**5. Lycopene stability**

492 Lipoproteins – Role in Health and Diseases

**4. Mechanisms action of lycopene**

A cellular and molecular study have shown lycopene to be one of the most potent antioxidants and has been suggested to prevent atherogenesis by protecting critical bimolecules such as DNA, proteins, lipids and low density lipoproteins (Pool-zobel *et al.,* 1997). Lycopene, because of its high number of conjugated double bonds, exhibits higher singlet oxygen quenching ability compared to β-carotene or α-tocopherol (Di-Mascio *et al.,* 1989). Cis lycopene has been shown to predominate in both benign and malignant prostate tissues, suggesting a possible beneficial effect of high cis-isomer concentrations, and also the involvement of tissue isomerases in vivo isomerization from all trans to cis form (Clinton *et al.,* 1996). Where as Levin *et al.,* (1997) have shown that 9- cis- β-carotene is a better antioxidant than its all-trans counterpart, no such mechanistic data have been reported in case of individual lycopene isomers. Handley *et al.,* (2003) reported a significant increase in 5-cis lycopene concentrations following a 1- week lycopene-restricted diet, and a subsequent reduction in 5-cis, and a concomitant increase in cis-β, cis-D and cis-E lycopene isomers during the 15-day dietary intervention with tomato products in healthy individuals. Although this study reported a decrease in LDL oxidizability due to the intervention with tomato lycopene, the individual antioxidant role of lycopene isomers and their inter conversions remain unclear. At a physiological concentration of 0.3 μmol/1, lycopene has been shown to inhibit growth of non-neoplastic human prostate epithelial cells in vitro, through cell cycle arrest which may be of significant implications in preventing benign prostate hyperplasia, a risk factor for prostate cancer (Obermuller-Jevic *et al.,* 2003). Lycopene has also been shown to significantly reduce LNCaP human prostate cancer cell survival in a dose-dependent manner, and this anti-neoplastic action may be explained by increased DNA damage at high lycopene concentrations (> 5μm), whereas lower levels of lycopene reduced malondialdehyde formation, with no effects on DNA (Hwang & Bowen, 2005). Physiologically attainable concentrations of lycopene have been shown to induce mitochondrial apoptosis in LNCaP human prostate cancer cells, although no effects were observed on cellular proliferation or necrosis (Hantz *et al.,* 2005). Lycopene has also been shown to interfere in lipid metabolism, lipid oxidation and corresponding development of atherosclerosis. Lycopene treatment has been shown to cause a 37% suppression of cellular cholesterol synthesis in J-774A.1 macrophage cell line, and augment the activity of macrophage LDL receptors (Fuhrman *et al.,* 1997). Oxidized LDLs are highly atherogenic as they stimulate cholesterol accumulation and foam cell formation, initiating the fatty streaks of atherosclerosis (Libby, 2006). LDL susceptibility to oxidative modifications is decrease by an acyl analog of platelet-activating (PAF), acyl-PAF, which experts its beneficial role during the initiation and progression of atherosclerosis. Purified lycopene in association with αtocopherol or tomato lipophillic extracts has been shown to enhance acyl-PAF biosynthesis in endothelial cells during oxidative stress (Balestrieri *et al.,* 2004). Fuhrman *et al.,* (2000) further reported comparative data in which tomato oleoresin exhibited superior capacity to inhibit in vitro LDL oxidation in comparison with pure lycopene by up to fivefold. A combination of purified lycopene (5μmol/I) with α-toopherol in the concentration range of 1-10μmol/I resulted in a significant greater inhibition of in vitro LDL oxidation, than the

Being acyclic, lycopene possesses symmetrical planarity and has no vitamin A activity, and as a highly conjugated polyene, it is particularly susceptible to oxidative degradation. Physical and chemical factors known to degrade other carotenoids, including elevated temperature, exposure to light, oxygen, extremes in pH, and molecules with active surfaces that can destabilize the double bonds, apply to lycopene as well (Rao *et al.,* 2003).

In a study to determine the photoprotective potential of dietary antioxidants including lycopene carried out by Handley *et al.,* (2003) carotenoids were prepared in special nanoparticle formulations together with vitamin C and/or vitamin E. The presence of vitamin E in the formulation further increased the stability and cellular uptake of lycopene, which suggests that vitamin E in the nanoparticle, protects lycopene against oxidative transformation. Their findings suggest that lycopene stability may be improved by nanoparticle formulation and incorporation of vitamin E in the lycopene formulation.

Badimon *et al.,* 2010 studied the stability of lycopene during heating and illumination. They carried out various pretreatment steps to the all-trans lycopene standard, which included; dissolving the lycopene standard into hexane and evaporating to dryness under nitrogen in vials, after which a thin film formed at the bottom surface. The resulting lycopene was heated at 50, 100, and 150°C or illuminated at a distance of 30 cm with illumination intensity in the range of 2000–3000 lux (25°C) for varied lengths of time (up to100 hours for heating and 5 days for illumination). After analysis, the degradation of total lycopene (all-*trans* plus *cis* forms) during heating or illumination was found to fit a firstorder model. At 50°C, the

isomerization dominated in the first 9 hours; however, degradation was favored afterwards. At 100 and 150°C, the degradation proceeded faster than the isomerization, whereas, during illumination, isomerization was the main reaction. The degradation rate constant (min−1) of lycopene was found to rise with increasing temperature with an activation energy calculated as 61.0 kJ/mol.

The stability of crystalline lycopene was determined under various temperature conditions (5, 25, and 35°C) while stored in airtight containers, sealed under inert gas, and protected from light. After 30 months of storage, crystalline lycopene remained stable when stored under the recommended conditions (Barros *et al.,* 2011).

Lycopene (synthetically prepared by the Wittig reaction) 5% TG (Tablet Grade) and lycopene 10% WS (Water Soluble) beadlet formulations tested for over 24 months of storage, and Lycopene 10% FS (Fluid Suspension) liquid formulation tested for over 12 months of storage under various temperature conditions (5 and 25°C), were all found to be stable.(25) For the 10% WS lycopene beadlet formulations, an important market application form, stability with respect to oxidation under ambient light conditions and room temperature for 12 months in beverages was found to be 93% of the initial content of the beverage lycopene (Pool-zobel *et al.,* 1997).
