Oxidative Stress Basics
Free radicals attack
They attack electron rich centers such as lipid membranes, proteins and nucleic acids.
What are the two main mechanisms by which antioxidants act?
Direct and indirect mechanisms
Name two enzymatic antioxidants found in both plants and humans.
Superoxide dismutase (SOD) and catalase
Which flavonoid protects DNA from oxidative damage but may become carcinogenic at high copper levels?
Quercetin
Enzymes made by the body to remove free radicals
Antioxidants
Name three neurodegenerative diseases linked to oxidative stress.
Alzheimer’s disease, Parkinson’s disease, Huntington’s disease
What are low molecular weight antioxidants (LMWA)?
Non-enzymatic antioxidants like ascorbic acid, glutathione, and flavonoids
What carotenoid has the strongest singlet oxygen quenching ability?
Lycopene
What condition occurs when reactive oxygen species exceed the body’s antioxidant defenses?
Oxidative stress
What kidney condition results from excess ROS accumulation?
Urolithiasis
How do direct antioxidants neutralize free radicals?
By scavenging, decomposing, or converting them into less reactive forms
Why are plants considered important sources of antioxidants?
They are rich in phytochemicals with antioxidant properties and ethnopharmacological uses
What bacterial infection increases ROS and RNS production leading to gastric cancer?
Helicobacter pylori
Why are plant antioxidant enzymes difficult to use therapeutically in humans?
They are difficult to isolate
What class of flavonoids inhibits lipid oxidation through metal ion chelation?
Anthocyanidins
How does hyperglycemia contribute to diabetic nephropathy?
By triggering ROS production that damages glomerular structure and function
What is the role of indirect antioxidant mechanisms?
Regulation of enzymes that generate ROS and repair oxidative damage
Which carotenoid can be converted into vitamin A?
β-carotene