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We used the human hepatoma cell line HepG2 to investigate the effects of oxidative stress on the transcriptome level by micro - arrays at seven time points ( 0 . 5 , 1 , 2 , 4 , 6 , 8 and 24h ) following exposure to the oxidants menadione , hydrogen peroxide and tert - butyl hydroperoxide including the effects on cell cycle and apoptosis by flow cytometry , protein carbonyl formation by spectrophotometry and oxidative DNA damage by FPG - comet .
 menadione, hydrogen peroxide, tert - butyl hydroperoxide, carbonyl
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 menadione, hydrogen peroxide, tert - butyl hydroperoxide, carbonyl