Trapping effects of green and black tea extracts on peroxidation-derived carbonyl substances of seal blubber oil.

Green and black tea extracts were employed to stabilize seal blubber oil at 60 degrees C for 140 h. On the basis of the headspace SPME-GC-MS analysis, with the addition of green/black tea extracts, the contents of acetaldehyde, acrolein, malondialdehyde, and propanal, four major lipid peroxidation products, were reduced. The inhibition rates of acrolein formation by green tea and black tea extracts were 98.40 and 96.41% respectively, and were 99.17 and 98.16% for malondialdehyde, respectively, much higher than the inhibition of the formation of acetaldehyde and propanal. Because malondialdehyde and acrolein are reactive carbonyl species (RCS) and recent studies have suggested that phenolics can directly trap RCS, this study also investigated whether green tea polyphenols can trap acrolein or not. Acrolein was reduced by 90.30% in 3 h of incubation with (-)-epigallocatechin-3-gallate (EGCG). Subsequent LC-MS analysis revealed the formation of new adducts of equal molars of acrolein and EGCG. The reaction site for acrolein was elucidated to be the A ring of EGCG as evidenced by LC-MS/MS analysis and by testing of the acrolein-trapping capacities of the analogous individual A, B, and C rings of EGCG. Thus, EGCG's direct trapping of RCS may also contribute to the significant reduction of acrolein and other aldehydes in the peroxidation of seal blubber oil.