Thesis & Dissertations

An increasing body of experimental, clinical and epidemiological evidence has accumulated demonstrating the beneficial effects of antioxidants against oxidative stressinduced degenerative and age-related diseases, cancer and ageing, thus renewing interest in medical importance and role of antioxidants. With the deleterious side effects associated with the use of drug-based medicine, a large shift toward medicinal plants has occurred over the last years in an attempt to identify natural antioxidants that are more potent, efficient and safer than synthetic antioxidants. The present study investigates the in vitro and in vivo antioxidant activity of aqueous and organic extracts of the different areal parts of Rubus hedycarpus Focke, a shrub distributed across Lebanon at different altitudes. The in vitro antioxidant activity was assessed and confirmed via two assays: the DPPH radical scavenging assay and β-carotene bleaching assay. In the DPPH radical scavenging assay, the methanolic leaves extract showed the highest antioxidant activity with a very low IC50 value of 0.0035 mg/mL, followed by aqueous leaves extract with IC50 value of 0.012 mg/mL, juice concentrate with IC50 value of 0.016 mg/mL, aqueous stem extract with IC50 value of 0.025 mg/mL, and methanolic stem extract with IC50 value of 0.03 mg/mL. Quercetin, a commonly known antioxidant flavonoid, exhibited an IC50 value of 0.002 mg/mL. When evaluated by the β-carotene bleaching assay, the juice extract showed the most antioxidant activity with an IC50 value of 0.3 mg/mL, followed by the methanolic leaves extract with IC50 value of 0.95 mg/mL, and methanolic stem extract IC50 value of 0.1.25 mg/mL. Aqueous leaves and stem extracts exhibited IC50 values > 3 mg/mL in the same assay. The in vivo antioxidant of the various extracts was tested on Female Sprague-Dawley mice in three experimental designs, where the ALT and AST liver levels were determined. Hepatotoxicity was created by injecting the animals with carbon tetrachloride intraperitoneally. Ascorbic acid, a natural antioxidant, was used as a positive control. In the first experimental design, the animals were injected twice a week with carbon tetrachloride and treated with the plant extracts for a month. Overall, the ALT and AST levels in plant extracts treated animals were significantly lower than those found in the animals treated carbon tetrachloride only, thus highlighting the antioxidant potential of the various extracts. In the second experimental setup (preventive), the animals received the juice extract for a week, followed by one acute dose of carbon tetrachloride. The ALT and AST levels clearly supported the preventive role of the juice extract in preventing hepatotoxicity. In the third setup (curative), the animals received one acute dose of carbon tetrachloride followed by juice extract for a week. The ALT levels in the mice group that received the juice extract was significantly lower than those found in the carbon tetrachloride and ascorbic acid groups. Histological analysis of the liver sections by H&E staining showed the effects of the various extracts on the liver morphology. In specific, administrating juice extract to mice exposed to an acute dose of carbon tetrachloride promoted attenuated hepatocellular lesion with regeneration of hepatocytes around portal tracts and completely normal hepatic lobules and minimal inflammation. The collective analysis of the data led to the conclusion that the different parts of Rubus hedycarpus as well as the juice extract have a promising antioxidant therapeutic potential and a dose-dependent anti-hepatotoxicity that is capable of promoting liver functions.