Classification of Natural Products

There are several ways to categorize natural products. They may be grouped according to a recurring structural feature. Flavonoid compounds, for example, are oxygenated derivatives of the aromatic ring structure 1; likewise, alkaloids having an indole ring, 2 are called indole alkaloids:

Or they may be grouped according to the genus of their plant source (morphine and codeine, are examples of opium alkaloids), or by their physiological effects (antimicrobials, antibiotics, analgesics), or by similarities in the route by which they are synthesized by the organism (biosynthesis). The structural and biosynthetic classifications make the most sense to the chemist and is the organization chosen here.