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Mitsuo Namiki

Other affiliations: Tokyo University of Agriculture
Bio: Mitsuo Namiki is an academic researcher from Nagoya University. The author has contributed to research in topics: Sesamolin & Amino acid. The author has an hindex of 33, co-authored 152 publications receiving 4788 citations. Previous affiliations of Mitsuo Namiki include Tokyo University of Agriculture.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a novel type of antioxidant was isolated from the leaf wax of Eucalyptus globulus and identified as n-tritriacontan-16,18-dione.
Abstract: As a search for natural antioxidants from plant materials, strong antioxidative activity was observed in leaf waxes extracted from Eucalyptus species. A novel type of antioxidant was isolated from the leaf wax of Eucalyptus globulus and identified as n-tritriacontan-16,18-dione. Antioxidative activities were determined by different methods; a thiocyanate method, a thiobarbituric acid method, a total carbonyl value method and a weighing test. The anti-oxidant showed remarkable antioxidative activity in a water/alcohol system and was more effective than α-tocopherol and BHA; however, it has no antioxidative activity in an oil system.

421 citations

Journal ArticleDOI
Mitsuo Namiki1
TL;DR: Sesame has been known empirically as a cooking oil which is highly resistant to oxidative deterioration in comparison with other edible oils as discussed by the authors, but until recently there were no scientific studies to elucidate these interesting aspects of sesame seed and oil, but the author and members of his group initiated studies on the chemical elucidation of antioxidative principles of raw and roasted sesame seeds and oils.
Abstract: Some historical facts on and botanical descriptions of sesame are given. Some flavor studies of raw and roasted sesame seeds and oils are described. Composition and some usages are also briefly reported. Sesame has long been regarded in the Orient as a health food which increases energy and prevents aging. Sesame oil has been known empirically as a cooking oil which is highly resistant to oxidative deterioration in comparison with other edible oils. Until recently there were no scientific studies to elucidate these interesting aspects of sesame seed and oil, but the author and members of his group initiated studies on the chemical elucidation of antioxidative principles of sesame seed and oil, and extensively investigated the antiaging effect of sesame. Presence of various new antioxidative lignan phenol compounds in sesame seed and oil is described. Sesaminol has been identified as a new antioxidative principle in raw sesame salad oil. The mechanism of the superior antioxidative activity of roas...

336 citations

Book ChapterDOI
Mitsuo Namiki1
TL;DR: The chapter discusses the need for more detailed information on the structure and properties of melanoidin to elucidate the mechanism of its antioxidative activity and application of MRPs in practical food processing.
Abstract: Publisher Summary In this chapter, the browning reaction mechanism, and the formation of antioxidants and mutagens are reviewed. The stages in browning reaction mechanism based on Hodge's scheme are described in detail. Different stages are initial stage involving the formation of glycosyl amino products followed by Amadori rearrangement, intermediate stage involving dehydration and fragmentation of sugars and final stage involving aldol condensation, polymerization, and formation of heterocyclic nitrogen compounds. Formation of free radicals and structure of novel free radicals in the initial stage are described in detail. The sugar fragmentation and carbonyl compounds in the formation of free radicals are effective in browning process. The steps in the intermediate stages described are Amadori rearrangement products, enolization and degradation of Amadori products and precursors of melanoidins. The final stage describes the chemistry of melanoidins. The chapter also discusses the antioxidants and Maillard reaction. The stability of foods increases when Maillard reactions occur. The stabilization is considered to be because of the antioxidative action of Maillard reaction products (MRPs). Conditions for induction of antioxidative activity are explained. Detailed explanation about the antioxidative property of reductones is presented. The antioxidative property of reductones is due to their reducing activity and metal cheating ability. Application of MRPs in practical food processing is also highlighted. The relationship between mutagen formation and browning of food is explained. The role of nitroso mutagens and antimutagens is also discussed. The chapter also discusses the need for more detailed information on the structure and properties of melanoidin to elucidate the mechanism of its antioxidative activity.

277 citations

Journal ArticleDOI
TL;DR: A lignan compound, named sesaminol, having strong antioxidative activity was found to be formed in high concentration during the industrial bleaching process of unroasted sesame seed oil as mentioned in this paper.
Abstract: A lignan compound, P3, having strong antioxidative activity was found to be formed in high concentration during the industrial bleaching process of unroasted sesame seed oil. P3 (named sesaminol) was identical to a minor constituent previously isolated from acetone extract of sesame seed. It was shown that sesamolin in unprocessed sesame oil is the source of seaseminol, and the formation of seasaminol was confirmed by the model experiment with corn oil to which sesamolin had been added. Sesaminol was not so greatly removed by the deodorization process that follows bleaching as was sesamol, and it was shown to be at a concentration of ca. 100 mg/100g in commercial refined unroasted seed oil. The antioxidative activity of sesaminol was foughly equal to those of sesamol and γ-tocopherol by the thiocyanate method. Therefore, it seems that the antionxidative activity of refined unroasted seed oil is mainly attributed to sesaminol.

265 citations

Journal ArticleDOI
Mitsuo Namiki1
TL;DR: Sesame lignans lowered the cholesterol concentration in serum, especially in combination with tocopherol, due to the inhibition of absorption from the intestine and suppression of synthesis in the liver, and showed other useful functions such as acceleration of alcohol decomposition in the Liver, antihypertensive activity, immunoregulatory activities, anticarcinogenic activity, and others.
Abstract: The results of recent food chemical and nutraceutical studies on the traditionally well-known health value of sesame are described, including some aspects of the utilization of sesame. The highly antioxidative activity of sesame oil was clarified and found to involve newly discovered lignans. The antiaging effect of sesame was elucidated to be due to the strong vitamin E activity caused by a novel synergistic effect of sesame lignans with tocopherols resulting from the inhibition of metabolic decomposition of tocopherols by sesame lignans. The specific inhibitory action of sesame lignans on Δ5 desaturase in polyunsaturated fatty acid synthesis was found in studies on the microbial production of polyunsaturated fatty acids. This effect of sesame lignans was extended to various effects on fatty acid metabolism involving lowering fatty acid concentration in liver and serum due to acceleration of fatty acid oxidation and suppression of fatty acid synthesis, and the controlling influence on the ratio of n-6/n-...

252 citations


Cited by
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Journal ArticleDOI
TL;DR: Phenolic compounds, ubiquitous in plants are an essential part of the human diet, and are of considerable interest due to their antioxidant properties as mentioned in this paper, and their structures may range from a simple phenolic molecule to a complex high-molecular weight polymer.

2,723 citations

Journal ArticleDOI
TL;DR: HPLC-DAD and HPLC-MS analyses of the juices revealed that commercial juices contained the pomegranate tannin punicalagin while only traces of this compound were detected in the experimental juice obtained from arils in the laboratory, which shows that pomesgranate industrial processing extracts some of the hydrolyzable tannins present in the fruit rind.
Abstract: The antioxidant activity of pomegranate juices was evaluated by four different methods (ABTS, DPPH, DMPD, and FRAP) and compared to those of red wine and a green tea infusion. Commercial pomegranate juices showed an antioxidant activity (18-20 TEAC) three times higher than those of red wine and green tea (6-8 TEAC). The activity was higher in commercial juices extracted from whole pomegranates than in experimental juices obtained from the arils only (12-14 TEAC). HPLC-DAD and HPLC-MS analyses of the juices revealed that commercial juices contained the pomegranate tannin punicalagin (1500-1900 mg/L) while only traces of this compound were detected in the experimental juice obtained from arils in the laboratory. This shows that pomegranate industrial processing extracts some of the hydrolyzable tannins present in the fruit rind. This could account for the higher antioxidant activity of commercial juices compared to the experimental ones. In addition, anthocyanins, ellagic acid derivatives, and hydrolyzable tannins were detected and quantified in the pomegranate juices.

2,139 citations

Journal ArticleDOI
TL;DR: A review of phenolic and polyphenolic compounds can be found in this article, which summarizes both the synthetic and natural phenolic antioxidants, emphasizing their mode of action, health effects, degradation products and toxicology.

1,800 citations

Journal ArticleDOI
TL;DR: The aim of this review is to summarize and analyze the vast and sometimes conflicting literature on tannins and to provide as accurately as possible the needed information for assessment of the overall effects of tannin effects on human health.
Abstract: Tannins (commonly referred to as tannic acid) are water-soluble polyphenols that are present in many plant foods. They have been reported to be responsible for decreases in feed intake, growth rate, feed efficiency, net metabolizable energy, and protein digestibility in experimental animals. Therefore, foods rich in tannins are considered to be of low nutritional value. However, recent findings indicate that the major effect of tannins was not due to their inhibition on food consumption or digestion but rather the decreased efficiency in converting the absorbed nutrients to new body substances. Incidences of certain cancers, such as esophageal cancer, have been reported to be related to consumption of tannins-rich foods such as betel nuts and herbal teas, suggesting that tannins might be carcinogenic. However, other reports indicated that the carcinogenic activity of tannins might be related to components associated with tannins rather than tannins themselves. Interestingly, many reports indicated negative association between tea consumption and incidences of cancers. Tea polyphenols and many tannin components were suggested to be anticarcinogenic. Many tannin molecules have also been shown to reduce the mutagenic activity of a number of mutagens. Many carcinogens and/or mutagens produce oxygen-free radicals for interaction with cellular macromolecules. The anticarcinogenic and antimutagenic potentials of tannins may be related to their antioxidative property, which is important in protecting cellular oxidative damage, including lipid peroxidation. The generation of superoxide radicals was reported to be inhibited by tannins and related compounds. The antimicrobial activities of tannins are well documented. The growth of many fungi, yeasts, bacteria, and viruses was inhibited by tannins. We have also found that tannic acid and propyl gallate, but not gallic acid, were inhibitory to foodborne bacteria, aquatic bacteria, and off-flavor-producing microorganisms. Their antimicrobial properties seemed to be associated with the hydrolysis of ester linkage between gallic acid and polyols hydrolyzed after ripening of many edible fruits. Tannins in these fruits thus serve as a natural defense mechanism against microbial infections. The antimicrobial property of tannic acid can also be used in food processing to increase the shelf-life of certain foods, such as catfish fillets. Tannins have also been reported to exert other physiological effects, such as to accelerate blood clotting, reduce blood pressure, decrease the serum lipid level, produce liver necrosis, and modulate immunoresponses. The dosage and kind of tannins are critical to these effects. The aim of this review is to summarize and analyze the vast and sometimes conflicting literature on tannins and to provide as accurately as possible the needed information for assessment of the overall effects of tannins on human health.

1,687 citations

Journal ArticleDOI
TL;DR: An overview of current knowledge about the antibacterial properties and antibacterial mode of action of essential oils and their constituents is provided, and research avenues that can facilitate implementation of essential oil constituents as natural preservatives in foods are identified.
Abstract: Essential oils are aromatic and volatile liquids extracted from plants. The chemicals in essential oils are secondary metabolites, which play an important role in plant defense as they often possess antimicrobial properties. The interest in essential oils and their application in food preservation has been amplified in recent years by an increasingly negative consumer perception of synthetic preservatives. Furthermore, food-borne diseases are a growing public health problem worldwide, calling for more effective preservation strategies. The antibacterial properties of essential oils and their constituents have been documented extensively. Pioneering work has also elucidated the mode of action of a few essential oil constituents, but detailed knowledge about most of the compounds’ mode of action is still lacking. This knowledge is particularly important to predict their effect on different microorganisms, how they interact with food matrix components, and how they work in combination with other antimicrobial compounds. The main obstacle for using essential oil constituents as food preservatives is that they are most often not potent enough as single components, and they cause negative organoleptic effects when added in sufficient amounts to provide an antimicrobial effect. Exploiting synergies between several compounds has been suggested as a solution to this problem. However, little is known about which interactions lead to synergistic, additive, or antagonistic effects. Such knowledge could contribute to design of new and more potent antimicrobial blends, and to understand the interplay between the constituents of crude essential oils. The purpose of this review is to provide an overview of current knowledge about the antibacterial properties and antibacterial mode of action of essential oils and their constituents, and to identify research avenues that can facilitate implementation of essential oils as natural preservatives in foods.

1,509 citations