Tetrahydrocurcumin (THC) is an antioxidative substance which is derived from curcumin by hydrogenation. Curcumin is the main component of turmeric and is responsible for the yellow color of curried foods.First, LDL derived from a normal human volunteer was incubated in the presence of an antioxidant with 10 microM CuSO(4) at 37 degrees C for 2 hours.All antioxidants tested (THC, curcumin, probucol, and alpha-tocopherol) dose-dependently (1-10 microM) inhibited the oxidative modification of LDL. Probucol was the strongest, followed by THC, alpha-tocopherol, and curcumin.Next, in order to evaluate the antioxidative activity of THC in vivo, we fed rabbits diets containing 1% cholesterol with or without 0.5% THC and examined their effects on oxidative stress and atherosclerosis. Animals were divided into two groups: the control group rabbits (n = 12) were fed a normal chow diet and the experimental group (n = 12) was fed a diet containing 0.5% THC for one week.Then, 1% cholesterol was added to the diets and the animals were allowed to feed further for either 6 (n = 4 for each group) or 12 weeks (n = 8 for each group). Although serum cholesterol levels rapidly increased after starting the high cholesterol diet, no difference was observed between the control and THC groups.TBARS formation in the absence of added copper ion was inhibited in the LDL separated from THC-treated animals compared with that from control animals.THC treatment tended to inhibit the area covered with atherosclerotic lesions compared with the control, although this was not significant (28.8 +/- 17.5% vs. 40.0 +/- 23.7%, p = 0.2). Formation of N(epsilon)-(hexanoyl) lysine, 4-hydroxynonenal and dityrosine in liver and kidney also had a tendency to be inhibited by THC treatment. Although free THC was not detected in serum and liver, THC was detected in samples treated with beta-glucuronidase and sulfatase, suggesting that THC is present as a conjugate with glucuronic acid or sulfate. In conclusion, the present results suggest that curcuminoids, particularly THC, which are contained in turmeric, may be useful as a functional food factor.

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Gold nanoparticles have particular properties distinct from those of bulk gold crystals, and such nanoparticles are used in various applications in optics, catalysis, and drug delivery. Many reports on microbial synthesis of gold nanoparticles have appeared. However, the molecular details (reduction and dispersion) of such synthesis remain unclear. In the present study, we studied gold nanoparticle synthesis by Lactobacillus casei. A comparison of L. casei components before and after addition of an auric acid solution showed that the level of unsaturated lipids decreased significantly after addition. NMR and mass spectrum analysis showed that the levels of diglycosyldiacylglycerol (DGDG) and triglycosyldiacylglycerol (TGDG) bearing unsaturated fatty acids were much reduced after formation of gold nanoparticles. DGDG purified from L. casei induced the synthesis of gold nanoparticles in vitro. These results suggested that glycolipids, such as DGDG, play important roles in reducing Au(III) to Au(0) and in ensuring that the nanoparticles synthesized remain small in size. Our work will lead to the development of novel, efficient methods by which gold nanoparticles may be produced by, and accumulated within, microorganisms.