Paranolin: a New Xanthene-Based Metabolite from Paraphaeosphaeria nolinae

A new xanthene-based, polycyclic metabolite, paranolin (= (2R,3aS,12aR)-3,3a-dihydro-3a-hydroxy-8-(hydroxymethyl)-2-(1-hydroxy-1-methylethyl)-9-methoxy-10-methylfuro[3,2-d]xanthen-6(2H)-one; 1) was isolated from a culture of Paraphaeosphaeria nolinae (IFB-E011), an endophytic fungus residing in the normal stem of the artemisinin-producing plant Artemisia annua (Asteraceae). The structure of 1 was elucidated by extensive spectroscopic analyses. Although not substantially active against the human colon (SW1116) and human cervical carcinoma (Hela) cell lines, this metabolite seems to be the first example of a xanthene-derived secondary metabolite. Its possible biosynthetic origin (Scheme) and its significance as a phyllogenetic marker are discussed in brief.

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