Stelliosphaerols A and B, sesquiterpene-polyol conjugates from an Ecuadorian fungal endophyte

Abstract

Endophytic fungi are plant tissue-associated fungi that represent a rich resource of unexplored biological and chemical diversity with potential applications in the fields of medicine, bioremediation, and agriculture. As part of an ongoing effort to explore endophytes from the Amazon forest, numerous fungi were isolated and cultured using plants collected from the rainforest in Ecuador. From these samples, DNA sequencing and scanning electron microscopy (SEM) revealed a previously undescribed fungus in the order Pleosporales that was cultured from the tropical tree Duroia hirsuta. Extracts of this fungal isolate displayed modest activity against Staphylococcus aureus, and were thus subjected to detailed chemical studies. Two compounds with very modest antibacterial activity were isolated and their structures were elucidated using a combination of NMR spectroscopic analysis, LC-MS studies, and chemical degradation. These efforts led to the identification of stelliosphaerol A (1) and B (2), new sesquiterpene-polyol conjugates that are responsible, at least in part, for the S. aureus inhibitory activity of the fungal extract. Funded by FNLCR contract HHSN261200800001E