Alleviation of aflatoxin B₁-induced oxidative stress in HepG2 cells by volatile extract from Allii Fistulosi Bulbus

The volatile extract from Allii Fistulosi Bulbus (VEAF) was isolated by steam distillation under reduced pressure, followed by continuous liquid-liquid extraction, and its effects on aflatoxin B₁ (AFB₁)-induced oxidative stress were investigated in human hepatoma cells (HepG2). The main constituents of the VEAF, identified by gas chromatography/mass spectrometry, were 2-octyl-5-methyl-3(2H)-furanone, 2-hexyl-5-methyl-3(2H)-furanone, 2,5-dimethylthiophene, 3,5-diethyl-1,2,4-trithiolane and 3,4-dimethyl-2,5- dihydro-thiophene-2-one. VEAF significantly inhibited the formation of intracellular reactive oxygen species caused by AFB₁ in a dose-dependent manner, concomitant with a significant decrease in the AFB ₁-induced cytotoxicity. VEAF pretreatment significantly reduced the levels of thiobarbituric acid reactive substances, an indicator of lipid peroxidation, whereas increased the level of reduced glutathione. The level of 8-hydroxy-2′-deoxyguanosine, a DNA oxidative stress marker, was also decreased by 49-59% with pretreatment of VEAF. With respect to the activity of AFB₁ metabolizing enzymes, VEAF significantly increased the activity of glutathione S-transferase, and significantly decreased the cytochrome (CYP) P450 3A4 activity, but had a little effect on the CYP1As. These results suggest that VEAF may be selectively effective in alleviating the AFB ₁-induced oxidative stress, and lead to cytoprotection against AFB₁ exposure.