Effect of Resveratrol Dimers and Tetramers Isolated from Vitaceous and Dipterocarpaceous Plants on Human SIRT1 Enzyme Activity

SIRT1 is a mammalian ortholog of the yeast enzyme Sir2, which is an NAD+-dependent deacetylase of histones, p53, FOXO, NF-κB, PGC-1α, and other transcription factors. The Sir2 protein is reported as a longevity protein in yeast. Resveratrol, a polyphenol isolated from various types of plant families, particularly the Vitaceae family, is a known naturally occurring SIRT1 activator. In this study, we evaluated the effects of four types of resveratrol dimers and four types of tetramers isolated from vitaceous plants, and one type of resveratrol tetramer isolated from a dipterocarpaceous plant on purified human SIRT1 enzyme activity. Of the resveratrol dimers examined, (+)-ε-viniferin and pallidol exhibited no effect on SIRT1 enzyme activity, whereas (+)-ampelopsin B and (-)-ampelopsin F showed inhibitory activity on SIRT1. However, all the resveratrol tetramers examined, i.e., (+)-vitisin A, (-)-vitisin B, (+)-hopeaphenol, (-)-hopeaphenol, and (-)-isohopeaphenol markedly inhibited the human SIRT1 enzyme activity. (+)-Hopeaphenol exhibited the most potent inhibitory activity, which was comparable with that exhibited by a known SIRT1 inhibitor suramin. Since SIRT1 inhibitors reportedly possess anticancer activity, (+)-hopeaphenol and other resveratrol oligomers can be used as a seed compound for anticancer drugs

ジツウンテン ジョウキョウ ヲ モギシタ オンド ジョウケン ニ オケル アツニク XLPE ゼツエン ケーブル ノ クウカン デンカ ソクテイ

This paper reports the space charge measurement results under actual operation temperature condition for a 23-mm-thick AC XLPE cable. A pulsed electro-acoustic (PEA) method which is newly proposed to measure the space charge characteristics of thick insulation samples accurately was applied. The AC XLPE cable was employed to observe the space charge accumulation clearly. The changes in space charge and electric field distributions corresponding to the changes in temperature and voltage were observed. As a result, we found that the space charge distribution under the heat cycle condition shows complex behavior as the temperature distribution changing. We concluded that it is important to measure space charge characteristics under heat cycle conditions in addition to the conventional space charge measurement under constant temperature conditions to understand the space charge characteristics of the full-size XLPE cable