Alzheimer's disease is the most common form of dementia, and neurological disorder from beta amyloid (Aβ) peptide is regarded as a cause of Alzheimer's disease. In this study, the authors evaluate Aβ toxicity reduction effects of major diterpenes isolated from sugi wood by bioassay using Caenorhabditis elegans and examined its relationship with the antioxidative activity. Among the six kinds of sugi wood diterpenes: ferruginol, 6,7-dehydroferruginol, sandaracopimarinal, sandaracopimarinol,

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... adiene, abietatriene and phyllocladenes, prominent Aβ toxicity reduction effects were found in ferruginol and 6,7-dehydroferruginol, and their activity was almost equivalent to that of the four kinds of anti-Alzheimer active agents that have been reported so far: ginkgolide A, morin, rosmarinic acid and carnosic acid. Antioxidative activity similar to other anti-Alzheimer active agents was found in ferruginol and 6,7-dehydroferruginol in a 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity test, which suggested that antioxidative activity is concerned with expression of the Aβ toxicity reduction effect of sugi wood diterpenes.