A new p-coumaric acid (4-hydroxycinnamic acid) hydroxylase was detected in mung bean seedlings treated with tentoxin, a fungal toxin, in which polyphenol oxidase that hydroxylates a wide variety of monophenols in vitro was completely eliminated. The enzyme required molecular oxygen and showed a pH optimum of 5.0. The enzyme acted only on p-coumaric acid (Km, 3.0 X 10(-5) M), while its specificity for the electron donor was rather broad. The Km value for NADPH (1.5 X 10(-4) M) was much lower than that for L-ascorbic acid (1.0 X 10(-2) M), although the Vmax value was almost the same with both electron donors. The enzyme was potently inhibited by beta-mercaptoethanol (Ki, 3.5 X 10(-6) M) and diethyldithiocarbamate (Ki, 2.3 X 10(-4) M), but was insensitive to p-chloromercuribenzoate. The enzyme was localized in the cell organelles which sedimented between mitochondria and endplasmic reticulum on sucrose density gradient centrifugation. The enzyme activity in the seedling was changed in response to induction by light in a manner suggesting its involvement in biosynthesis of phenolic compounds in mung bean seedlings.

Diosgenin (Dio) is a steroid sapogenin found in plants such as Dioscorea species, and is recognized as a phytochemical against various disorders as well as a natural precursor of steroidal drugs. The present study used rats fed high-cholesterol (Chol) diets supplemented with or without 0.5% Dio for 6 wk to investigate the effects of dietary Dio on lipid metabolism. Dio supplementation significantly increased serum high-density lipoprotein Chol concentrations and fecal Chol content, and significantly decreased fecal bile acid content compared rats fed a high-Chol diet alone, showing that dietary Dio may facilitate excretion of Chol rather than bile acids. A reduction in the liver triglyceride content and intra-abdominal visceral fat was observed in Dio-supplemented rats. Interestingly, dietary Dio also significantly increased the skeletal muscle-fiber diameter and area in the thigh muscles of the rats. Mouse myoblast-derived C2C12 cells were used to examine whether Dio directly affected skeletal muscle. Dio promoted fusion of myoblasts into multinucleated cells or myotubes. Furthermore, in myotube C2C12 cells, protein levels of phosphorylated AMPactivated protein kinase (AMPK) increased with Dio treatment in a dose-dependent manner. These results indicate that Dio may not only induce myoblast fusion and enhance skeletal muscle as an energy expenditure organ, but may also activate the catabolic pathway via AMPK in skeletal muscle cells. Thus, these effects of Dio on skeletal muscles may contribute to inhibition of visceral fat accumulation. Key Words dietary supplements, lipid metabolism, cholesterol, visceral fat, skeletal muscle, skeletal muscle cells, myoblast fusion, AMPK Diosgenin (Dio; Pubchem ID 99474) is a steroid sapogenin found in plants such as Dioscorea, Trigonella, Costus, and Smilax species, and is a constituent of the saponin, dioscin, which is found in the rootstock of yam (Dioscorea) (1, 2). Dio is a natural precursor of steroidal drugs, including sex hormones and corticosteroids, indicating its importance in the pharmaceutical industry. Additionally, Dio itself has pharmacological potential and behaves as a biologically active phytochemical that is used in the treatment of various disorders, including inflammation, hypercholesterolemia, cancer, and several types of infections. Tohda et al. identified 1,25D3-membrane-associated, rapid response steroidbinding protein (1,25D3-MARRS) as a target protein of Dio and demonstrated that Dio induces axonal growth and regrowth of neurons as an exogenous stimulator of 1,25D3-MARRS, and may act on critical signaling path

SummaryWe investigated the effects of dietary Japanese yam (Dioscorea japonica Thunb.) on lipid metabolism. Male Wistar rats (6 wk old) were fed a high-cholesterol diet for 6 wk and then supplemented with 26% of Japanese yam or 0.5% of its constituent diosgenin for a further 4 wk of high-cholesterol feeding (C6-J4 and C6-D4 groups, respectively). In the C6-J4 group, body weight gains significantly decreased, but skeletal muscle fiber sizes in quadriceps significantly increased compared with the other groups. Furthermore, Japanese yam supplementation resulted in the reduction of triglyceride contents in their liver, quadriceps, and intra-abdominal visceral fat. Diosgenin supplementation resulted in an increase in the numbers of skeletal muscle fibers and decrease in the fat accumulations in liver and of the lipid contents in quadriceps. Although quadriceps cholesterol contents decreased concomitantly with increased serum HDL-cholesterol in both the groups, fecal bile acid, fecal cholesterol contents, and fecal weight were higher in the C6-J4 group than in the C6-D4 group. Meanwhile, we demonstrated that Japanese yam inhibited micellar cholesterol solubility in vitro in a concentration-dependent manner. These results suggest that Japanese yam is more effective than diosgenin in reducing fat accumulation and improving cholesterol metabolism during chronic consumption of a high-cholesterol diet.

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The consumption of rice, which is the main food of Japanese, tends to decrease accompanied with the diversifi cation of food. Thus, the development of new methods of consuming rice and breeding of rice varieties with various healthsupport functions is expected. Under such circumstances, the health-support function of germinated brown rice (GBR) is greatly appreciated, and it is now used not only for cooking but also as an ingredient in processed foods. 1)Germination activates the metabolism in the rice grains, and produces various functional components such as γ-amino butyric acid and ferulic acid.2,3) These components in GBR are reported to be effective for preventing life style-related disease. In addition, the starch in brown rice (BR) is hydrolyzed during germination; therefore, GBR is a good foodstuff for human digestion and absorption. 4) Hitherto, grain starch has been handled to prevent degradation during storage, because degradation of starch lowers the quality of grain. Therefore, we can say that the already hydrolyzed GBR resulted from a change in attitude.With the diversifi cation of the usage of GBR, it will be important to elucidate the germination conditions suitable to increase the contents of its desired factors. To improve the palatability of GBR, we prepared it by two different methods, measured the concentration of glucose, water-soluble pectin, and polyphenol, and investigated their compositional changes.

The non-enzymatic hydroxylation of aromatic compounds has been investigated in various systems. 1-9) These systems included ascorbic acid, Fe 2 + and ethylenediaminetetraacetic acid (EDTA)1,2) H 2 0 2 ,3) EDTA