Hisayoshi Kofujita

Condensed tannins exhibit diverse bioactivities that render them promising for applications in the food and medical fields. For the analysis and monitoring of condensed tannins, ¹³C-labeled derivatives would provide a useful tool. In this study, condensed tannin polymers regioselectively labeled with a stable isotope were synthesized using ¹³C-labeled acetic acid or ¹³C-labeled dimethylformamide as the starting material. The resulting synthetic polymers were labeled with ¹³C at the C-4 or C-2 positions. A GPC analysis revealed that all model polymers comprised mainly tetramer to hexamer structures. According to the ¹³C-NMR data of the synthetic tannin models and natural condensed tannin obtained from sugi bark, the chemical structure of both compounds was very similar. Furthermore, compared with the natural condensed tannin and unlabeled synthetic polymer, the labeled compound showed more intense C-4 and C-2 ¹³C signals, indicating that the ¹³C labeling proceeded regioselectively. These compounds are useful for analyzing the chemical reactions of condensed tannins and monitoring structural transformation processes in vivo.

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, abietadiene, 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.

The growth-inhibitory activity of extracts obtained from Sugi (Cryptomeria japonica) effective against Microcystis aeruginosa, an alga that causes harmful algal blooms in freshwater environments, was examined. Each sample of the inner bark, outer bark, heartwood, and leaves of Sugi was extracted with hexane, ethyl acetate, and methanol successively. Inhibitory activities were observed in the inner bark ethyl acetate and methanol extracts, the heartwood hexane extract, the outer bark hexane extract, and the leaf ethyl acetate extract. The inner bark ethyl acetate and methanol extracts showed stronger activities than the other extracts. Catechin, epicatechin, and procyanidin B3 were identified as the active components in the inner bark ethyl acetate and methanol extracts. The terpenoids 1-epicubenol, 4-epicubebol, cubenol, δ-cadinol, sandaracopimarinal, and sandaracopimarinol were the active components of the heartwood hexane extract. Thus, it was indicated that not only the polyphenolic components but also non-phenolic terpenoids had growth inhibition activity against M. aeruginosa.

Bioassay-guided isolation of compounds from n-hexane extracts of the bark of Cryptomeria japonica resulted in six abietane- and two pimarane-type diterpenoids, including a new compound, 12-methoxy-6α,11-dihydroxyabieta-8,11,13-triene. The structure of the new substance was established by spectral analyses and comparison with related compounds. The antifungal activities of these diterpenes were evaluated against the phytopathogenic fungi Alternaria alternata, Pyricularia oryzae, Rhizoctonia solani and Fusarium oxysporum. The diterpenes showed moderate antifungal activity against the fungi examined.