Food includes complicated and wide-ranging ingredients. In order to support life, we digest and absorb only necessary ingredients (nutrients), which are selectively metabolized for the formation of energy and/ or body components, to utilize the necessary nutrients. However, eating habits under full-feeding in our country seem to be in the process to transform disrupted eating habits leading to health damage, because a gap between health expectancy and life expectancy remains still large due to the development of lifestyle diseases including obesity which are caused by an unbalanced diet and/or disrupted food style. In order to bring health expectancy near to life expectancy by correcting disrupted eating habits as much as possible, we should consider the factor to reduce the gap between health expectancy and life expectancy. One of the ways to reduce the gap is a skillful application of food functions to the improvement of disrupted eating habits and also the combination of the improvement of disrupted eating habits by application of food functions with exercise can be thought to be an important factor to reduce the gap. As an example of the application of food functions to the improvement of disrupted eating habits, we will introduce the application of Euglena (Japanese name, Euglena gracilis) based on its physiological functions as a nutrient to improve disrupted eating habits in this review.

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Vitamin K is an essential cofactor of γ-carboxylase which is involved in the activation of the cascade of blood coagulation and bone formation. Recent researches have revealed that vitamin K possesses physiological functions to regulate the transcription of factors participating in bone formation via the steroid and xenobiotic receptor (SXR), a nuclear receptor, and to induce the differentiation of cranial nerve progenitor cells to neuronal cells. Therefore, we synthesized vitamin K analogues by introducing substituent groups to the side chain part at ω-position and explored whether the synthesized vitamin K analogues possesses new biological activities for transcription via SXR and neuronal differentiation. The vitamin K derivatives with modification of the structure of vitamin K2 were found to have much more potent biological activities for transcription via SXR and neuronal differentiation than original vitamin K2.

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L-Ascorbic acid (AsA), known as vitamin C, plays key roles in many biological processes such as collagen formation, carnitine synthesis, and iron absorption. AsA is also an important antioxidant in food and biological systems, but it is unstable under various oxidative conditions, resulting in its rapid degradation. 2-O--D-Glucopyranosyl-L-ascorbic acid (AA-2G), a stable AsA derivative, has been developed to achieve an efficient action as an AsA source, a pro-vitamin C agent. AA-2G has been approved by the Japanese Government as a quasi-drug principal ingredient in skin care and as a food additive. AA-2G is now widely used as a medical additive in commercial cosmetics. This stable AsA derivative exhibits vitamin C activity in vitro and in vivo after enzymatic hydrolysis to AsA by -glucosidase. Recently, we have synthesized two types of monoacylated derivatives of AA-2G, 6-O-acyl-2-O--D-glucopyranosyl-L-ascorbic acids having a straight-acyl chain of varying length from C4 to C18 (6-sAcyl-AA-2G) and a branched-acyl chain of varying length from C6 to C16 (6-bAcyl-AA-2G), in order to improve the bioavailability of AA-2G and have indicated that 6-sAcyl-AA-2G and 6-bAcyl-AA-2G exert usually known vitamin C functions efficiently in vitro and in vivo. More recently, we found that, unexpectedly, 6-sAcyl-AA-2G per se had antiallergic activity based on a degranulation inhibiting action and that a 6-O-acyl AsA, an intermediate in the hydrolysis of 6-bAcyl-AA-2G to AsA, showed a significant antitumor activity in tumor-bearing mice. In this review, the author presents a possible application of created AsA derivatives to drug development.

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