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Yuki Hirakawa

Other affiliations: Osaka Prefecture University
Bio: Yuki Hirakawa is an academic researcher from Kobe Gakuin University. The author has contributed to research in topics: Roasting & Fatty acid. The author has an hindex of 13, co-authored 16 publications receiving 452 citations. Previous affiliations of Yuki Hirakawa include Osaka Prefecture University.

Papers
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TL;DR: EGCG and EGC protected the depletion of α-tocopherol in the cells, and the glutathione content was enhanced by all four catechins.
Abstract: Tea catechins inhibited TBARS accumulation in HepG2 cells, the order of effectiveness being (−)-epigallocatechin gallate (EGCG)>(−)-epigallocatechin (EGC)≥(−)-epicatechin gallate (ECG)>(−)-epicatechin (EC). EGCG and EGC protected the depletion of α-tocopherol in the cells, and the glutathione content was enhanced by all four catechins. Moreover, all four catechins suppressed the formation of glutathione disulfide and the activation of glutathione peroxidase induced by tert-butylated hydroperoxide.

59 citations

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TL;DR: In this article, a modified AgNO3-TLC procedure provided 11 different groups of TAG, based on both the degrees of unsaturation and the total fatty acid chain length.

55 citations

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TL;DR: In this paper, the fatty acid distributions of triacylglycerols (TAGs) and phospholipids (PLs) isolated from total lipids in these seeds were investigated.

54 citations

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TL;DR: The positional distribution of fatty acids in triacylglycerols (TAGs) and phosphatidylcholine (PC) isolated from total lipids in these seeds was investigated as well as the naturally occurring antioxidants that are present.
Abstract: Sesame seeds were roasted at different temperatures (180–220 °C) using a domestic electric oven. The positional distribution of fatty acids in triacylglycerols (TAGs) and phosphatidylcholine (PC) isolated from total lipids in these seeds was investigated as well as the naturally occurring antioxidants that are present. Major lipid components were TAGs and phospholipids (PLs), while steryl esters (SEs), free fatty acids (FFAs) and sn-1,3- and sn-1,2-diacylglycerols (DAGs) were minor ones. Following roasting, a significant increase (P < 0.05) was observed in FFAs and in both forms of DAG (primarily sn-1,3-DAG). The greatest PL losses (P < 0.05) were observed in phosphatidylethanolamine (PE), followed by PC and phosphatidylinositol (PI). On the other hand, the amounts of γ-tocopherol and sesamin remained at over 80 and 90% respectively of the original levels after roasting at 220 °C. The principal characteristics of the positional distribution of fatty acids were still retained after 25 min of roasting: unsaturated fatty acids, especially linoleic and/or oleic, were predominantly concentrated in the sn-2-position, and saturated fatty acids, especially stearic and/or palmitic, primarily occupied the sn-1- or sn-3-position. The results suggest that unsaturated fatty acids located in the sn-2-position are significantly protected from oxidation during roasting at elevated temperatures. © 2001 Society of Chemical Industry

48 citations

Journal ArticleDOI
TL;DR: In this paper, the quality characteristics and the compositions of the oils, i.e. their tocopherol distributions and the molecular species of the triacylglycerols (TAGs), were investigated.
Abstract: Peanut seeds (Arachis hypogaea) were roasted for 6, 12, 20, or 30 min at a frequency of 2450 MHz using a microwave oven. The quality characteristics and the compositions of the oils, i.e. their tocopherol distributions and the molecular species of the triacylglycerols (TAGs) were investigated. These results were compared with those of an unroasted oil sample. Only minor increases (p 0.05) was observed in the molecular species of the TAGs during microwave roasting. These results indicate that phospholipids may be attributed to the quality characteristics of peanut oils during microwave roasting.

41 citations


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TL;DR: In this article, the authors studied the role of chlorophyll as a photosensitizer for the formation of 1O2; however, carotenoids and tocopherols decrease the oxidation through 1O 2 quenching.
Abstract: : Edible oil is oxidized during processing and storage via autoxidation and photosensitized oxidation, in which triplet oxygen (3O2) and singlet oxygen (1O2) react with the oil, respectively. Autoxidation of oils requires radical forms of acylglycerols, whereas photosensitized oxidation does not require lipid radicals since 1O2 reacts directly with double bonds. Lipid hydroperoxides formed by 3O2 are conjugated dienes, whereas 1O2 produces both conjugated and nonconjugated dienes. The hydroperoxides are decomposed to produce off-flavor compounds and the oil quality decreases. Autoxidation of oil is accelerated by the presence of free fatty acids, mono- and diacylglycerols, metals such as iron, and thermally oxidized compounds. Chlorophylls and phenolic compounds decrease the autoxidation of oil in the dark, and carotenoids, tocopherols, and phospholipids demonstrate both antioxidant and prooxidant activity depending on the oil system. In photosensitized oxidation chlorophyll acts as a photosensitizer for the formation of 1O2; however, carotenoids and tocopherols decrease the oxidation through 1O2 quenching. Temperature, light, oxygen concentration, oil processing, and fatty acid composition also affect the oxidative stability of edible oil.

1,435 citations

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TL;DR: Green tea catechin has great potential in cancer prevention because of its safety, low cost and bioavailability, and its mechanism of action at numerous points regulating cancer cell growth, survival, angiogenesis and metastasis.

1,177 citations

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TL;DR: Insight is provided into the molecular basis of potential chemopreventive and therapeutic activities of dietary polyphenols with emphasis in their ability to control intracellular signalling cascades considered as relevant targets in a cancer preventive approach.
Abstract: Prevention of cancer through dietary intervention recently has received an increasing interest, and dietary polyphenols have become not only important potential chemopreventive, but also therapeutic, natural agents. Polyphenols have been reported to interfere at the initiation, promotion and progression of cancer. They might lead to the modulation of proteins in diverse pathways and require the integration of different signals for the final chemopreventive or therapeutic effect. Polyphenols have been demonstrated to act on multiple key elements in signal transduction pathways related to cellular proliferation, differentiation, apoptosis, inflammation, angiogenesis and metastasis; however, these molecular mechanisms of action are not completely characterized and many features remain to be elucidated. The aim of this review is to provide insights into the molecular basis of potential chemopreventive and therapeutic activities of dietary polyphenols with emphasis in their ability to control intracellular signalling cascades considered as relevant targets in a cancer preventive approach.

631 citations

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TL;DR: The study showed potential for pumpkin seed oil from all 12 cultivars to have high oxidative stability that would be suitable for food and industrial applications, as well as high unsaturation and tocopherol content that could potentially improve the nutrition of human diets.
Abstract: Twelve pumpkin cultivars (Cucurbita maxima D.), cultivated in Iowa, were studied for their seed oil content, fatty acid composition, and tocopherol content. Oil content ranged from 10.9 to 30.9%. Total unsaturated fatty acid content ranged from 73.1 to 80.5%. The predominant fatty acids present were linoleic, oleic, palmitic, and stearic. Significant differences were observed among the cultivars for stearic, oleic, linoleic, and gadoleic acid content of oil. Low linolenic acid levels were observed (<1%). The tocopherol content of the oils ranged from 27.1 to 75.1 microg/g of oil for alpha-tocopherol, from 74.9 to 492.8 microg/g for gamma-tocopherol, and from 35.3 to 1109.7 microg/g for delta-tocopherol. The study showed potential for pumpkin seed oil from all 12 cultivars to have high oxidative stability that would be suitable for food and industrial applications, as well as high unsaturation and tocopherol content that could potentially improve the nutrition of human diets.

362 citations

Journal ArticleDOI
TL;DR: Multiple studies investigating the role of dietary phytochemicals such as, curcumin, epigallocatechin gallate, resveratrol, phenethyl isothiocyanate, sulforaphane, hesperidin, quercetin and 2'-hydroxyflavanone in regulating oxidative stress and associated signaling pathways in the context of cancer chemoprevention and treatment are reviewed.

358 citations