| Co-Investigator(Kenkyū-buntansha) |
HAMADA Nobuo Osaka City Institute of Public Health and Environmental Sciences, Chief Researcher, 研究主任 (40270764)
TAKENAKA Yukiko Faculty of Pharmaceutical Sciences, Kobe Pharmaceutical University Assistant, 薬学部, 助手 (90289041)
ITOH Atsuko Faculty of Pharmaceutical Sciences, Kobe Pharmaceutical University Lecturer, 薬学部, 講師 (10223132)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
One characteristic of lichens, a symbiotic association, is the production of diverse secondary metabolites. Our recent studies demonstrated that cultures of lichen mycobionts have an ability under osmotically stressed conditions to produce certain lichen substances or novel metabolites. It was pointed out that cultures of lichen mycobionts could be new sources of bioactive compounds and also good tools for investigating the symbiotic mechanism in lichens. We cultivated the spore-derived mycobionts of several species of lichens collected in Philippines, U.S.A.or Japan, and isolated diverse compounds from their cultures. The cultured lichen mycobionts of the genus Graphis yielded isocoumarines, coumarine, chromones, γ-lactones, dicarboxylic acids, and phenyl ethers. Mycobionts of Ramalina otenospora produced a new azaphilone derivative along with fatty acids, lipids and usnic acid. Furthermore, the cultured mycobionts of Lecanora spp. yielded dibenzofurans, a naphthopyran and an isocouma
… More
rine, while the cultured mycobionts of Pyrenula sp. yielded another naphthopyran.
It is of great interest to know that lichen mycobionts are able to produce substances which have never been detected in the lichenized state but were structurally related to fungal metabolites and that γ-lactones and dicarboxylic acids isolated from the cultured mycobionts could be recognized as prototypes of several natural lichen substances. From the viewpoint of evolution, the mycobionts of the lichens seem to conserve the secondary metabolism of free-living fungi in the pre-symbiosis age. Namely, the origin of isolated mycobionts is the same as that of free-living fungi, for example, Alternaria, and they gained different lifestyles and were separated in the evolutional process. In symbiotic state with photobionts, the mycobionts might conserve the original metabolic ability of ancient mycobionts. These metabolic pathways might be normally supressed by any action of the photobiont, but expressed in the isolated mycobiont. Further studies on secondary metabolites form the cultured mycobionts will provide significant information on the evolution of mycobiont and symbiosis in the lichen. Less
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