Yuki Hirakawa

Effect of tea catechins on cellular lipid peroxidation and cytotoxicity in HepG2 cells.

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.

The content of tocopherols and oxidative quality of oils prepared from sunflower (Helianthus annuus L.) seeds roasted in a microwave oven

Sunflower seeds ((Helianthus annuus were roasted for 6, 12, 20 or 30 min at a frequency of 2450 MHz using a domestic microwave oven. After the kernels were separated from the sunflower seeds, the quality characteristics and the compositions of the oils were investigated in relation to their tocopherol distributions, and they were further evaluated as compared with an unroasted oil sample. Only minor increases (p < 0.05) in chemical and physical changes of the oils, such as the carbonyl value, the p-anisidine value and the color development, occurred at a prolonged roasting period. Significant decrease (p < 0.05) was observed in the amounts of phospholipids in the oils after microwave roasting. Nevertheless, compared to the original level, more than 92 wt-% tocopherols still remained after 30 min of roasting. With a few exceptions, these results indicate that the exposure of sunflower seeds to microwaves for 12 min caused no significant (p < 0.05) loss or change in the content of tocopherols and polyunsaturated fatty acids in the kernels.

Influence of microwave roasting on positional distribution of fatty acids of triacylglycerols and phospholipids in sunflower seeds (Helianthus annuus L.)

Whole sunflower seeds were exposed to microwave roasting for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The kernels were then separated from the sunflower seeds, and the lipid components and the positional distribution of fatty acids in triacylglycerols (TAGs) and phospholipids (PLs) were investigated. Major lipid components were TAGs and PLs, while steryl esters, free fatty acids and diacylglycerols were also present in minor proportions. The greatest PL losses (p < 0.05) were observed in phosphatidyl ethanolamine, followed by phosphatidyl choline or phosphatidyl inositol. Significant differences (p < 0.05) in fatty acid distributions occurred (with few exceptions) when sunflower seeds were microwaved for 20 min or more. Nevertheless, the principal characteristics for the positional distribution of fatty acids still remained after 20 min of microwave roasting; unsaturated fatty acids, especially linoleic, were predominantly concentrated in the sn-2-position and saturated fatty acids, especially stearic and palmitic acids, primarily occupied the sn-1- or sn-3-position. These results indicate that no significant changes in fatty acid distribution of TAGs and PLs would occur within 12 min of microwave roasting, ensuring that a good-quality product would be attained.

Variation in the content of tocopherols and distribution of fatty acids within soya bean seeds (Glycine max L.)

Abstract Regional distribution of tocopherols and fatty acids within three soya beans was investigated by high-performance liquid chromatography and gas–liquid chromatography, respectively. Tocopherols were predominantly detected in axis, followed by cotyledons and seed coat. Dominant components were γ- and δ-tocopherols, with much smaller amounts of α- and β-tocopherols. However, α-tocopherol was higher (P

Molecular species of triacylglycerols in the seed coats of soybeans (glycine max L.) following microwave treatment

Soybeans (glycine max) were exposed to microwaves for 6 or 12 min at a frequency of 2450 MHz. The seed coats were then stripped from the soybeans and roasted in a microwave oven. Molecular species and fatty acid distributions of triacylglycerols (TAG), isolated from total lipids in the seed coats were analysed by a combination of argentation thin-layer chromatography (TLC) and gas chromatography (GC). Based on their different degrees of unsaturation and total chain-length of fatty acid groups, 15 molecular species of TAG were still detectable in the seed coats after the roasting treatment. However, roasting caused a significant decrease (P<0.05), not only in molecular species containing more than four double bonds, but also in the amounts of diene and triene species present in a TAG. These results indicate that microwaves could (P<0.05) affect TAG in the seed coats more signficantly than those in the other structural parts of soybeans.

Roasting influences on molecular species of triacylglycerols in sunflower seeds (Helianthus annuus L.)

Sunflower seeds (Helianthus annuus L.) were exposed to microwaves for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The nucleoluses were separated from the seeds roasted in a domestic microwave oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from the total lipids in the nucleoluses were analysed by a combination of argentation thin-layer chromatography (TLC) and gas–liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 14 different groups of TAGs, based on both the degree of unsaturation and the total chain-length of fatty acid groups. Dilinoleolein (25–26.2%), trilinolein (14.4–17.7%), dilinoleostearin (15.1–15.8%), dioleolinolein (12.2–12.4%) and triolein (10.5–11.3%) were the main components during microwave roasting. Roasting for 20 min caused a significant decrease (P<0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene species present in TAGs.

Roasting influences on molecular species of triacylglycerols in sesame seeds (Sesamum indicum)

Sesame seeds were roasted at different temperatures (180–220 °C) using a domestic electric oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from total lipids in the sesame seeds were analysed by a combination of argentation thin-layer chromatography (TLC) and gas–liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each zone. Eleven molecular species of TAGs were still detected in the sesame seeds following roasting treatment. Dilinoleolein (33.7–35.8%), palmitoleolinolein (20.3–22.8%), dioleolinolein (15.0–15.4%) and trilinolein (8.8–10.7%) were the main components during roasting. However, roasting for 10 min at 220 °C caused a significant decrease (P < 0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene and triene species present in TAGs (with a few exceptions). These results suggest that no significant changes in molecular species or fatty acid distribution of TAGs would occur within 25 min of roasting at 180 °C, ensuring that a good-quality product would be attained. © 2000 Society of Chemical Industry

Molecular species of triacylglycerols in the hulls of sunflower seeds (Helianthus annuus L.) following microwave treatment

Whole sunflower seeds (Helianthus annuus L.) were exposed to microwaves for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The hulls were then stripped from the seeds. Molecular species and fatty acid distributions of triacylglycerols (TAGs), isolated from total lipids in the hulls, were analyzed by a combination of argentation thin-layer chromatography (TLC) and gas chromatography. A modified argentation TLC procedure, developed to optimize the separation of the TAGs, provided 10 different groups of TAGs, based on both the degree of unsaturation and the total fatty acid chain-length. Dilinoleolein (29.5-30.2 wt-%), trilinolein (18.2-24.2 wt-%), dilinoleopalmitin and dilinoleostearin (17.0-18.1 wt-%), palmitoleolinolein and stearoleolinolein (11.4-14.0 wt-%) and dioleolinolein (7.5-8.6 wt-%) were the main TAGs detected after microwave roasting. However, roasting caused a significant decrease (p Des graines entieres de tournesol sont exposees a des micro-ondes pendant 6, 12, 20 ou 30 min a une frequence de 2450 MHz. Les enveloppes sont ensuite enlevees des graines. Les especes moleculaires et les distributions en acides gras des triacylglycerols, isoles a partir des lipides des enveloppes, sont analysees a la fois par chromatographie en couche mince et chromatographie gazeuse.