Laura Hill Oxidation of low density lipoprotein (LDL) Forms

1
Bioactivity Antioxidative Properties of
Lycopene versus Other Carotenoids

• Laura Hill

2
Oxidative Damage in the Human Body

• Oxidation of low density lipoprotein (LDL)
• Forms foam cells plaque in vessels
• Leads to cardiovascular disease
• Free radical oxidative damage to proteins, DNA,
  lipids1
• Development of carcinogenesis, atherosclerosis,
  heart disease, inflammation, physiological
  aging.

3
Role of Antioxidants in the Body

• Oxidative stress stems from an imbalance between
  production removal of reactive oxygen species
  (ROS)
• Human body contains endogenous cellular defense
  systems to prevent oxidative damage
• Ex glutathione peroxidase, catalase, superoxide
  dismutase, etc.
• These endogenous defense mechanisms are not
  sufficient to protect the body from certain types
  of oxygen species (singlet oxygen)
• Food derived antioxidants are needed

4
Food-Based Antioxidants

• Scavenge free radicals from the body by
• Reacting with free radicals to yield stable
  harmless products
• Disrupting free radical chain reactions
• Carotenoids are one of the major groups of
  antioxidants found in fruits vegetables
• Over 600 known carotenoid compounds
• a-carotene, ß-carotene, lutein, lycopene,
  zeaxanthin, astaxanthin, canthaxanthin
• Polyene chain structure determines reactivity
  antioxidant capacity

5
Carotenoid Food Sources
6
Lycopene Structure

• Lineal acyclic isomer of beta-carotene
• Longest carotenoid
• No ß-ionone ring?cannot be converted to Vitamin A
• Lipophilic
• Incorporates into cell membrane or associates
  with lipoprotein
• Most stable form is all-trans-isomer, which is
  present in raw tomatoes
• Converts to cis-isomer when it is exposed to
  light, heat, or chemical reaction
• The cis-isomer is better absorbed by the human
  body

Lycopene
ß-carotene
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Lycopene as an Antioxidant

• Conjugated double bond system considered most
  important structural factor for enabling
  carotenoids to quench energy from ROS and
  scavenge free radicals2
• Large number of double bonds and the opening of
  the ß-ionone ring believed responsible for
  increased antioxidant ability of lycopene2
• Lycopene is most efficient quencher of singlet
  oxygen among carotenoids
• Rate constant for lycopene quenching singlet
  oxygen is 2x that of ß-carotene3

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Lycopene vs. Other carotenoids

• Study found that UV irradiation caused a greater
  decrease in concentration of lycopene than
  ß-carotene in human skin4
• Suggests lycopene is being consumed by free
  radical and ROS quenching reactions in the skin
• Some epidemiological research has shown high
  ß-carotene has no significant effect on heart
  disease breast cancer5,6
• ß-carotene may increase incidence of lung cancer
  among smokers7,8
• Lycopene has been shown to decrease growth of
  carcinoma cells and development of cancer
• In a rat tumor study, a pre-injection of lycopene
  before tumor induction significantly reduced the
  number and size of tumors9
• Lycopene was more effective for inhibiting
  mammary cancer cell proliferation than a-carotene
  or ß-carotene3

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Conclusions

• Antioxidant activity is believed to be the
  mechanism for lycopenes anti-cancer action
  health promoting activity, but other mechanisms
  may also be involved
• Antioxidant activity can be increased through
  synergistic effects with other antioxidants
• A diet rich in fruits vegetables will provide a
  wide variety of nutrients and antioxidants that
  will benefit human health

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Questions?
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References

• 1) Cross, C.E. 1987. Oxygen Radicals and Human
  Disease. Ann. Internal Med. 107 526-545.
• 2) Young, A.J. and G.M. Lowe. 2001. Antioxidant
  and prooxidant properties of carotenoids.
  Archives of Biochemistry Biophysics. 385(1)
  20-27.
• 3) Levy, J., Bosin, E., Feldman, B., Giat, Y.,
  Miinster, A., Danilenko, M., and Sharoni, Y.
  1995. Lycopene is a more potent inhibitor of
  human cancer cell proliferation than either
  alpha-carotene or beta-carotene. Nutr. Cancer,
  24 257-266.
• 4) Ribaya-Mercado, J.D., Garmyn, M., Gilchrest,
  B.A., and Russell, R.M. 1995. Skin lycopene is
  destroyed preferentially over beta-carotene
  during ultraviolet irradiation in humans. J.
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• 6) Verhoeven, D.T., N. Assen, R.A. Goldbohm, E.
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  of beta-carotene and vitamin A on lung cancer and
  cardiovascular disease. N. Engl. J. Med.
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• Albanes, D., O.P. Heinonen, J.K. Huttunen, P.R.
  Taylor, J. Virtamo, B.K. Edwards, J. Haapakoski,
  M. Rautalahti, A.M. Hartman, J. Palmgren, and P.
  Greenwald. Effects of alpha-tocopherol and
  beta-carotene supplements on cancer incidence in
  the Alpha-Tocopherol Beta-Carotene Cancer
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  1427S-1430S.
• Sharoni, Y., E. Giron, M. Rise, and J. Levy.
  1997. Effects of lycopene-enriched tomato
  oleoresin on 7,12-dimethyl-benzaanthracene-induc
  ed rat mammary tumors. Cancer Detect. Prev. 21
  118-123.