Water extract of licorice (Glycyrrhiza uralensis Fisch.) Supplementation is related with decreased lipid peroxidation among healthy male smokers with glutathione-S-transferase M1 positive genotype

Recently, licorice (Glycyrrhiza uralensis Fisch., GU) has demonstrated significant in vitro and in vivo antioxidant properties. In this study, it was tested that a daily regimen of supplementation with water extract of GU would ameliorate oxidative stress and whether effects were modulated by the glutathion-S-transferase (GST) polymorphisms. Forty healthy male smokers aged 20–60 were divided evenly into 2 groups and given either 260 mL of GU extracted with hot water or 260 mL of oligosaccharide based placebo every day for 8 weeks without any change of usual food intake, and blood samples were drawn before and after the intervention. Eight weeks of GU supplementation significantly decreased plasma conjugated dienes (a maker for lipid peroxidation) in GSTM1 positive subjects, but not in the GSTM1 null genotype group. Our finding suggests that consumption of licorice water extract might be effectively decreasing lipid peroxidation in the subgroup of smokers who have GSTM1 gene.     

Antioxidant activity and antiproliferative action of methanol extracts of 4 different colored bell peppers (Capsicum annuum l.)

Methanol extracts of 4 different colored (red, orange, yellow, and green) bell peppers (Capsicum annuum L.) were examined to (1) determine the total phenolic content (TPC), (2) compare the antioxidant activities, (3) assess the protective effects of extracts on H₂O₂-induced and 4-hydroxy-2-nonenal (HNE)-induced DNA damage using the Comet assay, and (4) examine the antiproliferative action of their extracts on HT-29 cells. Red and orange bell peppers had significantly higher levels of TPC than yellow or green bell peppers. Orange bell pepper exhibited the highest level of radical scavenging activity and total antioxidant activity, while green bell pepper exhibited the highest superoxide dismutase-like activity. These results suggest that the difference in antioxidant activities may depend on the kinds of antioxidant compounds related to the color of the pepper. It was found a significant negative correlation between TPC and radical scavenging activity inhibiting capacity (IC)₅₀, and a significant positive corretation between TPC and total antioxidant activity. All extracts of bell pepper inhibited H₂O₂-induced and 4-hydroxy-2-nonenal-induced DNA damage in human leukocytes and showed potential toxicity on HT-29 cells. These findings suggest that the 4 different colored bell peppers may be useful as antioxidants and cancer prevention in food.     

Effect of onion juice supplementation on antioxidant status in participants with mild hypercholesterolemia

Hypercholesterolemia is known to be associated with enhanced oxidative stress related to increased lipid peroxidation. Several epidemiological and clinical studies have reported the benefits of consuming fruits and vegetables, leading to reduced risks for cardiovascular diseases and several types of cancers. Flavonoids are potential antioxidants found in foods such as onions. The aim of this study was to investigate the effect of decocted onion juice (about 300 g onion) supplementation for 10 weeks on antioxidant status in mild hypercholesterolemic subjects. Twenty-seven participants were studied in a randomized, single-blind, placebo-controlled, crossover design. Indices of antioxidant status used were plasma total antioxidant capacity, antioxidant vitamins, LDL oxidation, erythrocyte antioxidant enzyme activity, and leukocyte DNA damage. After 10 weeks of consuming decocted onion juice, there were no significant differences in all the tested parameters. In conclusion we failed to find any antioxidant effect of onion supplementation in subjects with mild hypercholesterolemia.