Abstract
A new indolyl-6,10b-dihydro-5aH-[1]benzofuro[2,3-b]indole derivative, varioloid A (1), was isolated from the marine alga-derived endophytic fungus Paecilomyces variotii EN-291. Its structure was elucidated on the basis of extensive analysis of 1D and 2D NMR data and the absolute configuration was determined by time-dependent density functional theory-electronic circular dichroism (TDDFT-ECD) calculations. A similar compound, whose planar structure was previously described but the relative and absolute configurations and 13C NMR data were not reported, was also identified and was tentatively named as varioloid B (2). Both compounds 1 and 2 exhibited cytotoxicity against A549, HCT116, and HepG2 cell lines, with IC50 values ranging from 2.6 to 8.2 µg/mL.
Highlights
The filamentous fungus Paecilomyces variotii is a ubiquitous species commonly occurring in air, compost, infected humans, and various foodstuffs [1]
During our ongoing effort to search for structurally unique and bioactive secondary metabolites from marine fungi, especially from marine alga-derived fungi [6,7,8], we discovered evident DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity and diverse antimicrobial activities in the EtOAc extract from Paecilomyces variotii EN-291, an endophytic fungus isolated from the red alga Grateloupia turuturu
The preliminary conformational search at MMFF (Merck Molecular Force Field) level resulted in 55 conformers within a 21 kJ/mol energy window
Summary
The filamentous fungus Paecilomyces variotii is a ubiquitous species commonly occurring in air, compost, infected humans, and various foodstuffs [1]. This fungus is well-known for its biotechnological applications and for its ability to produce enzymes and proteins [2]. During our ongoing effort to search for structurally unique and bioactive secondary metabolites from marine fungi, especially from marine alga-derived fungi [6,7,8], we discovered evident DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity and diverse antimicrobial activities in the EtOAc extract from Paecilomyces variotii EN-291, an endophytic fungus isolated from the red alga Grateloupia turuturu. We describe the isolation, structural elucidation including the assignment of the absolute configuration, and the cytotoxicity studies of these compounds
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