**2. Oxidative Stress and Antioxidants**

Oxidative modification of low density lipoprotein cholesterol (LDL-C) play an important role in the initiation and progression of the atherosclerotic process, a *continuum pathophysiological process* that includes oxidative stress, endothelial dysfunction, inflammatory process, and vascular remodelling [5]. 

Specifically, CVD are associated with increased production of reactive oxygen species (ROS) and a compromised endogenous anti-oxidant defense system. Oxidative stress is tightly regulated by a balance between production and removal of ROS [6], which are natural by-products of metabolism with important roles in cell signaling. However, excessive levels of ROS can be toxic to cells, *i.e.*, whenever the expression of anti-oxidant enzymes, including superoxide dismutases (SODs), heme oxygenase-1 (HO-1), NAD(P)H quinine oxidoreductase-1 (NQO-1), catalase and thioredoxin are not sufficient to control ROS and minimize ROS-induced damage [7]. A compromised anti-oxidant defense system can lead to excessive oxidative stress and ultimately result in cell damage [8]. 

Numerous studies indicate that increased oxidative stress may be involved in the pathogenesis of CVD. Several animal models suggest that when endogenous antioxidant systems are overwhelmed, exogenous antioxidant supplementation can be used for preventive and/or therapeutic intervention of oxidative cardiovascular disorders [9]. In particular, SODs, catalase and glutathione peroxidase (GSHPx) are endogenous natural antioxidants present within human cells. In addition, antioxidants such as vitamin E, vitaminC, polyphenols and carotenoids are available from foods [10]. 

Current dietary guidelines to combat chronic diseases, including cancer and CHD, recommend increased intake of plant foods, including fruits and vegetables, which are rich sources of antioxidants [11]. The role of such dietary antioxidants in diseaseprevention has received much attention recently and appears to have a wide range of antiatherogenic properties [12,13]. These observations may explain the epidemiological data indicating that diets richin fruits and vegetables are associated with a reduced risk of numerous chronic diseases [14].

Carotenoids are ubiquitous in nature and present in plants, algae and microorganisms. However, humans and other animals are unable to manufacture carotenoids and hence require these in their diet. There are two class types of carotenoids based on their chemical composition: carotenes and xanthopylls [15]. Astaxanthin and fucoxanthin are major marine carotenoids. Both these carotenoids show strong antioxidant activity which is attributed to quenching singlet oxygen and scavenging free radicals (FRs) [16]. 

## **3. Astaxanthin**
