Natural and Synthetic Antioxidants

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Antioxidants are substances that stable enough to prevent or retard the oxidation of easily oxidisable biomolecules such as lipids, proteins and DNA, thus preventing oxidative damage (Lobo et al. 2010). Antioxidants can be classified into two classes, according to their action, into primary or chain breaking antioxidants and secondary or preventative antioxidants. Primary antioxidants, when present in low concentration, can either delay or inhibit the lipid oxidation by reacting with a lipid radical or peroxyl radicals. Secondary antioxidants on the other hand, retard the rate of oxidation by chelating of metal ions or quenching of singlet oxygen (Amalia et al. 2005). These antioxidants are widely used as food additives in foods, especially those with high lipid content, to protect against oxidative degradation, maintain nutritional quality and increase the shelf life of the food.

Generally, antioxidants can be divided into natural and synthetic antioxidants. Natural antioxidants are normally found in the plant extracts which are believed to exhibit strong antioxidant activity and protection against oxidant-induced damage such as diabetes, neurodegenerative and cardiovascular disease (Maganha et al. 2010). Plants, fruits and vegetables are all known to be rich sources of natural antioxidants due to the presence of phenolic compounds, which are the secondary metabolites in plants (Misan 2010; Arya and Yadav 2011). Polyphenols, or phenolic compounds, constitute one of the most numerous and widely-distributed groups of substances in the plant kingdom (Urquiaga and Leighton 2000; Gan et al. 2010). They exist naturally in the form of glycosylated which makes them the most common water-soluble antioxidant compounds present in plants ...

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... antioxidant is effective for all stages (Jaswir et al. 2004). A combination of antioxidants in which the antioxidants produce a synergistic effect may be successful in inhibiting the lipid peroxidation. Recently, most of the studies have been focused on the antioxidant activity of the leaves crude extract and their individual polyphenols, only few studies have investigated the interaction of leaves crude extraction with other common antioxidants including α-tocopherol. Moreover, to date, there has been no scientific report of interaction between Aquilaria crassna young leaves crude extract and α-tocopherol. Therefore, in present study, agarwood leaves (Aquilaria crassna) crude extract are combined with α-tocopherol to investigate their antioxidant interaction against lipid peroxidation and to evaluate if the interaction promotes a synergistic antioxidant effect.

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