Antioxidant properties biological activity

These structurally diverse compounds exhibit a range of biological activities in vitro that may explain their potential health-promoting properties, including antioxidant and anti-inflammatory effects and the induction of apoptosis (Hooper and others 2008). Most of the recent interest in flavonoids as health-promoting compounds is related to their powerful antioxidant properties. The criteria to establish the antioxidant capacity of these compounds is based on several structural characteristics that include (a) the presence of o-dihydroxyl substituents in the B-ring (b) a double bond between positions 2 and 3 and (c) hydroxyl groups in positions 3 and 5. 

Several different tocopherols are known to have vitamin E activity, but a-tocopherol, a trimethyltocol (Figure 12.9) is the most biologically active. Other less potent forms are the /3-, y- and S-tocopherols, which contain fewer methyl groups. They all have antioxidant properties and a deficiency results in a lack of protection of the unsaturated fatty acids in the membrane phospholipids against oxidation by molecular oxygen. 

Some biologically important o-quinones can react with the superoxide ion giving catechol derivatives, which may play a role in many diseases. For example, compounds bearing a nitro-catechol moiety have been claimed to be efficient catechol-0-methyl transferase inhibitors (Suzuki et al. 1992, Perez et al. 1992). The transferase is the first enzyme in the metabolism of catecholamine a hyperactivity of this enzyme leads to Parkinson s disease. Therefore, prediction of biological activity and antioxidant properties of quinones is an important challenge for researchers. 

Iridoids have shown a broad range of biological activities, such as an antibacterial, antifungal, anti-inflammatory, antitumoral, hepatoprotective, cardioprotective, antioxidative, antiprotozoal and anti-insect properties [13,14,15,16,17,18,19]. In vitro activities inhibiting the hepatitis C virus, the differentiation of the adipocyte, and PPARa activation activities have been also described [20, 21]. 

Because it has a variety of biological activities such as antioxidant, antimicrobial, anti-inflammatory, anticancer, and immune-stimulating effects, chitosan offers a number of uses in food, cosmetic, biomedical, and pharmaceutical industries. In this section, the nutraceutical properties of chitosan and its derivatives are discussed. 

Chlorogenic acids are shown to have some desirable biological activities. Most of their property relates to their function as antioxidants, evidenced by their activity to scavenge free radicals, to inhibit the formation of free radicals, and to block the oxidation reaction. However, other activities based on mechanisms other than scavenging capacity cannot be ignored. Also, further tests for the in vivo bioactivity of chlorogenic acids are to be needed. However, it is expected that chlorogenic acids may be beneficial to human health. 

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