In both Western and developing countries it was reported that CVDs are now a major problem in causing mortality [1]. Lipoprotein has been considered a cardiovascular risk factor for many years [2]. LDL level change from normal can cause several problems in our body. Polyphenols display protective action against LDL oxidation and potentially against CVD. The purpose of this article to established the beneficial effect of polyphenol to prevent the CVD. Herein we have briefly demonstrated that how polyphenol control LDL level by inhibiting the LDL oxidation with the scavenging of reactive oxygen species. Polyphenols are well distributed the plant product such as fruits, vegetables, green tea leafs, wine etc. This paper reviews previous studies on the prevention of cardiovascular disease focusing on the in vivo studies.

However the regular dietary intake of these compounds will be a valuable to reduce the risk of occurring CVD by controlling plasma LDL.

Plasma LDL management by polyphenol

The polyphenol compound has beneficial role to control the level of the LDL. However the effect of polyphenol on the reduction of the oxidation of the LDL depends on their structure, type and concentration (Figure 1).

Figure 1: Structure of Polyphenol.

Plasma lipoprotein consisting of a cholesterol-rich LDL particle with one molecule of apolipoprotein B100 and an additional protein, apolipoprotein, attached via a disulfide bond. Elevated LDL levels can potentially increase the risk of CVD via two ways (Figure 2).

Figure 2: Effect of oxidised LDL.

• Prothrombotic/anti fibrinolytic effects as apolipoprotein possesses structural homology with plasminogen and plasmin but has no fibrinolytic activity and

• Accelerate atherogenesis as a result of intimal deposition of lipoprotein cholesterol, or both. Not only that, when LDL is oxidised by ROS it display cardiovascular injury (Figure 3).

Figure 3: Oxidation of Normal LDL by ROS.

Oxidised LDL particle damage endothelial cells stimulate the production of local hormone from blood vessel wall. Promote inflammation, attract macrophage and discourage their exit. Thus oxidised LDL promotes heart disease.

Because of their antioxidant and chelating properties, polyphenols inactivate reactive oxygen species (ROS) and this way counteract plasma LDL oxidation and improve inflammation of the blood vessel endothelium [3]. Ingestion of the grape and apple juice reduces the plasma lipid concentration. The consumption of polyphenol also reported to be reducing the cholesterol level of hypercholesterolic patient and reduce the oxidation of the LDL [4]. B cells can also react with oxidized lipoproteins and cause antibodies and arterial inflammation.

Mode of action of Polyphenol by scavange ROS

F-OH + R. → F-O. + RH

F = Polyphenol, R.= free radical

The phenol groups of polyphenol serve as a source of a readily available ‘‘H” atoms such that the subsequent radicals produced can be delocalized over the polyphenol structure. Scavenging capacity is primarily attributed to high reactivates of hydroxyl substituent.

Polyphenol inhibit lipid peroxidation in vitro at an early stage by acting as scavengers of superoxide anion and hydroxyl radicals. They terminate chain radical reaction by donating hydrogen atom to a peroxy radical forming flavonoids radical, which, further reacts with free radicals thus terminating propagating chain (Table 1). Thus by scavenging ROS it help to inhibit the LDL oxidation (Table 2).

Table 1: Clinical trial help to prove the cardio-protecting effect of polyphenol effecting on lipid profile. Characteristics of study population, study design, intervention are included in these trials.

Table 2: Effects of several polyphenol on reduction of CVD risk/CVD occurrence are included with references with study design.

Oxidized low-density lipoproteins (ox-LDLs) appear to play a significant role in atherogenesis. In fact, circulating ox-LDL concentrations have been recognized as a risk factor for cardiovascular disease [5]. Polyphenols display protective action against LDL oxidation and potentially against CVD like atherogenesis. Polyphenols could exert health benefits not only by scavenging free radicals but also by modulating gene expression [6].

Lipid level-lowering medications are not always successful in reducing increased low-density lipoprotein. Among the natural substances polyphenol is found to be beneficial than other compound. Several natural compound, leaves, fruits seeds etc are essential for our health due to their antioxidant capacity [17]. Flavonoids from almond skins are bioavailable and act synergistically with vitamins C and E to enhance hamster and human LDL resistance to oxidation [18]. Olive oil and red wine antioxidant polyphenols inhibit endothelial activation which is one of the antiatherogenic properties of Mediterranean diet polyphenols [19]. In addition to reducing LDL oxidation, the dietary intake of polyphenol-rich olive oil is capable of reducing the expression of CD40L gene, its downstream products, and related genes those are actively involved in atherogenic and inflammatory processes in humans [6].

Currently change of lifestyle and food habit is major cause of the increase plasma LDL level.

These findings provide evidence those polyphenol-rich food can act through molecular mechanisms to provide cardiovascular health benefits. The question arises that when to use these substances to enable their most effective action, and which polyphenol is the most beneficial to human health. Therefore more research is needed about LDL oxidation and action of Polyphenol.

Acknowledgement

This article is completely Dedicated to My Respected Sir Prof. Asru K. Sinha., D.Sc.

I am extremely thankful to my senior researcher in my lab specially Mr. Sarbashri Bank for his suggestion and encouragement in each and every moment. I am also thankful to Mr. Pradipta Jana, Mr. Suman Bhattacharyya.

I am also thankful to Dr. Smarajit Maiti, Reader & Head, and Department of Biochemistry, Oriental Institute of science and Technology (OIST) for guidance to write this article.