Extract from milk thistle (Silybum marianum (L.) Gaertn., synonym Carduus marianus L., Asteraceae) silymarin contains among others primarily bioactive flavonolignans. They have hepatoprotective and antioxidative effects and also anticancer, chemoprotective, dermatoprotective and hypocholesterolemic activity. This thesis focuses on the preparation of metabolites of the second phase of biotransformation unexplored flavonolignans 2,3-dehydrosilybin (DHSB), silychristin (SCH), 2,3-dehydrosilychristin (DHSCH). Pure sulfated derivatives were prepared using aryl sulfotransferase from Desulfitobacterium hafniense and p-nitrophenyl sulfate (p- NPS) as a donor. Flavonolignans yield exclusively monosulfates at the position C- 20 (C-19 in the case of silychristin and 2,3-dehydrosilychristin), except for 2,3- dehydrosilybin that gives also the 7,20-disulfated derivatives. For all samples were made antioxidant tests - DPPH assay (the highest activity had 2,3-dehydrosilychristin sulfate: IC50= 7,87 µM), Folin-Ciocalteau reduction assay (the highest activity had 2,3-dehydrosilychristin: 1,58 ekvivalents of gallic acid), ABTS+ scavenging (the highest activity had silychristin: 1,50 ekvivalents of vitamin C), inhibition of microsomal lipid peroxidation (the highest activity had 2,3-dehydrosilybin: IC50 = 10,6 µM),...

The purpose of this study is to determine the reduced and dehydroascorbic acid of certain frozen fruits prepared with and without ascorbic acid as an antioxidant.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19764号 / 農博第2160号 / 新制||農||1039(附属図書館) / 学位論文||H28||N4980(農学部図書室) / 32800 / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 阪井 康能, 教授 植田 和光, 教授 三芳 秀人 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Muscadine seeds from three cultivars (‘Carlos’, ‘Noble’ and ‘Ison’) were processed by 100% v:v methanol, 95% v:v ethanol and 70% v:v acetone. The acetone seed extracts exhibited the highest (p<0.05) total phenolics (21.62~24.84mg/g of dw) and antioxidant activity. A strong correlation (R2=0.891, p<0.01) was found between total phenolics and antioxidant activity. Methanol and ‘Carlos’ seed extracts generally showed the highest antimicrobial capacity against pathogen strains tested, which correlated well with tannic acid, catechin, epicatechin and tartaric acid content. Hot water-soluble muscadine skin extracts from 17 muscadine cultivars (6 bronze and 11 dark) showed effective antioxidant properties. Significant variations (p<0.05) were observed among the 17 cultivars in total phenolics, organic acids and antioxidant activity. ‘Alachua’, ‘Albermarle’, ‘Southland’, ‘Janebell’ and ‘CA9-37’ were the cultivars found to have the highest antioxidant capacity. Skin extracts of dark-skin cultivars showed higher (p<0.05) content than bronze-skin cultivars in phenolics, tartaric acid, tannic acid and ellagic acids.

Hydrolysis of casein using chymotrypsin results in the formation of polypeptides (CH) with a hydrophobic aromatic amino acid on one end of the chain because the enzyme selectively cleaves the adjacent peptide-bond. Due to resonance of the aromatic micro-domain, thiols become redox-sensitive and actively participate in electron transfer. These types of amphipathic peptides also tend to be membrane-lytic. The two prong approach of this investigation was to, (1) assess antibacterial effect of the CH in beef steak, and (2), to determine its antioxidative efficacy as a constituent of Cheddar whey based edible coating mix. The edible coating prevented coliform growth even at a minute concentration range of 0.15-0.2 % (w/v). Marked antioxidative efficacy of the CH, particularly at a concentration of 0.3% (w/v), was also evident from its remarkable free radical scavenging ability and extended resilience in an abusive model system saturated with peroxyl-radicals generated through controlled pyrolysis.

Vaccinium cyanococcus, most commonly known as blueberry, is a fruit native to North America that is known for its unique taste and high antioxidant content. The skin, seed and juice of both organically and conventionally grown blueberry extract were analyzed for antioxidant content using both the Hydrophilic and Lipophilic Oxygen Radical Absorbance Capacity (ORAC) assays. Results from the Hydrophilic ORAC test showed that conventionally grown blue berries had a higher antioxidant capacity across all samples, while the Lipophilic ORAC assay showed that the antioxidant concentration of organically cultivated blueberry juice was highest, but conventionally grown blueberry seed and skin extract showed higher antioxidant content. The vitamin C content of both conventional and organic blueberries were analyzed using High Performance Liquid Chromatography (HPLC), where the organic blueberries showed a higher vitamin C concentration. In general, both organic and conventional blueberries are rich in antioxidants, and therefore, possess potential health benefits that require further study.

The oxidative degradation of organic materials typically operates through a radical-mediated chain mechanism known as autoxidation; a process that has severe consequences in both biological settings (i.e. accumulation of lipid peroxides) and non-living substrates (i.e. breakdown of petroleum-derived materials, such as lubricants/oils, plastics, polymers, rubbers, etc.). However, autoxidation can be retarded by radical-trapping antioxidants (RTAs); chemical species that capture chain-carrying radicals to break the chain of oxidation. A particular class of RTA, diarylamines, have proven especially effective at elevated temperatures due to a purported catalytic mechanism of inhibiting autoxidation, and thus, have found significant use as protective agents in engine lubricant oils. However, the current diarylamine technology struggles to manage the increased oxidative stress placed on it by modern internal combustion engines (ICEs), which burn fuel at higher temperatures in order to meet emission standards. Designing superior diarylamines is not straightforward, however, as the mechanisms by which they are forced from their catalytic cycle are not well understood. Herein, we report our investigations into the fate of an industrially-representative, isotopically-enriched diarylamine during hydrocarbon autoxidation at elevated temperatures using a novel 2D 1H – 15N heteronuclear multiple bond correlation (HMBC) spectroscopic technique. Synthesis of a small scope of oxidation products allowed for the identification of a previously unreported product of diarylamine autoxidation. Additionally, a consistent pattern of diarylamine speciation under varying conditions was observed spectroscopically. Use of the HMBC technique also confirmed previous reports of the regenerative ability of the diarylamine and the intermediates of its purported catalytic cycle. Quantification studies using ultra performance liquid chromatography (UPLC) during the early stages of autoxidation provided insight into the formation of initial diarylaminic intermediates. Additionally, we examined the fate of the diarylamine during autoxidations in the presence of nitrogen oxides (NOx), which are found in the blow-by gas of ICEs and have been shown to exacerbate hydrocarbon autoxidation. The performance of diarylamine was drastically reduced under such conditions, and HMBC spectroscopy illustrated its rapid conversion to a number of intermediates. The most prominent two intermediates were identified as mono- and di-nitrated analogues of the original diarylamine, and were demonstrated to possess no RTA activity; regardless of temperature or substrate. HMBC spectroscopy also illustrated the differences in product distribution under each set of conditions.

Oxidative storage stability was conducted to determine the optimum antioxidant for the production of catfish methyl esters (CFME) for use as biodiesel. Peroxide value, anisidine value, 2-thiobarbituric reaction substances, acid value, iodine value, UV absorbance, and induction period were measured. Antioxidant, stability parameters changed over a storage time of one year when stored at 25°C. The CFME were not stable to oxidation without the addition of TBHQ. When stored at 25°C, oxidative parameters indicated that CFME was a stable product that met oxidative stability standards when TBHQ was added. When held at 80°C for 28 days, the samples with TBHQ were stable to oxidation. However, the acid value rose above the maximum at 28 days. Thus, CFME can be stable to oxidative breakdown when THBQ was added at 800 ppm, but when exposed to high temperatures, one will have to limit water or protect CFME against hydrolytic rancidity.

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