Yukihiro Ishikawa

Flavoglaucin, a metabolite ofEurotium chevalieri, its antioxidation and synergism with tocopherol

Screening tests of fungal metabolites were performed for developing new types of antioxidants and synergists for tocopherol (Toc). Flavoglaucin has been found to be an excellent antioxidant and synergist. It is a phenolic compound isolated from mycelial mats ofEurotium chevalieri. Under autoxidation conditions, flavoglaucin remarkably synergized with Toc and stabilized many edible oils and fats. After the addition of flavoglaucin (0.05 %) the vegetable oils retained their original stabilities even after thermal treatment at 180 C for 25 hr. During the oxidation of lard containing Toc (0.04%) under the simulated deep-fat frying conditions, the addition of flavoglaucin didn’t retard the oxidative decomposition of Toc. However, the stability of lard always was higher in the presence of flavoglaucin than in its absence. Flavoglaucin is not mutagenic to Salmonella typhimurium TA 100 and TA 98.

Atrovenetin as a potent antioxidant compound from penicillium species

We have established a program to screen large numbers of wild-type fungi isolated from soil for potential producers of antioxidants and synergists for tocopherol (Toe). An antioxidant and potent Toc synergist was isolated from mycelial mats ofPenicillium paraherquei. It was one of the deoxyherqueinone-type phenalenones and has been identified as atrovenetin.Under autoxidation conditions, the induction periods of this compound (0.025%) tested by the active oxygen method were 571 and 171 hr in lard with and without Toc (0.04%), respectively. It was also capable of stabilizing vegetable oils such as soybean, rapeseed and palm oils.

The Expression of Presenilin 1 mRNA in Skin Fibroblasts and Brains from Sporadic Alzheimer’s Disease

We examined the expression of presenilin 1 (PS-1) mRNA in cultured skin fibroblasts taken from living patients with Alzheimer’s disease (AD) and human brains taken postmortem from AD patients by RT-PCR analysis. The donors of fibroblasts consisted of 28 cases with AD and 19 neurological patient without dementia (CTL). The brains came from 17 cases with AD and 23 cases with CTL. We found that PS-1 mRNA levels in skin fibroblasts of AD patients were significantly higher than those of CTL patients (p < 0.0001). Moreover, we found that PS-1 mRNA levels in human brains with AD were significantly higher than in those with CTL (p < 0.0001). These findings suggest that high levels of PS-1 mRNA in AD may play an important role in developing AD and that the examination of PS-1 mRNA in skin fibroblasts may be helpful for the diagnosis of AD.

Effects of amino compounds on the formation of γ-tocopherol reducing dimers in autoxidizing linoleate

The effects of various amino compounds trimethylamine oxide (TMAO), tri-n-octylamine (TOA), phosphatidyl choline (PC), and phosphatidyl ethanolamine (PE) on the oxidative decomposition of γ-tocopherol (γ-Toc) and on the formation of its reducing dimers were investigated during the autoxidation of methyl linoleate (ML). In general, γ-Toc diphenyl ether dimer (γ-TED) was formed in preference to two atropisomers of γ-Toc biphenyl dimers [γ-TBD(H) and (L)] in autoxidizing ML. This relationship, however, was reversed when TMAO was added. As the presence of TOA, PC, or PE did not promote the formation of γ-TBD, the preferential formation of γ-TBD was believed to be based on the interaction between TMAO and oxidation products formed from γ-Toc. Effects of TMAO and TOA on the interconversion of γ-Toc reducing dimers were investigated. γ-TED was found to be converted into γ-Toc and γ-TBD(L) in autoxidizing ML. But γ-TBD(H) could not be detected, and the amount of γ-TBD(L) formed was very small. γ-TBD(H) and (L) were formed from their respective atropisomers. In this case, the formations of γ-Toc and γ-TED could not be detected. Therefore, it was concluded that the conversion of γ-TED into γ-TBD and vice versa can be neglected in any event.