PHYTOCHEMICALS of TALAMPUNAY (ANGELS TRUMPET) and Their Molecular Mechanisms

Angel’s Trumpet, known scientifically as Brugmansia species, is a plant revered for its strikingly beautiful flowers and infamous for its toxic properties. This plant, also referred to as “Talaumpunay” in some cultures, contains several potent phytochemicals that exert significant physiological effects. The primary bioactive compounds in Angel’s Trumpet include tropane alkaloids such as scopolamine, hyoscyamine, and atropine. This discussion will delve into the detailed molecular mechanisms of these compounds.

1. Tropane Alkaloids

Tropane alkaloids are the most notable compounds found in Angel’s Trumpet. The primary alkaloids are:

Scopolamine

Hyoscyamine

Atropine

Scopolamine

Scopolamine (also known as hyoscine) is a tropane alkaloid that acts as a non-selective muscarinic antagonist. It exerts its effects by blocking acetylcholine receptors in the central and peripheral nervous systems.

Molecular Mechanism:

Binding to Muscarinic Receptors: Scopolamine binds to muscarinic acetylcholine receptors (mAChRs), specifically M1, M2, M3, M4, and M5 subtypes, preventing acetylcholine from binding and activating these receptors.

Inhibition of Parasympathetic Nervous System: By blocking mAChRs, scopolamine inhibits the parasympathetic nervous system, leading to a decrease in bodily secretions, dilation of the pupils (mydriasis), increased heart rate (tachycardia), and relaxation of smooth muscles.

CNS Effects: Scopolamine can cross the blood-brain barrier, leading to central nervous system effects such as sedation, amnesia, and, at higher doses, hallucinations and delirium.

Hyoscyamine

Hyoscyamine is another tropane alkaloid present in Angel’s Trumpet, which also acts as a non-selective muscarinic antagonist, but with a slightly different profile of activity and potency compared to scopolamine.

Molecular Mechanism:

Receptor Binding: Hyoscyamine binds to mAChRs, inhibiting the action of acetylcholine. This effect is similar to that of scopolamine, leading to anticholinergic effects such as reduced secretions, pupil dilation, and increased heart rate.

Peripheral and Central Effects: While hyoscyamine affects both the peripheral and central nervous systems, its ability to cross the blood-brain barrier is slightly less than that of scopolamine, leading to relatively weaker central nervous system effects.

Atropine

Atropine is the racemic mixture of hyoscyamine, consisting of both levo (L)- and dextro (D)-isomers. The L-isomer (hyoscyamine) is pharmacologically active, while the D-isomer is much less active.

Molecular Mechanism:

Non-Selective Muscarinic Antagonism: Atropine exerts its effects by competitively inhibiting the binding of acetylcholine to mAChRs, similar to scopolamine and hyoscyamine.

Clinical Uses and Toxicity: Due to its ability to inhibit the parasympathetic nervous system, atropine is used clinically to treat bradycardia (slow heart rate), as a pre-anesthetic to reduce salivation, and to counteract organophosphate poisoning. However, in large doses, atropine can cause significant toxicity, including tachycardia, blurred vision, dry mouth, urinary retention, and central effects like confusion and hallucinations.

Pharmacological and Toxicological Implications

The potent anticholinergic effects of these tropane alkaloids render Angel’s Trumpet both medically valuable and potentially dangerous. In therapeutic settings, these compounds are used for their anticholinergic properties, but their narrow therapeutic index means that they can easily cause toxicity.

Therapeutic Uses:

Scopolamine is used for motion sickness, postoperative nausea and vomiting, and to induce sedation.

Hyoscyamine is used to treat various gastrointestinal disorders, such as irritable bowel syndrome, due to its antispasmodic properties.

Atropine is utilized in emergency medicine for bradycardia and as an antidote for certain types of poisoning.

Toxicity and Poisoning:

Overdose or improper use of Angel’s Trumpet can lead to severe anticholinergic poisoning, characterized by symptoms like dry mouth, blurred vision, hyperthermia, hallucinations, delirium, and potentially fatal cardiovascular complications.

Conclusion

Angel’s Trumpet (Brugmansia species) is a plant with significant pharmacological properties due to its content of tropane alkaloids, primarily scopolamine, hyoscyamine, and atropine. These compounds act as potent muscarinic antagonists, influencing both the central and peripheral nervous systems. While they have valuable therapeutic uses, the potential for toxicity necessitates careful and controlled use. Understanding the molecular mechanisms of these phytochemicals helps in both utilizing their benefits and mitigating their risks.