LIFESCI 2N03 Study Guide - Final Guide: Tumor Suppressor Gene, Cruciferous Vegetables, Stomach Cancer
10 Feb 2019
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Antioxidants:
• What are they?
o Small molecules or larger proteins naturally occurring in foods and beverages
(can be extracted from food and added to products)
• What do they do?
o They prevent and delay oxidative damage to biological molecules and tissues
o They remove ROS by being oxidized themselves and taking the reactive electron
o They prevent production of ROS
o They repair the oxidative damage done by ROS
• What are some examples of antioxidants?
o Carotenoids
o Flavonoids
o Vitamin E (alpha-tocopherol)
o Vitamin C (Ascorbate acid)
• What are ROS?
o Reactive radical: have an unpaired electron
▪ Ex: superoxide anion is a O2 molecule with a gained electron
• Oxidative stress is involved in pathophysiology of many diseases – especially brain
health, GI diseases, heart health
• How can antioxidants affect health conditions?
o CVD:
▪ Antioxidants can decrease lipid peroxidation that causes atherosclerosis
by increasing the molecule’s resistance to oxidation
▪ Vitamin E specifically received more attention, studies done on effects of
adding almonds and walnuts to diet
• Consumption of 1/5 cup of almonds showed decreased risk of
CVD
• May not be related to Vitamin E because almonds have many
other nutrients, better to get from nutrients than supplements
because of other benefits
o Cancer:
▪ Antioxidants can contribute to cancer development by decreasing
mutation in tumor suppressor gene p53
▪ Carotenoids (alpha and beta): play a role in modifying intracellular
signalling and tumor growth in addition to having an antioxidant effect
• Lycopene: may reduce cell multiplication
▪ Vitamin C (Ascorbate): inhibit formation of carcinogenic molecules and
prevent DNA damage seen in gastric cancer patients
▪ Mostly raw vegetables, cruciferous vegetables, leafy greens, orange
coloured veggies and fruits
o Neuronal diseases:
▪ Protein oxidation and accumulation of amyloid beta in brain (Alzheimer’s
disease). Amyloid beta can cause memory loss and impair cognitive
functioning
▪ Also related to lipid (LDL) peroxidation
▪ Carotenoids (vitamin A), vitamin E, vitamin C of interest
• Lipid peroxidation
o Lipids are most susceptible to oxidative stress, if oxidized it increases free
radicals
o Free radicals interact with Arachidonic Acid (OMEGA-6 FA) in cell membrane,
and its anionic properties allows it to attract and abstract a proton from FA
o Now the carbon chain for FA and thus the membrane becomes accessible to
oxidative damage
o MDA (malondialdehyde) Most common PUFA oxidative degeneration product
o End result:
▪ Increase Permeability of cell membrane
▪ Loss of structural integrity of membrane
▪ Altered cell signaling (ion gradients)
▪ Can lead to cell death
o In obese people with impaired lipid profile, MDA and thus susceptibility to lipid
peroxidation was higher
• Antioxidant nutrients:
o Vitamins (C and E)
o Minerals: selenium
o Carotenoids
▪ Vitamin A (retinol) precursors (alpha and beta carotene)
▪ Non-vitamin A molecules include lycopene, cryptoxanthin, lutein
o Phytochemical
▪ Flavonoids (green tea, coffee, dark chocolate)
▪ Resveratrol (wine, raisins)
• Vitamin A
o Fat soluble vitamin
o Stored in liver and travels via chylomicrons (retinol binding proteins)
o Main forms of retinoids
▪ Retinal: participates in vision
▪ Retinol: most active and potent form in body, Helps to conserve
reproduction
▪ Retinoic acid (derived from retinol) – orange products likes carrots, kale
color masked by chlorophyll, regulates growth
o Dietary sources:
▪ Animal products provide retinyl esters that are converted to retinol
• liver, fish oil, milk, eggs
▪ Plant products provide carotenoids like beta-carotene
o Retinyl is converted to retinol in the body to support reproduction, and can be
interconverted to retinal, supporting vision. Retinal is synthesized from beta
