Tetrahydroprotoberberines inhibit lipid peroxidation and scavenge hydroxyl free radicals

To study the effects of tetrahydroprotoberberines (THPB) on rat liver and brain lipid peroxidation (LPO) and oxygen free radicals generation.The malondialdehyde (MDA) levels in rat brain and liver homogenates, induction of MDA by Fe(2+)-Vit C in mitochondria, OH. generation by Fenton reaction, and O2.- generation by pyrogallol oxidation were observed in vitro.(1) THPB lowered the MDA contents in the liver homogenate and mitochondria, and the IC50 values of l-THPB-18 and l-stepholidine (SPD) in the liver mitochondria were 3.1 and 12.7 mumol.L-1 respectively. SPD decreased the MDA contents in the brain homogenate and mitochondria with IC50 values of 102 and 35.0 mumol.L-1 respectively. (2) THPB scavenged OH., and the IC50 values of l-THPB-18 and SPD were 0.21 and 3.8 mumol.L-1 respectively, but no effect on O2.- was observed.THPB could reduce the MDA contents and scavenge OH. and THPB-18 was the most potent amongst them.