Page 174 - Natural Antioxidants, Applications in Foods of Animal Origin

Natural Antioxidants: Control of Oxidation in Fish and Fish Products 153
VetBooks.ir

4.4.2.2 PLANT ORIGIN

Plant-derived additives offer natural alternatives to synthetic antioxidants. In
the modern world changes in lifestyle have triggered a growing awareness
that particular ingredients in food may favorably modify diet-related prob-
lems. The interest in using naturally occurring nutritive and non-nutrient
antioxidants for food preservative purpose is due to their possible prevention
of a number of diseases, in the etiology of which oxidation mechanisms are
involved. Antioxidants can be sourced from selected herbs, spices, fruits,
nuts, and other plants (Boskou, 2006). The classes of compounds that act as

antioxidants from plant sources include: tocochromanols (lipophilic plant-
derived antioxidants) and the more polar phenolic compounds, including
phenolic acids, simple phenolics, flavonoids, anthocyanins, tannins,
hydroxytyrosol and derivatives, and constituents of essential oils (Pokorný,

2007). Frequently encountered natural antioxidants in plants are phenolic
acids and hydroxybenzoic acid (vanillic acid), hydroxycinnamic acid series
(ferulic acids, chlorogenic acid), flavonoids (quercetin, catechin, rutin),
anthocyanins (delphidin), tannins (procyanidin, ellagic acid, tannic acid),
lignans (sesamol), stibenes (resveratrol), coumarines (ortho-coumarine), and
essential oils (S-carvone).
Phenolic compounds are plant secondary metabolites and are commonly
found in herbs, vegetables, fruits, grains and cereals, coffee, red and white
wines, and green and black tea. Phenolic acids are phenols that possess
carboxylic acid functionality and they are made up of two distinguishing
constitutive carbon frameworks. The flavonoids consist of a group of low-
molecular weight polyphenolic substances. According to the degree of
oxidation of the C-ring, flavonoids can be categorized into the subclasses
flavones, isoflavones, flavanones, flavanonols (dihydroflavonols), flava-
nols (catechins), flavonols, anthocyanins, and proanthocyanidins. The anti-
oxidant activity of these compounds arises from their direct reaction with
free radicals (acting as primary antioxidants) and via their chelation of free
metals, which prevents further involvement of these metals in reactions that
finally generate radicals.
Tocochromanols are natural compounds known as tocopherols and toco-
trienols. They are found mainly in plant oils, nuts, and seeds. Experimental
data indicate that they have a radical chain-breaking activity and reducing
ability (Kamal-Eldin & Appelqvist, 1996).