Abstract

In this study, in vitro and cellular nitric oxide (NO)-generating systems were used to investigate the NO-scavenging effects of the butanol (BuOH) fraction, the active fraction of bitter melon (Momordica charantia). The BuOH fraction of bitter melon showed NO scavenging activities as concentration-dependent manners. These results suggest that BuOH fraction of bitter melon would be a promising antioxidant through scavenging NO. Furthermore, under LLC-PK₁ cellular model, the cells showed declines in viability and increases NO formation against oxidative stress induced by sodium nitroprusside (SNP), generators of NO. However, BuOH fraction of bitter melon significantly and dose-dependently inhibited cell cytotoxicity and NO formation. In addition, the over-expressions of cyclooxygenase-2 and inducible NO synthase induced by SNP were observed, but BuOH fraction of bitter melon down-regulated the expression level of both genes. These results indicate that BuOH fraction of bitter melon would have a protective activity against NO-induced oxidative stress.

Key words: Bitter melon, nitric oxide (NO), LLC-PK₁ cell, antioxidative effect, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2).