| Summary: | Chemical investigation of the Antarctic lichen-derived fungal strain <i>Acremonium</i> sp. SF-7394 yielded a new amphilectane-type diterpene, acrepseudoterin (<b>1</b>), and a new acorane-type sesquiterpene glycoside, isocordycepoloside A (<b>2</b>). In addition, three known fungal metabolites, (−)-ternatin (<b>3</b>), [D-Leu]-ternatin (<b>4</b>), and pseurotin A (<b>5</b>), were isolated from the EtOAc extract of the fungal strain. Their structures were mainly elucidated by analyzing their NMR and MS data. The absolute configuration of <b>1</b> was proposed by electronic circular dichroism calculations, and the absolute configuration of the sugar unit in <b>2</b> was determined by a chemical method. The inhibitory effects of the isolated compounds on protein tyrosine phosphatase 1B (PTP1B) were evaluated by enzymatic assays; results indicated that acrepseudoterin (<b>1</b>) and [D-Leu]-ternatin (<b>4</b>) dose-dependently inhibited the enzyme activity with IC<sub>50</sub> values of 22.8 ± 1.1 μM and 14.8 ± 0.3 μM, respectively. Moreover, compound <b>1</b> was identified as a competitive inhibitor of PTP1B.
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