Some things in nature taste very bitter. 
Many living things make special parts. 

Alkaloids are special parts found in many living things. 
People have used alkaloids for a very long time. Ancient people in Mesopotamia used medicinal plants. Some used toxic alkaloids to poison arrows. In 1804, a chemist named Friedrich Sertürner found morphine. 
Alkaloids can do many different jobs. Some work as medicine. For example, quinine helps fight malaria. Others can act as stimulants. This means they make you feel more awake. Caffeine and nicotine are two examples. Some alkaloids can also be toxic. This means they can make you sick. Scientists study them to find new drugs. They use special tools to find and name them. By 2008, experts found more than 12,000 different alkaloids.
Alkaloids are a huge group of natural compounds found in many living things. 
These compounds work in many different ways inside the body.
Humans have used these substances for thousands of years. 

There are many different types of alkaloids to learn about.
Learning about alkaloids helps us understand how nature works.
Alkaloids are a vast class of naturally occurring organic compounds.
Scientists use specific methods to isolate these compounds from living things. One common process is acid-base extraction. This method uses changes in acidity to separate the alkaloids from a crude extract. Another way to purify them is through solvent extractions. This is often followed by silica-gel column chromatography to refine the substance.
Alkaloids serve many different roles in medicine and biology. Some provide antimalarial effects, such as quinine. Others act as antiasthma treatments, like ephedrine. Certain alkaloids are used for anticancer purposes, such as homoharringtonine. Many others have specific uses, including being vasodilatory, antiarrhythmic, or analgesic. For example, morphine is a well-known analgesic used to manage pain. 
Humans have interacted with alkaloid-containing plants since ancient times. In Mesopotamia, medicinal plants were used around 2000 BC. Ancient Chinese books from the 1st to 3rd centuries BC mentioned the use of opium poppies. Indigenous South Americans have used coca leaves since antiquity. Some cultures even used toxic alkaloids, like aconitine, to poison arrows. 

There is no single way to name these compounds. Many individual names are created by adding the suffix "ine" to a plant's genus or species name. This suffix is a Greek patronymic meaning "daughter of." For instance, atropine is the "daughter of" the plant Atropa belladonna.
Scientists classify alkaloids in several different ways. Early researchers used botanical classification based on the source plant, but this is now considered obsolete. Modern classifications often look at the carbon skeleton or the biochemical precursor. One major group is "true alkaloids." These contain nitrogen in a heterocycle and originate from amino acids. Examples include nicotine and morphine.
Other specialized groups include polyamine alkaloids and peptide alkaloids. Some alkaloids are categorized by their specific chemical rings, such as pyridine or isoquinoline derivatives.
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