Alkaloids

Alkaloids vary widely from one plant to another in their components and their actions, but are all compounds that contain nitrogen. They tend to have potent effects and in some cases are toxic in large amounts - they are frequently found in herbs whose use is restricted to qualified medical herbalists and doctors in specified doses, and are often unsuitable for home use.

They include morphine from the opium poppy, nicotine in tobacco, atrophine in deadly nightshade, caffeine and thobromide in coffee, black tea and cocoa.

Alkaloids also occur in small non-toxic amounts in some medicinal herbs where they act as catalysts to other healing agents without being involved themselves - pyrrolizidine alkaloids in comfrey and coltsfoot are good examples.