Until 1980, interest in carotenoids was exclusively focused in the field of natural product chemistry and fisheries science in Japan. In particular, many interesting structural carotenoids were identified in aquatic animals. Since then, several biological functions of natural carotenoids have been established through investigations of aquaculture, human-health science and photosynthesis, for example. Now carotenoids are well known to be important for human health, playing roles in prevention of cancer and lifestyle diseases and contributing to human beauty products. Some carotenoids, such as astaxanthin, are therefore industrially produced and used for supplements and cosmetics.
In 2007, the FFI journal published a special issue on carotenoids. Since them, carotenoid science has dramatically progressed and carotenoids are widely accepted as highly functional substances. In this special issue, Prof Misawa, Prof Miyashita and myself respectively describe biotechnology of carotenoids, functions of fucoxanthin as a major carotenoid in brown algae, and characteristics of natural carotenoids.

View full abstract

Fucoxanthin, a marine carotenoid found in edible brown seaweeds, contains the carotenoid end of the polyene chromophore containing an allenic bond and two hydroxyl groups. This unique structure endows anti-obesity effects based on specific molecular mechanisms that have not been established for other carotenoids. Studies have revealed that fucoxanthin induces expression of uncoupling protein 1 (UCP1) in mitochondria of abdominal white adipose tissue (WAT) leading to oxidation of fatty acids and heat production in this site, although UCP1 is usually only found in brown adipose tissue. Since obesity is a pathology with rapidly growing prevalence in most of the world and UCP1 is a key target for ideal therapy, much attention has been paid to the anti-obesity effects of fucoxanthin. Furthermore, this marine carotenoid can improve insulin resistance and decrease blood glucose level through regulation of adipocytokine secretion from abdominal WAT. Another important molecular mechanism for its improvement of glucose utilization is thought to be glucose transporter 4 (GLUT4) up-regulation and promotion of its translocation to cell membranes from the cytosol. In the application of fucoxanthin in functional foods and neutraceutical materials, brown seaweed lipids will be a very important source. Although the lipid content of brown seaweeds is less than those of other nutrients, it is rich in biologically active compounds such as fucoxanthin and omega-3 polyunsaturated fatty acids (PUFAs). For commercial use, a search for lipid-rich seaweed materials is a high priority. Studies on seasonal, regional and species variation in lipid components have shown that several examples collected in the growing stage feature high levels of lipids, fucoxanthin and omega-3 PUFAs.

View full abstract

Carotenoids are tetraterpene pigments that are composed of carbon 40 (C₄₀) skeletons, and de novo synthesized in photosynthetic eukaryotes (plants including algae) and some microorganisms. Land plants produce β-carotene, lutein, zeaxanthin, violaxanthin, and neoxanthin as main carotenoids. Several higher plants can accumulate astaxanthin, or capsanthin and capsorubin, which are carotenoids unique to plant species, in their appropriate organs. Some higher plants also accumulate lycopene, α-carotene, or β-cryptoxanthin, which is a biosynthetic intermediate. On the other hand, carotenogenic bacteria are known to produce a great diversity of carotenoids, e.g., C₄₀ carotenoids such as zeaxanthin, astaxanthin, nostoxanthin, spheroidenone, myxoxanthophyll, and isorenieratene, in addition to C₃₀ linear carotenoids. Such diversity of carotenoids is derived from an abundance of carotenoid biosynthesis genes. The carotenoid biosynthetic pathway has been well elucidated in higher plants at the gene level. Moreover, increasing information on microbial genome sequences provides us with tools to investigate evolution of carotenoid biosynthesis genes. In this review, we describe the carotenoid biosynthetic pathway in both plants and microorganisms, and relevant biosynthesis genes. In addition, we discuss the phylogenetic relationship and evolution of these genes. Comparative analysis suggests that gene duplication, gene transfer, and gene modification resulted in the diversity and species-specificity of the carotenoid biosynthesis genes. In the future, more knowledge of carotenoid biosynthesis genes of various organisms is likely to reveal a detailed pathway for carotenogenic gene evolution.

View full abstract

Carotenoids are tetra-terpene pigments which are distributed in bacteria, fungi, algae, plants and animals. About 800 naturally occurring carotenoids had been reported by 2010. Bacteria, fungi, algae, and plants can synthesize carotenoids de novo. Animals cannot synthesize carotenoids de novo, and so those found in animals are either directly accumulated from food or partly modified through metabolic reactions. So, animal carotenoids show structural diversity. Carotenoids are essential pigments in photosynthetic organs along with chlorophylls. Carotenoids also act as photo-protectors, antioxidants, color attractants, precursors of plant hormone etc. in non-photosynthetic organs such as flower, fruits, seed, root etc. in plants. Carotenoids are also beneficial for animal health. It is well-known that carotenoids having an unsubstituted β-end group, such as β-carotene, α-carotene, β-cryptoxanthin etc. are precursors of vitamin A in animals. Marine animals accumulate carotenoids in their gonads. Carotenoids are assumed to be essential for reproduction in marine animals through their antioxidative activities. Many animals also accumulate carotenoids in their integuments. Integumentary carotenoids contribute to photoprotection, camouflage, and signaling such as breeding color. In the present review, I describe the structural diversity, function, and metabolic pathway of natural carotenoids.

View full abstract

HACCP (Hazard Analysis and Critical Control Point) is a global standard of the food safety management system. The Japanese food industry has carried on HACCP as an elective system until now in Japan, but HACCP will be mandated within several years. For the enforcement of HACCP regulations, we should deepen our understanding about control measures for food safety hazards and their validation as the essence of HACCP. Time/temperature, water-activity, and pH are the parameters of control measures for biological hazards in general, but, in fact, they are also used together with various food additives. Therefore, the author suggests that an inoculated challenge study is necessary for the validation of control measure combinations.

View full abstract

Human intestinal microbiota form a complex community consisting of more than 500 species, with Firmicutes and Bacteroidetes as dominant phyla. The protein-coding genes in intestinal microbiota outnumber our own genes more than 100-fold. Many of these microbial genes are involved in major metabolic pathways such as carbon metabolism and amino acid synthesis. Furthermore, colonization of commensal bacteria critically contributes to the development of the mammalian immune system by promoting maturation of gut-associated lymphoid tissues and by regulating differentiation of helper T cell subsets. Gut microbe-derived metabolites such as short chain fatty acids play key roles in regulation of the host immune system and metabolism. At the same time, aging, a high-fat diet and inflammation disturb the microbial community, leading to dysbiosis and an altered luminal metabolic profile. Dysbiosis-associated metabolites are now emerging as predisposing factors for systemic as well as gastrointestinal disorders. We here review recent investigations on molecular links between gut metabolites and host physiology.

View full abstract

Pectin constitutes a group of complex polysaccharides containing mostly galacturonic acid units, and is present in primary cell walls and middle lamella of many plants. Although the structures of pectins extracted from different plants have some common characteristics, several structural aspects change with the species of origin, as well as with the physiological stage of the material and the extraction conditions. The common structure of pectin is composed of various fragments of linear and ramified regions. The most abundant pectic polysaccharide is homogalacturonan, a linear homopolymer of alpha-1,4-linked D-galacturonic acid residues that account for about 65 % of the total polysaccharide constituents. Rhamnogalacturonan-I and　rhamnogalacturonan-II are also common. Pectin is a component of dietary fibers that are resistant to digestion in the human stomach and small intestine, and has found extensive use as gelling and thickening agents in foods. Although many physiological effects of pectin as a dietary fiber are mediated by colonic microflora, direct interaction of pectin with the small intestine has also been suggested. Several studies have shown that pectin caused morphological changes and promoted crypt branching in the small intestine. However, the mechanisms underlying these pectin-induced effects are largely unknown. As heparan sulfate plays important roles in development of the small intestine, we hypothesized that this cell-surface component may be affected by pectin when it interacts with the small intestine. To verify involvement of heparan sulfate in pectin-induced morphological changes in the small intestine, differentiated Caco-2 cells, which are often used as an intestinal epithelial cell model, were investigated. Disaccharide compositional analysis revealed that sulfated structures of heparan sulfate were markedly changed by pectin administration, structural alterations being caused by upregulation of 6-O-endosulfatase. Such upregulation was suppressed by appendant fibronectin fragments and inhibition of phosphorylation for signal transduction. These observations indicate that pectin may induce the expression of 6-O-endosulfatase through interaction with fibronectin and integrin, thereby regulating the sulfated structure of heparan sulfate on differentiated Caco-2 cells. Taking advantage of our findings we will push forward studies of novel physiological functions of pectin in future.

View full abstract

Delicious food gives people a sense of comfort of mind and happiness. In terms of “deliciousness” of food, we tend to think of just “taste” when we feel the food is tasty while eating, but in fact “deliciousness” of food is not really determined only by the savor that is perceived by the sense of taste. Indeed, “taste” is an underlying element of “deliciousness”, but other senses including sight, smell, touch, and hearing are also responsible for “deliciousness”. In this review, we present the concept of “deliciousness” of food with some examples while taking into consideration other factors influencing “deliciousness” such as “time, place, and occasion”.

View full abstract

Porridge-type barley preparations were born about eight thousand years ago in Western Asia. The method, along with the cultivation technique for the cereals such as barley and wheat, was spread to various places in the Eurasia and Africa Continents between 5000~2000BC. Barley porridge along with the cultivation technique of barley and rice was introduced from India to China in 3000BC and was spread to the whole land of China. Barley porridge was the staple diet in China in those days. But the various porridges with rice and many other kinds of foodstuffs were born in the area from the barley porridge about five thousand years ago. At present there are more than a thousand kinds of the various porridges. There are the porridges for traditional events and Yakuzen porridges (medical porridges) in the Chinese porridges. In general the people eat the porridges as their breakfast and midnight meals.

View full abstract