Assessment of Flavonoid Content, Free Radical Scavenging and Hepatoprotective Activities of Ocimum gratissimum and Spondias mombin in Rats Treated with Dimethylnitrosamine

Abstrakt

Formation of reactive oxygen species (ROS) has been implicated in the metabolism of nitrosamines resulting in oxidative stress. Ocimum gratissimum and Spondias mombin are valued ethnomedicinally in folkloric medicine. The in vitro antioxidant activities and hepatoprotective effects of methanol leaf extracts of Ocimum gratissimum and Spondias mombin in rats intoxicated with dimethylnitrosamine were investigated in this study. Results revealed a copious flavonoid content in the extracts of Ocimum gratissimum (43.04 ± 4.18 mg/g catechin equivalent [CE]/g extract) and Spondias mombin (55.90 ± 6.3 mg/g CE/g extract). The extracts showed high DPPH radical scavenging activity: Ocimum gratissimum (79.4% at 200 μg) and Spondias mombin (71.27% at 200 μg), and a significant inhibition of AAPH-induced lipid peroxidation: Ocimum gratissimum (84.6% at 25 μg) and Spondias mombin (85.29% at 400 μg). The methanol extracts also showed strong reductive potential: Ocimum gratissimum (0.806 ± 0.001 at 400 μg) and Spondias mombin (0.908 ± 0.022 at 200 μg). Acute oral dimethylnitrosamine (DMN) administration led to hepatotoxicity as evident by elevated levels of ALT and AST. The antioxidant status and oxidative stress were monitored by determining the levels of hepatic reduced glutathione (GSH), hydrogen peroxide (H2O2) and glutathione peroxidase (GPx) activity. H2O2 generation was significantly enhanced, GSH level was significantly reduced and GPx activity was significantly induced in DMN intoxicated group. However, pretreatments with the extracts, at 100mg/kg and 200mg/kg, ameliorated the levels of ALT, AST and H2O2. In addition, the induction of GPx was also decreased by the two extracts at both doses. Moreover, the extracts significantly raised the level of non-enzymic antioxidant, GSH. These findings demonstrated that methanol leaf extracts of Ocimum gratissimum and Spondias mombin are potent in reversing the dimethylnitrosamine induced hepatotoxicity and as such will be promising therapeutic agents against free radical mediated diseases.