刺菝葜(Smilax spinosa Mill.) 根部萃取物之抗氧化活性

Abstract

Chainey root (Smilax spinosa Mill.) is popularly used in Nicaragua’s traditional medicine for its believed anti-bacterial, anti-toxin and antioxidant properties. Despite the widespread use of this plant in Nicaragua, especially on the Atlantic coast, literature contains few reports on the antioxidant activity and chemical composition of S. spinosa. Scientific evidence is required to verify its medicinal effects. Therefore, the aims of this study were to investigate the antioxidant properties of S. spinosa’s root methanolic (ME) extract and its ethyl acetate (EA), n-butanol and water soluble fractions. The total phenolic and flavonoid content, 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) free radical scavenging capacity and Iron (II) chelating activity were investigated. The cytotoxic effect of the EA fraction on human liver hepatoma (HepG2) cells and its cytoprotective properties against H2O2 induced oxidative stress on healthy human liver (FL83B) cells were established. Results demonstrated the antioxidant activity of S. spinosa root to be concentration dependant. Phenolics and flavonoids were found in the ME extract as well as in the EA, n-butanol and water soluble fractions. EA fraction revealed the highest gallic acid equivalence (GAE) of 71.81± 0.36 mg/g DW. Quercetin equivalent was also highest for the EA fraction (45.27± 31.27 mg/g). On the other hand, lowest phenolics and flavonoids were observed in the water soluble fraction. The DPPH scavenging capacity and Iron (II) chelating activity of all four fractions were above 70% at 0.1 mg/ mL. However, none of the fractions were better iron chelators than positive control EDTA. EA showed the highest DPPH scavenging percentage (93%) at 0.2 mg/mL. Among all test samples, the EC50 value of EA soluble fraction was the lowest (0.033 ± 0.002 mg/mL), indicating stronger antioxidant activity than those of positive controls ascorbic acid (0.067 ± 0.0002 mg/mL) and gallic acid (0.068 ± 0.0004 mg/mL). Because of its outstanding antioxidant activity, the EA fraction was selected for further assessment of cytotoxic and cytoprotective effects on the viability of human liver cells. Cytotoxic effect of S. spinosa root EA fraction on the proliferation of human liver hepatoma (HepG2) cells was assessed with the 2-(4-Iodophenyl)-3 - (4-nitrophenyl-5 (2, 4-disulfophenyl) - 2H-tetrazolium (WST-1) assay. S. spinosa EA fraction was capable of interrupting the development and proliferation of HepG2 cells at a concentration dependant manner. At 1500 µg/mL the scavenging of 100% cancerous cells was accomplish by the EA fraction. The Protective effect of the EA fraction on healthy human liver (FL83B) cells viability was assessed by treating the cells with EA for 1 hr prior to the addition of H2O2. The relative cell survival was determined by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. At a concentration of 12.5 µg/mL, the EA fraction enhanced a protective effect on the cells viability allowing 77% cells survival. Results provided a scientific support to the antioxidant properties of S. spinosa Mill. root extract in vitro. Further evaluation of its antioxidative properties in vivo is needed to ensure functionality and long term safety.