Isolation and insecticidal activities of new cyclic peptides from mangrove endophytic fungus Aspergillus sp. GXNU-4QQY1a.

An investigation on bioactive metabolites from the mangrove endophytic fungus Aspergillus sp. GXNU-4QQY1a led to the isolation of two undescribed cyclic peptides, guaspertide A (1) and guaspertide B (2), together with six known compounds, 3-8. These structures and the new compounds' absolute configuration were determined by mass spectrometry analysis, nuclear magnetic resonance spectrum, electronic circular dichroism, and single-crystal X-ray diffraction. Insecticidal assays were carried out with compounds 1-8, and the results showed that compounds 1-3 and 8 exhibited good insecticidal activity against citrus psyllids.