aglycone)

Sugar

•typically carbon ring(s) with many hydroxyl groups

Glycosidic bond

•Oxygen is the common glycosidic linkage between sugar & aglycone

Aglycone

various

Monarch Butterfly and Milkweed Plant

Caterpillar feasts on Asclepias spp. Stores toxin to adult stages

Community Education on Plant Toxicity

  • Safety Guidelines:

    • Avoid placing any plant parts in the mouth

    • No sucking nectar from unknown flowers

    • Knowledge about toxic plants in homes

    • Keep plants away from children and pets.

Conclusion

  • Awareness and knowledge of toxic plants are essential for safety in gardening and floral arrangements.