A Natural Bioactive Compound Lycopene and Its Role on Cancer Related to Oxidative Stress

Introduction

The balance between pro-oxidants and antioxidants is extremely important for maintaining vital cellular and biochemical functions. Changing the balance in favor of the pro-oxidant over the antioxidant capacity is defined as oxidative stress and can lead to oxidative damage (Kohen & Nyska, 2002). Biological systems contain specific mechanisms that keep this stress under control. Oxidative stress may occur in cases where control mechanisms are insufficient (Serafini & Del Rio,2004). The cell and the entire organism have developed indirect and direct activities of defense systems to guard against reactive metabolites because of constant exposure to various types of oxidative stress from different sources. These defense systems are repair and prevention mechanisms, physical defenses, and antioxidant defenses (Kohen & Nyska, 2002).

Antioxidants can protect cells by converting reactive oxygen species (ROS) to non-radical species (depending on the antioxidant), stopping the auto-oxidative chain reaction started by ROS, and lowering localized oxygen concentrations. Exogenous antioxidants contained in widely ingested fruits, vegetables, drinks, cereals, and other dietary products, such as ascorbic acid (Vitamin C), -tocopherol (Vitamin E), carotenoids, and polyphenols, may help to promote the antioxidative defense (Lourenço et al., 2019).

Carotenoids primarily exhibit antioxidant activity through their conjugated double-bonded structures that de-localize unpaired electrons and provide substantial tissue protection against oxidative damage (Flora, 2009). Carotenoids are antioxidants with significant protective effects against oxidative damage in tissue. It has provided insights into the health effects of lycopene to minimize the risks and complications associated with various chronic diseases, such as cardiovascular diseases (CVD), obesity, type 2 diabetes, cancer, and neurodegenerative diseases, that are based on recent cognitive studies. These chronic diseases are mainly connected with systemic and low-grade chronic inflammation caused by oxidative stress.

Lycopene, one of the important carotenoids with its strong antioxidant capacity, is one of the most significant non-enzymatic antioxidant agents that are not synthesized in the human body but obtained from consumed foods. Lycopene is a major component of the carotenoids found in serum. Lycopene levels have also been shown to be high in the testes, adrenal glands, and prostate (Rao & Agarwal, 1999). Lycopene can potentially minimize elevated levels of pro-inflammatory mediators (e.g., pro-inflammatory cytokines IL-8, IL-6, and IL-1). It prevents NF-kB activation by modulating oxidative stress due to its strong antioxidant properties. Lycopene appears to protect lipoproteins and vascular cells from oxidation in vitro, although there is no evidence in vivo. Several studies are reporting consuming high content lycopene food lowers the risk of cardiovascular disease and cancer. In several clinical studies, lycopene has been found as a natural origin agent to reduce oxidative stress, especially by preventing LDL oxidation (Chen et al.,2019; Saini et al., 2020). Lycopene is the strongest antioxidant among carotenoids since it has 11 conjugated double bonds. Therefore, lycopene protects DNA, lipids, and proteins from oxidative damage. Cell cycle arrest, immune function regulation, and activation of apoptotic cell death are all possible lycopene mechanisms. Lycopene also reduces phosphorylation of the kinase (ERK) regulated by extracellular signaling through inhibition of ROS production, thereby inhibiting cancer cell growth (Kim & Kim, 2015).

In this chapter, firstly free radicals and oxidative stress will be briefly discussed. In the next part a summary of lycopene, its main properties, functions, and oxidative stress-related studies will be presented. Lastly, lycopene's therapeutic effect of cancer will be discussed in detail.