Geoscience Reference
In-Depth Information
aromatic plant material. In Spain, it is estimated that about
800 medicinal and aromatic plant species are used of which
450 species are associated with commercial use (Blanco and
Breaux, 1997; Lange, 1998).
The fragrance of these plants is carried in the essential
oil fraction. Many aromatic plants are spices. Chandarana et
al
.
(2005) defined spices as any dried, fragrant, aromatic or
pungent vegetables or plant substances in whole, broken or
ground forms that contribute, to the piquancy of foods and
beverages.
Medicinal and aromatic plants contain biologically active
chemical substances such as saponins, tannins, essential oils,
flavonoids, alkaloids and other chemical compounds (Harborne,
1973; Sofowora, 1993), which have curative properties. These
phytochemicals are chemical compounds formed during the
normal metabolic processes of plants. These chemicals are
often referred to as 'secondary metabolites' of which there are
several classes, including alkaloids, flavonoids, coumarins, gly-
cosides, gums, polysaccharides, phenols, tannins, terpenes and
terpenoids (Harborne, 1973; Okwu, 2004).
12.2
Selected phytochemical classes
Alkaloids
The term 'alkaloid' was first proposed by Meissner in 1819
to characterise these 'alkali-like' compounds found in plants
(Trier, 1931; Pelletier, 1970). Alkaloids rank among the most
efficient and therapeutically significant plant substances
(Okwu, 2005). Some 5500 alkaloids are known and they
comprise the largest single class of secondary plant sub-
stances which contain one or more nitrogen atoms, usually
in combination as part of a cyclic structure (Harborne, 1973).
They are usually organic bases and form salts with acids and
when soluble give alkaline solutions. Examples include nico-
tine (
1
), cocaine (
2
), morphine (
3
) and codeine (
4
) (
Papaver
sominferum
), quinine (
5
) (
Cinchona succirubra
), reserpine
and (
6
) (
(Rauwolfia vomitoria
), all of which has a large
demand worldwide. Alkaloid production is a characteristic
of all plant organs. They exhibit marked physiological activ-
ity when administered to animals (Okwu and Okwu, 2004).
Furthermore, alkaloids are often toxic to man and many
have dramatic physiological activities, hence their wide use
in medicine for the development of drugs (Harborne, 1973;
Okwu, 2005).
