Natural products or active components with a protective effect against oxidative stress have attracted significant attention for prevention and treatment of degenerative disease. Oligonol is a low molecular weight polyphenol containing catechin-type monomers and oligomers derived from Litchi chinensis Sonn. We investigated the protective effect and its related mechanism of oligonol against oxidative stress.

Oxidative stress in C6 glial cells was induced by hydrogen peroxide (H₂O₂) and the protective effects of oligonol on cell viability, nitric oxide (NO) and reactive oxygen species (ROS) synthesis, and mRNA expression related to oxidative stress were determined.

Treatment with oligonol inhibited NO and ROS formation under cellular oxidative stress in C6 glial cells. In addition, it recovered cell viability in a dose dependent-manner. Treatment with oligonol also resulted in down-regulated mRNA expression related to oxidative stress, nuclear factor kappa-B (NF-κB) p65, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS), compared with the control group treated with H₂O₂. In particular, expression of NF-κB p65, COX-2, and iNOS was effectively reduced to the normal level by treatment with 10 µg/mL and 25 µg/mL of oligonol.

These results indicate that oligonol has protective activity against oxidative stress-induced inflammation. Oligonol might be a promising agent for treatment of degenerative diseases through inhibition of ROS formation and NF-κB pathway gene expression.