Yukiko Takenaka

6H-dibenzo[b,d]pyran-6-one derivatives from the cultured lichen mycobionts of Graphis spp. and their biosynthetic origin.

The spore-derived mycobionts of the lichen Graphis prunicola, G. cognata and G. scripta were cultivated on a malt-yeast extract medium supplemented with 10% sucrose and their metabolites were investigated. Graphislactones A-D were isolated from the cultures of G. prunicola, while alternariol and graphislactones A and C were isolated from those of G. cognata. From the cultured mycobionts of G. scripta, a new 6H-dibenzo[b,d]pyran-6-one derivative, graphislactone E with graphislactones A and C was obtained. On the other hand, cultivation of the mycobionts of G. prunicola on a malt-yeast extract medium supplemented with 2.5% sucrose and 0.25% sodium acetate produced two new metabolites, graphislactones E and F. Their structures were determined by spectroscopic methods. The biogenetic origin of the carbon skeleton in both compounds was verified by administering sodium [1-13C]-acetate and sodium [1,2-13C(2)]-acetate.

Xanthones from the cultured lichen mycobionts of Pyrenula japonica and Pyrenula pseudobufonia

Cultures of the spore-derived mycobionts of the Asian lichen Pyrenula japonica and the North American species P. pseudobufonia gave two xanthones, 1,5,8-trihydroxy-3-methylxanthone and 1,8-dihydroxy-5-methoxy-3-methylxanthone along with the known 1,7-dihydroxy-3-methylxanthone. Their structures were determined by spectroscopic methods. This is the first instance of the isolation of xanthones with a methyl group at C-3 from lichen mycobionts.

Dibenzofurans from the cultured lichen mycobionts of Lecanora cinereocarnea.

From the cultures of the spore-derived mycobionts of the lichen Lecanora cinereocarnea, five dibenzofurans, 3,7-dihydroxy-1,9-dimethyldibenzofuran, 2-chloro-3,7-dihydroxy-1,9-dimethyldibenzofuran, 2,8-dichloro-3,7-dihydroxy-1,9-dimethyldibenzofuran, 3-hydroxy-7-methoxy-1,9-dimethyldibenzofuran, and 2-chloro-7-hydroxy-3-methoxy-1,9-dimethyldibenzofuran, were isolated. Their structures were determined by spectroscopic methods.

Phenolic compounds from the cultured mycobionts of Graphis proserpens.

Spore-derived mycobionts of the lichen Graphis proserpens were cultivated on a malt-yeast extract medium supplemented with 10% sucrose and their metabolites were investigated. Isocoumarin derivatives 1-3 and 7-oxo-5,7-dihydrooxepino[4,3,2-de]isochromene derivatives, proserins A-C (4-6), were isolated along with three known isocoumarin derivatives and three benzoic acid derivatives. Their structures were determined by spectroscopic methods.

Four secoiridoid glucosides from Fraxinus insularis

Abstract Investigation of the leaves of Fraxinus insularis has led to the isolation of four new secoiridoid glucosides, insularoside-3′- O - β - d -glucoside, insularoside-3′, 6‴-di- O - β - d -glucoside, insuloside and desrhamnosyloleoacteoside, together with ligstroside. The structures of the new compounds were determined on the basis of spectroscopic methods.

Eremophilane-type sesquiterpenes from cultured lichen mycobionts of Sarcographa tricosa

Spore-derived mycobionts of the crustose lichen Sarcographa tricosa were cultivated on a malt-yeast extract medium supplemented with 10% sucrose. Chemical investigation of the cultivated colonies led to isolation of three eremophilane-type sesquiterpenes, 3-epi-petasol (1), dihydropetasol (2) and sarcographol (3), together with six known eremophilanes and ergosterol peroxide. These structures were elucidated by spectroscopic and chemical methods. This is the first report of eremophilane-type sesquiterpenes from the cultured mycobionts of lichen.

New phenolic compounds from the lichen Parmotrema praesorediosum (Nyl.) Hale (Parmeliaceae).

Lichens, symbiotic combination of fungi and algae, comprise more than 20 000 species that are found in most of the environmental habitats from the tropics to polar regions. Lichens produce a great variety of metabolites, most of them occur only in lichens and the others are also present in fungi and higher plants. Characteristic secondary metabolites of lichens are depsides, depsidones, diphenyl ethers, benzofuran, usnic acid, and anthraquinone derivatives. Parmotrema is one of the largest genera of the family Parmeliaceae. This genus of foliose lichen is widely distributed in tropical regions and composed of c. 350 species worldwide. Previous phytochemical examination on Parmotrema praesorediosum (Nyl.) Hale, collected on a betel nut tree, in southern Thailand, revealed that this species contained some lactone fatty acids. Sample collected in south Korea contained atranorin, chloroatranorin, and fatty acids, i.e. protopraesorediosic acid and praesorediosic acid. In the course of our systematic research on lichen substances from the Vietnamese flora, we have examined P. praesorediosum (Nyl.) Hale that is distributed in the south of Vietnam. In our previous study on this species, nine compounds, including methyl haematommate, butyl haematommate,methyl chlorohaematommate, methyl β-orsellinate, methyl divaricatinate, atranol, atranorin, (+)-(12R)isousnic acid, and (+)-(12R)-usnic acid were isolated. Further chemical investigation on this species by using modern separation techniques has led to the isolation of seven novel phenolic compounds, four diphenyl ethers (1–4) and three phthalide derivatives (5–7). In this paper, we report the isolation and structure elucidation of these compounds.

Three acetophenones from Acronychia pedunculata

Phytochemical investigation of the leaves and twigs of Acronychia pedunculata has led to the isolation of three new acetophenone monomers 1–3 as well as 1-[2′,4′-dihydroxy-3′,5′-di-(3″-methyl-2″-butenyl)-6′-methoxy]phenylethanone (4), acronyculatin E (5), a mixture of β-sitosterol and stigmasterol, and sesamin. The structures of these new compounds were elucidated spectroscopically. The inhibitory activities of the isolated acetophenone derivatives against mammalian DNA polymerases and human cancer cell growth were also assessed.

Naphthopyrones from cultured lichen mycobionts of Pyrenula sp.

Spore-derived mycobionts of the lichen Pyrenula sp. were cultivated on a malt-yeast extract medium supplemented with 10% sucrose and their metabolites were investigated. A new naphthopyrone derivative, pyrenulin, as well as toralactone were isolated. Their structures were determined by spectroscopic methods. This is the first instance of the isolation of naphthalene derivatives from lichen mycobionts.

Polyketides from the cultured lichen mycobiont of a Vietnamese Pyrenula sp.

A spore-derived mycobiont of a crustose Pyrenula sp. lichen collected in Vietnam was cultivated on a malt-yeast extract medium supplemented with 10% sucrose. Chemical investigation of the cultivated colonies led to the isolation of eight new alkylated decalin-type polyketides (1-8) along with three known compounds. The structures of these compounds were elucidated by spectroscopic and chemical means. This is the first instance of this type of polyketide being isolated from a cultured lichen mycobiont. The isolated polyketides 1 and 7 exhibited inhibitory activities against mammalian DNA polymerases α and β with IC50 values ranging from 8.1 to 19.5 μM. Compound 1 showed cytotoxic effects against the HCT116 human colon carcinoma cultured cell line with an IC50 value of 6.4 ± 0.7 μM.