Bioactive Indole Diketopiperazine Alkaloids from the Marine Endophytic Fungus <i>Aspergillus</i> sp. YJ191021

Abstract

Six new prenylated indole diketopiperazine alkaloids, asperthrins A–F (1–6), along with eight known analogues (7–14), were isolated from the marine-derived endophytic fungus Aspergillus sp. YJ191021. Their planar structures and absolute configurations were elucidated by HR-ESI-MS, 1D/2D NMR data, and time-dependent density functional theory (TDDFT)/ECD calculation. The isolated compounds were assayed for their inhibition against three agricultural pathogenic fungi, four fish pathogenic bacteria, and two agricultural pathogenic bacteria. Compound 1 exhibited moderate antifungal and antibacterial activities against Vibrioanguillarum, Xanthomonas oryzae pv. Oryzicola, and Rhizoctoniasolani with minimal inhibitory concentration (MIC) values of 8, 12.5, and 25 μg/mL, respectively. Furthermore, 1 displayed notable anti-inflammatory activity with IC50 value of 1.46 ± 0.21 μM in Propionibacteriumacnes induced human monocyte cell line (THP-1).

Keywords

• indole diketopiperazine alkaloids
• endophytic fungus
• <i>Aspergillus</i> sp.
• antimicrobial