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Poisonous! Every bit of it - except the pithy bit (aril) around the seeds, but then the seeds are deadly so I wouldn’t risk it. Usually found at church entrances and linked to folklore and superstition.
Yew tree (Taxus baccata) poison biochemistry involves taxine alkaloids, particularly Taxine B, which act as calcium and sodium channel antagonists, disrupting heart function by increasing cytoplasmic calcium levels. These alkaloids cause cardiotoxicity, leading to symptoms like bradycardia, heart block, and potentially fatal cardiovascular collapse. While other substances like taxanes and glycosides are also present, taxine alkaloids are considered the primary toxic component, and are found in all parts of the plant except the red aril.
Toxic Components
Taxine Alkaloids: The main toxic compounds, including Taxine B, which is more potent than Taxine A.
Other Compounds: Also present are taxane derivatives and glycosides, though the alkaloids are the primary cause of cardiotoxicity.
Mechanism of Action
Sodium and Calcium Channel Antagonism: Taxine alkaloids block sodium and calcium channels in cardiac myocytes, which are the cells of the heart muscle.
Increased Cytoplasmic Calcium: This blockade leads to an accumulation of calcium within the heart cells, disrupting the heart's normal electrical and contractile functions.
Reduced Myocardial Contractility: The increased calcium impairs the ability of the heart to contract effectively.
Symptoms and Effects
Cardiovascular Effects: The most prominent effects are on the heart, including bradycardia (slow heart rate), atrioventricular (AV) conduction block, widened QRS complexes, and ventricular arrhythmias.
Other Symptoms: Initial symptoms can include dizziness, nausea, and vomiting, followed by neurological disturbances, paralysis, and ultimately, cardiovascular collapse.
Cardiovascular Collapse: Death often results from the failure of the cardiovascular system.