7756
Natural polyphenols were tested for their ability to protect against glyoxal - and methylglyoxal - induced cytotoxicity , reactive oxygen species formation and improved mitochondrial membrane potential maintenance .
 polyphenols, glyoxal, methylglyoxal, oxygen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 polyphenols, glyoxal, methylglyoxal, oxygen