The Classification of Alkaloids

These compounds are separated into three general classes of materials. 

True alkaloids These compounds contain nitrogen in a heterocyclic ring are almost always basic (the lone pair of the nitrogen is responsible for 

Protoalkaloids These compounds are simple amines, derived from amino acids, in which the basic nitrogen atom is not incorporated into a ring system they are often referred to as biological amines. An example of a protoalkaloid is mescaline. 

Pseudoalkaloids These compounds contain nitrogen atoms usually not derived from amino acids. There are two main classes into which pseudoalkaloids are divided, the steroidal alkaloids and the purines. Caffeine has been assigned to this latter class of alkaloids. 

Solid-Liquid Extraction (p. 79) Liquid-Liquid Extraction (p. 72) Technique 9 Sublimation 

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Several approaches to the classification of alkaloids are available, including, chemical, taxonomic, biological, and biosynthetic. At various times, each of these approaches has been used in terms of the presentation and discussion of alkaloid development. We will discuss these approaches in turn. 

Nicotine and anabasine are considered to be alkaloids derived firom nicotinic acid (pyridine-3-carboxylic acid).These alkaloids can be also classified as derived from ornithine and lysine, respectively. Therefore, these alkaloids are described in Chapter 10.1 (as alkaloids derived from nicotinic acid), in Chapter 3.1 (alkaloids derived from ornithine and arginine), and in Chapter 4.3 (alkaloids derived from lysine). However, such exceptions are relatively rare if the classification of alkaloids is conducted based on their biosynthetic origin. 

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