Studies on the Metabolism of Sesaminol Triglucoside Extract and its Impact on Antioxidant Status in Rats

• Main Authors: Chian-Ru Shyr, 石倩如
• Other Authors: Hwang, Lucy Sun
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/95590029518731032809

碩士 === 國立臺灣大學 === 食品科技研究所 === 95 === Sesame seeds contain abundant lignans, like sesamol and sesaminol, exhibiting excellent antioxidative activity in vitro. Some of them possess phenolic OH group to react with free radicals, thus protect sesame oil from oxidation and are considered beneficial to health. In defatted sesame seed, lignans are usually present as lignan glucosides, and sesaminol triglucoside (ST) is the major lignan glucoside. Previous studies reported that sesame lignan glucosides have poor antioxidative properties in DPPH scavenging activity in vitro. But in high fructose-fed rats model, supplementation with sesame lignan glucosides extract could lower oxidative stress and increase insulin sensitivity. These results indicated that lignan glucosides may be converted to lignans after oral administration and express biological effects. Therefore, the aim of this work was to investigate the metabolites, distribution and elimination of ST in vivo and to determine the impact of a ST-enriched diet on the antioxidant status in rats. Unroasted black sesame seeds were pressed and defatted with n-hexane, extracted with 80 % methanol, and separated by XAD-2 gel open column chromatography eluting with a serious of concentrations of aqueous methanol solutions (20 %, 40 % and 60 %). The 60 % methanol eluate, which contained higher content of ST compound, were collected and freeze-dried to obtain the ST extract powder. In animal experiment, we used vitamin E deficient rat model to increase oxidative stress. First, SD rats were divided into three groups, eight rats per group, and fed different diets: group B, normal diet；group C and group ST, vitamin E deficient diet. After 10 days, animals in group ST were tube fed with 300 mg kg-1 body weight of ST extract daily for 2 weeks. Group B and group C animals were tube fed with water to replace ST extract. Results showed that feeding with a vitamin E-deficient diet for 10 days, the plasma α-tocopherol levels of group C and group ST rats were significantly lower than group B and decreasing with time. In antioxidative capacity analyses, rats fed with a vitaminE-deficient diet for 3 weeks, the lag time of plasma LDL oxidation was shortened, and the TBARS in plasma, liver and kidney were increased in group C. This indicated that the oxidative stress in vitaminE-deficient diet-fed rats is increased. On the other hand, a ST-enriched diet significantly enhanced antioxidant capacity in plasma LDL oxidation and lowered the TBARS in plasma, liver and kidney. HPLC system was used to analyze ST and its metabolites in rats. Results showed that there was 5 % and 40 % of tube-fed ST found in the small-intestinal mucosa and cecum, respectively, indicating that the absorption of ST may be low. However, ST and its aglycone were detected in all tissues, urine and feces. With the aid of LC/MS/MS system to analyze urine sample obtained from a ST tube-fed rat, we confirmed that ST and sesaminol existed in urine. The metabolite-sesaminol existed mainly in sulfate form in rats tissues and urine, but it existed as aglycone in cecum, indicating that intestinal microorganism have the ability in hydrolyzing ST to sesaminol aglycone. Our results show that ST can be absorbed as glucoside directly, and some of them could be converted to aglycone then absorbed into blood and tissues, finally eliminated in urine. Based on these results, we suggest that the antioxidative abilities of ST may come from its aglycone found in vivo.