Agriculture Reference
In-Depth Information
relatively large amounts of arginine and glutamic acid, and these may be
important N reserves. Onion skins contain large amounts of pectin and are
suitable sources for the extraction of pectic substances for processing (see 'Onion
Waste Processing', below). A number of sterols and saponins have been extracted
including, from leek leaves, aginosid, a steroidal saponin that exhibits growth
inhibitory activity against leek moth (see Chapter 5). Several other complex
chemical structures have been isolated from alliums, including prostaglandins.
Introduction
The study of the health benefits of alliums is a burgeoning field of research, to
which whole topics have already been devoted (e.g. Koch and Lawson, 1996).
The subject is complex because it involves the interaction of pharmacologically
active compounds from alliums with the intricate biochemistry and physiology
of human disease. Moreover, as mentioned above, pharmacologically active
substances derived from ACSOs are chemically complex and can be unstable
and short-lived, and their quantity and nature depends on the chemical
environment during and subsequent to the alliinase reaction that releases
them (Block, 1992).
However, the subject is exciting, because alliums and the substances
derived from them are therapeutic for many of the diseases of affluent societies,
notably heart disease (arteriosclerosis), cancer, asthma and diabetes, as well as
having powerful anti-microbial properties for countering infectious diseases.
Medicinal effects have been reviewed by Fenwick and Hanley (1985a), Augusti
(1990), Koch and Lawson (1996), Griffiths
et al.
(2002), Keusgen (2002) and
several authors in Guangshu (2005).
Alliums have a long history of medicinal use and are ascribed to curing of
a wide range of ailments in traditional medical writings. Scientific studies have
shown considerable pharmacological effects that have, in some cases, been
attributable to specific molecular structures, mostly derived from the flavour-
inducing sulfur compounds discussed above. Herein is a brief review of the
subject, with an indication of the therapeutically active compounds present in
alliums, and some striking examples of research findings at different levels of
organization, ranging from molecular pharmacology to human epidemiology,
that together are building up evidence for benefit to health from alliums.
Four types of compound found within alliums are of therapeutic interest.
First are the substances derived from ACSOs that are largely responsible for
flavour and pungency. Second are the flavonoids, including quercetin, which is a
powerful antioxidant and which is found in higher concentration in onion than
in any other vegetable or fruit. Third there are the fructo-oligosaccharides
and fructans, soluble but non-digestible carbohydrates that promote a health-
