Sesquiterpene derivatives from cultured lichen mycobionts of Diorygma sp.

Lichens are distinctive organisms resulting from a symbiosis between algae and fungi. Lichens are well known for their production of unique lichen substances, some of which are potentially useful and biologically active compounds. Although the cooperative mechanisms for the biosyntheses of lichen substances are not fully understood, they are thought to be produced by the fungal portion (mycobiont) of the symbiotic system. However, our previous studies demonstrated that isolated lichen mycobionts are, in some cases, capable of producing new compounds, which are not detected in the natural lichen thalli [1,2]. These findings suggested that laboratory cultures of isolated lichen mycobionts could provide a potential source of novel secondary metabolites. In continuing our chemical studies on the cultured lichen mycobionts [3], we have cultivated the spore-derived mycobionts of Diorygma sp. collected in Vietnam on conventional malt-yeast extract medium supplemented with 10% sucrose at 18 °C in the dark. Purification of their metabolites afforded four new sesquiterpene derivatives 1-4 related to cameroonanol (5) and presilphiperfol-7-ene (6) [4]. Their structures were elucidated by spectroscopic and chemical means. This is the first instance of isolation of this type of metabolites from cultured mycobionts of lichen.

References:

[1] Tanahashi T et al. Chem. Pharm. Bull. 1997; 45: 1183 – 1185.

[2] Takenaka Y et al. Phytochemistry 2011; 72: 1431 – 1435.

[3] Le DH et al. Phytochemistry 2013; 91: 242 – 248.

[4] Weyeratahl P et al. Eur Org Chem 1998; 1205 – 1212.