Alkaloids Basic nitrogen-containing

The compounds best known for their bitter taste belong to the alkaloids and glycosides. Alkaloids are basic nitrogen-containing organic compounds that are derived from pyridine, pyrrolidine, quinoline, isoquinoline, or purine. Quinine is often used as a standard for testing bitterness (Figure 7-13). 

Alkaloid (Section 25.6A) A basic, nitrogen-containing compound isolated from a plant source. 

Chemistry provides a definition of alkaloids in purely chemical terms. Chemists stress that alkaloids are any group of complex heterocyclic nitrogen compounds, which have strong physiological activity, are often toxic, and retain their own basic chemical properties. It is also stated that there are a few exceptions to this definition.Another chemical definition states only that alkaloids are nitrogen-containing compounds derived from plants and animals. Later, chemists stressed that alkaloids were bio-... 

Many compounds, including acids, can act as gas phase bases in their reactions with gaseous H30 (H20) ion clusters. However, the method is particularly suitable for the detection of compounds with high gas phase basicities. Nitrogen-containing bases tend to be particularly reactive in the APCI ion source. As a result, APCI provides an excellent method for detecting and determining concentrations of gas phase alkaloids. It should be noted, however, that this method is not suitable for the detection of any alkaloids which may be associated with the particulate phase of ETS. 

Alkaloids are basic, nitrogen-containing compounds of plant or animal origin, often having complex structures and significant pharmacological properties. Nicotine (from tobacco) and the amine obtained by deprotonation of squalamine (from sharks) are examples of alkaloids... 

Alkaloids are basic nitrogen-containing compounds of plant origin, many of which are physiologically active in humans. 

Alkaloids are nitrogen-containing organic compounds, which are basic and often poisonous. 

Alkaloids were formerly defined as basic, nitrogen-containing plant substances, but examples have also been found in fungi, marine organisms, amphibians, insects and even mammals. There are over 10,000 plant alkaloids known, very varied in structure, from simple ones like coniine to complex structures like strychnine and reserpine (Figure 9.1). The biosynthesis of alkaloids in plants has received a lot of study. Less is known about the biosynthesis of the much smaller number of insect alkaloids, except for a few examples, like the coccinellines, adaline and epilachnine (Chapter 3). 

Alkaloids, nitrogen-containing compounds generally found as secondary metabolites in plants, are also classical examples of renewables. In contrast to terpenes, they show a great variety in molecular structure, and the different classes of alkaloids are usually based on their basic ring systems. Many pharmaceutically active... 

Alkaloids are a group of nitrogen-containing natural products that occur primarily in higher plants, although they are also found in some fungi, such as mushrooms. The name alkaloid (meaning alkali-like ) is applied because they are amines and thus basic. Their basic character allows them to be readily isolated from their plant source. The plant material is extracted with aqueous acid. This converts the alkaloid to an ammonium cation, which is water soluble. Neutralization of the acidic extract with base causes the alkaloid to precipitate. 

Finally, we should point out that even today the term alkaloid is ambiguous (a discussion on the definition of alkaloid is presented in Chapter 4). The initial definition of Winterstein and Trier (1910) ("nitrogen-containing basic compounds of plant or animal origin") has obviously been superseded. The most recent definition of alkaloid can be attributed to S. W. Pelletier (1984) "compound containing nitrogen at a negative oxidation level characterized by a limited distribution in Nature". In the preparation of this handbook we have decided to follow this last definition and, thus, to include "borderline" compounds such as capsaicins and non-ribosomal polypeptides. 

Caffeine belongs to a large class of compounds known as alkaloids. These are of plant origin, contain basic nitrogen, often have a bitter taste and complex structure, and usually have physiological activity. Their... 

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