Understanding Anticholinergic Action
Anticholinergic substances work by blocking the action of acetylcholine, a key neurotransmitter [1.7.6]. Acetylcholine plays a vital role in the parasympathetic nervous system, which controls involuntary bodily functions like salivation, digestion, urination, and heart rate [1.7.1, 1.7.5]. By competitively inhibiting acetylcholine at muscarinic receptors, these compounds disrupt these processes, leading to a wide range of effects [1.7.2, 1.7.3]. This mechanism is not unique to herbs; many prescription and over-the-counter drugs, such as certain antidepressants and antihistamines, also possess anticholinergic properties [1.3.3, 1.4.6]. The primary active compounds in the most potent anticholinergic plants are tropane alkaloids, such as atropine, scopolamine, and hyoscyamine [1.2.3, 1.3.2].
A Word of Warning
The herbs discussed below are highly toxic and should not be ingested or handled without extreme caution and expert guidance. Misuse can lead to severe poisoning and death. "Natural" does not mean "safe."
The "Deadly Nightshades": Classic High-Potency Anticholinergic Herbs
The Solanaceae family, or nightshade family, is notorious for containing some of the most poisonous plants known, many of which are rich in anticholinergic tropane alkaloids [1.3.2, 1.2.8].
Atropa belladonna (Deadly Nightshade)
This plant is perhaps the most famous anticholinergic herb. All parts of the plant, especially the sweet-tasting black berries, are toxic and contain high levels of atropine, scopolamine, and hyoscyamine [1.6.2, 1.6.5]. Historically, its extracts were used in cosmetics to dilate pupils [1.2.8]. Ingestion leads to a classic anticholinergic toxidrome: dry mouth, blurred vision, rapid heartbeat, confusion, hallucinations, and delirium [1.2.8, 1.4.1]. The ingestion of just two to three berries can be toxic to a child [1.6.2].
Datura stramonium (Jimsonweed)
Also known as thorn apple or locoweed, Jimsonweed is found worldwide [1.6.4, 1.6.1]. It contains atropine and scopolamine, with the highest concentration of alkaloids often found in the seeds and flowers [1.4.1, 1.2.8]. Datura is often ingested intentionally for its hallucinogenic effects, which can be terrifying and dangerous, leading to severe delirium, agitation, hyperthermia, and tachycardia [1.2.3]. Fatalities, though rare, are often a result of trauma or drowning during the state of delirium [1.2.8].
Hyoscyamus niger (Henbane)
Henbane has a long history of use in traditional medicine and rituals for its sedative and hallucinogenic properties [1.2.2, 1.2.8]. It contains the tropane alkaloids hyoscyamine and scopolamine [1.2.8]. Similar to belladonna and datura, henbane poisoning causes severe anticholinergic symptoms, including hallucinations, dilated pupils, flushed skin, and restlessness [1.2.8].
Mandragora officinarum (Mandrake)
The Mandrake root, famous in folklore for its human-like shape, is another potent member of the nightshade family [1.2.8]. It contains deliriant hallucinogenic tropane alkaloids including atropine and scopolamine [1.2.8]. Historically, it was used as an anesthetic for surgery due to its narcotic effects [1.2.8].
Other Plants with Anticholinergic Properties
While the Solanaceae family contains the most potent examples, other plants also exhibit anticholinergic effects, though often to a lesser degree.
- Brugmansia (Angel's Trumpet): Closely related to Datura, these woody trees are rich in scopolamine and hyoscyamine and are highly toxic, causing severe hallucinations and paralysis of smooth muscles [1.2.3, 1.2.8].
- Scopolia: This genus, native to Europe and Asia, contains chemicals like hyoscyamine, atropine, and scopolamine and is used medicinally for spasms and pain relief, but an overdose can cause anticholinergic syndrome [1.2.8, 1.5.4].
- Dandelion (Taraxacum officinale): While generally considered safe, there is at least one case report of a 55-year-old man presenting with anticholinergic symptoms (confusion, mydriatic pupils, tachycardia) after consuming dandelion [1.5.5].
- Ashwagandha, Valerian, St. John's-wort, Ginger, and Lemon Balm: These herbs are listed in some sources as having anticholinergic effects, though their potency is significantly lower than the nightshade plants [1.2.1, 1.2.4]. Their effects are often considered mild.
Comparison of Potent Anticholinergic Herbs
| Herb | Primary Alkaloids | Potency/Toxicity | Key Characteristics |
|---|---|---|---|
| Atropa belladonna | Atropine, Scopolamine, Hyoscyamine [1.6.2] | Very High | Sweet, black berries attractive to children; causes severe central and peripheral symptoms [1.6.2, 1.2.8]. |
| Datura stramonium | Atropine, Scopolamine [1.6.1] | Very High | Spiky seed pods; often abused for hallucinogenic properties, leading to dangerous delirium [1.2.8, 1.6.1]. |
| Hyoscyamus niger | Hyoscyamine, Scopolamine [1.2.8] | High | Foul smell; historically used in rituals; causes hallucinations and restlessness [1.2.8]. |
| Mandragora officinarum | Atropine, Scopolamine [1.2.8] | High | Large root resembling a human figure; historically used as an anesthetic and associated with witchcraft [1.2.8]. |
| Brugmansia | Scopolamine, Hyoscyamine [1.2.8] | Very High | Large, pendulous, trumpet-shaped flowers; causes paralysis of smooth muscles and severe hallucinations [1.2.8]. |
Risks, Side Effects, and Anticholinergic Burden
The effects of anticholinergic substances are extensive and can impact multiple body systems. Common peripheral side effects include dry mouth, blurred vision, inability to sweat, urinary retention, and constipation [1.4.2, 1.4.3]. Central nervous system effects can range from confusion, drowsiness, and memory problems to severe agitation, delirium, hallucinations, and coma [1.4.1, 1.4.5].
A significant concern, especially for older adults, is the concept of anticholinergic burden [1.5.1]. This refers to the cumulative effect of taking one or more substances with anticholinergic activity [1.5.3]. Even weak anticholinergic effects from multiple sources (including prescription drugs and herbs) can add up, increasing the risk of cognitive impairment, falls, and even dementia [1.4.6]. Older adults are more susceptible to these effects due to changes in metabolism and a more permeable blood-brain barrier [1.4.8].
Conclusion
While many plants have medicinal properties, a distinct group, primarily within the nightshade family, contains powerful and dangerous anticholinergic alkaloids like atropine and scopolamine [1.2.5, 1.2.8]. Herbs such as Deadly Nightshade, Jimsonweed, and Henbane can cause severe and life-threatening poisoning [1.2.3, 1.2.8]. Even herbs with milder effects can contribute to a cumulative anticholinergic burden, posing significant health risks, particularly for the elderly [1.4.6]. It is essential to treat these plants with extreme respect and caution, recognizing that their use falls squarely in the domain of toxicology and pharmacology, not casual herbal remedies. Always consult with a healthcare professional before using any herbal product.
For more authoritative information on plant toxicity, you can visit the California Poison Control System.
