carotenoids

Potentially, more than 600 carotenoids have been discovered and the total number of compounds in this class including all isomers can successfully reach more than 20,000. In this vast bag of compounds, lycopene is a 40 carbon alicyclic and highly unsaturated compound[1,5]. It is found in numerous fruits and vegetables including tomatoes, apricots, cabbage, grapefruit, cauliflower, cucumber, pumpkin, lettuce, guava, orange, spinach, and watermelon[2], with tomato being the most concentrated source. It is lycopene that provides tomato its vibrant red color [3]. Lycopene possesses anticarcinogenic properties due to several physiological and cellular mechanisms[4,5,7]. Lycopene shows antioxidant properties due to its tendency to quench singlet oxygen and it is indeed the most efficient of all carotenoids in oxygen quenching tendency[6]. It reduces mutagenesis in the Ames test[4] and also owes it’s antioxidant properties to high reactivity towards free radicals due to its conjugated double bond system[5,7]. Lycopene affects several growth factors and signaling pathways leading to changes in proliferation responses, maturation, decreased apoptosis, etc.[4,5,7] Lycopene inhibits proliferation in various cancer cells and causes a reduction in HL-60 cell growth. Lycopene’s inhibitory effect on IGF signaling is due to suppression of IGF stimulated cell cycle progression of serum-starved, synchronized cells[4]. Lycopene is also responsible for the increase in antineoplastic effects of docetaxel[7], inhibits PDGF-BB induced human Hs68 skin fibroblast migration, and helps control the progression of melanoma[5]. Hence lycopene tends to inactivate growth factors like (PDGF, VEGF, and IGF) and signaling pathways that prove effective against carcinogenic processes[7]. Lycopene also behaves as a potential chemotherapeutic agent by promoting apoptosis[5] via death receptors[7]. Studies also show that lycopene has hypocholesterolemic effects which may have implications on several processes of carcinogenesis[4]. Also, there have been certain reports suggesting that lycopene can induce cell cycle arrest at the G1 phase[5] through the interaction between cyclin-dependent kinases[7]. Apart from these physiological processes, lycopene is also known to regulate antioxidant response elements [5], show anti-Invasive and antimetastatic Effects of Lycopene on Colon, Liver, and Prostate Cancers and act as an adjuvant for Cancer Therapy[7].