Resistant hydrogenated starch hydrolysate (resistant HSH) was prepared by hydrogenating resistant maltodextrin, and its effects on postprandial blood glucose (BG) levels were investigated in animals and humans. In a glucose tolerance test with male SD rats, resistant HSH ranging from 2.5 to 80% to glucose were orally administered and showed the most suppressive effect on postprandial BG levels at 5%. Administration of more than 5% showed no further increase of effectiveness. Postprandial BG levels were examined in 9 healthy adults administered a test meal contained 2.5-10g of resistant HSH. In this test, ingestion of 5 g and above significantly suppressed the postprandial rise in BG levels in a dose-dependent manner. Subsequently, the effects of resistant HSH and resistant maltodextrin on postprandial BG were compared in 10 healthy adults. Both substances showed approximately equivalent suppressive effects on the postprandial rise in BG when 5g each was ingested with the test meal.

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The present investigation was designed to determine whether any synergism exists between surfactin and natto in improving the lipid metabolism of rat. Rats were divided into four groups and fed four different diets each having a high cholesterol and lard content. The diet of the control group did not contain either surfactin or natto, whereas the three experimental groups were given a diet containing surfactin alone (surfactin group), natto alone (natto group), and a mixture of surfactin and natto (surfactin-natto group). Analyses revealed that the levels of serum lipids, total cholesterol (T-chol), arteriosclerosis index (AI), and triacylglycerol (TG) were decreased significantly or tended to decrease in the three experimental groups. With regard to the amount of lipids in liver, total lipid (TL) was decreased in the surfactin-natto group, cholesterol was decreased in both the surfactin and the surfactin-natto groups, and TG was decreased in all the experimental groups. The cholesterol excretion ratio was increased in the surfactin-natto group and cholic acid excretion was markedly increased in all the experimental groups, while the enzyme activity responsible for lipid synthesis in the liver was decreased in the natto and surfactin-natto groups. These results indicate that surfactin and natto exhibit synergism in improving the lipid metabolism of rats by lowering the levels of serum T-chol and liver TG and by increasing the cholesterol excretion ratio, suggesting that the development of surfactin-rich natto would be of potential value.

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Coral sand (CS) contains the highest level of soluble silicon (Si), an essential element for bone formation, among several raw materials with calcium tested. The effects of CS on bone metabolism were studied by maintaining weanling mice on basal diets containing 0.5 and 3% CS for 3 or 6 months. In comparison with the control basal diet containing calcium carbonate, the CS diet increased the bone ash weight and collagen content at peak bone mass in 4-month-old mice, resulting in increased strength and stiffness of the femur. In 7-month-old mice showing initiation of bone loss, increased bone collagen and calcium concentrations and alkaline phosphatase activity suggested stimulation of bone metabolic turnover in favor of bone formation, as reflected in increased bone weight. Mice on the 3% CS diet with intake of 171% Ca and 117% Si compared to the control demonstrated an increase in all 4 indices of mechanical bone strength, whereas mice on the 0.5% CS diet with intake of 102% Ca and 105% Si showed increased strength, deflection, and energy absorbed. These findings suggest that coral sand has distinctive characteristics of bone metabolism differing from those of calcium salts when included in the basal diet, possibly due to its high concentration of soluble silicon.

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We have been screening selective inhibitors of eukaryotic DNA polymerases from natural food materials. A 50% ethanol leaf extract (“Gaba-leaves 1”) of a higher plant, Osidium guajava L., inhibited activities of DNA polymerases α (replicative polymerase) and λ (repair-related polymerase), and the purified fraction obtained by hydrophobic chromatography (“Gaba-leaves 2” was a stronger inhibitor than Gaba-leaves 1. We also found that the extract of a well-known mushroom possessing anti-cancer activity, Agaricus blazei Murill (“Agaricus”) inhibited the activity of DNA polymerases. A mixture of Gaba-leaves and Agaricus stimulated the inhibitory activity of DNA polymerase α, and decreased the inhibitory activity of DNA polymerase λ.

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